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1<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html lang="EN" xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html;charset=UTF-8" /><title>Extensible Markup Language (XML) 1.1</title><style type="text/css"> 1<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html lang="en" xml:lang="en" xmlns="http://www.w3.org/1999/xhtml"><head><title>Extensible Markup Language (XML) 1.1 (Second Edition)</title><style type="text/css">
2code { font-family: monospace; } 2code { font-family: monospace; }
3 3
4div.constraint, 4div.constraint,
5div.issue, 5div.issue,
6div.note, 6div.note,
7div.notice { margin-left: 2em; } 7div.notice { margin-left: 2em; }
8 8
9li p { margin-top: 0.3em; 9ol.enumar { list-style-type: decimal; }
10 margin-bottom: 0.3em; } 10ol.enumla { list-style-type: lower-alpha; }
11 11ol.enumlr { list-style-type: lower-roman; }
12div.exampleInner pre { margin-left: 1em; 12ol.enumua { list-style-type: upper-alpha; }
13 margin-top: 0em; margin-bottom: 0em} 13ol.enumur { list-style-type: upper-roman; }
14div.exampleOuter {border: 4px double gray; 14
15 margin: 0em; padding: 0em} 15
16div.exampleInner { background-color: #d5dee3; 16div.exampleInner pre { margin-left: 1em;
17 border-top-width: 4px; 17 margin-top: 0em; margin-bottom: 0em}
18 border-top-style: double; 18div.exampleOuter {border: 4px double gray;
19 border-top-color: #d3d3d3; 19 margin: 0em; padding: 0em}
20 border-bottom-width: 4px; 20div.exampleInner { background-color: #d5dee3;
21 border-bottom-style: double; 21 border-top-width: 4px;
22 border-bottom-color: #d3d3d3; 22 border-top-style: double;
23 padding: 4px; margin: 0em } 23 border-top-color: #d3d3d3;
24div.exampleWrapper { margin: 4px } 24 border-bottom-width: 4px;
25div.exampleHeader { font-weight: bold; 25 border-bottom-style: double;
26 margin: 4px} 26 border-bottom-color: #d3d3d3;
27 27 padding: 4px; margin: 0em }
28em.rfc2119 { text-transform: lowercase; 28div.exampleWrapper { margin: 4px }
29 font-variant: small-caps; 29div.exampleHeader { font-weight: bold;
30 font-style: normal; } 30 margin: 4px}
31</style><link rel="stylesheet" type="text/css" href="http://www.w3.org/StyleSheets/TR/W3C-REC.css" /></head><body><div class="head"><p><a href="http://www.w3.org/"><img src="http://www.w3.org/Icons/w3c_home" alt="W3C" height="48" width="72" /></a></p> 31
32<h1><a name="title" id="title" />Extensible Markup Language (XML) 1.1</h1> 32em.rfc2119 { text-transform: lowercase;
33<h2><a name="w3c-doctype" id="w3c-doctype" />W3C Recommendation 04 33 font-variant: small-caps;
34 February 2004, edited in place 15 April 2004</h2><dl><dt>This version:</dt><dd><a href="http://www.w3.org/TR/2004/REC-xml11-20040204/">http://www.w3.org/TR/2004/REC-xml11-20040204/</a></dd><dt>Latest version:</dt><dd><a href="http://www.w3.org/TR/xml11">http://www.w3.org/TR/xml11</a></dd><dt>Previous version:</dt><dd><a href="http://www.w3.org/TR/2003/PR-xml11-20031105/">http://www.w3.org/TR/2003/PR-xml11-20031105/</a></dd><dt>Editors:</dt><dd>Tim Bray, Textuality and Netscape <a href="mailto:tbray@textuality.com">&lt;tbray@textuality.com&gt;</a></dd><dd>Jean Paoli, Microsoft <a href="mailto:jeanpa@microsoft.com">&lt;jeanpa@microsoft.com&gt;</a></dd><dd>C. M. Sperberg-McQueen, W3C <a href="mailto:cmsmcq@w3.org">&lt;cmsmcq@w3.org&gt;</a></dd><dd>Eve Maler, Sun Microsystems, Inc. <a href="mailto:elm@east.sun.com">&lt;eve.maler@east.sun.com&gt;</a></dd><dd>François Yergeau <a href="mailto:fyergeau@alis.com">&lt;fyergeau@alis.com&gt;</a></dd><dd>John Cowan <a href="mailto:cowan@ccil.org">&lt;cowan@ccil.org&gt;</a></dd></dl><p>Please refer to the <a href="http://www.w3.org/XML/xml-V11-1e-errata"><strong>errata</strong></a> for this document, which may include some normative corrections.</p><p>This document is also available in these non-normative formats: <a href="REC-xml11-20040204.xml">XML</a> and <a href="REC-xml11-20040204-review.html">XHTML with color-coded revision indicators</a>.</p><p>See also <a href="http://www.w3.org/2003/03/Translations/byTechnology?technology=xml11"><strong>translations</strong></a>.</p><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2004 <a href="http://www.w3.org/"><acronym title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><acronym title="Massachusetts Institute of Technology">MIT</acronym></a>, <a href="http://www.ercim.org/"><acronym title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>, <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-software">software licensing</a> rules apply.</p></div><hr /><div> <h2><a name="abstract" id="abstract" />Abstract</h2><p>The Extensible Markup Language (XML) is a subset of SGML that is completely 34 font-style: normal; }
35described in this document. Its goal is to enable generic SGML to be served, 35</style><link rel="stylesheet" type="text/css" href="http://www.w3.org/StyleSheets/TR/W3C-REC.css" /></head><body><div class="head"><p><a href="http://www.w3.org/"><img src="http://www.w3.org/Icons/w3c_home" alt="W3C" height="48" width="72" /></a></p> <h1><a name="title" id="title" />Extensible Markup Language (XML) 1.1 (Second Edition)</h1> <h2><a name="w3c-doctype" id="w3c-doctype" />W3C Recommendation 16 August 2006, edited in place 29 September 2006</h2><dl><dt>This version:</dt><dd>
36received, and processed on the Web in the way that is now possible with HTML. 36 <a href="http://www.w3.org/TR/2006/REC-xml11-20060816">http://www.w3.org/TR/2006/REC-xml11-20060816</a>
37XML has been designed for ease of implementation and for interoperability 37 </dd><dt>Latest version:</dt><dd>
38with both SGML and HTML.</p></div><div> <h2><a name="status" id="status" />Status of this Document</h2><p><em>This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the <a href="http://www.w3.org/TR/">W3C technical reports index</a> at http://www.w3.org/TR/.</em></p><p>This document is a <a href="http://www.w3.org/2003/06/Process-20030618/tr.html#RecsW3C">Recommendation</a> of the W3C. 38 <a href="http://www.w3.org/TR/xml11">http://www.w3.org/TR/xml11</a>
39It has been reviewed by W3C Members and other interested parties, and has 39 </dd><dt>Previous version:</dt><dd>
40been endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited as a normative reference from another document. W3C's role in making the 40 <a href="http://www.w3.org/TR/2006/PER-xml11-20060614">http://www.w3.org/TR/2006/PER-xml11-20060614</a>
41Recommendation is to draw attention to the specification and to promote its widespread deployment. 41 </dd><dt>Editors:</dt><dd>Tim Bray, Textuality and Netscape <a href="mailto:tbray@textuality.com">&lt;tbray@textuality.com&gt;</a></dd><dd>Jean Paoli, Microsoft <a href="mailto:jeanpa@microsoft.com">&lt;jeanpa@microsoft.com&gt;</a></dd><dd>C. M. Sperberg-McQueen, W3C <a href="mailto:cmsmcq@w3.org">&lt;cmsmcq@w3.org&gt;</a></dd><dd>Eve Maler, Sun Microsystems, Inc. <a href="mailto:elm@east.sun.com">&lt;eve.maler@east.sun.com&gt;</a></dd><dd>François Yergeau</dd><dd>John Cowan <a href="mailto:cowan@ccil.org">&lt;cowan@ccil.org&gt;</a></dd></dl><p>Please refer to the <a href="http://www.w3.org/XML/xml-V11-2e-errata"><strong>errata</strong></a> for this document, which may
42This enhances the functionality and interoperability of the Web.</p><p>This document specifies a syntax created by subsetting an existing, widely 42 include some normative corrections.</p><p>The <a href="http://www.w3.org/XML/xml-V11-1e-errata">previous errata</a> for this document, are also available.</p><p>See also <a href="http://www.w3.org/2003/03/Translations/byTechnology?technology=xml11"><strong>translations</strong></a>.</p><p>This document is also available in these non-normative formats: <a href="REC-xml11-20060816.xml">XML</a> and <a href="REC-xml11-20060816-review.html">XHTML with color-coded revision indicators</a>.</p><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2006 <a href="http://www.w3.org/"><acronym title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><acronym title="Massachusetts Institute of Technology">MIT</acronym></a>, <a href="http://www.ercim.org/"><acronym title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> rules apply.</p></div><hr/><div> <h2><a name="abstract" id="abstract"/>Abstract</h2><p>The Extensible Markup Language (XML) is a subset of SGML that is completely
43used international text processing standard (Standard Generalized Markup Language, 43described in this document. Its goal is to enable generic SGML to be served,
44ISO 8879:1986(E) as amended and corrected) for use on the World Wide Web. 44received, and processed on the Web in the way that is now possible with HTML.
45It is a product of the <a 45XML has been designed for ease of implementation and for interoperability
46 href="http://www.w3.org/XML/Activity.html">W3C XML 46with both SGML and HTML.</p></div><div> <h2><a name="status" id="status"/>Status of this Document</h2><p><em>This section describes the status of this document at the time of its publication.
47 Activity</a>.</p> 47 Other documents may supersede this document. A list of current W3C publications and the
48 48 latest revision of this technical report can be found in the <a href="http://www.w3.org/TR/">W3C technical reports index</a> at
49<p>On 15 April 2004, this document was edited in place to add two 49 http://www.w3.org/TR/.</em></p><p>This document specifies a syntax created by subsetting an existing, widely
50missing spaces to <a 50used international text processing standard (Standard Generalized Markup Language,
51href="http://www.w3.org/TR/2004/REC-xml11-20040204/Overview.html#NT-document">production 51ISO 8879:1986(E) as amended and corrected) for use on the World Wide Web.
52[1]</a> in section 2.1</p> 52It is a product of the <a href="http://www.w3.org/XML/Core/">XML Core Working Group</a>
53 53as part of the <a href="http://www.w3.org/XML/Activity">XML Activity</a>.</p>
54<p>The English version of this specification is the only normative version. However, 54<p>On 29 September 2006 this document was edited in place to remove a
55for translations of this document, see <a href="http://www.w3.org/2003/03/Translations/byTechnology?technology=xml11">http://www.w3.org/2003/03/Translations/byTechnology?technology=xml11</a>. 55number of spurious and potentially misleading spaces.</p>
56</p><p>Documentation of intellectual property possibly relevant to this recommendation 56<p>The English version of this specification is the only normative version. However,
57may be found at the Working Group's public 57for translations of this document, see <a href="http://www.w3.org/2003/03/Translations/byTechnology?technology=xml11">http://www.w3.org/2003/03/Translations/byTechnology?technology=xml11</a>.</p><p>This document is a <a href="http://www.w3.org/2005/10/Process-20051014/tr.html#q74">W3C Recommendation</a>.
58<a href="http://www.w3.org/2002/08/xmlcore-IPR-statements">IPR disclosure page</a>.</p><p>An implementation report for XML 1.1 is available at <a href="http://www.w3.org/XML/2002/09/xml11-implementation.html">http://www.w3.org/XML/2002/09/xml11-implementation.html</a>.</p><p>Please report errors in this document to <a href="mailto:xml-editor@w3.org">xml-editor@w3.org</a>; <a href="http://lists.w3.org/Archives/Public/xml-editor">archives</a> are available. The errata list for this edition is available 58 This second edition is <em>not</em> a new version of XML. As a convenience to readers,
59at <a href="http://www.w3.org/XML/xml-V11-1e-errata">http://www.w3.org/XML/xml-V11-1e-errata</a>.</p><p>A <a href="http://www.w3.org/XML/Test/">Test Suite</a> is maintained to help assessing conformance to this specification.</p></div><div class="toc"> <h2><a name="contents" id="contents" />Table of Contents</h2><p class="toc">1 <a href="#sec-intro">Introduction</a><br />     1.1 <a href="#sec-origin-goals">Origin and Goals</a><br />     1.2 <a href="#sec-terminology">Terminology</a><br />     1.3 <a href="#sec-xml11">Rationale and list of changes for XML 1.1</a><br /> 2 <a href="#sec-documents">Documents</a><br />     2.1 <a href="#sec-well-formed">Well-Formed XML Documents</a><br />     2.2 <a href="#charsets">Characters</a><br />     2.3 <a href="#sec-common-syn">Common Syntactic Constructs</a><br />     2.4 <a href="#syntax">Character Data and Markup</a><br />     2.5 <a href="#sec-comments">Comments</a><br />     2.6 <a href="#sec-pi">Processing Instructions</a><br />     2.7 <a href="#sec-cdata-sect">CDATA Sections</a><br />     2.8 <a href="#sec-prolog-dtd">Prolog and Document Type Declaration</a><br />     2.9 <a href="#sec-rmd">Standalone Document Declaration</a><br />     2.10 <a href="#sec-white-space">White Space Handling</a><br />     2.11 <a href="#sec-line-ends">End-of-Line Handling</a><br />     2.12 <a href="#sec-lang-tag">Language Identification</a><br />     2.13 <a href="#sec-normalization-checking">Normalization Checking</a><br /> 3 <a href="#sec-logical-struct">Logical Structures</a><br />     3.1 <a href="#sec-starttags">Start-Tags, End-Tags, and Empty-Element Tags</a><br />     3.2 <a href="#elemdecls">Element Type Declarations</a><br />         3.2.1 <a href="#sec-element-content">Element Content</a><br />         3.2.2 <a href="#sec-mixed-content">Mixed Content</a><br />     3.3 <a href="#attdecls">Attribute-List Declarations</a><br />         3.3.1 <a href="#sec-attribute-types">Attribute Types</a><br />         3.3.2 <a href="#sec-attr-defaults">Attribute Defaults</a><br />         3.3.3 <a href="#AVNormalize">Attribute-Value Normalization</a><br />     3.4 <a href="#sec-condition-sect">Conditional Sections</a><br /> 4 <a href="#sec-physical-struct">Physical Structures</a><br />     4.1 <a href="#sec-references">Character and Entity References</a><br />     4.2 <a href="#sec-entity-decl">Entity Declarations</a><br />         4.2.1 <a href="#sec-internal-ent">Internal Entities</a><br />         4.2.2 <a href="#sec-external-ent">External Entities</a><br />     4.3 <a href="#TextEntities">Parsed Entities</a><br />         4.3.1 <a href="#sec-TextDecl">The Text Declaration</a><br />         4.3.2 <a href="#wf-entities">Well-Formed Parsed Entities</a><br />         4.3.3 <a href="#charencoding">Character Encoding in Entities</a><br />         4.3.4 <a href="#sec-version-info">Version Information in Entities</a><br />     4.4 <a href="#entproc">XML Processor Treatment of Entities and References</a><br />         4.4.1 <a href="#not-recognized">Not Recognized</a><br />         4.4.2 <a href="#included">Included</a><br />         4.4.3 <a href="#include-if-valid">Included If Validating</a><br />         4.4.4 <a href="#forbidden">Forbidden</a><br />         4.4.5 <a href="#inliteral">Included in Literal</a><br />         4.4.6 <a href="#notify">Notify</a><br />         4.4.7 <a href="#bypass">Bypassed</a><br />         4.4.8 <a href="#as-PE">Included as PE</a><br />         4.4.9 <a href="#error">Error</a><br />     4.5 <a href="#intern-replacement">Construction of Entity Replacement Text</a><br />     4.6 <a href="#sec-predefined-ent">Predefined Entities</a><br />     4.7 <a href="#Notations">Notation Declarations</a><br />     4.8 <a href="#sec-doc-entity">Document Entity</a><br /> 5 <a href="#sec-conformance">Conformance</a><br />     5.1 <a href="#proc-types">Validating and Non-Validating Processors</a><br />     5.2 <a href="#safe-behavior">Using XML Processors</a><br /> 6 <a href="#sec-notation">Notation</a><br /> </p> <h3><a name="appendices" id="appendices" />Appendices</h3><p class="toc">A <a href="#sec-bibliography">References</a><br />     A.1 <a href="#sec-existing-stds">Normative References</a><br />     A.2 <a href="#null">Other References</a><br /> B <a href="#sec-CharNorm">Definitions for Character Normalization</a><br /> C <a href="#sec-entexpand">Expansion of Entity and Character References</a> (Non-Normative)<br /> D <a href="#determinism">Deterministic Content Models</a> (Non-Normative)<br /> E <a href="#sec-guessing">Autodetection of Character Encodings</a> (Non-Normative)<br />     E.1 <a href="#sec-guessing-no-ext-info">Detection Without External Encoding Information</a><br />     E.2 <a href="#sec-guessing-with-ext-info">Priorities in the Presence of External Encoding Information</a><br /> F <a href="#sec-xml-wg">W3C XML Working Group</a> (Non-Normative)<br /> G <a href="#sec-core-wg">W3C XML Core Working Group</a> (Non-Normative)<br /> H <a href="#prod-notes">Production Notes</a> (Non-Normative)<br /> I <a href="#sec-suggested-names">Suggestions for XML Names</a> (Non-Normative)<br /> </p></div><hr /><div class="body"><div class="div1"> <h2><a name="sec-intro" id="sec-intro" />1 Introduction</h2><p>Extensible Markup Language, abbreviated XML, describes a class of data 59 it incorporates the changes dictated by the accumulated errata (available at
60objects called <a title="XML Document" href="#dt-xml-doc">XML documents</a> and partially 60 <a href="http://www.w3.org/XML/xml-V11-1e-errata">http://www.w3.org/XML/xml-V11-1e-errata</a>) to the <a href="http://www.w3.org/TR/2004/REC-xml11-20040204/">First
61describes the behavior of computer programs which process them. XML is an 61 Edition of XML 1.1, dated 4 February 2004</a>. In addition, the markup introduced to clarify when prescriptive
62application profile or restricted form of SGML, the Standard Generalized Markup 62 keywords are used
63Language <a href="#ISO8879">[ISO 8879]</a>. By construction, XML documents are conforming 63 in the formal sense defined in <a href="#rfc2119">[IETF RFC 2119]</a>, has been modified to better match the intent of <a href="#rfc2119">[IETF RFC 2119]</a>.
64SGML documents.</p><p>XML documents are made up of storage units called <a title="Entity" href="#dt-entity">entities</a>, 64 This edition supersedes the previous <a href="http://www.w3.org/TR/2004/REC-xml11-20040204">W3C Recommendation
65which contain either parsed or unparsed data. Parsed data is made up of <a title="Character" href="#dt-character">characters</a>, some of which form <a title="Character Data" href="#dt-chardata">character 65 of 4 February 2004</a>.</p><p>Please report errors in this document to the public <a href="mailto:xml-editor@w3.org">xml-editor@w3.org</a> mailing list; <a href="http://lists.w3.org/Archives/Public/xml-editor/">archives</a> are available. For the convenience of readers,
66data</a>, and some of which form <a title="Markup" href="#dt-markup">markup</a>. 66 an <a href="REC-xml11-20060816-review.html">XHTML version with color-coded revision indicators</a> is
67Markup encodes a description of the document's storage layout and logical 67 also provided; this version highlights each change due to an erratum published in the
68structure. XML provides a mechanism to impose constraints on the storage layout 68 <a href="http://www.w3.org/XML/xml-V11-1e-errata">errata list</a>, together with a link to the particular
69and logical structure.</p><p>[<a name="dt-xml-proc" id="dt-xml-proc" title="XML Processor">Definition</a>: A software module called 69 erratum in that list. Most of the errata in the list provide a rationale for the change.
70an <b>XML processor</b> is used to read XML documents and provide access 70 The errata list for this second edition is available at <a href="http://www.w3.org/XML/xml-V11-2e-errata">http://www.w3.org/XML/xml-V11-2e-errata</a>.</p><p>An implementation report is available at <a href="http://www.w3.org/XML/2006/06/xml11-2e-implementation.html">http://www.w3.org/XML/2006/06/xml11-2e-implementation.html</a>. A <a href="http://www.w3.org/XML/Test/">Test Suite</a> is maintained to help assessing conformance to this specification.</p><p>This document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.</p><p>This document is governed by the <a href="http://www.w3.org/TR/2002/NOTE-patent-practice-20020124">24
71to their content and structure.] [<a name="dt-app" id="dt-app" title="Application">Definition</a>: It 71 January 2002 CPP</a> as amended by the <a href="http://www.w3.org/2004/02/05-pp-transition">W3C Patent Policy
72is assumed that an XML processor is doing its work on behalf of another module, 72 Transition Procedure</a>. W3C maintains a <a href="http://www.w3.org/2002/08/xmlcore-IPR-statements" rel="disclosure">public list of
73called the <b>application</b>.] This specification describes 73 any patent disclosures</a> made in connection with the deliverables of
74the required behavior of an XML processor in terms of how it must read XML 74 the group; that page also includes instructions for disclosing a patent.
75data and the information it must provide to the application.</p><div class="div2"> <h3><a name="sec-origin-goals" id="sec-origin-goals" />1.1 Origin and Goals</h3><p>XML was developed by an XML Working Group (originally known as the SGML 75 An individual who has actual knowledge of a patent which the individual
76Editorial Review Board) formed under the auspices of the World Wide Web Consortium 76 believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
77(W3C) in 1996. It was chaired by Jon Bosak of Sun Microsystems with the active 77 Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
78participation of an XML Special Interest Group (previously known as the SGML 78 6 of the W3C Patent Policy</a>.</p></div><div class="toc"> <h2><a name="contents" id="contents"/>Table of Contents</h2><p class="toc">1 <a href="#sec-intro">Introduction</a><br/>     1.1 <a href="#sec-origin-goals">Origin and Goals</a><br/>     1.2 <a href="#sec-terminology">Terminology</a><br/>     1.3 <a href="#sec-xml11">Rationale and list of changes for XML 1.1</a><br/> 2 <a href="#sec-documents">Documents</a><br/>     2.1 <a href="#sec-well-formed">Well-Formed XML Documents</a><br/>     2.2 <a href="#charsets">Characters</a><br/>     2.3 <a href="#sec-common-syn">Common Syntactic Constructs</a><br/>     2.4 <a href="#syntax">Character Data and Markup</a><br/>     2.5 <a href="#sec-comments">Comments</a><br/>     2.6 <a href="#sec-pi">Processing Instructions</a><br/>     2.7 <a href="#sec-cdata-sect">CDATA Sections</a><br/>     2.8 <a href="#sec-prolog-dtd">Prolog and Document Type Declaration</a><br/>     2.9 <a href="#sec-rmd">Standalone Document Declaration</a><br/>     2.10 <a href="#sec-white-space">White Space Handling</a><br/>     2.11 <a href="#sec-line-ends">End-of-Line Handling</a><br/>     2.12 <a href="#sec-lang-tag">Language Identification</a><br/>     2.13 <a href="#sec-normalization-checking">Normalization Checking</a><br/> 3 <a href="#sec-logical-struct">Logical Structures</a><br/>     3.1 <a href="#sec-starttags">Start-Tags, End-Tags, and Empty-Element Tags</a><br/>     3.2 <a href="#elemdecls">Element Type Declarations</a><br/>         3.2.1 <a href="#sec-element-content">Element Content</a><br/>         3.2.2 <a href="#sec-mixed-content">Mixed Content</a><br/>     3.3 <a href="#attdecls">Attribute-List Declarations</a><br/>         3.3.1 <a href="#sec-attribute-types">Attribute Types</a><br/>         3.3.2 <a href="#sec-attr-defaults">Attribute Defaults</a><br/>         3.3.3 <a href="#AVNormalize">Attribute-Value Normalization</a><br/>     3.4 <a href="#sec-condition-sect">Conditional Sections</a><br/> 4 <a href="#sec-physical-struct">Physical Structures</a><br/>     4.1 <a href="#sec-references">Character and Entity References</a><br/>     4.2 <a href="#sec-entity-decl">Entity Declarations</a><br/>         4.2.1 <a href="#sec-internal-ent">Internal Entities</a><br/>         4.2.2 <a href="#sec-external-ent">External Entities</a><br/>     4.3 <a href="#TextEntities">Parsed Entities</a><br/>         4.3.1 <a href="#sec-TextDecl">The Text Declaration</a><br/>         4.3.2 <a href="#wf-entities">Well-Formed Parsed Entities</a><br/>         4.3.3 <a href="#charencoding">Character Encoding in Entities</a><br/>         4.3.4 <a href="#sec-version-info">Version Information in Entities</a><br/>     4.4 <a href="#entproc">XML Processor Treatment of Entities and References</a><br/>         4.4.1 <a href="#not-recognized">Not Recognized</a><br/>         4.4.2 <a href="#included">Included</a><br/>         4.4.3 <a href="#include-if-valid">Included If Validating</a><br/>         4.4.4 <a href="#forbidden">Forbidden</a><br/>         4.4.5 <a href="#inliteral">Included in Literal</a><br/>         4.4.6 <a href="#notify">Notify</a><br/>         4.4.7 <a href="#bypass">Bypassed</a><br/>         4.4.8 <a href="#as-PE">Included as PE</a><br/>         4.4.9 <a href="#error">Error</a><br/>     4.5 <a href="#intern-replacement">Construction of Entity Replacement Text</a><br/>     4.6 <a href="#sec-predefined-ent">Predefined Entities</a><br/>     4.7 <a href="#Notations">Notation Declarations</a><br/>     4.8 <a href="#sec-doc-entity">Document Entity</a><br/> 5 <a href="#sec-conformance">Conformance</a><br/>     5.1 <a href="#proc-types">Validating and Non-Validating Processors</a><br/>     5.2 <a href="#safe-behavior">Using XML Processors</a><br/> 6 <a href="#sec-notation">Notation</a><br/> </p> <h3><a name="appendices" id="appendices"/>Appendices</h3><p class="toc">A <a href="#sec-bibliography">References</a><br/>     A.1 <a href="#sec-existing-stds">Normative References</a><br/>     A.2 <a href="#null">Other References</a><br/> B <a href="#sec-CharNorm">Definitions for Character Normalization</a><br/> C <a href="#sec-entexpand">Expansion of Entity and Character References</a> (Non-Normative)<br/> D <a href="#determinism">Deterministic Content Models</a> (Non-Normative)<br/> E <a href="#sec-guessing">Autodetection of Character Encodings</a> (Non-Normative)<br/>     E.1 <a href="#sec-guessing-no-ext-info">Detection Without External Encoding Information</a><br/>     E.2 <a href="#sec-guessing-with-ext-info">Priorities in the Presence of External Encoding Information</a><br/> F <a href="#sec-xml-wg">W3C XML Working Group</a> (Non-Normative)<br/> G <a href="#sec-core-wg">W3C XML Core Working Group</a> (Non-Normative)<br/> H <a href="#prod-notes">Production Notes</a> (Non-Normative)<br/> I <a href="#sec-suggested-names">Suggestions for XML Names</a> (Non-Normative)<br/> </p></div><hr/><div class="body"><div class="div1"> <h2><a name="sec-intro" id="sec-intro"/>1 Introduction</h2><p>Extensible Markup Language, abbreviated XML, describes a class of data
79Working Group) also organized by the W3C. The membership of the XML Working 79objects called <a title="XML Document" href="#dt-xml-doc">XML documents</a> and partially
80Group is given in an appendix. Dan Connolly served as the Working Group's contact with 80describes the behavior of computer programs which process them. XML is an
81the W3C.</p><p>The design goals for XML are:</p><ol type="1"><li><p>XML shall be straightforwardly usable over the Internet.</p></li><li><p>XML shall support a wide variety of applications.</p></li><li><p>XML shall be compatible with SGML.</p></li><li><p>It shall be easy to write programs which process XML documents.</p></li><li><p>The number of optional features in XML is to be kept to the absolute 81application profile or restricted form of SGML, the Standard Generalized Markup
82minimum, ideally zero.</p></li><li><p>XML documents should be human-legible and reasonably clear.</p></li><li><p>The XML design should be prepared quickly.</p></li><li><p>The design of XML shall be formal and concise.</p></li><li><p>XML documents shall be easy to create.</p></li><li><p>Terseness in XML markup is of minimal importance.</p></li></ol><p>This specification, together with associated standards (Unicode 82Language <a href="#ISO8879">[ISO 8879]</a>. By construction, XML documents are conforming
83<a href="#Unicode">[Unicode]</a> and ISO/IEC 10646 <a href="#ISO10646">[ISO/IEC 10646]</a> 83SGML documents.</p><p>XML documents are made up of storage units called <a title="Entity" href="#dt-entity">entities</a>,
84for characters, Internet RFC 3066 <a href="#RFC1766">[IETF RFC 3066]</a> for 84which contain either parsed or unparsed data. Parsed data is made up of <a title="Character" href="#dt-character">characters</a>, some of which form <a title="Character Data" href="#dt-chardata">character
85language identification tags, ISO 639 <a href="#ISO639">[ISO 639]</a> 85data</a>, and some of which form <a title="Markup" href="#dt-markup">markup</a>.
86for language name codes, and ISO 3166 <a href="#ISO3166">[ISO 3166]</a> for 86Markup encodes a description of the document's storage layout and logical
87country name codes), provides all the information necessary to 87structure. XML provides a mechanism to impose constraints on the storage layout
88understand XML Version 1.1 and construct computer 88and logical structure.</p><p>
89programs to process it.</p><p>This version of the XML specification may be distributed freely, as long as 89 [<a name="dt-xml-proc" id="dt-xml-proc" title="XML Processor">Definition</a>: A software module called
90all text and legal notices remain intact.</p></div><div class="div2"> <h3><a name="sec-terminology" id="sec-terminology" />1.2 Terminology</h3><p>The terminology used to describe XML documents is defined in the body of 90an <b>XML processor</b> is used to read XML documents and provide access
91this specification. <span class="mustard">The key words <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">SHALL</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">SHALL NOT</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD NOT</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">RECOMMENDED</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em>, and <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>, when <em class="rfc2119" title="Keyword in RFC 2119 context">EMPHASIZED</em>, are to be interpreted as described in <a href="#rfc2119">[IETF RFC 2119]</a>. In addition, </span>the terms defined in the following list are used in building 91to their content and structure.]
92those definitions and in describing the actions of an XML processor:</p><dl><dt class="label">error</dt><dd><p>[<a name="dt-error" id="dt-error" title="Error">Definition</a>: A violation of the rules of this specification; 92 [<a name="dt-app" id="dt-app" title="Application">Definition</a>: It
93results are undefined. <span class="mustard">Unless otherwise specified, failure to observe a prescription of this specification indicated by one of the keywords <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">SHALL</em> and <em class="rfc2119" title="Keyword in RFC 2119 context">SHALL NOT</em> is an error.</span> Conforming software <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> detect and report an error 93is assumed that an XML processor is doing its work on behalf of another module,
94and <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> recover from it.]</p></dd><dt class="label">fatal error</dt><dd><p>[<a name="dt-fatal" id="dt-fatal" title="Fatal Error">Definition</a>: An error which a conforming <a title="XML Processor" href="#dt-xml-proc">XML processor</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> detect and report to the application. 94called the <b>application</b>.] This specification describes
95After encountering a fatal error, the processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> continue processing the 95the required behavior of an XML processor in terms of how it must read XML
96data to search for further errors and <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> report such errors to the application. 96data and the information it must provide to the application.</p><div class="div2"> <h3><a name="sec-origin-goals" id="sec-origin-goals"/>1.1 Origin and Goals</h3><p>XML was developed by an XML Working Group (originally known as the SGML
97In order to support correction of errors, the processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> make unprocessed 97Editorial Review Board) formed under the auspices of the World Wide Web Consortium
98data from the document (with intermingled character data and markup) available 98(W3C) in 1996. It was chaired by Jon Bosak of Sun Microsystems with the active
99to the application. Once a fatal error is detected, however, the processor 99participation of an XML Special Interest Group (previously known as the SGML
100<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> continue normal processing (i.e., it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> continue to pass character 100Working Group) also organized by the W3C. The membership of the XML Working
101data and information about the document's logical structure to the application 101Group is given in an appendix. Dan Connolly served as the Working Group's contact with
102in the normal way).]</p></dd><dt class="label">at user option</dt><dd><p>[<a name="dt-atuseroption" id="dt-atuseroption" title="At user option">Definition</a>: Conforming software 102the W3C.</p><p>The design goals for XML are:</p><ol class="enumar"><li><p>XML shall be straightforwardly usable over the Internet.</p></li><li><p>XML shall support a wide variety of applications.</p></li><li><p>XML shall be compatible with SGML.</p></li><li><p>It shall be easy to write programs which process XML documents.</p></li><li><p>The number of optional features in XML is to be kept to the absolute
103<em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> or <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> (depending on the modal verb in the sentence) behave as described; 103minimum, ideally zero.</p></li><li><p>XML documents should be human-legible and reasonably clear.</p></li><li><p>The XML design should be prepared quickly.</p></li><li><p>The design of XML shall be formal and concise.</p></li><li><p>XML documents shall be easy to create.</p></li><li><p>Terseness in XML markup is of minimal importance.</p></li></ol><p>This specification, together with associated standards (Unicode
104if it does, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> provide users a means to enable or disable the behavior 104<a href="#Unicode">[Unicode]</a> and ISO/IEC 10646 <a href="#ISO10646">[ISO/IEC 10646]</a>
105described.]</p></dd><dt class="label">validity constraint</dt><dd><p>[<a name="dt-vc" id="dt-vc" title="Validity constraint">Definition</a>: A rule which applies to 105for characters, Internet RFC 3066 <a href="#RFC1766">[IETF RFC 3066]</a> for
106all <a title="Validity" href="#dt-valid">valid</a> XML documents. Violations of validity 106language identification tags, ISO 639 <a href="#ISO639">[ISO 639]</a>
107constraints are errors; they <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>, at user option, be reported by <a title="Validating Processor" href="#dt-validating">validating XML processors</a>.]</p></dd><dt class="label">well-formedness constraint</dt><dd><p>[<a name="dt-wfc" id="dt-wfc" title="Well-formedness constraint">Definition</a>: A rule which applies 107for language name codes, and ISO 3166 <a href="#ISO3166">[ISO 3166]</a> for
108to all <a title="Well-Formed" href="#dt-wellformed">well-formed</a> XML documents. Violations 108country name codes), provides all the information necessary to
109of well-formedness constraints are <a title="Fatal Error" href="#dt-fatal">fatal errors</a>.]</p></dd><dt class="label">match</dt><dd><p>[<a name="dt-match" id="dt-match" title="match">Definition</a>: (Of strings or names:) Two strings 109understand XML Version 1.1 and construct computer
110or names being compared <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be identical. Characters with multiple possible 110programs to process it.</p><p>This version of the XML specification may be distributed freely, as long as
111representations in Unicode (e.g. characters with both precomposed and 111all text and legal notices remain intact.</p></div><div class="div2"> <h3><a name="sec-terminology" id="sec-terminology"/>1.2 Terminology</h3><p>The terminology used to describe XML documents is defined in the body of
112base+diacritic forms) match only if they have the same representation in both 112this specification. The key words <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">SHALL</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">SHALL NOT</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD NOT</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">RECOMMENDED</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em>, and <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>, when <em class="rfc2119" title="Keyword in RFC 2119 context">EMPHASIZED</em>, are to be interpreted as described in <a href="#rfc2119">[IETF RFC 2119]</a>. In addition, the terms defined in the following list are used in building
113strings. No 113those definitions and in describing the actions of an XML processor:</p><dl><dt class="label">error</dt><dd><p>
114case folding is performed. (Of strings and rules in the grammar:) A string 114 [<a name="dt-error" id="dt-error" title="Error">Definition</a>: A violation of the rules of this specification;
115matches a grammatical production if it belongs to the language generated by 115results are undefined. Unless otherwise specified, failure to observe a prescription of this specification indicated by one of the keywords <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em>, <em class="rfc2119" title="Keyword in RFC 2119 context">SHALL</em> and <em class="rfc2119" title="Keyword in RFC 2119 context">SHALL NOT</em> is an error. Conforming software <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> detect and report an error
116that production. (Of content and content models:) An element matches its declaration 116and <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> recover from it.]
117when it conforms in the fashion described in the constraint <b>[VC: <a href="#elementvalid">Element Valid</a>]</b>.]</p></dd><dt class="label">for compatibility</dt><dd><p>[<a name="dt-compat" id="dt-compat" title="For Compatibility">Definition</a>: Marks 117 </p></dd><dt class="label">fatal error</dt><dd><p>
118a sentence describing a feature of XML included solely to ensure 118 [<a name="dt-fatal" id="dt-fatal" title="Fatal Error">Definition</a>: An error which a conforming <a title="XML Processor" href="#dt-xml-proc">XML processor</a>
119that XML remains compatible with SGML.]</p></dd><dt class="label">for interoperability</dt><dd><p>[<a name="dt-interop" id="dt-interop" title="For interoperability">Definition</a>: Marks 119 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> detect and report to the application.
120a sentence describing a non-binding recommendation included to increase 120After encountering a fatal error, the processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> continue processing the
121the chances that XML documents can be processed by the existing installed 121data to search for further errors and <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> report such errors to the application.
122base of SGML processors which predate the WebSGML Adaptations Annex to ISO 8879.]</p></dd></dl><p></p></div><div class="div2"> <h3><a name="sec-xml11" id="sec-xml11" />1.3 Rationale and list of changes for XML 1.1</h3><p>The W3C's XML 1.0 Recommendation was first issued in 1998, and 122In order to support correction of errors, the processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> make unprocessed
123despite the issuance of many errata culminating in a Third Edition 123data from the document (with intermingled character data and markup) available
124of 2004, has remained (by intention) unchanged with respect to what 124to the application. Once a fatal error is detected, however, the processor
125is well-formed XML and what is not. This stability has been 125<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> continue normal processing (i.e., it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> continue to pass character
126extremely useful for interoperability. However, the Unicode 126data and information about the document's logical structure to the application
127Standard on which XML 1.0 relies for character specifications has 127in the normal way).]
128not remained static, evolving from version 2.0 to version 4.0 and 128 </p></dd><dt class="label">at user option</dt><dd><p>
129beyond. Characters not present in Unicode 2.0 may already be used 129 [<a name="dt-atuseroption" id="dt-atuseroption" title="At user option">Definition</a>: Conforming software
130in XML 1.0 character data. However, they are not allowed in XML 130<em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> or <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> (depending on the modal verb in the sentence) behave as described;
131names such as element type names, attribute names, enumerated 131if it does, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> provide users a means to enable or disable the behavior
132attribute values, processing instruction targets, and so on. In 132described.]
133addition, some characters that should have been permitted in XML 133 </p></dd><dt class="label">validity constraint</dt><dd><p>
134names were not, due to oversights and inconsistencies in Unicode 134 [<a name="dt-vc" id="dt-vc" title="Validity constraint">Definition</a>: A rule which applies to
1352.0.</p><p>The overall philosophy of names has changed since XML 1.0. 135all <a title="Validity" href="#dt-valid">valid</a> XML documents. Violations of validity
136Whereas XML 1.0 provided a rigid definition of names, wherein 136constraints are errors; they <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>, at user option, be reported by <a title="Validating Processor" href="#dt-validating">validating XML processors</a>.]
137everything that was not permitted was forbidden, XML 1.1 names are 137 </p></dd><dt class="label">well-formedness constraint</dt><dd><p>
138designed so that everything that is not forbidden (for a specific 138 [<a name="dt-wfc" id="dt-wfc" title="Well-formedness constraint">Definition</a>: A rule which applies
139reason) is permitted. Since Unicode will continue to grow past 139to all <a title="Well-Formed" href="#dt-wellformed">well-formed</a> XML documents. Violations
140version 4.0, further changes to XML can be avoided by allowing 140of well-formedness constraints are <a title="Fatal Error" href="#dt-fatal">fatal errors</a>.]
141almost any character, including those not yet assigned, in 141 </p></dd><dt class="label">match</dt><dd><p>
142names.</p><p>In addition, XML 1.0 attempts to adapt to the line-end 142 [<a name="dt-match" id="dt-match" title="match">Definition</a>: (Of strings or names:) Two strings
143conventions of various modern operating systems, but discriminates 143or names being compared
144against the conventions used on IBM and IBM-compatible mainframes. 144 <span>are</span> identical. Characters with multiple possible
145As a result, XML documents on mainframes are not plain text files 145representations in Unicode (e.g. characters with both precomposed and
146according to the local conventions. XML 1.0 documents generated on 146base+diacritic forms) match only if they have the same representation in both
147mainframes must either violate the local line-end conventions, or 147strings. No
148employ otherwise unnecessary translation phases before parsing and 148case folding is performed. (Of strings and rules in the grammar:) A string
149after generation. Allowing straightforward interoperability is 149matches a grammatical production if it belongs to the language generated by
150particularly important when data stores are shared between 150that production. (Of content and content models:) An element matches its declaration
151mainframe and non-mainframe systems (as opposed to being copied 151when it conforms in the fashion described in the constraint <b>[VC: <a href="#elementvalid">Element Valid</a>]</b>.]
152from one to the other). Therefore XML 1.1 adds NEL (#x85) to the 152 </p></dd><dt class="label">for compatibility</dt><dd><p>
153list of line-end characters. For completeness, the Unicode line 153 [<a name="dt-compat" id="dt-compat" title="For Compatibility">Definition</a>: Marks
154separator character, #x2028, is also supported. 154a sentence describing a feature of XML included solely to ensure
155</p><p>Finally, there is considerable demand to define a standard representation 155that XML remains compatible with SGML.]
156of arbitrary Unicode characters in XML documents. Therefore, XML 1.1 156 </p></dd><dt class="label">for interoperability</dt><dd><p>
157allows the use of character references to the control characters #x1 through 157 [<a name="dt-interop" id="dt-interop" title="For interoperability">Definition</a>: Marks
158#x1F, most of which are forbidden in XML 1.0. For reasons of robustness, 158a sentence describing a non-binding recommendation included to increase
159however, these characters still cannot be used directly in documents. In 159the chances that XML documents can be processed by the existing installed
160order to improve the robustness of character encoding detection, the additional 160base of SGML processors which predate the WebSGML Adaptations Annex to ISO 8879.]
161control characters #x7F through #x9F, which were freely allowed in XML 1.0 161 </p></dd></dl><p>
162documents, now must also appear only as character references. (Whitespace 162 </p></div><div class="div2"> <h3><a name="sec-xml11" id="sec-xml11"/>1.3 Rationale and list of changes for XML 1.1</h3><p>The W3C's XML 1.0 Recommendation was first issued in 1998, and
163characters are of course exempt.) The minor sacrifice of backward compatibility 163despite the issuance of many errata culminating in a Third Edition
164is considered not significant. Due to potential problems with APIs, 164of 2004, has remained (by intention) unchanged with respect to what
165#x0 is still forbidden both directly and as a character reference. 165is well-formed XML and what is not. This stability has been
166</p><p>Finally, XML 1.1 defines a set of constraints called "full 166extremely useful for interoperability. However, the Unicode
167normalization" on XML documents, which document creators 167Standard on which XML 1.0 relies for character specifications has
168<em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> adhere to, and document processors 168not remained static, evolving from version 2.0 to version 4.0 and
169<em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> verify. Using fully normalized documents 169beyond. Characters not present in Unicode 2.0 may already be used
170ensures that identity comparisons of names, attribute values, and 170in XML 1.0 character data. However, they are not allowed in XML
171character content can be made correctly by simple binary comparison of 171names such as element type names, attribute names, enumerated
172Unicode strings.</p><p>A new XML version, rather than a set of errata to XML 1.0, is 172attribute values, processing instruction targets, and so on. In
173being created because the changes affect the definition of 173addition, some characters that should have been permitted in XML
174well-formed documents. XML 1.0 processors must continue to reject 174names were not, due to oversights and inconsistencies in Unicode
175documents that contain new characters in XML names, new line-end 1752.0.</p><p>The overall philosophy of names has changed since XML 1.0.
176conventions, and references to control characters. The distinction between XML 1.0 and XML 1.1 documents 176Whereas XML 1.0 provided a rigid definition of names, wherein
177is indicated by the version number information in the XML 177everything that was not permitted was forbidden, XML 1.1 names are
178declaration at the start of each document. 178designed so that everything that is not forbidden (for a specific
179</p></div></div><div class="div1"> <h2><a name="sec-documents" id="sec-documents" />2 Documents</h2><p>[<a name="dt-xml-doc" id="dt-xml-doc" title="XML Document">Definition</a>: A data object is an <b>XML 179reason) is permitted. Since Unicode will continue to grow past
180document</b> if it is <a title="Well-Formed" href="#dt-wellformed">well-formed</a>, 180version 4.0, further changes to XML can be avoided by allowing
181as defined in this specification. A well-formed XML document <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> in addition 181almost any character, including those not yet assigned, in
182be <a title="Validity" href="#dt-valid">valid</a> if it meets certain further constraints.]</p><p>Each XML document has both a logical and a physical structure. Physically, 182names.</p><p>In addition, XML 1.0 attempts to adapt to the line-end
183the document is composed of units called <a title="Entity" href="#dt-entity">entities</a>. 183conventions of various modern operating systems, but discriminates
184An entity <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> <a title="Entity Reference" href="#dt-entref">refer</a> to other entities to 184against the conventions used on IBM and IBM-compatible mainframes.
185cause their inclusion in the document. A document begins in a "root" 185As a result, XML documents on mainframes are not plain text files
186or <a title="Document Entity" href="#dt-docent">document entity</a>. Logically, the document 186according to the local conventions. XML 1.0 documents generated on
187is composed of declarations, elements, comments, character references, and 187mainframes must either violate the local line-end conventions, or
188processing instructions, all of which are indicated in the document by explicit 188employ otherwise unnecessary translation phases before parsing and
189markup. The logical and physical structures <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> nest properly, as described 189after generation. Allowing straightforward interoperability is
190in <a href="#wf-entities"><b>4.3.2 Well-Formed Parsed Entities</b></a>.</p><div class="div2"> <h3><a name="sec-well-formed" id="sec-well-formed" />2.1 Well-Formed XML Documents</h3><p>[<a name="dt-wellformed" id="dt-wellformed" title="Well-Formed">Definition</a>: A textual object is a <b>well-formed</b> 190particularly important when data stores are shared between
191XML document if:]</p><ol type="1"><li><p>Taken as a whole, it matches the production labeled <a href="#NT-document">document</a>.</p></li><li><p>It meets all the well-formedness constraints given in this specification.</p></li><li><p>Each of the <a title="Text Entity" href="#dt-parsedent">parsed entities</a> 191mainframe and non-mainframe systems (as opposed to being copied
192which is referenced directly or indirectly within the document is <a 192from one to the other). Therefore XML 1.1 adds NEL (#x85) to the
193title="Well-Formed" 193list of line-end characters. For completeness, the Unicode line
194href="#dt-wellformed">well-formed</a>.</p></li></ol> <h5><a 194separator character, #x2028, is also supported.
195name="document" id="document" />Document</h5><table class="scrap" 195</p><p>Finally, there is considerable demand to define a standard representation
196summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-document" 196of arbitrary Unicode characters in XML documents. Therefore, XML 1.1
197id="NT-document" 197allows the use of character references to the control characters #x1 through
198/>[1]   </td><td><code>document</code></td><td>   ::=   </td><td><code><a 198#x1F, most of which are forbidden in XML 1.0. For reasons of robustness,
199href="#NT-prolog">prolog</a> <a href="#NT-element">element</a> <a 199however, these characters still cannot be used directly in documents. In
200href="#NT-Misc">Misc</a>* - <a href="#NT-Char">Char</a>* <a 200order to improve the robustness of character encoding detection, the additional
201href="#NT-RestrictedChar">RestrictedChar</a> <a href="#NT-Char">Char</a>*</code></td></tr></tbody></table><p>Matching the <a href="#NT-document">document</a> production implies that:</p><ol type="1"><li><p>It contains one or more <a title="Element" href="#dt-element">elements</a>.</p></li><li><p>[<a name="dt-root" id="dt-root" title="Root Element">Definition</a>: There is exactly one element, 201control characters #x7F through #x9F, which were freely allowed in XML 1.0
202called the <b>root</b>, or document element, no part of which appears 202documents, now must also appear only as character references. (Whitespace
203in the <a title="Content" href="#dt-content">content</a> of any other element.] For 203characters are of course exempt.) The minor sacrifice of backward compatibility
204all other elements, if the <a title="Start-Tag" href="#dt-stag">start-tag</a> is in 204is considered not significant. Due to potential problems with APIs,
205the content of another element, the <a title="End Tag" href="#dt-etag">end-tag</a> 205#x0 is still forbidden both directly and as a character reference.
206is in the content of the same element. More simply stated, the elements, 206</p><p>Finally, XML 1.1 defines a set of constraints called "full
207delimited by start- and end-tags, nest properly within each other.</p></li></ol><p>[<a name="dt-parentchild" id="dt-parentchild" title="Parent/Child">Definition</a>: As a consequence of this, 207normalization" on XML documents, which document creators
208for each non-root element <code>C</code> in the document, there is one other element <code>P</code> 208<em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> adhere to, and document processors
209in the document such that <code>C</code> is in the content of <code>P</code>, but 209<em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> verify. Using fully normalized documents
210is not in the content of any other element that is in the content of <code>P</code>. <code>P</code> 210ensures that identity comparisons of names, attribute values, and
211is referred to as the <b>parent</b> of <code>C</code>, and <code>C</code> as 211character content can be made correctly by simple binary comparison of
212a <b>child</b> of <code>P</code>.]</p></div><div class="div2"> <h3><a name="charsets" id="charsets" />2.2 Characters</h3><p>[<a name="dt-text" id="dt-text" title="Text">Definition</a>: A parsed entity contains <b>text</b>, 212Unicode strings.</p><p>A new XML version, rather than a set of errata to XML 1.0, is
213a sequence of <a title="Character" href="#dt-character">characters</a>, which may 213being created because the changes affect the definition of
214represent markup or character data.] [<a name="dt-character" id="dt-character" title="Character">Definition</a>: A <b>character</b> 214well-formed documents. XML 1.0 processors must continue to reject
215is an atomic unit of text as specified by <span>ISO/IEC 10646 <a href="#ISO10646">[ISO/IEC 10646]</a></span>. Legal characters are tab, carriage 215documents that contain new characters in XML names, new line-end
216return, line feed, and the legal characters 216conventions, and references to control characters. The distinction between XML 1.0 and XML 1.1 documents
217of Unicode and ISO/IEC 10646. The 217is indicated by the version number information in the XML
218versions of these standards cited in <a href="#sec-existing-stds"><b>A.1 Normative References</b></a> were 218declaration at the start of each document.
219current at the time this document was prepared. New characters may be added 219</p></div></div><div class="div1"> <h2><a name="sec-documents" id="sec-documents"/>2 Documents</h2><p>
220to these standards by amendments or new editions. Consequently, XML processors 220 [<a name="dt-xml-doc" id="dt-xml-doc" title="XML Document">Definition</a>: A data object is an <b>XML
221<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> accept any character in the range specified for <a href="#NT-Char">Char</a>.]</p> <h5><a name="char32" id="char32" />Character Range</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-Char" id="NT-Char" />[2]   </td><td><code>Char</code></td><td>   ::=   </td><td><code>[#x1-#xD7FF] | [#xE000-#xFFFD] | [#x10000-#x10FFFF]</code></td><td><i>/* any Unicode character, excluding the surrogate blocks, FFFE, and FFFF. */</i></td></tr><tr valign="baseline"><td><a name="NT-RestrictedChar" id="NT-RestrictedChar" />[2a]   </td><td><code>RestrictedChar</code></td><td>   ::=   </td><td><code>[#x1-#x8] | [#xB-#xC] | [#xE-#x1F] | [#x7F-#x84] | [#x86-#x9F]</code></td></tr></tbody></table><p>The mechanism for encoding character code points into bit patterns <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> 221document</b> if it is <a title="Well-Formed" href="#dt-wellformed">well-formed</a>,
222vary from entity to entity. All XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> accept the UTF-8 and UTF-16 222as defined in this specification. <span>In addition, the XML document is</span>
223encodings of <span> Unicode 223 <a title="Validity" href="#dt-valid">valid</a> if it meets certain further constraints.]
224<a href="#Unicode">[Unicode]</a></span>; 224 </p><p>Each XML document has both a logical and a physical structure. Physically,
225the mechanisms for signaling which of the two is in use, 225the document is composed of units called <a title="Entity" href="#dt-entity">entities</a>.
226or for bringing other encodings into play, are discussed later, in <a href="#charencoding"><b>4.3.3 Character Encoding in Entities</b></a>.</p><div class="note"><p class="prefix"><b>Note:</b></p><p>Document authors are encouraged to avoid 226An entity <span>may</span> <a title="Entity Reference" href="#dt-entref">refer</a> to other entities to
227"compatibility characters", as defined 227cause their inclusion in the document. A document begins in a "root"
228in Unicode <a href="#Unicode">[Unicode]</a>. 228or <a title="Document Entity" href="#dt-docent">document entity</a>. Logically, the document
229The characters defined in the following ranges are also 229is composed of declarations, elements, comments, character references, and
230discouraged. They are either control characters or permanently undefined Unicode 230processing instructions, all of which are indicated in the document by explicit
231characters:</p><div class="exampleInner"><pre> 231markup. The logical and physical structures <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> nest properly, as described
232[#x7F-#x84], [#x86-#x9F], [#xFDD0-#xFDDF], 232in <a href="#wf-entities"><b>4.3.2 Well-Formed Parsed Entities</b></a>.</p><div class="div2"> <h3><a name="sec-well-formed" id="sec-well-formed"/>2.1 Well-Formed XML Documents</h3><p>
233[#1FFFE-#x1FFFF], [#2FFFE-#x2FFFF], [#3FFFE-#x3FFFF], 233 [<a name="dt-wellformed" id="dt-wellformed" title="Well-Formed">Definition</a>: A textual object is a <b>well-formed</b>
234[#4FFFE-#x4FFFF], [#5FFFE-#x5FFFF], [#6FFFE-#x6FFFF], 234XML document if:]
235[#7FFFE-#x7FFFF], [#8FFFE-#x8FFFF], [#9FFFE-#x9FFFF], 235 </p><ol class="enumar"><li><p>Taken as a whole, it matches the production labeled <a href="#NT-document">document</a>.</p></li><li><p>It meets all the well-formedness constraints given in this specification.</p></li><li><p>Each of the <a title="Text Entity" href="#dt-parsedent">parsed entities</a>
236[#AFFFE-#xAFFFF], [#BFFFE-#xBFFFF], [#CFFFE-#xCFFFF], 236which is referenced directly or indirectly within the document is <a title="Well-Formed" href="#dt-wellformed">well-formed</a>.</p></li></ol> <h5><a name="document" id="document"/>Document</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-document" id="NT-document"/>[1]   </td><td><code>document</code></td><td>   ::=   </td><td><code>
237[#DFFFE-#xDFFFF], [#EFFFE-#xEFFFF], [#FFFFE-#xFFFFF], 237 <span>
238[#10FFFE-#x10FFFF].</pre></div></div></div><div class="div2"> <h3><a name="sec-common-syn" id="sec-common-syn" />2.3 Common Syntactic Constructs</h3><p>This section defines some symbols used widely in the grammar.</p><p><a href="#NT-S">S</a> (white space) consists of one or more space (#x20) 238 (</span>
239characters, carriage returns, line feeds, or tabs.</p> <h5><a name="white" id="white" />White Space</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-S" id="NT-S" />[3]   </td><td><code>S</code></td><td>   ::=   </td><td><code>(#x20 | #x9 | #xD | #xA)+</code></td></tr></tbody></table><div class="note"><p class="prefix"><b>Note:</b></p><p>The presence of #xD in the above production is 239 <a href="#NT-prolog">prolog</a>
240maintained purely for backward compatibility with the 240 <a href="#NT-element">element</a>
241<a href="http://www.w3.org/TR/1998/REC-xml-19980210">First Edition</a>. 241 <a href="#NT-Misc">Misc</a>*<span>
242As explained in <a href="#sec-line-ends"><b>2.11 End-of-Line Handling</b></a>, 242 )</span>
243all #xD characters literally present in an XML document 243 <span>
244are either removed or replaced by #xA characters before 244
245any other processing is done. The only way to get a #xD character to match this production is to 245 </span>- <span>
246use a character reference in an entity value literal.</p></div><p>[<a name="dt-name" id="dt-name" title="Name">Definition</a>: A <b>Name</b> is a token beginning 246 (</span>
247with a letter or one of a few punctuation characters, and continuing with 247 <a href="#NT-Char">Char</a>* <a href="#NT-RestrictedChar">RestrictedChar</a>
248letters, digits, hyphens, underscores, colons, or full stops, together known 248 <span>
249as name characters.] Names beginning with the string "<code>xml</code>", 249
250or <span>with</span> any string which would match <code>(('X'|'x') ('M'|'m') ('L'|'l'))</code>, 250 </span>
251are reserved for standardization in this or future versions of this specification.</p><div class="note"><p class="prefix"><b>Note:</b></p><p>The 251 <a href="#NT-Char">Char</a>*<span>
252Namespaces in XML Recommendation <a href="#xml-names">[XML Names]</a> assigns a meaning 252 )</span>
253to names containing colon characters. Therefore, authors should not use the 253 </code></td></tr></tbody></table><p>Matching the <a href="#NT-document">document</a> production implies that:</p><ol class="enumar"><li><p>It contains one or more <a title="Element" href="#dt-element">elements</a>.</p></li><li><p>
254colon in XML names except for namespace purposes, but XML processors must 254 [<a name="dt-root" id="dt-root" title="Root Element">Definition</a>: There is exactly one element,
255accept the colon as a name character.</p></div><p>An <a href="#NT-Nmtoken">Nmtoken</a> (name token) is any mixture of name 255called the <b>root</b>, or document element, no part of which appears
256characters.</p><p>The first character of a Name <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be a NameStartChar, and any 256in the <a title="Content" href="#dt-content">content</a> of any other element.] For
257other characters <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be NameChars; this mechanism is used to 257all other elements, if the <a title="Start-Tag" href="#dt-stag">start-tag</a> is in
258prevent names from beginning with European (ASCII) digits or with 258the content of another element, the <a title="End Tag" href="#dt-etag">end-tag</a>
259basic combining characters. Almost all characters are permitted in 259is in the content of the same element. More simply stated, the elements,
260names, except those which either are or reasonably could be used as 260delimited by start- and end-tags, nest properly within each other.</p></li></ol><p>
261delimiters. The intention is to be inclusive rather than exclusive, 261 [<a name="dt-parentchild" id="dt-parentchild" title="Parent/Child">Definition</a>: As a consequence of this,
262so that writing systems not yet encoded in Unicode can be used in 262for each non-root element <code>C</code> in the document, there is one other element <code>P</code>
263XML names. See <a href="#sec-suggested-names"><b>I Suggestions for XML Names</b></a> for suggestions on the creation of 263in the document such that <code>C</code> is in the content of <code>P</code>, but
264names.</p><p>Document authors are encouraged to use names which are 264is not in the content of any other element that is in the content of <code>P</code>. <code>P</code>
265meaningful words or combinations of words in natural languages, and 265is referred to as the <b>parent</b> of <code>C</code>, and <code>C</code> as
266to avoid symbolic or white space characters in names. Note that 266a <b>child</b> of <code>P</code>.]
267COLON, HYPHEN-MINUS, FULL STOP (period), LOW LINE (underscore), and 267 </p></div><div class="div2"> <h3><a name="charsets" id="charsets"/>2.2 Characters</h3><p>
268MIDDLE DOT are explicitly permitted.</p><p>The ASCII symbols and punctuation marks, along with a fairly 268 [<a name="dt-text" id="dt-text" title="Text">Definition</a>: A parsed entity contains <b>text</b>,
269large group of Unicode symbol characters, are excluded from names 269a sequence of <a title="Character" href="#dt-character">characters</a>, which may
270because they are more useful as delimiters in contexts where XML 270represent markup or character data.]
271names are used outside XML documents; providing this group gives 271 [<a name="dt-character" id="dt-character" title="Character">Definition</a>: A <b>character</b>
272those contexts hard guarantees about what <em>cannot</em> be part of 272is an atomic unit of text as specified by ISO/IEC 10646 <a href="#ISO10646">[ISO/IEC 10646]</a>. Legal characters are tab, carriage
273an XML name. The character #x037E, GREEK QUESTION MARK, is excluded 273return, line feed, and the legal characters
274because when normalized it becomes a semicolon, which could change 274of Unicode and ISO/IEC 10646. The
275the meaning of entity references.</p> <h5><a name="IDABN1S" id="IDABN1S" />Names and Tokens</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-NameStartChar" id="NT-NameStartChar" />[4]   </td><td><code>NameStartChar</code></td><td>   ::=   </td><td><code>":" | [A-Z] | "_" | [a-z] | [#xC0-#xD6] | [#xD8-#xF6] | [#xF8-#x2FF] | [#x370-#x37D] | [#x37F-#x1FFF] | [#x200C-#x200D] | [#x2070-#x218F] | [#x2C00-#x2FEF] | [#x3001-#xD7FF] | [#xF900-#xFDCF] | [#xFDF0-#xFFFD] | [#x10000-#xEFFFF]</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-NameChar" id="NT-NameChar" />[4a]   </td><td><code>NameChar</code></td><td>   ::=   </td><td><code><a href="#NT-NameStartChar">NameStartChar</a> | "-" | "." | [0-9] | #xB7 | [#x0300-#x036F] | [#x203F-#x2040]</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Name" id="NT-Name" />[5]   </td><td><code>Name</code></td><td>   ::=   </td><td><code><a href="#NT-NameStartChar">NameStartChar</a> (<a href="#NT-NameChar">NameChar</a>)*</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Names" id="NT-Names" />[6]   </td><td><code>Names</code></td><td>   ::=   </td><td><code><a href="#NT-Name">Name</a> (#x20 <a href="#NT-Name">Name</a>)*</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Nmtoken" id="NT-Nmtoken" />[7]   </td><td><code>Nmtoken</code></td><td>   ::=   </td><td><code>(<a href="#NT-NameChar">NameChar</a>)+</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Nmtokens" id="NT-Nmtokens" />[8]   </td><td><code>Nmtokens</code></td><td>   ::=   </td><td><code><a href="#NT-Nmtoken">Nmtoken</a> (#x20 <a href="#NT-Nmtoken">Nmtoken</a>)*</code></td></tr></tbody></table><div class="note"><p class="prefix"><b>Note:</b></p><p>The <a href="#NT-Names">Names</a> 275versions of these standards cited in <a href="#sec-existing-stds"><b>A.1 Normative References</b></a> were
276and <a href="#NT-Nmtokens">Nmtokens</a> productions are used to define the validity 276current at the time this document was prepared. New characters may be added
277of tokenized attribute values after normalization (see <a href="#sec-attribute-types"><b>3.3.1 Attribute Types</b></a>).</p></div><p>Literal data is any quoted string not containing the quotation mark used 277to these standards by amendments or new editions. Consequently, XML processors
278as a delimiter for that string. Literals are used for specifying the content 278<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> accept any character in the range specified for <a href="#NT-Char">Char</a>.]
279of internal entities (<a href="#NT-EntityValue">EntityValue</a>), the values 279 </p> <h5><a name="char32" id="char32"/>Character Range</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-Char" id="NT-Char"/>[2]   </td><td><code>Char</code></td><td>   ::=   </td><td><code>[#x1-#xD7FF] | [#xE000-#xFFFD] | [#x10000-#x10FFFF]</code></td><td><i>/* any Unicode character, excluding the surrogate blocks, FFFE, and FFFF. */</i></td></tr><tr valign="baseline"><td><a name="NT-RestrictedChar" id="NT-RestrictedChar"/>[2a]   </td><td><code>RestrictedChar</code></td><td>   ::=   </td><td><code>[#x1-#x8] | [#xB-#xC] | [#xE-#x1F] | [#x7F-#x84] | [#x86-#x9F]</code></td></tr></tbody></table><p>The mechanism for encoding character code points into bit patterns <span>may</span>
280of attributes (<a href="#NT-AttValue">AttValue</a>), and external identifiers 280vary from entity to entity. All XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> accept the UTF-8 and UTF-16
281(<a href="#NT-SystemLiteral">SystemLiteral</a>). Note that a <a href="#NT-SystemLiteral">SystemLiteral</a> 281encodings of Unicode <a href="#Unicode">[Unicode]</a>;
282can be parsed without scanning for markup.</p> <h5><a name="IDAFR1S" id="IDAFR1S" />Literals</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EntityValue" id="NT-EntityValue" />[9]   </td><td><code>EntityValue</code></td><td>   ::=   </td><td><code>'"' ([^%&amp;"] | <a href="#NT-PEReference">PEReference</a> 282the mechanisms for signaling which of the two is in use,
283| <a href="#NT-Reference">Reference</a>)* '"' </code></td></tr><tr valign="baseline"><td /><td /><td /><td><code>|  "'" ([^%&amp;'] | <a href="#NT-PEReference">PEReference</a> | <a href="#NT-Reference">Reference</a>)* "'"</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-AttValue" id="NT-AttValue" />[10]   </td><td><code>AttValue</code></td><td>   ::=   </td><td><code>'"' ([^&lt;&amp;"] | <a href="#NT-Reference">Reference</a>)* 283or for bringing other encodings into play, are discussed later, in <a href="#charencoding"><b>4.3.3 Character Encoding in Entities</b></a>.</p><div class="note"><p class="prefix"><b>Note:</b></p><p>Document authors are encouraged to avoid
284'"' </code></td></tr><tr valign="baseline"><td /><td /><td /><td><code>|  "'" ([^&lt;&amp;'] | <a href="#NT-Reference">Reference</a>)* 284"compatibility characters", as defined
285"'"</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-SystemLiteral" id="NT-SystemLiteral" />[11]   </td><td><code>SystemLiteral</code></td><td>   ::=   </td><td><code>('"' [^"]* '"') | ("'" [^']* "'") </code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PubidLiteral" id="NT-PubidLiteral" />[12]   </td><td><code>PubidLiteral</code></td><td>   ::=   </td><td><code>'"' <a href="#NT-PubidChar">PubidChar</a>* '"' 285in Unicode <a href="#Unicode">[Unicode]</a>.
286| "'" (<a href="#NT-PubidChar">PubidChar</a> - "'")* "'"</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PubidChar" id="NT-PubidChar" />[13]   </td><td><code>PubidChar</code></td><td>   ::=   </td><td><code>#x20 | #xD | #xA | [a-zA-Z0-9] | [-'()+,./:=?;!*#@$_%]</code></td></tr></tbody></table><div class="note"><p class="prefix"><b>Note:</b></p><p>Although 286The characters defined in the following ranges are also
287the <a href="#NT-EntityValue">EntityValue</a> production allows the definition 287discouraged. They are either control characters or permanently undefined Unicode
288of a general entity consisting of a single explicit <code>&lt;</code> in the literal 288characters:</p><div class="exampleInner"><pre><span>[#x1-#x8], [#xB-#xC], [#xE-#x1F], </span>[#x7F-#x84], [#x86-#x9F], [#xFDD0-#xFDDF],
289(e.g., <code>&lt;!ENTITY mylt "&lt;"&gt;</code>), it is strongly advised to avoid 289[#<span>x</span>1FFFE-#x1FFFF], [#<span>x</span>2FFFE-#x2FFFF], [#<span>x</span>3FFFE-#x3FFFF],
290this practice since any reference to that entity will cause a well-formedness 290[#<span>x</span>4FFFE-#x4FFFF], [#<span>x</span>5FFFE-#x5FFFF], [#<span>x</span>6FFFE-#x6FFFF],
291error.</p></div></div><div class="div2"> <h3><a name="syntax" id="syntax" />2.4 Character Data and Markup</h3><p><a title="Text" href="#dt-text">Text</a> consists of intermingled <a title="Character Data" href="#dt-chardata">character data</a> and markup. [<a name="dt-markup" id="dt-markup" title="Markup">Definition</a>: <b>Markup</b> takes the form of <a title="Start-Tag" href="#dt-stag">start-tags</a>, <a title="End Tag" href="#dt-etag">end-tags</a>, <a title="Empty" href="#dt-empty">empty-element tags</a>, <a title="Entity Reference" href="#dt-entref">entity references</a>, <a title="Character Reference" href="#dt-charref">character 291[#<span>x</span>7FFFE-#x7FFFF], [#<span>x</span>8FFFE-#x8FFFF], [#<span>x</span>9FFFE-#x9FFFF],
292references</a>, <a title="Comment" href="#dt-comment">comments</a>, <a title="CDATA Section" href="#dt-cdsection">CDATA section</a> delimiters, <a title="Document Type Declaration" href="#dt-doctype">document 292[#<span>x</span>AFFFE-#xAFFFF], [#<span>x</span>BFFFE-#xBFFFF], [#<span>x</span>CFFFE-#xCFFFF],
293type declarations</a>, <a title="Processing instruction" href="#dt-pi">processing instructions</a>, <a href="#NT-XMLDecl">XML declarations</a>, <a href="#NT-TextDecl">text declarations</a>, 293[#<span>x</span>DFFFE-#xDFFFF], [#<span>x</span>EFFFE-#xEFFFF], [#<span>x</span>FFFFE-#xFFFFF],
294and any white space that is at the top level of the document entity (that 294[#<span>x</span>10FFFE-#x10FFFF].</pre></div></div></div><div class="div2"> <h3><a name="sec-common-syn" id="sec-common-syn"/>2.3 Common Syntactic Constructs</h3><p>This section defines some symbols used widely in the grammar.</p><p>
295is, outside the document element and not inside any other markup).]</p><p>[<a name="dt-chardata" id="dt-chardata" title="Character Data">Definition</a>: All text that is not markup 295 <a href="#NT-S">S</a> (white space) consists of one or more space (#x20)
296constitutes the <b>character data</b> of the document.]</p><p>The ampersand character (&amp;) and the left angle bracket (&lt;) <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em></span> appear 296characters, carriage returns, line feeds, or tabs.</p> <h5><a name="white" id="white"/>White Space</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-S" id="NT-S"/>[3]   </td><td><code>S</code></td><td>   ::=   </td><td><code>(#x20 | #x9 | #xD | #xA)+</code></td></tr></tbody></table><div class="note"><p class="prefix"><b>Note:</b></p><p>The presence of #xD in the above production is
297in their literal form<span class="mustard">, except</span> when used as markup delimiters, or 297maintained purely for backward compatibility with the
298within a <a title="Comment" href="#dt-comment">comment</a>, a <a title="Processing instruction" href="#dt-pi">processing 298<a href="http://www.w3.org/TR/1998/REC-xml-19980210">First Edition</a>.
299instruction</a>, or a <a title="CDATA Section" href="#dt-cdsection">CDATA section</a>. 299As explained in <a href="#sec-line-ends"><b>2.11 End-of-Line Handling</b></a>,
300 300all #xD characters literally present in an XML document
301If they are needed elsewhere, they <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be <a title="escape" href="#dt-escape">escaped</a> 301are either removed or replaced by #xA characters before
302using either <a title="Character Reference" href="#dt-charref">numeric character references</a> 302any other processing is done. The only way to get a #xD character to match this production is to
303or the strings "<code>&amp;amp;</code>" and "<code>&amp;lt;</code>" 303use a character reference in an entity value literal.</p></div><p>
304respectively. The right angle bracket (&gt;) <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be represented using the string "<code>&amp;gt;</code>", 304 [<a name="dt-name" id="dt-name" title="Name">Definition</a>: A <b>Name</b> is a token beginning
305and <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>, <a title="For Compatibility" href="#dt-compat">for compatibility</a>, be escaped 305with a letter or one of a few punctuation characters, and continuing with
306using <span>either</span> "<code>&amp;gt;</code>" or a character reference when it 306letters, digits, hyphens, underscores, colons, or full stops, together known
307appears in the string "<code>]]&gt;</code>" in content, when 307as name characters.] Names beginning with the string "<code>xml</code>",
308that string is not marking the end of a <a title="CDATA Section" href="#dt-cdsection">CDATA 308or with any string which would match <code>(('X'|'x') ('M'|'m') ('L'|'l'))</code>,
309section</a>.</p><p>In the content of elements, character data is any string of characters 309are reserved for standardization in this or future versions of this specification.</p><div class="note"><p class="prefix"><b>Note:</b></p><p>The
310which does not contain the start-delimiter of any markup or the 310Namespaces in XML Recommendation <a href="#xml-names">[XML Names]</a> assigns a meaning
311CDATA-section-close delimiter, 311to names containing colon characters. Therefore, authors should not use the
312"<code>]]&gt;</code>". 312colon in XML names except for namespace purposes, but XML processors must
313In a CDATA section, 313accept the colon as a name character.</p></div><p>An <a href="#NT-Nmtoken">Nmtoken</a> (name token) is any mixture of name
314character data is any string of characters not including the CDATA-section-close 314characters.</p><p>The first character of a Name <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be a NameStartChar, and any
315delimiter.</p><p>To allow attribute values to contain both single and double quotes, the 315other characters <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be NameChars; this mechanism is used to
316apostrophe or single-quote character (') <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be represented as "<code>&amp;apos;</code>", 316prevent names from beginning with European (ASCII) digits or with
317and the double-quote character (") as "<code>&amp;quot;</code>".</p> <h5><a name="IDASZ1S" id="IDASZ1S" />Character Data</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-CharData" id="NT-CharData" />[14]   </td><td><code>CharData</code></td><td>   ::=   </td><td><code>[^&lt;&amp;]* - ([^&lt;&amp;]* ']]&gt;' [^&lt;&amp;]*)</code></td></tr></tbody></table></div><div class="div2"> <h3><a name="sec-comments" id="sec-comments" />2.5 Comments</h3><p>[<a name="dt-comment" id="dt-comment" title="Comment">Definition</a>: <b>Comments</b> <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> appear 317basic combining characters. Almost all characters are permitted in
318anywhere in a document outside other <a title="Markup" href="#dt-markup">markup</a>; 318names, except those which either are or reasonably could be used as
319in addition, they <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> appear within the document type declaration at places 319delimiters. The intention is to be inclusive rather than exclusive,
320allowed by the grammar. They are not part of the document's <a title="Character Data" href="#dt-chardata">character 320so that writing systems not yet encoded in Unicode can be used in
321data</a>; an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em>, but need not, make it possible for an 321XML names. See <a href="#sec-suggested-names"><b>I Suggestions for XML Names</b></a> for suggestions on the creation of
322application to retrieve the text of comments. <a title="For Compatibility" href="#dt-compat">For 322names.</p><p>Document authors are encouraged to use names which are
323compatibility</a>, the string "<code>--</code>" (double-hyphen) 323meaningful words or combinations of words in natural languages, and
324<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> occur within comments.] Parameter 324to avoid symbolic or white space characters in names. Note that
325entity references <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be</span> recognized within comments.</p> <h5><a name="IDAL11S" id="IDAL11S" />Comments</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-Comment" id="NT-Comment" />[15]   </td><td><code>Comment</code></td><td>   ::=   </td><td><code>'&lt;!--' ((<a href="#NT-Char">Char</a> - '-') | ('-' 325COLON, HYPHEN-MINUS, FULL STOP (period), LOW LINE (underscore), and
326(<a href="#NT-Char">Char</a> - '-')))* '--&gt;'</code></td></tr></tbody></table><p>An example of a comment:</p><div class="exampleInner"><pre>&lt;!-- declarations for &lt;head&gt; &amp; &lt;body&gt; --&gt;</pre></div><p>Note 326MIDDLE DOT are explicitly permitted.</p><p>The ASCII symbols and punctuation marks, along with a fairly
327that the grammar does not allow a comment ending in <code>---&gt;</code>. The 327large group of Unicode symbol characters, are excluded from names
328following example is <em>not</em> well-formed.</p><div class="exampleInner"><pre>&lt;!-- B+, B, or B---&gt;</pre></div></div><div class="div2"> <h3><a name="sec-pi" id="sec-pi" />2.6 Processing Instructions</h3><p>[<a name="dt-pi" id="dt-pi" title="Processing instruction">Definition</a>: <b>Processing instructions</b> 328because they are more useful as delimiters in contexts where XML
329(PIs) allow documents to contain instructions for applications.]</p> <h5><a name="IDAD31S" id="IDAD31S" />Processing Instructions</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-PI" id="NT-PI" />[16]   </td><td><code>PI</code></td><td>   ::=   </td><td><code>'&lt;?' <a href="#NT-PITarget">PITarget</a> (<a href="#NT-S">S</a> 329names are used outside XML documents; providing this group gives
330(<a href="#NT-Char">Char</a>* - (<a href="#NT-Char">Char</a>* '?&gt;' <a href="#NT-Char">Char</a>*)))? '?&gt;'</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PITarget" id="NT-PITarget" />[17]   </td><td><code>PITarget</code></td><td>   ::=   </td><td><code><a href="#NT-Name">Name</a> - (('X' | 'x') ('M' | 330those contexts hard guarantees about what <em>cannot</em> be part of
331'm') ('L' | 'l'))</code></td></tr></tbody></table><p>PIs are not part of the document's <a title="Character Data" href="#dt-chardata">character 331an XML name. The character #x037E, GREEK QUESTION MARK, is excluded
332data</a>, but <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be passed through to the application. The PI begins 332because when normalized it becomes a semicolon, which could change
333with a target (<a href="#NT-PITarget">PITarget</a>) used to identify the application 333the meaning of entity references.</p> <h5><a name="IDAKUDS" id="IDAKUDS"/>Names and Tokens</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-NameStartChar" id="NT-NameStartChar"/>[4]   </td><td><code>NameStartChar</code></td><td>   ::=   </td><td><code>":" | [A-Z] | "_" | [a-z] | [#xC0-#xD6] | [#xD8-#xF6] | [#xF8-#x2FF] | [#x370-#x37D] | [#x37F-#x1FFF] | [#x200C-#x200D] | [#x2070-#x218F] | [#x2C00-#x2FEF] | [#x3001-#xD7FF] | [#xF900-#xFDCF] | [#xFDF0-#xFFFD] | [#x10000-#xEFFFF]</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-NameChar" id="NT-NameChar"/>[4a]   </td><td><code>NameChar</code></td><td>   ::=   </td><td><code>
334to which the instruction is directed. The target names "<code>XML</code>", "<code>xml</code>", 334 <a href="#NT-NameStartChar">NameStartChar</a> | "-" | "." | [0-9] | #xB7 | [#x0300-#x036F] | [#x203F-#x2040]</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Name" id="NT-Name"/>[5]   </td><td><code>Name</code></td><td>   ::=   </td><td><code>
335and so on are reserved for standardization in this or future versions of this 335 <a href="#NT-NameStartChar">NameStartChar</a> (<a href="#NT-NameChar">NameChar</a>)*</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Names" id="NT-Names"/>[6]   </td><td><code>Names</code></td><td>   ::=   </td><td><code>
336specification. The XML <a title="Notation" href="#dt-notation">Notation</a> mechanism 336 <a href="#NT-Name">Name</a> (#x20 <a href="#NT-Name">Name</a>)*</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Nmtoken" id="NT-Nmtoken"/>[7]   </td><td><code>Nmtoken</code></td><td>   ::=   </td><td><code>(<a href="#NT-NameChar">NameChar</a>)+</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Nmtokens" id="NT-Nmtokens"/>[8]   </td><td><code>Nmtokens</code></td><td>   ::=   </td><td><code>
337<em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be used for formal declaration of PI targets. Parameter 337 <a href="#NT-Nmtoken">Nmtoken</a> (#x20 <a href="#NT-Nmtoken">Nmtoken</a>)*</code></td></tr></tbody></table><div class="note"><p class="prefix"><b>Note:</b></p><p>The <a href="#NT-Names">Names</a>
338entity references <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be</span> recognized within processing instructions.</p></div><div class="div2"> <h3><a name="sec-cdata-sect" id="sec-cdata-sect" />2.7 CDATA Sections</h3><p>[<a name="dt-cdsection" id="dt-cdsection" title="CDATA Section">Definition</a>: <b>CDATA sections</b> <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> occur anywhere character data may occur; they are used to escape blocks 338and <a href="#NT-Nmtokens">Nmtokens</a> productions are used to define the validity
339of text containing characters which would otherwise be recognized as markup. 339of tokenized attribute values after normalization (see <a href="#sec-attribute-types"><b>3.3.1 Attribute Types</b></a>).</p></div><p>Literal data is any quoted string not containing the quotation mark used
340CDATA sections begin with the string "<code>&lt;![CDATA[</code>" 340as a delimiter for that string. Literals are used for specifying the content
341and end with the string "<code>]]&gt;</code>":]</p> <h5><a name="IDAOA2S" id="IDAOA2S" />CDATA Sections</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-CDSect" id="NT-CDSect" />[18]   </td><td><code>CDSect</code></td><td>   ::=   </td><td><code><a href="#NT-CDStart">CDStart</a> <a href="#NT-CData">CData</a> <a href="#NT-CDEnd">CDEnd</a></code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-CDStart" id="NT-CDStart" />[19]   </td><td><code>CDStart</code></td><td>   ::=   </td><td><code>'&lt;![CDATA['</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-CData" id="NT-CData" />[20]   </td><td><code>CData</code></td><td>   ::=   </td><td><code>(<a href="#NT-Char">Char</a>* - (<a href="#NT-Char">Char</a>* 341of internal entities (<a href="#NT-EntityValue">EntityValue</a>), the values
342']]&gt;' <a href="#NT-Char">Char</a>*)) </code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-CDEnd" id="NT-CDEnd" />[21]   </td><td><code>CDEnd</code></td><td>   ::=   </td><td><code>']]&gt;'</code></td></tr></tbody></table><p>Within a CDATA section, only the <a href="#NT-CDEnd">CDEnd</a> string is 342of attributes (<a href="#NT-AttValue">AttValue</a>), and external identifiers
343recognized as markup, so that left angle brackets and ampersands may occur 343(<a href="#NT-SystemLiteral">SystemLiteral</a>). Note that a <a href="#NT-SystemLiteral">SystemLiteral</a>
344in their literal form; they need not (and cannot) be escaped using "<code>&amp;lt;</code>" 344can be parsed without scanning for markup.</p> <h5><a name="IDAKYDS" id="IDAKYDS"/>Literals</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EntityValue" id="NT-EntityValue"/>[9]   </td><td><code>EntityValue</code></td><td>   ::=   </td><td><code>'"' ([^%&amp;"] | <a href="#NT-PEReference">PEReference</a>
345and "<code>&amp;amp;</code>". CDATA sections cannot nest.</p><p>An example of a CDATA section, in which "<code>&lt;greeting&gt;</code>" 345| <a href="#NT-Reference">Reference</a>)* '"' </code></td></tr><tr valign="baseline"><td/><td/><td/><td><code>|  "'" ([^%&amp;'] | <a href="#NT-PEReference">PEReference</a> | <a href="#NT-Reference">Reference</a>)* "'"</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-AttValue" id="NT-AttValue"/>[10]   </td><td><code>AttValue</code></td><td>   ::=   </td><td><code>'"' ([^&lt;&amp;"] | <a href="#NT-Reference">Reference</a>)*
346and "<code>&lt;/greeting&gt;</code>" are recognized as <a title="Character Data" href="#dt-chardata">character data</a>, not <a title="Markup" href="#dt-markup">markup</a>:</p><div class="exampleInner"><pre>&lt;![CDATA[&lt;greeting&gt;Hello, world!&lt;/greeting&gt;]]&gt; </pre></div></div><div class="div2"> <h3><a name="sec-prolog-dtd" id="sec-prolog-dtd" />2.8 Prolog and Document Type Declaration</h3><p>[<a name="dt-xmldecl" id="dt-xmldecl" title="XML Declaration">Definition</a>: XML 1.1 documents <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> 346'"' </code></td></tr><tr valign="baseline"><td/><td/><td/><td><code>|  "'" ([^&lt;&amp;'] | <a href="#NT-Reference">Reference</a>)*
347begin with an <b>XML declaration</b> which specifies the version of 347"'"</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-SystemLiteral" id="NT-SystemLiteral"/>[11]   </td><td><code>SystemLiteral</code></td><td>   ::=   </td><td><code>('"' [^"]* '"') | ("'" [^']* "'") </code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PubidLiteral" id="NT-PubidLiteral"/>[12]   </td><td><code>PubidLiteral</code></td><td>   ::=   </td><td><code>'"' <a href="#NT-PubidChar">PubidChar</a>* '"'
348XML being used.] For example, the following is a complete XML 1.1 document, <a title="Well-Formed" href="#dt-wellformed">well-formed</a> but not <a title="Validity" href="#dt-valid">valid</a>:</p><div class="exampleInner"><pre>&lt;?xml version="1.1"?&gt; 348| "'" (<a href="#NT-PubidChar">PubidChar</a> - "'")* "'"</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PubidChar" id="NT-PubidChar"/>[13]   </td><td><code>PubidChar</code></td><td>   ::=   </td><td><code>#x20 | #xD | #xA | [a-zA-Z0-9] | [-'()+,./:=?;!*#@$_%]</code></td></tr></tbody></table><div class="note"><p class="prefix"><b>Note:</b></p><p>Although
349&lt;greeting&gt;Hello, world!&lt;/greeting&gt; </pre></div><p>but the following is an XML 1.0 document because it 349the <a href="#NT-EntityValue">EntityValue</a> production allows the definition
350does not have an XML declaration:</p><div class="exampleInner"><pre>&lt;greeting&gt;Hello, world!&lt;/greeting&gt;</pre></div><p>The function of the markup in an XML document is to describe its storage and 350of a general entity consisting of a single explicit <code>&lt;</code> in the literal
351logical structure and to associate <span>attribute 351(e.g., <code>&lt;!ENTITY mylt "&lt;"&gt;</code>), it is strongly advised to avoid
352name-value</span> pairs with its logical structures. XML provides a mechanism, the 352this practice since any reference to that entity will cause a well-formedness
353<a title="Document Type Declaration" href="#dt-doctype">document 353error.</p></div></div><div class="div2"> <h3><a name="syntax" id="syntax"/>2.4 Character Data and Markup</h3><p>
354type declaration</a>, to define constraints on the logical structure 354 <a title="Text" href="#dt-text">Text</a> consists of intermingled <a title="Character Data" href="#dt-chardata">character data</a> and markup. [<a name="dt-markup" id="dt-markup" title="Markup">Definition</a>:
355and to support the use of predefined storage units. [<a name="dt-valid" id="dt-valid" title="Validity">Definition</a>: An XML document is <b>valid</b> if it has an associated 355 <b>Markup</b> takes the form of <a title="Start-Tag" href="#dt-stag">start-tags</a>, <a title="End Tag" href="#dt-etag">end-tags</a>, <a title="Empty" href="#dt-empty">empty-element tags</a>, <a title="Entity Reference" href="#dt-entref">entity references</a>, <a title="Character Reference" href="#dt-charref">character
356document type declaration and if the document complies with the constraints 356references</a>, <a title="Comment" href="#dt-comment">comments</a>, <a title="CDATA Section" href="#dt-cdsection">CDATA section</a> delimiters, <a title="Document Type Declaration" href="#dt-doctype">document
357expressed in it.]</p><p>The document type declaration <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> appear before the first <a title="Element" href="#dt-element">element</a> 357type declarations</a>, <a title="Processing instruction" href="#dt-pi">processing instructions</a>, <a href="#NT-XMLDecl">XML declarations</a>, <a href="#NT-TextDecl">text declarations</a>,
358in the document.</p> <h5><a name="xmldoc" id="xmldoc" />Prolog</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-prolog" id="NT-prolog" />[22]   </td><td><code>prolog</code></td><td>   ::=   </td><td><code><a href="#NT-XMLDecl">XMLDecl</a> <a href="#NT-Misc">Misc</a>* 358and any white space that is at the top level of the document entity (that
359(<a href="#NT-doctypedecl">doctypedecl</a> <a href="#NT-Misc">Misc</a>*)?</code></td></tr><tr valign="baseline"><td><a name="NT-XMLDecl" id="NT-XMLDecl" />[23]   </td><td><code>XMLDecl</code></td><td>   ::=   </td><td><code>'&lt;?xml' <a href="#NT-VersionInfo">VersionInfo</a> <a href="#NT-EncodingDecl">EncodingDecl</a>? <a href="#NT-SDDecl">SDDecl</a>? <a href="#NT-S">S</a>?'?&gt;'</code></td></tr><tr valign="baseline"><td><a name="NT-VersionInfo" id="NT-VersionInfo" />[24]   </td><td><code>VersionInfo</code></td><td>   ::=   </td><td><code><a href="#NT-S">S</a> 'version' <a href="#NT-Eq">Eq</a> 359is, outside the document element and not inside any other markup).]
360("'" <a href="#NT-VersionNum">VersionNum</a> "'" | '"' <a href="#NT-VersionNum">VersionNum</a> 360 </p><p>
361'"')</code></td></tr><tr valign="baseline"><td><a name="NT-Eq" id="NT-Eq" />[25]   </td><td><code>Eq</code></td><td>   ::=   </td><td><code><a href="#NT-S">S</a>? '=' <a href="#NT-S">S</a>?</code></td></tr><tr valign="baseline"><td><a name="NT-VersionNum" id="NT-VersionNum" />[26]   </td><td><code>VersionNum</code></td><td>   ::=   </td><td><code>'1.1'</code></td></tr><tr valign="baseline"><td><a name="NT-Misc" id="NT-Misc" />[27]   </td><td><code>Misc</code></td><td>   ::=   </td><td><code><a href="#NT-Comment">Comment</a> | <a href="#NT-PI">PI</a> 361 [<a name="dt-chardata" id="dt-chardata" title="Character Data">Definition</a>: All text that is not markup
362| <a href="#NT-S">S</a></code></td></tr></tbody></table><p>[<a name="dt-doctype" id="dt-doctype" title="Document Type Declaration">Definition</a>: The XML <b>document 362constitutes the <b>character data</b> of the document.]
363type declaration</b> contains or points to <a title="markup declaration" href="#dt-markupdecl">markup 363 </p><p>The ampersand character (&amp;) and the left angle bracket (&lt;) <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear
364declarations</a> that provide a grammar for a class of documents. This 364in their literal form, except when used as markup delimiters, or
365grammar is known as a document type definition, or <b>DTD</b>. The document 365within a <a title="Comment" href="#dt-comment">comment</a>, a <a title="Processing instruction" href="#dt-pi">processing
366type declaration can point to an external subset (a special kind of <a title="External Entity" href="#dt-extent">external entity</a>) containing markup declarations, 366instruction</a>, or a <a title="CDATA Section" href="#dt-cdsection">CDATA section</a>.
367or can contain the markup declarations directly in an internal subset, or 367
368can do both. The DTD for a document consists of both subsets taken together.]</p><p>[<a name="dt-markupdecl" id="dt-markupdecl" title="markup declaration">Definition</a>: A <b>markup declaration</b> 368If they are needed elsewhere, they <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be <a title="escape" href="#dt-escape">escaped</a>
369is an <a title="Element Type declaration" href="#dt-eldecl">element type declaration</a>, an <a title="Attribute-List Declaration" href="#dt-attdecl">attribute-list declaration</a>, an <a title="entity declaration" href="#dt-entdecl">entity 369using either <a title="Character Reference" href="#dt-charref">numeric character references</a>
370declaration</a>, or a <a title="Notation Declaration" href="#dt-notdecl">notation declaration</a>.] 370or the strings "<code>&amp;amp;</code>" and "<code>&amp;lt;</code>"
371These declarations <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be contained in whole or in part within <a title="Parameter entity" href="#dt-PE">parameter 371respectively. The right angle bracket (&gt;) <span>may</span> be represented using the string "<code>&amp;gt;</code>",
372entities</a>, as described in the well-formedness and validity constraints 372and <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>, <a title="For Compatibility" href="#dt-compat">for compatibility</a>, be escaped
373below. For further 373using either "<code>&amp;gt;</code>" or a character reference when it
374information, see <a href="#sec-physical-struct"><b>4 Physical Structures</b></a>.</p> <h5><a name="dtd" id="dtd" />Document Type Definition</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-doctypedecl" id="NT-doctypedecl" />[28]   </td><td><code>doctypedecl</code></td><td>   ::=   </td><td><code>'&lt;!DOCTYPE' <a href="#NT-S">S</a> <a href="#NT-Name">Name</a> 374appears in the string "<code>]]&gt;</code>" in content, when
375(<a href="#NT-S">S</a> <a href="#NT-ExternalID">ExternalID</a>)? <a href="#NT-S">S</a>? 375that string is not marking the end of a <a title="CDATA Section" href="#dt-cdsection">CDATA
376('[' <a href="#NT-intSubset">intSubset</a> ']' <a href="#NT-S">S</a>?)? '&gt;'</code></td><td><a href="#vc-roottype">[VC: Root Element Type]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#ExtSubset">[WFC: External Subset]</a></td></tr><tr valign="baseline"><td><a name="NT-DeclSep" id="NT-DeclSep" />[28a]   </td><td><code>DeclSep</code></td><td>   ::=   </td><td><code><a href="#NT-PEReference">PEReference</a> | <a href="#NT-S">S</a></code></td><td><a href="#PE-between-Decls">[WFC: PE Between Declarations]</a></td></tr><tr valign="baseline"><td><a name="NT-intSubset" id="NT-intSubset" />[28b]   </td><td><code>intSubset</code></td><td>   ::=   </td><td><code>(<a href="#NT-markupdecl">markupdecl</a> | <a href="#NT-DeclSep">DeclSep</a>)*</code></td></tr><tr valign="baseline"><td><a name="NT-markupdecl" id="NT-markupdecl" />[29]   </td><td><code>markupdecl</code></td><td>   ::=   </td><td><code><a href="#NT-elementdecl">elementdecl</a> | <a href="#NT-AttlistDecl">AttlistDecl</a> | <a href="#NT-EntityDecl">EntityDecl</a> 376section</a>.</p><p>In the content of elements, character data is any string of characters
377| <a href="#NT-NotationDecl">NotationDecl</a> | <a href="#NT-PI">PI</a> | <a href="#NT-Comment">Comment</a></code></td><td><a href="#vc-PEinMarkupDecl">[VC: Proper Declaration/PE Nesting]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#wfc-PEinInternalSubset">[WFC: PEs in Internal Subset]</a></td></tr></tbody></table><p>Note 377which does not contain the start-delimiter of any markup or the
378that it is possible to construct a well-formed document containing a <a href="#NT-doctypedecl">doctypedecl</a> 378CDATA-section-close delimiter,
379that neither points to an external subset nor contains an internal subset.</p><p>The markup declarations <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be made up in whole or in part of the <a title="Replacement Text" href="#dt-repltext">replacement text</a> of <a title="Parameter entity" href="#dt-PE">parameter 379"<code>]]&gt;</code>".
380entities</a>. The productions later in this specification for individual 380In a CDATA section,
381nonterminals (<a href="#NT-elementdecl">elementdecl</a>, <a href="#NT-AttlistDecl">AttlistDecl</a>, 381character data is any string of characters not including the CDATA-section-close
382and so on) describe the declarations <em>after</em> all the parameter 382delimiter.</p><p>To allow attribute values to contain both single and double quotes, the
383entities have been <a title="Include" href="#dt-include">included</a>.</p><p>Parameter 383apostrophe or single-quote character (') <span>may</span> be represented as "<code>&amp;apos;</code>",
384entity references are recognized anywhere in the DTD (internal and external 384and the double-quote character (") as "<code>&amp;quot;</code>".</p> <h5><a name="IDAABES" id="IDAABES"/>Character Data</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-CharData" id="NT-CharData"/>[14]   </td><td><code>CharData</code></td><td>   ::=   </td><td><code>[^&lt;&amp;]* - ([^&lt;&amp;]* ']]&gt;' [^&lt;&amp;]*)</code></td></tr></tbody></table></div><div class="div2"> <h3><a name="sec-comments" id="sec-comments"/>2.5 Comments</h3><p>
385subsets and external parameter entities), except in literals, processing instructions, 385 [<a name="dt-comment" id="dt-comment" title="Comment">Definition</a>:
386comments, and the contents of ignored conditional sections (see <a href="#sec-condition-sect"><b>3.4 Conditional Sections</b></a>). 386 <b>Comments</b> <span>may</span> appear
387They are also recognized in entity value literals. The use of parameter entities 387anywhere in a document outside other <a title="Markup" href="#dt-markup">markup</a>;
388in the internal subset is restricted as described below.</p><div class="constraint"><p class="prefix"><a name="vc-roottype" id="vc-roottype" /><b>Validity constraint: Root Element Type</b></p><p>The <a href="#NT-Name">Name</a> 388in addition, they <span>may</span> appear within the document type declaration at places
389in the document type declaration <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the element type of the <a title="Root Element" href="#dt-root">root element</a>.</p></div><div class="constraint"><p class="prefix"><a name="vc-PEinMarkupDecl" id="vc-PEinMarkupDecl" /><b>Validity constraint: Proper Declaration/PE Nesting</b></p><p>Parameter-entity <a title="Replacement Text" href="#dt-repltext">replacement text</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be properly nested with markup declarations. That is to say, if either 389allowed by the grammar. They are not part of the document's <a title="Character Data" href="#dt-chardata">character
390the first character or the last character of a markup declaration (<a href="#NT-markupdecl">markupdecl</a> 390data</a>; an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em>, but need not, make it possible for an
391above) is contained in the replacement text for a <a title="Parameter-entity reference" href="#dt-PERef">parameter-entity 391application to retrieve the text of comments. <a title="For Compatibility" href="#dt-compat">For
392reference</a>, both <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be contained in the same replacement text.</p></div><div class="constraint"><p class="prefix"><a name="wfc-PEinInternalSubset" id="wfc-PEinInternalSubset" /><b>Well-formedness constraint: PEs in Internal Subset</b></p><p>In 392compatibility</a>, the string "<code>--</code>" (double-hyphen)
393the internal DTD subset, <a title="Parameter-entity reference" href="#dt-PERef">parameter-entity references</a> <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> occur within markup declarations; they <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> occur where markup declarations can occur</span>. 393<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> occur within comments.] Parameter
394(This does not apply to references that occur in external parameter entities 394entity references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be recognized within comments.</p> <h5><a name="IDA5CES" id="IDA5CES"/>Comments</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-Comment" id="NT-Comment"/>[15]   </td><td><code>Comment</code></td><td>   ::=   </td><td><code>'&lt;!--' ((<a href="#NT-Char">Char</a> - '-') | ('-'
395or to the external subset.)</p></div><div class="constraint"><p class="prefix"><a name="ExtSubset" id="ExtSubset" /><b>Well-formedness constraint: External Subset</b></p><p>The external subset, if any, <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the production for <a href="#NT-extSubset">extSubset</a>.</p></div><div class="constraint"><p class="prefix"><a name="PE-between-Decls" id="PE-between-Decls" /><b>Well-formedness constraint: PE Between Declarations</b></p><p>The replacement text of a parameter entity reference 395(<a href="#NT-Char">Char</a> - '-')))* '--&gt;'</code></td></tr></tbody></table><p>An example of a comment:</p><div class="exampleInner"><pre>&lt;!-- declarations for &lt;head&gt; &amp; &lt;body&gt; --&gt;</pre></div><p>Note
396in a <a href="#NT-DeclSep">DeclSep</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the production <a href="#NT-extSubsetDecl">extSubsetDecl</a>.</p></div><p>Like the internal subset, the external subset and any external parameter 396that the grammar does not allow a comment ending in <code>---&gt;</code>. The
397entities referenced 397following example is <em>not</em> well-formed.</p><div class="exampleInner"><pre>&lt;!-- B+, B, or B---&gt;</pre></div></div><div class="div2"> <h3><a name="sec-pi" id="sec-pi"/>2.6 Processing Instructions</h3><p>
398in a <a href="#NT-DeclSep">DeclSep</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> consist of a series of 398 [<a name="dt-pi" id="dt-pi" title="Processing instruction">Definition</a>:
399complete markup declarations of the types allowed by the non-terminal symbol <a href="#NT-markupdecl">markupdecl</a>, interspersed with white space or <a title="Parameter-entity reference" href="#dt-PERef">parameter-entity references</a>. However, portions of 399 <b>Processing instructions</b>
400the contents of the external subset or of these 400(PIs) allow documents to contain instructions for applications.]
401external parameter entities <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> conditionally be ignored by using the <a title="conditional section" href="#dt-cond-section">conditional section</a> construct; this is not 401 </p> <h5><a name="IDAREES" id="IDAREES"/>Processing Instructions</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-PI" id="NT-PI"/>[16]   </td><td><code>PI</code></td><td>   ::=   </td><td><code>'&lt;?' <a href="#NT-PITarget">PITarget</a> (<a href="#NT-S">S</a>
402allowed in the internal subset<span> but is 402(<a href="#NT-Char">Char</a>* - (<a href="#NT-Char">Char</a>* '?&gt;' <a href="#NT-Char">Char</a>*)))? '?&gt;'</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PITarget" id="NT-PITarget"/>[17]   </td><td><code>PITarget</code></td><td>   ::=   </td><td><code>
403allowed in external parameter entities referenced in the internal subset</span>.</p> <h5><a name="ext-Subset" id="ext-Subset" />External Subset</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-extSubset" id="NT-extSubset" />[30]   </td><td><code>extSubset</code></td><td>   ::=   </td><td><code><a href="#NT-TextDecl">TextDecl</a>? <a href="#NT-extSubsetDecl">extSubsetDecl</a></code></td></tr><tr valign="baseline"><td><a name="NT-extSubsetDecl" id="NT-extSubsetDecl" />[31]   </td><td><code>extSubsetDecl</code></td><td>   ::=   </td><td><code>( <a href="#NT-markupdecl">markupdecl</a> | <a href="#NT-conditionalSect">conditionalSect</a> | <a href="#NT-DeclSep">DeclSep</a>)*</code></td></tr></tbody></table><p>The external subset and external parameter entities also differ from the 403 <a href="#NT-Name">Name</a> - (('X' | 'x') ('M' |
404internal subset in that in them, <a title="Parameter-entity reference" href="#dt-PERef">parameter-entity 404'm') ('L' | 'l'))</code></td></tr></tbody></table><p>PIs are not part of the document's <a title="Character Data" href="#dt-chardata">character
405references</a> are permitted <em>within</em> markup declarations, 405data</a>, but <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be passed through to the application. The PI begins
406not only <em>between</em> markup declarations.</p><p>An example of an XML document with a document type declaration:</p><div class="exampleInner"><pre>&lt;?xml version="1.1"?&gt; 406with a target (<a href="#NT-PITarget">PITarget</a>) used to identify the application
407&lt;!DOCTYPE greeting SYSTEM "hello.dtd"&gt; 407to which the instruction is directed. The target names "<code>XML</code>", "<code>xml</code>",
408&lt;greeting&gt;Hello, world!&lt;/greeting&gt; </pre></div><p>The <a title="System Identifier" href="#dt-sysid">system identifier</a> "<code>hello.dtd</code>" 408and so on are reserved for standardization in this or future versions of this
409gives the address (a URI reference) of a DTD for the document.</p><p>The declarations can also be given locally, as in this example:</p><div class="exampleInner"><pre>&lt;?xml version="1.1" encoding="UTF-8" ?&gt; 409specification. The XML <a title="Notation" href="#dt-notation">Notation</a> mechanism
410&lt;!DOCTYPE greeting [ 410<span>may</span> be used for formal declaration of PI targets. Parameter
411&lt;!ELEMENT greeting (#PCDATA)&gt; 411entity references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be recognized within processing instructions.</p></div><div class="div2"> <h3><a name="sec-cdata-sect" id="sec-cdata-sect"/>2.7 CDATA Sections</h3><p>
412]&gt; 412 [<a name="dt-cdsection" id="dt-cdsection" title="CDATA Section">Definition</a>:
413&lt;greeting&gt;Hello, world!&lt;/greeting&gt;</pre></div><p>If both the external and internal subsets are used, the internal subset 413 <b>CDATA sections</b> <span>may</span> occur anywhere character data may occur; they are used to escape blocks
414<span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be</span> considered to occur before the external subset. 414of text containing characters which would otherwise be recognized as markup.
415This has the effect that entity and attribute-list declarations in the internal 415CDATA sections begin with the string "<code>&lt;![CDATA[</code>"
416subset take precedence over those in the external subset.</p><p>XML 1.1 processors <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> accept XML 1.0 416and end with the string "<code>]]&gt;</code>":]
417documents as well. If a document is well-formed or valid XML 1.0, and provided it 417 </p> <h5><a name="IDA2HES" id="IDA2HES"/>CDATA Sections</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-CDSect" id="NT-CDSect"/>[18]   </td><td><code>CDSect</code></td><td>   ::=   </td><td><code>
418does not contain any control characters 418 <a href="#NT-CDStart">CDStart</a>
419in the range [#x7F-#x9F] other than as character escapes, it may be 419 <a href="#NT-CData">CData</a>
420made well-formed or valid XML 1.1 respectively simply by changing the 420 <a href="#NT-CDEnd">CDEnd</a>
421version number.</p></div><div class="div2"> <h3><a name="sec-rmd" id="sec-rmd" />2.9 Standalone Document Declaration</h3><p>Markup declarations can affect the content of the document, as passed from 421 </code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-CDStart" id="NT-CDStart"/>[19]   </td><td><code>CDStart</code></td><td>   ::=   </td><td><code>'&lt;![CDATA['</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-CData" id="NT-CData"/>[20]   </td><td><code>CData</code></td><td>   ::=   </td><td><code>(<a href="#NT-Char">Char</a>* - (<a href="#NT-Char">Char</a>*
422an <a title="XML Processor" href="#dt-xml-proc">XML processor</a> to an application; examples 422']]&gt;' <a href="#NT-Char">Char</a>*)) </code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-CDEnd" id="NT-CDEnd"/>[21]   </td><td><code>CDEnd</code></td><td>   ::=   </td><td><code>']]&gt;'</code></td></tr></tbody></table><p>Within a CDATA section, only the <a href="#NT-CDEnd">CDEnd</a> string is
423are attribute defaults and entity declarations. The standalone document declaration, 423recognized as markup, so that left angle brackets and ampersands may occur
424which <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> appear as a component of the XML declaration, signals whether or 424in their literal form; they need not (and cannot) be escaped using "<code>&amp;lt;</code>"
425not there are such declarations which appear external to the <a title="Document Entity" href="#dt-docent">document 425and "<code>&amp;amp;</code>". CDATA sections cannot nest.</p><p>An example of a CDATA section, in which "<code>&lt;greeting&gt;</code>"
426entity</a> 426and "<code>&lt;/greeting&gt;</code>" are recognized as <a title="Character Data" href="#dt-chardata">character data</a>, not <a title="Markup" href="#dt-markup">markup</a>:</p><div class="exampleInner"><pre>&lt;![CDATA[&lt;greeting&gt;Hello, world!&lt;/greeting&gt;]]&gt; </pre></div></div><div class="div2"> <h3><a name="sec-prolog-dtd" id="sec-prolog-dtd"/>2.8 Prolog and Document Type Declaration</h3><p>
427or in parameter entities. [<a name="dt-extmkpdecl" id="dt-extmkpdecl" title="External Markup Declaration">Definition</a>: An <b>external 427 [<a name="dt-xmldecl" id="dt-xmldecl" title="XML Declaration">Definition</a>: XML 1.1 documents <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
428markup declaration</b> is defined as a markup declaration occurring in 428begin with an <b>XML declaration</b> which specifies the version of
429the external subset or in a parameter entity (external or internal, the latter 429XML being used.] For example, the following is a complete XML 1.1 document, <a title="Well-Formed" href="#dt-wellformed">well-formed</a> but not <a title="Validity" href="#dt-valid">valid</a>:</p><div class="exampleInner"><pre>&lt;?xml version="1.1"?&gt;
430being included because non-validating processors are not required to read 430&lt;greeting&gt;Hello, world!&lt;/greeting&gt; </pre></div><p>but the following is an XML 1.0 document because it
431them).]</p> <h5><a name="fulldtd" id="fulldtd" />Standalone Document Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-SDDecl" id="NT-SDDecl" />[32]   </td><td><code>SDDecl</code></td><td>   ::=   </td><td><code>#x20+ 'standalone' <a href="#NT-Eq">Eq</a> 431does not have an XML declaration:</p><div class="exampleInner"><pre>&lt;greeting&gt;Hello, world!&lt;/greeting&gt;</pre></div><p>The function of the markup in an XML document is to describe its storage and
432(("'" ('yes' | 'no') "'") | ('"' ('yes' | 'no') '"')) </code></td><td><a href="#vc-check-rmd">[VC: Standalone Document Declaration]</a></td></tr></tbody></table><p>In a standalone document declaration, the value "yes" indicates 432logical structure and to associate attribute
433that there are no <a title="External Markup Declaration" href="#dt-extmkpdecl">external markup declarations</a> which 433name-value pairs with its logical structures. XML provides a mechanism, the
434affect the information passed from the XML processor to the application. The 434<a title="Document Type Declaration" href="#dt-doctype">document
435value "no" indicates that there are or may be such external 435type declaration</a>, to define constraints on the logical structure
436markup declarations. Note that the standalone document declaration only denotes 436and to support the use of predefined storage units. [<a name="dt-valid" id="dt-valid" title="Validity">Definition</a>: An XML document is <b>valid</b> if it has an associated
437the presence of external <em>declarations</em>; the presence, in a document, 437document type declaration and if the document complies with the constraints
438of references to external <em>entities</em>, when those entities are internally 438expressed in it.]
439declared, does not change its standalone status.</p><p>If there are no external markup declarations, the standalone document declaration 439 </p><p>The document type declaration <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> appear before the first <a title="Element" href="#dt-element">element</a>
440has no meaning. If there are external markup declarations but there is no 440in the document.</p> <h5><a name="xmldoc" id="xmldoc"/>Prolog</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-prolog" id="NT-prolog"/>[22]   </td><td><code>prolog</code></td><td>   ::=   </td><td><code>
441standalone document declaration, the value "no" is assumed.</p><p>Any XML document for which <code>standalone="no"</code> holds can be converted 441 <a href="#NT-XMLDecl">XMLDecl</a>
442algorithmically to a standalone document, which may be desirable for some 442 <a href="#NT-Misc">Misc</a>*
443network delivery applications.</p><div class="constraint"><p class="prefix"><a name="vc-check-rmd" id="vc-check-rmd" /><b>Validity constraint: Standalone Document Declaration</b></p><p>The 443(<a href="#NT-doctypedecl">doctypedecl</a>
444standalone document declaration <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> have the value "no" if 444 <a href="#NT-Misc">Misc</a>*)?</code></td></tr><tr valign="baseline"><td><a name="NT-XMLDecl" id="NT-XMLDecl"/>[23]   </td><td><code>XMLDecl</code></td><td>   ::=   </td><td><code>'&lt;?xml' <a href="#NT-VersionInfo">VersionInfo</a>
445any external markup declarations contain declarations of:</p><ul><li><p>attributes with <a title="Attribute Default" href="#dt-default">default</a> values, 445 <a href="#NT-EncodingDecl">EncodingDecl</a>? <a href="#NT-SDDecl">SDDecl</a>? <a href="#NT-S">S</a>? '?&gt;'</code></td></tr><tr valign="baseline"><td><a name="NT-VersionInfo" id="NT-VersionInfo"/>[24]   </td><td><code>VersionInfo</code></td><td>   ::=   </td><td><code>
446if elements to which these attributes apply appear in the document without 446 <a href="#NT-S">S</a> 'version' <a href="#NT-Eq">Eq</a>
447specifications of values for these attributes, or</p></li><li><p>entities (other than <code>amp</code>, 447("'" <a href="#NT-VersionNum">VersionNum</a> "'" | '"' <a href="#NT-VersionNum">VersionNum</a>
448<code>lt</code>, 448'"')</code></td></tr><tr valign="baseline"><td><a name="NT-Eq" id="NT-Eq"/>[25]   </td><td><code>Eq</code></td><td>   ::=   </td><td><code>
449<code>gt</code>, 449 <a href="#NT-S">S</a>? '=' <a href="#NT-S">S</a>?</code></td></tr><tr valign="baseline"><td><a name="NT-VersionNum" id="NT-VersionNum"/>[26]   </td><td><code>VersionNum</code></td><td>   ::=   </td><td><code>'1.1'</code></td></tr><tr valign="baseline"><td><a name="NT-Misc" id="NT-Misc"/>[27]   </td><td><code>Misc</code></td><td>   ::=   </td><td><code>
450<code>apos</code>, 450 <a href="#NT-Comment">Comment</a> | <a href="#NT-PI">PI</a>
451<code>quot</code>), if <a title="Entity Reference" href="#dt-entref">references</a> 451| <a href="#NT-S">S</a>
452to those entities appear in the document, or</p></li><li><p>attributes with 452 </code></td></tr></tbody></table><p>
453tokenized types, where the 453 [<a name="dt-doctype" id="dt-doctype" title="Document Type Declaration">Definition</a>: The XML <b>document
454attribute appears in the document with a value such that 454type declaration</b> contains or points to <a title="markup declaration" href="#dt-markupdecl">markup
455<a href="#AVNormalize"><cite>normalization</cite></a> 455declarations</a> that provide a grammar for a class of documents. This
456will produce a different value from that which would be produced 456grammar is known as a document type definition, or <b>DTD</b>. The document
457in the absence of the declaration, or</p></li><li><p>element types with <a title="Element content" href="#dt-elemcontent">element content</a>, 457type declaration can point to an external subset (a special kind of <a title="External Entity" href="#dt-extent">external entity</a>) containing markup declarations,
458if white space occurs directly within any instance of those types.</p></li></ul></div><p>An example XML declaration with a standalone document declaration:</p><div class="exampleInner"><pre>&lt;?xml version="1.1" standalone='yes'?&gt;</pre></div></div><div class="div2"> <h3><a name="sec-white-space" id="sec-white-space" />2.10 White Space Handling</h3><p>In editing XML documents, it is often convenient to use "white space" 458or can contain the markup declarations directly in an internal subset, or
459(spaces, tabs, and blank lines) 459can do both. The DTD for a document consists of both subsets taken together.]
460to set apart the markup for greater readability. Such white space is typically 460 </p><p>
461not intended for inclusion in the delivered version of the document. On the 461 [<a name="dt-markupdecl" id="dt-markupdecl" title="markup declaration">Definition</a>: A <b>markup declaration</b>
462other hand, "significant" white space that should be preserved 462is an <a title="Element Type declaration" href="#dt-eldecl">element type declaration</a>, an <a title="Attribute-List Declaration" href="#dt-attdecl">attribute-list declaration</a>, an <a title="entity declaration" href="#dt-entdecl">entity
463in the delivered version is common, for example in poetry and source code.</p><p>An <a title="XML Processor" href="#dt-xml-proc">XML processor</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> always pass 463declaration</a>, or a <a title="Notation Declaration" href="#dt-notdecl">notation declaration</a>.]
464all characters in a document that are not markup through to the application. 464These declarations <span>may</span> be contained in whole or in part within <a title="Parameter entity" href="#dt-PE">parameter
465A <a title="Validating Processor" href="#dt-validating"> validating XML processor</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> also 465entities</a>, as described in the well-formedness and validity constraints
466inform the application which of these characters constitute white space appearing 466below. For further
467in <a title="Element content" href="#dt-elemcontent">element content</a>.</p><p>A special <a title="Attribute" href="#dt-attr">attribute</a> named <code>xml:space</code> <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be attached to an element to signal an intention that in that element, 467information, see <a href="#sec-physical-struct"><b>4 Physical Structures</b></a>.</p> <h5><a name="dtd" id="dtd"/>Document Type Definition</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-doctypedecl" id="NT-doctypedecl"/>[28]   </td><td><code>doctypedecl</code></td><td>   ::=   </td><td><code>'&lt;!DOCTYPE' <a href="#NT-S">S</a>
468white space should be preserved by applications. In valid documents, this 468 <a href="#NT-Name">Name</a>
469attribute, like any other, <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be <a title="Attribute-List Declaration" href="#dt-attdecl">declared</a> 469(<a href="#NT-S">S</a>
470if it is used. When declared, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be given as an <a title="Enumerated Attribute&#xA;Values" href="#dt-enumerated">enumerated 470 <a href="#NT-ExternalID">ExternalID</a>)? <a href="#NT-S">S</a>?
471type</a> whose values 471('[' <a href="#NT-intSubset">intSubset</a> ']' <a href="#NT-S">S</a>?)? '&gt;'</code></td><td><a href="#vc-roottype">[VC: Root Element Type]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#ExtSubset">[WFC: External Subset]</a></td></tr><tr valign="baseline"><td><a name="NT-DeclSep" id="NT-DeclSep"/>[28a]   </td><td><code>DeclSep</code></td><td>   ::=   </td><td><code>
472are one or both of "default" and "preserve". 472 <a href="#NT-PEReference">PEReference</a> | <a href="#NT-S">S</a>
473For example:</p><div class="exampleInner"><pre>&lt;!ATTLIST poem xml:space (default|preserve) 'preserve'&gt; 473 </code></td><td><a href="#PE-between-Decls">[WFC: PE Between Declarations]</a></td></tr><tr valign="baseline"><td><a name="NT-intSubset" id="NT-intSubset"/>[28b]   </td><td><code>intSubset</code></td><td>   ::=   </td><td><code>(<a href="#NT-markupdecl">markupdecl</a> | <a href="#NT-DeclSep">DeclSep</a>)*</code></td></tr><tr valign="baseline"><td><a name="NT-markupdecl" id="NT-markupdecl"/>[29]   </td><td><code>markupdecl</code></td><td>   ::=   </td><td><code>
474&lt;!ATTLIST pre xml:space (preserve) #FIXED 'preserve'&gt;</pre></div><p>The value "default" signals that applications' default white-space 474 <a href="#NT-elementdecl">elementdecl</a> | <a href="#NT-AttlistDecl">AttlistDecl</a> | <a href="#NT-EntityDecl">EntityDecl</a>
475processing modes are acceptable for this element; the value "preserve" 475| <a href="#NT-NotationDecl">NotationDecl</a> | <a href="#NT-PI">PI</a> | <a href="#NT-Comment">Comment</a>
476indicates the intent that applications preserve all the white space. This 476 </code></td><td><a href="#vc-PEinMarkupDecl">[VC: Proper Declaration/PE Nesting]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#wfc-PEinInternalSubset">[WFC: PEs in Internal Subset]</a></td></tr></tbody></table><p>Note
477declared intent is considered to apply to all elements within the content 477that it is possible to construct a well-formed document containing a <a href="#NT-doctypedecl">doctypedecl</a>
478of the element where it is specified, unless <span>overridden</span> with 478that neither points to an external subset nor contains an internal subset.</p><p>The markup declarations <span>may</span> be made up in whole or in part of the <a title="Replacement Text" href="#dt-repltext">replacement text</a> of <a title="Parameter entity" href="#dt-PE">parameter
479another instance of the <code>xml:space</code> attribute. <span>This specification does not give meaning to any value of <code>xml:space</code> other than "default" and "preserve". It is an error for other values to be specified; the XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> report the error or <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> recover by ignoring the attribute specification or by reporting the (erroneous) value to the application. Applications may ignore or reject erroneous values.</span></p><p>The <a title="Root Element" href="#dt-root">root element</a> of any document is considered 479entities</a>. The productions later in this specification for individual
480to have signaled no intentions as regards application space handling, unless 480nonterminals (<a href="#NT-elementdecl">elementdecl</a>, <a href="#NT-AttlistDecl">AttlistDecl</a>,
481it provides a value for this attribute or the attribute is declared with a 481and so on) describe the declarations <em>after</em> all the parameter
482default value.</p></div><div class="div2"> <h3><a name="sec-line-ends" id="sec-line-ends" />2.11 End-of-Line Handling</h3><p>XML <a title="Text Entity" href="#dt-parsedent">parsed entities</a> are often stored 482entities have been <a title="Include" href="#dt-include">included</a>.</p><p>Parameter
483in computer files which, for editing convenience, are organized into lines. 483entity references are recognized anywhere in the DTD (internal and external
484These lines are typically separated by some combination of the characters 484subsets and external parameter entities), except in literals, processing instructions,
485CARRIAGE RETURN (#xD) and LINE FEED (#xA).</p><p>To 485comments, and the contents of ignored conditional sections (see <a href="#sec-condition-sect"><b>3.4 Conditional Sections</b></a>).
486simplify the tasks of <a title="Application" href="#dt-app">applications</a>, the 486They are also recognized in entity value literals. The use of parameter entities
487<span><a title="XML Processor" href="#dt-xml-proc">XML 487in the internal subset is restricted as described below.</p><div class="constraint"><p class="prefix"><a name="vc-roottype" id="vc-roottype"/><b>Validity constraint: Root Element Type</b></p><p>The <a href="#NT-Name">Name</a>
488processor</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> behave as if it</span> normalized all line breaks in external parsed 488in the document type declaration <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the element type of the <a title="Root Element" href="#dt-root">root element</a>.</p></div><div class="constraint"><p class="prefix"><a name="vc-PEinMarkupDecl" id="vc-PEinMarkupDecl"/><b>Validity constraint: Proper Declaration/PE Nesting</b></p><p>Parameter-entity <a title="Replacement Text" href="#dt-repltext">replacement text</a>
489entities (including the document entity) on input, before parsing, by translating 489 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be properly nested with markup declarations. That is to say, if either
490 490the first character or the last character of a markup declaration (<a href="#NT-markupdecl">markupdecl</a>
491<span>all of the following to a single #xA character:</span></p><ol type="1"><li><p>the two-character sequence #xD #xA</p></li><li><p>the two-character sequence #xD #x85</p></li><li><p>the single character #x85</p></li><li><p>the single character #x2028</p></li><li><p>any #xD character that is not immediately followed by #xA or #x85.</p></li></ol><p> The characters #x85 and #x2028 cannot be reliably recognized and 491above) is contained in the replacement text for a <a title="Parameter-entity reference" href="#dt-PERef">parameter-entity
492translated until an entity's encoding declaration (if present) has 492reference</a>, both <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be contained in the same replacement text.</p></div><div class="constraint"><p class="prefix"><a name="wfc-PEinInternalSubset" id="wfc-PEinInternalSubset"/><b>Well-formedness constraint: PEs in Internal Subset</b></p><p>In
493been read. Therefore, it is a fatal error to use them within the XML 493the internal DTD subset, <a title="Parameter-entity reference" href="#dt-PERef">parameter-entity references</a>
494declaration or text declaration. 494 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> occur within markup declarations; they <span>may</span> occur where markup declarations can occur.
495</p></div><div class="div2"> <h3><a name="sec-lang-tag" id="sec-lang-tag" />2.12 Language Identification</h3><p>In document processing, it is often useful to identify the natural or formal 495(This does not apply to references that occur in external parameter entities
496language in which the content is written. A special <a title="Attribute" href="#dt-attr">attribute</a> 496or to the external subset.)</p></div><div class="constraint"><p class="prefix"><a name="ExtSubset" id="ExtSubset"/><b>Well-formedness constraint: External Subset</b></p><p>The external subset, if any, <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the production for <a href="#NT-extSubset">extSubset</a>.</p></div><div class="constraint"><p class="prefix"><a name="PE-between-Decls" id="PE-between-Decls"/><b>Well-formedness constraint: PE Between Declarations</b></p><p>The replacement text of a parameter entity reference
497named <code>xml:lang</code> <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be inserted in documents to specify the language 497in a <a href="#NT-DeclSep">DeclSep</a>
498used in the contents and attribute values of any element in an XML document. 498 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the production <a href="#NT-extSubsetDecl">extSubsetDecl</a>.</p></div><p>Like the internal subset, the external subset and any external parameter
499In valid documents, this attribute, like any other, <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be <a title="Attribute-List Declaration" href="#dt-attdecl">declared</a> 499entities referenced
500if it is used. The 500in a <a href="#NT-DeclSep">DeclSep</a>
501values of the attribute are language identifiers as defined by <a href="#RFC1766">[IETF RFC 3066]</a>, <cite>Tags 501 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> consist of a series of
502for the Identification of Languages</cite>, or its successor<span>; in addition, the empty string <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be specified</span>.</p><p>(Productions 33 through 38 have been removed.)</p><p>For example:</p><div class="exampleInner"><pre>&lt;p xml:lang="en"&gt;The quick brown fox jumps over the lazy dog.&lt;/p&gt; 502complete markup declarations of the types allowed by the non-terminal symbol <a href="#NT-markupdecl">markupdecl</a>, interspersed with white space or <a title="Parameter-entity reference" href="#dt-PERef">parameter-entity references</a>. However, portions of
503&lt;p xml:lang="en-GB"&gt;What colour is it?&lt;/p&gt; 503the contents of the external subset or of these
504&lt;p xml:lang="en-US"&gt;What color is it?&lt;/p&gt; 504external parameter entities <span>may</span> conditionally be ignored by using the <a title="conditional section" href="#dt-cond-section">conditional section</a> construct; this is not
505&lt;sp who="Faust" desc='leise' xml:lang="de"&gt; 505allowed in the internal subset but is
506&lt;l&gt;Habe nun, ach! Philosophie,&lt;/l&gt; 506allowed in external parameter entities referenced in the internal subset.</p> <h5><a name="ext-Subset" id="ext-Subset"/>External Subset</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-extSubset" id="NT-extSubset"/>[30]   </td><td><code>extSubset</code></td><td>   ::=   </td><td><code>
507&lt;l&gt;Juristerei, und Medizin&lt;/l&gt; 507 <a href="#NT-TextDecl">TextDecl</a>? <a href="#NT-extSubsetDecl">extSubsetDecl</a>
508&lt;l&gt;und leider auch Theologie&lt;/l&gt; 508 </code></td></tr><tr valign="baseline"><td><a name="NT-extSubsetDecl" id="NT-extSubsetDecl"/>[31]   </td><td><code>extSubsetDecl</code></td><td>   ::=   </td><td><code>( <a href="#NT-markupdecl">markupdecl</a> | <a href="#NT-conditionalSect">conditionalSect</a> | <a href="#NT-DeclSep">DeclSep</a>)*</code></td></tr></tbody></table><p>The external subset and external parameter entities also differ from the
509&lt;l&gt;durchaus studiert mit hei&amp;#xDF;em Bem&amp;#xFC;h'n.&lt;/l&gt; 509internal subset in that in them, <a title="Parameter-entity reference" href="#dt-PERef">parameter-entity
510&lt;/sp&gt;</pre></div><p>The intent declared with <code>xml:lang</code> is considered to apply to 510references</a> are permitted <em>within</em> markup declarations,
511all attributes and content of the element where it is specified, unless overridden 511not only <em>between</em> markup declarations.</p><p>An example of an XML document with a document type declaration:</p><div class="exampleInner"><pre>&lt;?xml version="1.1"?&gt;
512with an instance of <code>xml:lang</code> on another element within that content. <span>In particular, the empty value of <code>xml:lang</code> is used on an element B to override a specification of <code>xml:lang</code> on an enclosing element A, without specifying another language. Within B, it is considered that there is no language information available, just as if <code>xml:lang</code> had not been specified on B or any of its ancestors.</span></p><div class="note"><p class="prefix"><b>Note:</b></p><p>Language information may also be provided by external transport protocols (e.g. HTTP or 512&lt;!DOCTYPE greeting SYSTEM "hello.dtd"&gt;
513MIME). When available, this information may be used by XML applications, but the more local 513&lt;greeting&gt;Hello, world!&lt;/greeting&gt; </pre></div><p>The <a title="System Identifier" href="#dt-sysid">system identifier</a>
514information provided by <code>xml:lang</code> should be considered to override it. 514 "<code>hello.dtd</code>"
515</p></div><p>A simple declaration for <code>xml:lang</code> might take the form</p><div class="exampleInner"><pre>xml:lang <span>CDATA</span> #IMPLIED</pre></div><p>but specific default values <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> also be given, if appropriate. In a collection 515gives the address (a URI reference) of a DTD for the document.</p><p>The declarations can also be given locally, as in this example:</p><div class="exampleInner"><pre>&lt;?xml version="1.1" encoding="UTF-8" ?&gt;
516of French poems for English students, with glosses and notes in English, the <code>xml:lang</code> 516&lt;!DOCTYPE greeting [
517attribute might be declared this way:</p><div class="exampleInner"><pre>&lt;!ATTLIST poem xml:lang <span>CDATA</span> 'fr'&gt; 517&lt;!ELEMENT greeting (#PCDATA)&gt;
518&lt;!ATTLIST gloss xml:lang <span>CDATA</span> 'en'&gt; 518]&gt;
519&lt;!ATTLIST note xml:lang <span>CDATA</span> 'en'&gt;</pre></div></div><div class="div2"> <h3><a name="sec-normalization-checking" id="sec-normalization-checking" />2.13 Normalization Checking</h3><p>All XML <a title="Text Entity" href="#dt-parsedent"> parsed 519&lt;greeting&gt;Hello, world!&lt;/greeting&gt;</pre></div><p>If both the external and internal subsets are used, the internal subset
520entities</a> (including <a title="Document Entity" href="#dt-docent"> document 520<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be considered to occur before the external subset.
521entities</a>) <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be <a title="fully normalized" href="#dt-fullnorm">fully 521This has the effect that entity and attribute-list declarations in the internal
522normalized</a> as per the definition of 522subset take precedence over those in the external subset.</p><p>
523<a href="#sec-CharNorm"><b>B Definitions for Character Normalization</b></a> supplemented by the following definitions of 523 If a document is well-formed or valid XML 1.0, and provided it
524<em><a name="dt-relconst" id="dt-relconst" />relevant constructs</em> for XML:</p><ol type="1"><li><p>The <a title="Replacement Text" href="#dt-repltext"> 524does not contain any control characters
525replacement text</a> of all <a title="Text Entity" href="#dt-parsedent">parsed 525in the range [#x7F-#x9F] other than as character escapes, it may be
526entities</a></p></li><li><p>All text matching, in context, one of the following 526made well-formed or valid XML 1.1 respectively simply by changing the
527productions:</p><ol type="a"><li><p><a href="#NT-CData"> 527version number.</p></div><div class="div2"> <h3><a name="sec-rmd" id="sec-rmd"/>2.9 Standalone Document Declaration</h3><p>Markup declarations can affect the content of the document, as passed from
528CData</a></p></li><li><p><a href="#NT-CharData"> 528an <a title="XML Processor" href="#dt-xml-proc">XML processor</a> to an application; examples
529CharData</a></p></li><li><p><a href="#NT-content"> 529are attribute defaults and entity declarations. The standalone document declaration,
530content</a></p></li><li><p><a href="#NT-Name"> Name</a></p></li><li><p><a href="#NT-Nmtoken"> 530which <span>may</span> appear as a component of the XML declaration, signals whether or
531Nmtoken</a></p></li></ol></li></ol><p>However, a document is still well-formed even if it is not 531not there are such declarations which appear external to the <a title="Document Entity" href="#dt-docent">document
532<a title="fully normalized" href="#dt-fullnorm">fully normalized</a>. 532entity</a>
533XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> provide a user option to verify that the document being 533or in parameter entities. [<a name="dt-extmkpdecl" id="dt-extmkpdecl" title="External Markup Declaration">Definition</a>: An <b>external
534processed is in <a title="fully normalized" href="#dt-fullnorm">fully normalized</a> form, and report to the application whether 534markup declaration</b> is defined as a markup declaration occurring in
535it is or not. The option to not verify <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be chosen only when the 535the external subset or in a parameter entity (external or internal, the latter
536input text is <a title="certified" href="#dt-certified">certified</a>, 536being included because non-validating processors are not required to read
537as defined by <a href="#sec-CharNorm"><b>B Definitions for Character Normalization</b></a>.</p><p>The verification of full normalization <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be carried out as if by 537them).]
538first verifying that the entity is in <a title="include-normalized" href="#dt-inclnorm">include-normalized</a> 538 </p> <h5><a name="fulldtd" id="fulldtd"/>Standalone Document Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-SDDecl" id="NT-SDDecl"/>[32]   </td><td><code>SDDecl</code></td><td>   ::=   </td><td><code>
539form as defined by <a href="#sec-CharNorm"><b>B Definitions for Character Normalization</b></a> and by then verifying that none of the relevant 539 <span>
540constructs listed above begins (after character references are 540
541expanded) with a <a title="composing character" href="#dt-compchar">composing character</a> as defined by 541 <a href="#NT-S">S</a>
542<a href="#sec-CharNorm"><b>B Definitions for Character Normalization</b></a>. 542 </span> 'standalone' <a href="#NT-Eq">Eq</a>
543Non-validating processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> ignore possible 543(("'" ('yes' | 'no') "'") | ('"' ('yes' | 'no') '"')) </code></td><td><a href="#vc-check-rmd">[VC: Standalone Document Declaration]</a></td></tr></tbody></table><p>In a standalone document declaration, the value "yes" indicates
544denormalizations that would be caused by inclusion of external 544that there are no <a title="External Markup Declaration" href="#dt-extmkpdecl">external markup declarations</a> which
545entities that they do not read.</p><div class="note"><p class="prefix"><b>Note:</b></p><p>The <a title="composing character" href="#dt-compchar">composing character</a> are all 545affect the information passed from the XML processor to the application. The
546Unicode characters of non-zero combining class, plus a small number 546value "no" indicates that there are or may be such external
547of class-zero characters that nevertheless take part as a 547markup declarations. Note that the standalone document declaration only denotes
548non-initial character in certain Unicode canonical 548the presence of external <em>declarations</em>; the presence, in a document,
549decompositions. Since these characters are meant to follow 549of references to external <em>entities</em>, when those entities are internally
550base characters, restricting relevant constructs (including 550declared, does not change its standalone status.</p><p>If there are no external markup declarations, the standalone document declaration
551content) from beginning with a <a title="composing character" href="#dt-compchar">composing character</a> does not 551has no meaning. If there are external markup declarations but there is no
552meaningfully diminish the expressiveness of XML.</p></div><p>If, while verifying full normalization, a processor encounters 552standalone document declaration, the value "no" is assumed.</p><p>Any XML document for which <code>standalone="no"</code> holds can be converted
553characters for which it cannot determine the normalization 553algorithmically to a standalone document, which may be desirable for some
554properties (i.e., characters introduced in a version of Unicode <a href="#Unicode">[Unicode]</a> 554network delivery applications.</p><div class="constraint"><p class="prefix"><a name="vc-check-rmd" id="vc-check-rmd"/><b>Validity constraint: Standalone Document Declaration</b></p><p>The
555later than the one used in the implementation of the processor), 555standalone document declaration <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> have the value "no" if
556then the processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em>, at user option, ignore any possible 556any external markup declarations contain declarations of:</p><ul><li><p>attributes with <a title="Attribute Default" href="#dt-default">default</a> values,
557denormalizations caused by these characters. The option to ignore 557if elements to which these attributes apply appear in the document without
558those denormalizations <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD NOT</em> be chosen by applications when 558specifications of values for these attributes, or</p></li><li><p>entities (other than <code>amp</code>,
559reliability or security are critical.</p><p> XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> transform the input to be in 559<code>lt</code>,
560<a title="fully normalized" href="#dt-fullnorm">fully normalized</a> form. 560<code>gt</code>,
561XML applications that create XML 1.1 output 561<code>apos</code>,
562from either XML 1.1 or XML 1.0 input <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> ensure that the output 562<code>quot</code>), if <a title="Entity Reference" href="#dt-entref">references</a>
563is <a title="fully normalized" href="#dt-fullnorm">fully normalized</a>; it is not necessary for internal processing 563to those entities appear in the document, or</p></li><li><p>attributes with
564forms to be <a title="fully normalized" href="#dt-fullnorm">fully normalized</a>.</p><p>The purpose of this section is to strongly encourage XML 564tokenized types, where the
565processors to ensure that the creators of XML documents have 565attribute appears in the document with a value such that
566properly normalized them, so that XML applications can make tests 566<a href="#AVNormalize"><cite>normalization</cite></a>
567such as identity comparisons of strings without having to worry 567will produce a different value from that which would be produced
568about the different possible "spellings" of strings which 568in the absence of the declaration, or</p></li><li><p>element types with <a title="Element content" href="#dt-elemcontent">element content</a>,
569Unicode allows. 569if white space occurs directly within any instance of those types.</p></li></ul></div><p>An example XML declaration with a standalone document declaration:</p><div class="exampleInner"><pre>&lt;?xml version="1.1" standalone='yes'?&gt;</pre></div></div><div class="div2"> <h3><a name="sec-white-space" id="sec-white-space"/>2.10 White Space Handling</h3><p>In editing XML documents, it is often convenient to use "white space"
570</p><p>When entities are in a non-Unicode encoding, if the processor 570(spaces, tabs, and blank lines)
571transcodes them to Unicode, it <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> use a normalizing transcoder. 571to set apart the markup for greater readability. Such white space is typically
572</p></div></div><div class="div1"> <h2><a name="sec-logical-struct" id="sec-logical-struct" />3 Logical Structures</h2><p>[<a name="dt-element" id="dt-element" title="Element">Definition</a>: Each <a title="XML Document" href="#dt-xml-doc">XML 572not intended for inclusion in the delivered version of the document. On the
573document</a> contains one or more <b>elements</b>, the boundaries 573other hand, "significant" white space that should be preserved
574of which are either delimited by <a title="Start-Tag" href="#dt-stag">start-tags</a> 574in the delivered version is common, for example in poetry and source code.</p><p>An <a title="XML Processor" href="#dt-xml-proc">XML processor</a>
575and <a title="End Tag" href="#dt-etag">end-tags</a>, or, for <a title="Empty" href="#dt-empty">empty</a> 575 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> always pass
576elements, by an <a title="empty-element tag" href="#dt-eetag">empty-element tag</a>. Each 576all characters in a document that are not markup through to the application.
577element has a type, identified by name, sometimes called its "generic 577A <a title="Validating Processor" href="#dt-validating"> validating XML processor</a>
578identifier" (GI), and <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> have a set of attribute specifications.] 578 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> also
579Each attribute specification has a <a title="Attribute Name" href="#dt-attrname">name</a> 579inform the application which of these characters constitute white space appearing
580and a <a title="Attribute Value" href="#dt-attrval">value</a>.</p> <h5><a name="IDATJ3S" id="IDATJ3S" />Element</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-element" id="NT-element" />[39]   </td><td><code>element</code></td><td>   ::=   </td><td><code><a href="#NT-EmptyElemTag">EmptyElemTag</a></code></td></tr><tr valign="baseline"><td /><td /><td /><td><code>| <a href="#NT-STag">STag</a> <a href="#NT-content">content</a> <a href="#NT-ETag">ETag</a></code></td><td><a href="#GIMatch">[WFC: Element Type Match]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#elementvalid">[VC: Element Valid]</a></td></tr></tbody></table><p>This specification does not constrain the semantics, use, or (beyond syntax) 580in <a title="Element content" href="#dt-elemcontent">element content</a>.</p><p>A special <a title="Attribute" href="#dt-attr">attribute</a> named <code>xml:space</code> <span>may</span> be attached to an element to signal an intention that in that element,
581names of the element types and attributes, except that names beginning with 581white space should be preserved by applications. In valid documents, this
582a match to <code>(('X'|'x')('M'|'m')('L'|'l'))</code> are reserved for standardization 582attribute, like any other, <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be <a title="Attribute-List Declaration" href="#dt-attdecl">declared</a>
583in this or future versions of this specification.</p><div class="constraint"><p class="prefix"><a name="GIMatch" id="GIMatch" /><b>Well-formedness constraint: Element Type Match</b></p><p>The <a href="#NT-Name">Name</a> 583if it is used. When declared, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be given as an <a title="Enumerated Attribute&#xA;Values" href="#dt-enumerated">enumerated
584in an element's end-tag <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the element type in the start-tag.</p></div><div class="constraint"><p class="prefix"><a name="elementvalid" id="elementvalid" /><b>Validity constraint: Element Valid</b></p><p>An element is valid 584type</a> whose values
585if there is a declaration matching <a href="#NT-elementdecl">elementdecl</a> 585are one or both of "default" and "preserve".
586where the <a href="#NT-Name">Name</a> matches the element type, and one of 586For example:</p><div class="exampleInner"><pre>&lt;!ATTLIST poem xml:space (default|preserve) 'preserve'&gt;
587the following holds:</p><ol type="1"><li><p>The declaration matches <b>EMPTY</b> and the element has no <a title="Content" href="#dt-content">content</a> <span>(not even entity 587&lt;!ATTLIST pre xml:space (preserve) #FIXED 'preserve'&gt;</pre></div><p>The value "default" signals that applications' default white-space
588references, comments, PIs or white space)</span>.</p></li><li><p>The declaration matches <a href="#NT-children">children</a> and the 588processing modes are acceptable for this element; the value "preserve"
589sequence of <a title="Parent/Child" href="#dt-parentchild">child elements</a> belongs 589indicates the intent that applications preserve all the white space. This
590to the language generated by the regular expression in the content model, 590declared intent is considered to apply to all elements within the content
591with optional white space<span>, comments and 591of the element where it is specified, unless overridden with
592PIs (i.e. markup matching production [27] <a href="#NT-Misc">Misc</a>)</span> between the 592another instance of the <code>xml:space</code> attribute. This specification does not give meaning to any value of <code>xml:space</code> other than "default" and "preserve". It is an error for other values to be specified; the XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> report the error or <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> recover by ignoring the attribute specification or by reporting the (erroneous) value to the application. Applications may ignore or reject erroneous values.</p><p>The <a title="Root Element" href="#dt-root">root element</a> of any document is considered
593start-tag and the first child element, between child elements, or between 593to have signaled no intentions as regards application space handling, unless
594the last child element and the end-tag. Note that a CDATA section containing 594it provides a value for this attribute or the attribute is declared with a
595only white space <span>or a reference 595default value.</p></div><div class="div2"> <h3><a name="sec-line-ends" id="sec-line-ends"/>2.11 End-of-Line Handling</h3><p>XML <a title="Text Entity" href="#dt-parsedent">parsed entities</a> are often stored
596to an entity whose replacement text is character references expanding to white 596in computer files which, for editing convenience, are organized into lines.
597space</span> <span>do</span> not 597These lines are typically separated by some combination of the characters
598match the nonterminal <a href="#NT-S">S</a>, and 598CARRIAGE RETURN (#xD) and LINE FEED (#xA).</p><p>To
599hence cannot appear in these positions<span>; however, a 599simplify the tasks of <a title="Application" href="#dt-app">applications</a>, the
600reference to an internal entity with a literal value consisting of character 600<a title="XML Processor" href="#dt-xml-proc">XML
601references expanding to white space does match <a href="#NT-S">S</a>, since its 601processor</a>
602replacement text is the white space resulting from expansion of the character 602 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> behave as if it normalized all line breaks in external parsed
603references</span>.</p></li><li><p>The declaration matches <a href="#NT-Mixed">Mixed</a> and the content 603entities (including the document entity) on input, before parsing, by translating
604<span>(after replacing 604all of the following to a single #xA character:</p><ol class="enumar"><li><p>the two-character sequence #xD #xA</p></li><li><p>the two-character sequence #xD #x85</p></li><li><p>the single character #x85</p></li><li><p>the single character #x2028</p></li><li><p>any #xD character that is not immediately followed by #xA or #x85.</p></li></ol><p> The characters #x85 and #x2028 cannot be reliably recognized and
605any entity references with their replacement text)</span> consists of 605translated until an entity's encoding declaration (if present) has
606<a title="Character Data" href="#dt-chardata">character data</a><span>, 606been read. Therefore, it is a fatal error to use them within the XML
607<a title="Comment" href="#dt-comment">comments</a>, <a title="Processing instruction" href="#dt-pi">PIs</a></span> and <a title="Parent/Child" href="#dt-parentchild">child elements</a> whose types match names in the 607declaration or text declaration.
608content model.</p></li><li><p>The declaration matches <b>ANY</b>, and the 608</p></div><div class="div2"> <h3><a name="sec-lang-tag" id="sec-lang-tag"/>2.12 Language Identification</h3><p>In document processing, it is often useful to identify the natural or formal
609<span>content 609language in which the content is written. A special <a title="Attribute" href="#dt-attr">attribute</a>
610<span>(after replacing 610named <code>xml:lang</code> <span>may</span> be inserted in documents to specify the language
611any entity references with their replacement text)</span> 611used in the contents and attribute values of any element in an XML document.
612consists of character data and <a title="Parent/Child" href="#dt-parentchild">child elements</a> 612In valid documents, this attribute, like any other, <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be <a title="Attribute-List Declaration" href="#dt-attdecl">declared</a>
613whose types</span> 613if it is used. The
614have been declared.</p></li></ol></div><div class="div2"> <h3><a name="sec-starttags" id="sec-starttags" />3.1 Start-Tags, End-Tags, and Empty-Element Tags</h3><p>[<a name="dt-stag" id="dt-stag" title="Start-Tag">Definition</a>: The beginning of every non-empty 614values of the attribute are language identifiers as defined by <a href="#RFC1766">[IETF RFC 3066]</a>, <cite>Tags
615XML element is marked by a <b>start-tag</b>.]</p> <h5><a name="IDA3O3S" id="IDA3O3S" />Start-tag</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-STag" id="NT-STag" />[40]   </td><td><code>STag</code></td><td>   ::=   </td><td><code>'&lt;' <a href="#NT-Name">Name</a> (<a href="#NT-S">S</a> <a href="#NT-Attribute">Attribute</a>)* <a href="#NT-S">S</a>? '&gt;'</code></td><td><a href="#uniqattspec">[WFC: Unique Att Spec]</a></td></tr><tr valign="baseline"><td><a name="NT-Attribute" id="NT-Attribute" />[41]   </td><td><code>Attribute</code></td><td>   ::=   </td><td><code><a href="#NT-Name">Name</a> <a href="#NT-Eq">Eq</a> <a href="#NT-AttValue">AttValue</a></code></td><td><a href="#ValueType">[VC: Attribute Value Type]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#NoExternalRefs">[WFC: No External Entity References]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#CleanAttrVals">[WFC: No &lt; in Attribute Values]</a></td></tr></tbody></table><p>The <a href="#NT-Name">Name</a> in the start- and end-tags gives the element's <b>type</b>. [<a name="dt-attr" id="dt-attr" title="Attribute">Definition</a>: The <a href="#NT-Name">Name</a>-<a href="#NT-AttValue">AttValue</a> 615for the Identification of Languages</cite>, or its successor; in addition, the empty string <span>may</span> be specified.</p><p>(Productions 33 through 38 have been removed.)</p><p>For example:</p><div class="exampleInner"><pre>&lt;p xml:lang="en"&gt;The quick brown fox jumps over the lazy dog.&lt;/p&gt;
616pairs are referred to as the <b>attribute specifications</b> of the 616&lt;p xml:lang="en-GB"&gt;What colour is it?&lt;/p&gt;
617element], [<a name="dt-attrname" id="dt-attrname" title="Attribute Name">Definition</a>: with the <a href="#NT-Name">Name</a> in each pair referred to as the <b>attribute name</b>] 617&lt;p xml:lang="en-US"&gt;What color is it?&lt;/p&gt;
618and [<a name="dt-attrval" id="dt-attrval" title="Attribute Value">Definition</a>: the content of the <a href="#NT-AttValue">AttValue</a> (the text between the <code>'</code> or <code>"</code> 618&lt;sp who="Faust" desc='leise' xml:lang="de"&gt;
619delimiters) as the <b>attribute value</b>.] Note 619&lt;l&gt;Habe nun, ach! Philosophie,&lt;/l&gt;
620that the order of attribute specifications in a start-tag or empty-element 620&lt;l&gt;Juristerei, und Medizin&lt;/l&gt;
621tag is not significant.</p><div class="constraint"><p class="prefix"><a name="uniqattspec" id="uniqattspec" /><b>Well-formedness constraint: Unique Att Spec</b></p><p><span class="mustard">An attribute name 621&lt;l&gt;und leider auch Theologie&lt;/l&gt;
622<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em></span> appear more than once in the same start-tag or empty-element tag.</p></div><div class="constraint"><p class="prefix"><a name="ValueType" id="ValueType" /><b>Validity constraint: Attribute Value Type</b></p><p>The attribute <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> 622&lt;l&gt;durchaus studiert mit hei&amp;#xDF;em Bem&amp;#xFC;h'n.&lt;/l&gt;
623have been declared; the value <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be of the type declared for it. (For attribute 623&lt;/sp&gt;</pre></div><p>The <span>
624types, see <a href="#attdecls"><b>3.3 Attribute-List Declarations</b></a>.)</p></div><div class="constraint"><p class="prefix"><a name="NoExternalRefs" id="NoExternalRefs" /><b>Well-formedness constraint: No External Entity References</b></p><p>Attribute 624 language specified by</span>
625values <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em></span> contain direct or indirect entity references to external entities.</p></div><div class="constraint"><p class="prefix"><a name="CleanAttrVals" id="CleanAttrVals" /><b>Well-formedness constraint: No <code>&lt;</code> in Attribute Values</b></p><p>The <a title="Replacement Text" href="#dt-repltext">replacement text</a> of any entity 625 <code>xml:lang</code>
626referred to directly or indirectly in an attribute value <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> contain a <code>&lt;</code>.</p></div><p>An example of a start-tag:</p><div class="exampleInner"><pre>&lt;termdef id="dt-dog" term="dog"&gt;</pre></div><p>[<a name="dt-etag" id="dt-etag" title="End Tag">Definition</a>: The end of every element that begins 626
627with a start-tag <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be marked by an <b>end-tag</b> containing a name 627 <span>
628that echoes the element's type as given in the start-tag:]</p> <h5><a name="IDA3U3S" id="IDA3U3S" />End-tag</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-ETag" id="NT-ETag" />[42]   </td><td><code>ETag</code></td><td>   ::=   </td><td><code>'&lt;/' <a href="#NT-Name">Name</a> <a href="#NT-S">S</a>? 628 applies</span>
629'&gt;'</code></td></tr></tbody></table><p>An example of an end-tag:</p><div class="exampleInner"><pre>&lt;/termdef&gt;</pre></div><p>[<a name="dt-content" id="dt-content" title="Content">Definition</a>: The <a title="Text" href="#dt-text">text</a> 629 to the element where it is specified<span>
630between the start-tag and end-tag is called the element's <b>content</b>:]</p> <h5><a name="IDAKW3S" id="IDAKW3S" />Content of Elements</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-content" id="NT-content" />[43]   </td><td><code>content</code></td><td>   ::=   </td><td><code><a href="#NT-CharData">CharData</a>? ((<a href="#NT-element">element</a> 630
631| <a href="#NT-Reference">Reference</a> | <a href="#NT-CDSect">CDSect</a> 631 (including the values of its attributes), and to all elements in its content</span> unless
632| <a href="#NT-PI">PI</a> | <a href="#NT-Comment">Comment</a>) <a href="#NT-CharData">CharData</a>?)*</code></td></tr></tbody></table><p>[<a name="dt-empty" id="dt-empty" title="Empty">Definition</a>: An element 632 overridden with <span>
633with no <a href="#NT-content">content</a> is said to be <b>empty</b>.] The representation 633 another</span> instance of <code>xml:lang</code>. In particular, the empty value of <code>xml:lang</code> is used on an element B to override
634of an empty element is either a start-tag immediately followed by an end-tag, 634 a specification of <code>xml:lang</code> on an enclosing element A, without specifying another language. Within B,
635or an empty-element tag. [<a name="dt-eetag" id="dt-eetag" title="empty-element tag">Definition</a>: An <b>empty-element 635 it is considered that there is no language information available, just as if <code>xml:lang</code> had not been specified
636tag</b> takes a special form:]</p> <h5><a name="IDARY3S" id="IDARY3S" />Tags for Empty Elements</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EmptyElemTag" id="NT-EmptyElemTag" />[44]   </td><td><code>EmptyElemTag</code></td><td>   ::=   </td><td><code>'&lt;' <a href="#NT-Name">Name</a> (<a href="#NT-S">S</a> <a href="#NT-Attribute">Attribute</a>)* <a href="#NT-S">S</a>? '/&gt;'</code></td><td><a href="#uniqattspec">[WFC: Unique Att Spec]</a></td></tr></tbody></table><p>Empty-element tags <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be used for any element which has no content, whether 636 on B or any of its ancestors.<span>
637or not it is declared using the keyword <b>EMPTY</b>. <a title="For interoperability" href="#dt-interop">For 637 Applications determine which of an element's attribute values
638interoperability</a>, the empty-element tag <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> 638 and which parts of its character content, if any, are treated as language-dependent values described by <code>xml:lang</code>.</span>
639be used, and <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> only be used, for elements which are declared 639 </p><div class="note"><p class="prefix"><b>Note:</b></p><p>Language information may also be provided by external transport protocols (e.g. HTTP or
640EMPTY.</p><p>Examples of empty elements:</p><div class="exampleInner"><pre>&lt;IMG align="left" 640MIME). When available, this information may be used by XML applications, but the more local
641src="http://www.w3.org/Icons/WWW/w3c_home" /&gt; 641information provided by <code>xml:lang</code> should be considered to override it.
642&lt;br&gt;&lt;/br&gt; 642</p></div><p>A simple declaration for <code>xml:lang</code> might take the form</p><div class="exampleInner"><pre>xml:lang CDATA #IMPLIED</pre></div><p>but specific default values <span>may</span> also be given, if appropriate. In a collection
643&lt;br/&gt;</pre></div></div><div class="div2"> <h3><a name="elemdecls" id="elemdecls" />3.2 Element Type Declarations</h3><p>The <a title="Element" href="#dt-element">element</a> structure of an <a title="XML Document" href="#dt-xml-doc">XML document</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em>, for <a title="Validity" href="#dt-valid">validation</a> 643of French poems for English students, with glosses and notes in English, the <code>xml:lang</code>
644purposes, be constrained using element type and attribute-list declarations. 644attribute might be declared this way:</p><div class="exampleInner"><pre>&lt;!ATTLIST poem xml:lang CDATA 'fr'&gt;
645An element type declaration constrains the element's <a title="Content" href="#dt-content">content</a>.</p><p>Element type declarations often constrain which element types can appear 645&lt;!ATTLIST gloss xml:lang CDATA 'en'&gt;
646as <a title="Parent/Child" href="#dt-parentchild">children</a> of the element. At user 646&lt;!ATTLIST note xml:lang CDATA 'en'&gt;</pre></div></div><div class="div2"> <h3><a name="sec-normalization-checking" id="sec-normalization-checking"/>2.13 Normalization Checking</h3><p>All XML <a title="Text Entity" href="#dt-parsedent"> parsed
647option, an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> issue a warning when a declaration mentions an 647entities</a> (including <a title="Document Entity" href="#dt-docent"> document
648element type for which no declaration is provided, but this is not an error.</p><p>[<a name="dt-eldecl" id="dt-eldecl" title="Element Type declaration">Definition</a>: An <b>element 648entities</a>) <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be <a title="fully normalized" href="#dt-fullnorm">fully
649type declaration</b> takes the form:]</p> <h5><a name="IDAV13S" id="IDAV13S" />Element Type Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-elementdecl" id="NT-elementdecl" />[45]   </td><td><code>elementdecl</code></td><td>   ::=   </td><td><code>'&lt;!ELEMENT' <a href="#NT-S">S</a> <a href="#NT-Name">Name</a> <a href="#NT-S">S</a> <a href="#NT-contentspec">contentspec</a> <a href="#NT-S">S</a>? 649normalized</a> as per the definition of
650'&gt;'</code></td><td><a href="#EDUnique">[VC: Unique Element Type Declaration]</a></td></tr><tr valign="baseline"><td><a name="NT-contentspec" id="NT-contentspec" />[46]   </td><td><code>contentspec</code></td><td>   ::=   </td><td><code>'EMPTY' | 'ANY' | <a href="#NT-Mixed">Mixed</a> 650<a href="#sec-CharNorm"><b>B Definitions for Character Normalization</b></a> supplemented by the following definitions of
651| <a href="#NT-children">children</a></code></td></tr></tbody></table><p>where the <a href="#NT-Name">Name</a> gives the element type being declared.</p><div class="constraint"><p class="prefix"><a name="EDUnique" id="EDUnique" /><b>Validity constraint: Unique Element Type Declaration</b></p><p><span class="mustard">An element 651<em><a name="dt-relconst" id="dt-relconst"/>relevant constructs</em> for XML:</p><ol class="enumar"><li><p>The <a title="Replacement Text" href="#dt-repltext">
652type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em></span> be declared more than once.</p></div><p>Examples of element type declarations:</p><div class="exampleInner"><pre>&lt;!ELEMENT br EMPTY&gt; 652replacement text</a> of all <a title="Text Entity" href="#dt-parsedent">parsed
653&lt;!ELEMENT p (#PCDATA|emph)* &gt; 653entities</a>
654&lt;!ELEMENT %name.para; %content.para; &gt; 654 </p></li><li><p>All text matching, in context, one of the following
655&lt;!ELEMENT container ANY&gt;</pre></div><div class="div3"> <h4><a name="sec-element-content" id="sec-element-content" />3.2.1 Element Content</h4><p>[<a name="dt-elemcontent" id="dt-elemcontent" title="Element content">Definition</a>: An element <a title="Start-Tag" href="#dt-stag">type</a> has <b>element content</b> when elements 655productions:</p><ol class="enumla"><li><p>
656of that type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> contain only <a title="Parent/Child" href="#dt-parentchild">child</a> 656 <a href="#NT-CData">
657elements (no character data), optionally separated by white space (characters 657CData</a>
658matching the nonterminal <a href="#NT-S">S</a>).] [<a name="dt-content-model" id="dt-content-model" title="Content model">Definition</a>: In this case, the constraint includes a <b>content 658 </p></li><li><p>
659model</b>, a simple grammar governing the allowed types of the 659 <a href="#NT-CharData">
660child elements and the order in which they are allowed to appear.] 660CharData</a>
661The grammar is built on content particles (<a href="#NT-cp">cp</a>s), which 661 </p></li><li><p>
662consist of names, choice lists of content particles, or sequence lists of 662 <a href="#NT-content">
663content particles:</p> <h5><a name="IDAP53S" id="IDAP53S" />Element-content Models</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-children" id="NT-children" />[47]   </td><td><code>children</code></td><td>   ::=   </td><td><code>(<a href="#NT-choice">choice</a> | <a href="#NT-seq">seq</a>) 663content</a>
664('?' | '*' | '+')?</code></td></tr><tr valign="baseline"><td><a name="NT-cp" id="NT-cp" />[48]   </td><td><code>cp</code></td><td>   ::=   </td><td><code>(<a href="#NT-Name">Name</a> | <a href="#NT-choice">choice</a> 664 </p></li><li><p>
665| <a href="#NT-seq">seq</a>) ('?' | '*' | '+')?</code></td></tr><tr valign="baseline"><td><a name="NT-choice" id="NT-choice" />[49]   </td><td><code>choice</code></td><td>   ::=   </td><td><code>'(' <a href="#NT-S">S</a>? <a href="#NT-cp">cp</a> ( <a href="#NT-S">S</a>? '|' <a href="#NT-S">S</a>? <a href="#NT-cp">cp</a> )+ <a href="#NT-S">S</a>? ')'</code></td><td><a href="#vc-PEinGroup">[VC: Proper Group/PE Nesting]</a></td></tr><tr valign="baseline"><td><a name="NT-seq" id="NT-seq" />[50]   </td><td><code>seq</code></td><td>   ::=   </td><td><code>'(' <a href="#NT-S">S</a>? <a href="#NT-cp">cp</a> ( <a href="#NT-S">S</a>? ',' <a href="#NT-S">S</a>? <a href="#NT-cp">cp</a> )* <a href="#NT-S">S</a>? ')'</code></td><td><a href="#vc-PEinGroup">[VC: Proper Group/PE Nesting]</a></td></tr></tbody></table><p>where each <a href="#NT-Name">Name</a> is the type of an element which 665 <a href="#NT-Name"> Name</a>
666<em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> appear as a <a title="Parent/Child" href="#dt-parentchild">child</a>. Any content 666 </p></li><li><p>
667particle in a choice list <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> appear in the <a title="Element content" href="#dt-elemcontent">element 667 <a href="#NT-Nmtoken">
668content</a> at the location where the choice list appears in the grammar; 668Nmtoken</a>
669content particles occurring in a sequence list <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> each appear in the <a title="Element content" href="#dt-elemcontent">element content</a> in the order given in the list. 669 </p></li></ol></li></ol><p>However, a document is still well-formed even if it is not
670The optional character following a name or list governs whether the element 670<a title="fully normalized" href="#dt-fullnorm">fully normalized</a>.
671or the content particles in the list may occur one or more (<code>+</code>), 671XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> provide a user option to verify that the document being
672zero or more (<code>*</code>), or zero or one times (<code>?</code>). The 672processed is in <a title="fully normalized" href="#dt-fullnorm">fully normalized</a> form, and report to the application whether
673absence of such an operator means that the element or content particle <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> 673it is or not. The option to not verify <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be chosen only when the
674appear exactly once. This syntax and meaning are identical to those used in 674input text is <a title="certified" href="#dt-certified">certified</a>,
675the productions in this specification.</p><p>The content of an element matches a content model if and only if it is 675as defined by <a href="#sec-CharNorm"><b>B Definitions for Character Normalization</b></a>.</p><p>The verification of full normalization <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be carried out as if by
676possible to trace out a path through the content model, obeying the sequence, 676first verifying that the entity is in <a title="include-normalized" href="#dt-inclnorm">include-normalized</a>
677choice, and repetition operators and matching each element in the content 677form as defined by <a href="#sec-CharNorm"><b>B Definitions for Character Normalization</b></a> and by then verifying that none of the relevant
678against an element type in the content model. <a title="For Compatibility" href="#dt-compat">For 678constructs listed above begins (after character references are
679compatibility</a>, it is an error if <span>the content model 679expanded) with a <a title="composing character" href="#dt-compchar">composing character</a> as defined by
680allows an element to match more than one occurrence of an element type in the 680<a href="#sec-CharNorm"><b>B Definitions for Character Normalization</b></a>.
681content model</span>. For more information, see <a href="#determinism"><b>D Deterministic Content Models</b></a>.</p><div class="constraint"><p class="prefix"><a name="vc-PEinGroup" id="vc-PEinGroup" /><b>Validity constraint: Proper Group/PE Nesting</b></p><p>Parameter-entity <a title="Replacement Text" href="#dt-repltext">replacement text</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be properly nested with parenthesized 681Non-validating processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> ignore possible
682groups. That is to say, if either of the opening or closing parentheses in 682denormalizations that would be caused by inclusion of external
683a <a href="#NT-choice">choice</a>, <a href="#NT-seq">seq</a>, or <a href="#NT-Mixed">Mixed</a> 683entities that they do not read.</p><div class="note"><p class="prefix"><b>Note:</b></p><p>The <a title="composing character" href="#dt-compchar">composing character</a> are all
684construct is contained in the replacement text for a <a title="Parameter-entity reference" href="#dt-PERef">parameter 684Unicode characters of non-zero combining class, plus a small number
685entity</a>, both <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be contained in the same replacement text.</p><p><a title="For interoperability" href="#dt-interop">For interoperability</a>, if a parameter-entity reference 685of class-zero characters that nevertheless take part as a
686appears in a <a href="#NT-choice">choice</a>, <a href="#NT-seq">seq</a>, or <a href="#NT-Mixed">Mixed</a> construct, its replacement text <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> contain at 686non-initial character in certain Unicode canonical
687least one non-blank character, and neither the first nor last non-blank character 687decompositions. Since these characters are meant to follow
688of the replacement text <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be a connector (<code>|</code> or <code>,</code>).</p></div><p>Examples of element-content models:</p><div class="exampleInner"><pre>&lt;!ELEMENT spec (front, body, back?)&gt; 688base characters, restricting relevant constructs (including
689&lt;!ELEMENT div1 (head, (p | list | note)*, div2*)&gt; 689content) from beginning with a <a title="composing character" href="#dt-compchar">composing character</a> does not
690&lt;!ELEMENT dictionary-body (%div.mix; | %dict.mix;)*&gt;</pre></div></div><div class="div3"> <h4><a name="sec-mixed-content" id="sec-mixed-content" />3.2.2 Mixed Content</h4><p>[<a name="dt-mixed" id="dt-mixed" title="Mixed Content">Definition</a>: An element <a title="Start-Tag" href="#dt-stag">type</a> 690meaningfully diminish the expressiveness of XML.</p></div><p>If, while verifying full normalization, a processor encounters
691has <b>mixed content</b> when elements of that type <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> contain character 691characters for which it cannot determine the normalization
692data, optionally interspersed with <a title="Parent/Child" href="#dt-parentchild">child</a> 692properties (i.e., characters introduced in a version of Unicode <a href="#Unicode">[Unicode]</a>
693elements.] In this case, the types of the child elements <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be constrained, 693later than the one used in the implementation of the processor),
694but not their order or their number of occurrences:</p> <h5><a name="IDAUHCU" id="IDAUHCU" />Mixed-content Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-Mixed" id="NT-Mixed" />[51]   </td><td><code>Mixed</code></td><td>   ::=   </td><td><code>'(' <a href="#NT-S">S</a>? '#PCDATA' (<a href="#NT-S">S</a>? 694then the processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em>, at user option, ignore any possible
695'|' <a href="#NT-S">S</a>? <a href="#NT-Name">Name</a>)* <a href="#NT-S">S</a>? 695denormalizations caused by these characters. The option to ignore
696')*' </code></td></tr><tr valign="baseline"><td /><td /><td /><td><code>| '(' <a href="#NT-S">S</a>? '#PCDATA' <a href="#NT-S">S</a>? ')' </code></td><td><a href="#vc-PEinGroup">[VC: Proper Group/PE Nesting]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#vc-MixedChildrenUnique">[VC: No Duplicate Types]</a></td></tr></tbody></table><p>where the <a href="#NT-Name">Name</a>s give the types of elements that 696those denormalizations <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD NOT</em> be chosen by applications when
697may appear as children. The 697reliability or security are critical.</p><p> XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> transform the input to be in
698keyword <b>#PCDATA</b> derives historically from the term "parsed 698<a title="fully normalized" href="#dt-fullnorm">fully normalized</a> form.
699character data."</p><div class="constraint"><p class="prefix"><a name="vc-MixedChildrenUnique" id="vc-MixedChildrenUnique" /><b>Validity constraint: No Duplicate Types</b></p><p>The 699XML applications that create XML 1.1 output
700same name <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear more than once in a single mixed-content declaration.</p></div><p>Examples of mixed content declarations:</p><div class="exampleInner"><pre>&lt;!ELEMENT p (#PCDATA|a|ul|b|i|em)*&gt; 700from either XML 1.1 or XML 1.0 input <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> ensure that the output
701&lt;!ELEMENT p (#PCDATA | %font; | %phrase; | %special; | %form;)* &gt; 701is <a title="fully normalized" href="#dt-fullnorm">fully normalized</a>; it is not necessary for internal processing
702&lt;!ELEMENT b (#PCDATA)&gt;</pre></div></div></div><div class="div2"> <h3><a name="attdecls" id="attdecls" />3.3 Attribute-List Declarations</h3><p><a title="Attribute" href="#dt-attr">Attributes</a> are used to associate name-value 702forms to be <a title="fully normalized" href="#dt-fullnorm">fully normalized</a>.</p><p>The purpose of this section is to strongly encourage XML
703pairs with <a title="Element" href="#dt-element">elements</a>. Attribute specifications 703processors to ensure that the creators of XML documents have
704<span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear outside of</span> <a title="Start-Tag" href="#dt-stag">start-tags</a> and <a title="empty-element tag" href="#dt-eetag">empty-element tags</a>; thus, the productions used to 704properly normalized them, so that XML applications can make tests
705recognize them appear in <a href="#sec-starttags"><b>3.1 Start-Tags, End-Tags, and Empty-Element Tags</b></a>. Attribute-list declarations 705such as identity comparisons of strings without having to worry
706<em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be used:</p><ul><li><p>To define the set of attributes pertaining to a given element type.</p></li><li><p>To establish type constraints for these attributes.</p></li><li><p>To provide <a title="Attribute Default" href="#dt-default">default values</a> for 706about the different possible "spellings" of strings which
707attributes.</p></li></ul><p>[<a name="dt-attdecl" id="dt-attdecl" title="Attribute-List Declaration">Definition</a>: <b>Attribute-list 707Unicode allows.
708declarations</b> specify the name, data type, and default value (if any) 708</p><p>When entities are in a non-Unicode encoding, if the processor
709of each attribute associated with a given element type:]</p> <h5><a name="IDADMCU" id="IDADMCU" />Attribute-list Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-AttlistDecl" id="NT-AttlistDecl" />[52]   </td><td><code>AttlistDecl</code></td><td>   ::=   </td><td><code>'&lt;!ATTLIST' <a href="#NT-S">S</a> <a href="#NT-Name">Name</a> <a href="#NT-AttDef">AttDef</a>* <a href="#NT-S">S</a>? '&gt;'</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-AttDef" id="NT-AttDef" />[53]   </td><td><code>AttDef</code></td><td>   ::=   </td><td><code><a href="#NT-S">S</a> <a href="#NT-Name">Name</a> <a href="#NT-S">S</a> <a href="#NT-AttType">AttType</a> <a href="#NT-S">S</a> <a href="#NT-DefaultDecl">DefaultDecl</a></code></td></tr></tbody></table><p>The <a href="#NT-Name">Name</a> in the <a href="#NT-AttlistDecl">AttlistDecl</a> 709transcodes them to Unicode, it <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> use a normalizing transcoder.
710rule is the type of an element. At user option, an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> issue 710</p></div></div><div class="div1"> <h2><a name="sec-logical-struct" id="sec-logical-struct"/>3 Logical Structures</h2><p>
711a warning if attributes are declared for an element type not itself declared, 711 [<a name="dt-element" id="dt-element" title="Element">Definition</a>: Each <a title="XML Document" href="#dt-xml-doc">XML
712but this is not an error. The <a href="#NT-Name">Name</a> in the <a href="#NT-AttDef">AttDef</a> 712document</a> contains one or more <b>elements</b>, the boundaries
713rule is the name of the attribute.</p><p>When more than one <a href="#NT-AttlistDecl">AttlistDecl</a> is provided 713of which are either delimited by <a title="Start-Tag" href="#dt-stag">start-tags</a>
714for a given element type, the contents of all those provided are merged. When 714and <a title="End Tag" href="#dt-etag">end-tags</a>, or, for <a title="Empty" href="#dt-empty">empty</a>
715more than one definition is provided for the same attribute of a given element 715elements, by an <a title="empty-element tag" href="#dt-eetag">empty-element tag</a>. Each
716type, the first declaration is binding and later declarations are ignored. <a title="For interoperability" href="#dt-interop">For interoperability,</a> writers of DTDs <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> choose 716element has a type, identified by name, sometimes called its "generic
717to provide at most one attribute-list declaration for a given element type, 717identifier" (GI), and <span>may</span> have a set of attribute specifications.]
718at most one attribute definition for a given attribute name in an attribute-list 718Each attribute specification has a <a title="Attribute Name" href="#dt-attrname">name</a>
719declaration, and at least one attribute definition in each attribute-list 719and a <a title="Attribute Value" href="#dt-attrval">value</a>.</p> <h5><a name="IDALUFS" id="IDALUFS"/>Element</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-element" id="NT-element"/>[39]   </td><td><code>element</code></td><td>   ::=   </td><td><code>
720declaration. For interoperability, an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> at user option 720 <a href="#NT-EmptyElemTag">EmptyElemTag</a>
721issue a warning when more than one attribute-list declaration is provided 721 </code></td></tr><tr valign="baseline"><td/><td/><td/><td><code>| <a href="#NT-STag">STag</a>
722for a given element type, or more than one attribute definition is provided 722 <a href="#NT-content">content</a>
723for a given attribute, but this is not an error.</p><div class="div3"> <h4><a name="sec-attribute-types" id="sec-attribute-types" />3.3.1 Attribute Types</h4><p>XML attribute types are of three kinds: a string type, a set of tokenized 723 <a href="#NT-ETag">ETag</a>
724types, and enumerated types. The string type may take any literal string as 724 </code></td><td><a href="#GIMatch">[WFC: Element Type Match]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#elementvalid">[VC: Element Valid]</a></td></tr></tbody></table><p>This specification does not constrain the
725a value; the tokenized types have varying lexical and semantic constraints. 725 <span>
726The validity constraints noted in the grammar are applied after the attribute 726 application </span>semantics, use, or (beyond syntax)
727value has been normalized as described in <span><a href="#AVNormalize"><b>3.3.3 Attribute-Value Normalization</b></a></span>.</p> <h5><a name="IDAPPCU" id="IDAPPCU" />Attribute Types</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-AttType" id="NT-AttType" />[54]   </td><td><code>AttType</code></td><td>   ::=   </td><td><code><a href="#NT-StringType">StringType</a> | <a href="#NT-TokenizedType">TokenizedType</a> 727names of the element types and attributes, except that names beginning with
728| <a href="#NT-EnumeratedType">EnumeratedType</a></code></td></tr><tr valign="baseline"><td><a name="NT-StringType" id="NT-StringType" />[55]   </td><td><code>StringType</code></td><td>   ::=   </td><td><code>'CDATA'</code></td></tr><tr valign="baseline"><td><a name="NT-TokenizedType" id="NT-TokenizedType" />[56]   </td><td><code>TokenizedType</code></td><td>   ::=   </td><td><code>'ID'</code></td><td><a href="#id">[VC: ID]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#one-id-per-el">[VC: One ID per Element Type]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#id-default">[VC: ID Attribute Default]</a></td></tr><tr valign="baseline"><td /><td /><td /><td><code>| 'IDREF'</code></td><td><a href="#idref">[VC: IDREF]</a></td></tr><tr valign="baseline"><td /><td /><td /><td><code>| 'IDREFS'</code></td><td><a href="#idref">[VC: IDREF]</a></td></tr><tr valign="baseline"><td /><td /><td /><td><code>| 'ENTITY'</code></td><td><a href="#entname">[VC: Entity Name]</a></td></tr><tr valign="baseline"><td /><td /><td /><td><code>| 'ENTITIES'</code></td><td><a href="#entname">[VC: Entity Name]</a></td></tr><tr valign="baseline"><td /><td /><td /><td><code>| 'NMTOKEN'</code></td><td><a href="#nmtok">[VC: Name Token]</a></td></tr><tr valign="baseline"><td /><td /><td /><td><code>| 'NMTOKENS'</code></td><td><a href="#nmtok">[VC: Name Token]</a></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="id" id="id" /><b>Validity constraint: ID</b></p><p>Values of type <b>ID</b> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the <a href="#NT-Name">Name</a> production. A name <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear more than once 728a match to <code>(('X'|'x')('M'|'m')('L'|'l'))</code> are reserved for standardization
729in an XML document as a value of this type; i.e., ID values <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> uniquely 729in this or future versions of this specification.</p><div class="constraint"><p class="prefix"><a name="GIMatch" id="GIMatch"/><b>Well-formedness constraint: Element Type Match</b></p><p>The <a href="#NT-Name">Name</a>
730identify the elements which bear them.</p></div><div class="constraint"><p class="prefix"><a name="one-id-per-el" id="one-id-per-el" /><b>Validity constraint: One ID per Element Type</b></p><p><span class="mustard">An element 730in an element's end-tag <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the element type in the start-tag.</p></div><div class="constraint"><p class="prefix"><a name="elementvalid" id="elementvalid"/><b>Validity constraint: Element Valid</b></p><p>An element is valid
731type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em></span> have more than one ID attribute specified.</p></div><div class="constraint"><p class="prefix"><a name="id-default" id="id-default" /><b>Validity constraint: ID Attribute Default</b></p><p>An ID attribute 731if there is a declaration matching <a href="#NT-elementdecl">elementdecl</a>
732<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> have a declared default of <b>#IMPLIED</b> or <b>#REQUIRED</b>.</p></div><div class="constraint"><p class="prefix"><a name="idref" id="idref" /><b>Validity constraint: IDREF</b></p><p>Values of type <b>IDREF</b> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> 732where the <a href="#NT-Name">Name</a> matches the element type, and one of
733match the <a href="#NT-Name">Name</a> production, and values of type <b>IDREFS</b> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match <a href="#NT-Names">Names</a>; each <a href="#NT-Name">Name</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the value of an ID attribute on some element in the XML document; 733the following holds:</p><ol class="enumar"><li><p>The declaration matches <b>EMPTY</b> and the element has no <a title="Content" href="#dt-content">content</a> (not even entity
734i.e. <b>IDREF</b> values <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the value of some ID attribute.</p></div><div class="constraint"><p class="prefix"><a name="entname" id="entname" /><b>Validity constraint: Entity Name</b></p><p>Values of type <b>ENTITY</b> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the <a href="#NT-Name">Name</a> production, values of type <b>ENTITIES</b> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match <a href="#NT-Names">Names</a>; each <a href="#NT-Name">Name</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the name of an <a title="Unparsed Entity" href="#dt-unparsed">unparsed entity</a> 734references, comments, PIs or white space).</p></li><li><p>The declaration matches <a href="#NT-children">children</a> and the
735declared in the <a title="Document Type Declaration" href="#dt-doctype">DTD</a>.</p></div><div class="constraint"><p class="prefix"><a name="nmtok" id="nmtok" /><b>Validity constraint: Name Token</b></p><p>Values of type <b>NMTOKEN</b> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the <a href="#NT-Nmtoken">Nmtoken</a> production; values of type <b>NMTOKENS</b> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match <a href="#NT-Nmtokens">Nmtokens</a>.</p></div><p>[<a name="dt-enumerated" id="dt-enumerated" title="Enumerated Attribute&#xA;Values">Definition</a>: <b>Enumerated attributes</b> <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em></span> take one of a list of values 735sequence of <a title="Parent/Child" href="#dt-parentchild">child elements</a> belongs
736provided in the declaration]. There are two kinds of enumerated types:</p> <h5><a name="IDAHXCU" id="IDAHXCU" />Enumerated Attribute Types</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EnumeratedType" id="NT-EnumeratedType" />[57]   </td><td><code>EnumeratedType</code></td><td>   ::=   </td><td><code><a href="#NT-NotationType">NotationType</a> 736to the language generated by the regular expression in the content model,
737| <a href="#NT-Enumeration">Enumeration</a></code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-NotationType" id="NT-NotationType" />[58]   </td><td><code>NotationType</code></td><td>   ::=   </td><td><code>'NOTATION' <a href="#NT-S">S</a> '(' <a href="#NT-S">S</a>? <a href="#NT-Name">Name</a> (<a href="#NT-S">S</a>? '|' <a href="#NT-S">S</a>? <a href="#NT-Name">Name</a>)* <a href="#NT-S">S</a>? ')' </code></td><td><a href="#notatn">[VC: Notation Attributes]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#OneNotationPer">[VC: One Notation Per Element Type]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#NoNotationEmpty">[VC: No Notation on Empty Element]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#NoDuplicateTokens">[VC: No Duplicate 737with optional white space, comments and
738Tokens]</a></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Enumeration" id="NT-Enumeration" />[59]   </td><td><code>Enumeration</code></td><td>   ::=   </td><td><code>'(' <a href="#NT-S">S</a>? <a href="#NT-Nmtoken">Nmtoken</a> 738PIs (i.e. markup matching production [27] <a href="#NT-Misc">Misc</a>) between the
739(<a href="#NT-S">S</a>? '|' <a href="#NT-S">S</a>? <a href="#NT-Nmtoken">Nmtoken</a>)* <a href="#NT-S">S</a>? ')'</code></td><td><a href="#enum">[VC: Enumeration]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#NoDuplicateTokens">[VC: No Duplicate 739start-tag and the first child element, between child elements, or between
740Tokens]</a></td></tr></tbody></table><p>A <b>NOTATION</b> attribute identifies a <a title="Notation" href="#dt-notation">notation</a>, 740the last child element and the end-tag. Note that a CDATA section containing
741declared in the DTD with associated system and/or public identifiers, to be 741only white space or a reference
742used in interpreting the element to which the attribute is attached.</p><div class="constraint"><p class="prefix"><a name="notatn" id="notatn" /><b>Validity constraint: Notation Attributes</b></p><p>Values of this type 742to an entity whose replacement text is character references expanding to white
743<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match one of the <a href="#Notations"><cite>notation</cite></a> names 743space do not
744included in the declaration; all notation names in the declaration <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be 744match the nonterminal <a href="#NT-S">S</a>, and
745declared.</p></div><div class="constraint"><p class="prefix"><a name="OneNotationPer" id="OneNotationPer" /><b>Validity constraint: One Notation Per Element Type</b></p><p><span class="mustard">An element type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em></span> have more than one <b>NOTATION</b> 745hence cannot appear in these positions; however, a
746attribute specified.</p></div><div class="constraint"><p class="prefix"><a name="NoNotationEmpty" id="NoNotationEmpty" /><b>Validity constraint: No Notation on Empty Element</b></p><p><a title="For Compatibility" href="#dt-compat">For compatibility</a>, 746reference to an internal entity with a literal value consisting of character
747an attribute of type <b>NOTATION</b> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be declared on an element 747references expanding to white space does match <a href="#NT-S">S</a>, since its
748declared <b>EMPTY</b>.</p></div><div class="constraint"><p class="prefix"><a name="NoDuplicateTokens" id="NoDuplicateTokens" /><b>Validity constraint: No Duplicate 748replacement text is the white space resulting from expansion of the character
749Tokens</b></p><p>The notation names in a single <a href="#NT-NotationType">NotationType</a> 749references.</p></li><li><p>The declaration matches <a href="#NT-Mixed">Mixed</a>
750attribute declaration, as well as the <a href="#NT-Nmtoken">NmToken</a>s in a single 750 <span>
751<a href="#NT-Enumeration">Enumeration</a> attribute declaration, <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> all be distinct.</p></div><div class="constraint"><p class="prefix"><a name="enum" id="enum" /><b>Validity constraint: Enumeration</b></p><p>Values of this type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match 751 ,</span> and the content
752one of the <a href="#NT-Nmtoken">Nmtoken</a> tokens in the declaration.</p></div><p><a title="For interoperability" href="#dt-interop">For interoperability,</a> the same <a href="#NT-Nmtoken">Nmtoken</a> <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD NOT</em> occur more than once in the enumerated 752(after replacing
753attribute types of a single element type.</p></div><div class="div3"> <h4><a name="sec-attr-defaults" id="sec-attr-defaults" />3.3.2 Attribute Defaults</h4><p>An <a title="Attribute-List Declaration" href="#dt-attdecl">attribute declaration</a> provides information 753any entity references with their replacement text) consists of
754on whether the attribute's presence is <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>, and if not, how an XML processor 754<a title="Character Data" href="#dt-chardata">character data</a>
755<span>is 755 <span>
756to</span> react if a declared attribute is absent in a document.</p> <h5><a name="IDAR4CU" id="IDAR4CU" />Attribute Defaults</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-DefaultDecl" id="NT-DefaultDecl" />[60]   </td><td><code>DefaultDecl</code></td><td>   ::=   </td><td><code>'#REQUIRED' | '#IMPLIED' </code></td></tr><tr valign="baseline"><td /><td /><td /><td><code>| (('#FIXED' S)? <a href="#NT-AttValue">AttValue</a>)</code></td><td><a href="#RequiredAttr">[VC: Required Attribute]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#defattrvalid">[VC: Attribute 756 (including <a title="CDATA Section" href="#dt-cdsection">CDATA sections</a>)</span>,
757Default Value Syntactically Correct]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#CleanAttrVals">[WFC: No &lt; in Attribute Values]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#FixedAttr">[VC: Fixed Attribute Default]</a></td></tr></tbody></table><p>In an attribute declaration, <b>#REQUIRED</b> means that the attribute 757<a title="Comment" href="#dt-comment">comments</a>, <a title="Processing instruction" href="#dt-pi">PIs</a> and <a title="Parent/Child" href="#dt-parentchild">child elements</a> whose types match names in the
758<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> always be provided, <b>#IMPLIED</b> that no default value is provided. 758content model.</p></li><li><p>The declaration matches <b>ANY</b>, and the
759[<a name="dt-default" id="dt-default" title="Attribute Default">Definition</a>: If 759content (after replacing
760the declaration is neither <b>#REQUIRED</b> nor <b>#IMPLIED</b>, then 760any entity references with their replacement text)
761the <a href="#NT-AttValue">AttValue</a> value contains the declared <b>default</b> 761consists of character data<span>
762value; the <b>#FIXED</b> keyword states that the attribute <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> always have 762 , <a title="CDATA Section" href="#dt-cdsection">CDATA
763the default value. 763 sections</a>, <a title="Comment" href="#dt-comment">comments</a>, <a title="Processing instruction" href="#dt-pi">PIs</a>
764When an XML processor encounters 764 </span> and <a title="Parent/Child" href="#dt-parentchild">child elements</a>
765an <span>element 765whose types have been declared.</p></li></ol></div><div class="div2"> <h3><a name="sec-starttags" id="sec-starttags"/>3.1 Start-Tags, End-Tags, and Empty-Element Tags</h3><p>
766without a specification for an attribute for which it has read a default 766 [<a name="dt-stag" id="dt-stag" title="Start-Tag">Definition</a>: The beginning of every non-empty
767value declaration, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> report the attribute with the declared default 767XML element is marked by a <b>start-tag</b>.]
768value to the application</span>.]</p><div class="constraint"><p class="prefix"><a name="RequiredAttr" id="RequiredAttr" /><b>Validity constraint: Required Attribute</b></p><p>If the default 768 </p> <h5><a name="IDA10FS" id="IDA10FS"/>Start-tag</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-STag" id="NT-STag"/>[40]   </td><td><code>STag</code></td><td>   ::=   </td><td><code>'&lt;' <a href="#NT-Name">Name</a> (<a href="#NT-S">S</a>
769declaration is the keyword <b>#REQUIRED</b>, then the attribute <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be 769 <a href="#NT-Attribute">Attribute</a>)* <a href="#NT-S">S</a>? '&gt;'</code></td><td><a href="#uniqattspec">[WFC: Unique Att Spec]</a></td></tr><tr valign="baseline"><td><a name="NT-Attribute" id="NT-Attribute"/>[41]   </td><td><code>Attribute</code></td><td>   ::=   </td><td><code>
770specified for all elements of the type in the attribute-list declaration.</p></div><div class="constraint"><p class="prefix"><a name="defattrvalid" id="defattrvalid" /><b>Validity constraint: <span>Attribute 770 <a href="#NT-Name">Name</a>
771Default Value Syntactically Correct</span></b></p><p>The declared default value <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> meet the <span>syntactic</span> 771 <a href="#NT-Eq">Eq</a>
772constraints of the declared attribute type.</p><p>Note that only the 772 <a href="#NT-AttValue">AttValue</a>
773syntactic constraints of the type are required here; other constraints (e.g. 773 </code></td><td><a href="#ValueType">[VC: Attribute Value Type]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#NoExternalRefs">[WFC: No External Entity References]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#CleanAttrVals">[WFC: No &lt; in Attribute Values]</a></td></tr></tbody></table><p>The <a href="#NT-Name">Name</a> in the start- and end-tags gives the element's <b>type</b>. [<a name="dt-attr" id="dt-attr" title="Attribute">Definition</a>: The <a href="#NT-Name">Name</a>-<a href="#NT-AttValue">AttValue</a>
774that the value be the name of a declared unparsed entity, for an attribute of 774pairs are referred to as the <b>attribute specifications</b> of the
775type ENTITY) may come into play if the declared default value is actually used 775element], [<a name="dt-attrname" id="dt-attrname" title="Attribute Name">Definition</a>: with the <a href="#NT-Name">Name</a> in each pair referred to as the <b>attribute name</b>
776(an element without a specification for this attribute occurs).</p></div><div class="constraint"><p class="prefix"><a name="FixedAttr" id="FixedAttr" /><b>Validity constraint: Fixed Attribute Default</b></p><p>If an attribute 776 ]
777has a default value declared with the <b>#FIXED</b> keyword, instances of 777and [<a name="dt-attrval" id="dt-attrval" title="Attribute Value">Definition</a>: the content of the <a href="#NT-AttValue">AttValue</a> (the text between the <code>'</code> or <code>"</code>
778that attribute <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the default value.</p></div><p>Examples of attribute-list declarations:</p><div class="exampleInner"><pre>&lt;!ATTLIST termdef 778delimiters) as the <b>attribute value</b>.] Note
779id ID #REQUIRED 779that the order of attribute specifications in a start-tag or empty-element
780name CDATA #IMPLIED&gt; 780tag is not significant.</p><div class="constraint"><p class="prefix"><a name="uniqattspec" id="uniqattspec"/><b>Well-formedness constraint: Unique Att Spec</b></p><p>An attribute name
781&lt;!ATTLIST list 781<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear more than once in the same start-tag or empty-element tag.</p></div><div class="constraint"><p class="prefix"><a name="ValueType" id="ValueType"/><b>Validity constraint: Attribute Value Type</b></p><p>The attribute <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
782type (bullets|ordered|glossary) "ordered"&gt; 782have been declared; the value <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be of the type declared for it. (For attribute
783&lt;!ATTLIST form 783types, see <a href="#attdecls"><b>3.3 Attribute-List Declarations</b></a>.)</p></div><div class="constraint"><p class="prefix"><a name="NoExternalRefs" id="NoExternalRefs"/><b>Well-formedness constraint: No External Entity References</b></p><p>Attribute
784method CDATA #FIXED "POST"&gt;</pre></div></div><div class="div3"> <h4><a name="AVNormalize" id="AVNormalize" />3.3.3 Attribute-Value Normalization</h4><p>Before the value of an attribute is passed to the application or checked 784values <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> contain direct or indirect entity references to external entities.</p></div><div class="constraint"><p class="prefix"><a name="CleanAttrVals" id="CleanAttrVals"/><b>Well-formedness constraint: No <code>&lt;</code> in Attribute Values</b></p><p>The <a title="Replacement Text" href="#dt-repltext">replacement text</a> of any entity
785for validity, the XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> normalize the attribute value by applying 785referred to directly or indirectly in an attribute value <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> contain a <code>&lt;</code>.</p></div><p>An example of a start-tag:</p><div class="exampleInner"><pre>&lt;termdef id="dt-dog" term="dog"&gt;</pre></div><p>
786the algorithm below, or by using some other method such that the value passed 786 [<a name="dt-etag" id="dt-etag" title="End Tag">Definition</a>: The end of every element that begins
787to the application is the same as that produced by the algorithm.</p><ol type="1"><li><p>All line breaks <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> have been normalized on input to #xA as described 787with a start-tag <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be marked by an <b>end-tag</b> containing a name
788in <a href="#sec-line-ends"><b>2.11 End-of-Line Handling</b></a>, so the rest of this algorithm operates 788that echoes the element's type as given in the start-tag:]
789on text normalized in this way.</p></li><li><p>Begin with a normalized value consisting of the empty string.</p></li><li><p>For each character, entity reference, or character reference in the 789 </p> <h5><a name="IDAZIIS" id="IDAZIIS"/>End-tag</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-ETag" id="NT-ETag"/>[42]   </td><td><code>ETag</code></td><td>   ::=   </td><td><code>'&lt;/' <a href="#NT-Name">Name</a>
790unnormalized attribute value, beginning with the first and continuing to the 790 <a href="#NT-S">S</a>?
791last, do the following:</p><ul><li><p>For a character reference, append the referenced character to the 791'&gt;'</code></td></tr></tbody></table><p>An example of an end-tag:</p><div class="exampleInner"><pre>&lt;/termdef&gt;</pre></div><p>
792normalized value.</p></li><li><p>For an entity reference, recursively apply step 3 of this algorithm 792 [<a name="dt-content" id="dt-content" title="Content">Definition</a>: The <a title="Text" href="#dt-text">text</a>
793to the replacement text of the entity.</p></li><li><p>For a white space character (#x20, #xD, #xA, #x9), append a space 793between the start-tag and end-tag is called the element's <b>content</b>:]
794character (#x20) to the normalized value.</p></li><li><p>For another character, append the character to the normalized value.</p></li></ul></li></ol><p>If the attribute type is not CDATA, then the XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> further 794 </p> <h5><a name="IDAHKIS" id="IDAHKIS"/>Content of Elements</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-content" id="NT-content"/>[43]   </td><td><code>content</code></td><td>   ::=   </td><td><code>
795process the normalized attribute value by discarding any leading and trailing 795 <a href="#NT-CharData">CharData</a>? ((<a href="#NT-element">element</a>
796space (#x20) characters, and by replacing sequences of space (#x20) characters 796| <a href="#NT-Reference">Reference</a> | <a href="#NT-CDSect">CDSect</a>
797by a single space (#x20) character.</p><p>Note that if the unnormalized attribute value contains a character reference 797| <a href="#NT-PI">PI</a> | <a href="#NT-Comment">Comment</a>) <a href="#NT-CharData">CharData</a>?)*</code></td></tr></tbody></table><p>
798to a white space character other than space (#x20), the normalized value contains 798 [<a name="dt-empty" id="dt-empty" title="Empty">Definition</a>: An element
799the referenced character itself (#xD, #xA or #x9). This contrasts with the 799with no <a href="#NT-content">content</a> is said to be <b>empty</b>.] The representation
800case where the unnormalized value contains a white space character (not a 800of an empty element is either a start-tag immediately followed by an end-tag,
801reference), which is replaced with a space character (#x20) in the normalized 801or an empty-element tag. [<a name="dt-eetag" id="dt-eetag" title="empty-element tag">Definition</a>: An <b>empty-element
802value and also contrasts with the case where the unnormalized value contains 802tag</b> takes a special form:]
803an entity reference whose replacement text contains a white space character; 803 </p> <h5><a name="IDAMMIS" id="IDAMMIS"/>Tags for Empty Elements</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EmptyElemTag" id="NT-EmptyElemTag"/>[44]   </td><td><code>EmptyElemTag</code></td><td>   ::=   </td><td><code>'&lt;' <a href="#NT-Name">Name</a> (<a href="#NT-S">S</a>
804being recursively processed, the white space character is replaced with a 804 <a href="#NT-Attribute">Attribute</a>)* <a href="#NT-S">S</a>? '/&gt;'</code></td><td><a href="#uniqattspec">[WFC: Unique Att Spec]</a></td></tr></tbody></table><p>Empty-element tags <span>may</span> be used for any element which has no content, whether
805space character (#x20) in the normalized value.</p><p>All attributes for which no declaration has been read <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be treated 805or not it is declared using the keyword <b>EMPTY</b>. <a title="For interoperability" href="#dt-interop">For
806by a non-validating processor as if declared <b>CDATA</b>.</p><p>It 806interoperability</a>, the empty-element tag <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em>
807is an error if an 807be used, and <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> only be used, for elements which are declared
808<span><a title="Attribute Value" href="#dt-attrval">attribute 808EMPTY.</p><p>Examples of empty elements:</p><div class="exampleInner"><pre>&lt;IMG align="left"
809value</a> contains a <a title="Entity Reference" href="#dt-entref">reference</a> to an 809src="http://www.w3.org/Icons/WWW/w3c_home" /&gt;
810entity for which no declaration has been read.</span></p><p>Following are examples of attribute normalization. Given the following 810&lt;br&gt;&lt;/br&gt;
811declarations:</p><div class="exampleInner"><pre>&lt;!ENTITY d "&amp;#xD;"&gt; 811&lt;br/&gt;</pre></div></div><div class="div2"> <h3><a name="elemdecls" id="elemdecls"/>3.2 Element Type Declarations</h3><p>The <a title="Element" href="#dt-element">element</a> structure of an <a title="XML Document" href="#dt-xml-doc">XML document</a> <span>may</span>, for <a title="Validity" href="#dt-valid">validation</a>
812&lt;!ENTITY a "&amp;#xA;"&gt; 812purposes, be constrained using element type and attribute-list declarations.
813&lt;!ENTITY da "&amp;#xD;&amp;#xA;"&gt;</pre></div><p>the attribute specifications in the left column below would be normalized 813An element type declaration constrains the element's <a title="Content" href="#dt-content">content</a>.</p><p>Element type declarations often constrain which element types can appear
814to the character sequences of the middle column if the attribute <code>a</code> 814as <a title="Parent/Child" href="#dt-parentchild">children</a> of the element. At user
815is declared <b>NMTOKENS</b> and to those of the right columns if <code>a</code> 815option, an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> issue a warning when a declaration mentions an
816is declared <b>CDATA</b>.</p><table border="1" frame="border" summary="Attribute normalization summary"><thead><tr><th rowspan="1" colspan="1">Attribute specification</th><th rowspan="1" colspan="1">a is NMTOKENS</th><th rowspan="1" colspan="1">a is CDATA</th></tr></thead><tbody><tr><td rowspan="1" colspan="1"><div class="exampleInner"><pre>a=" 816element type for which no declaration is provided, but this is not an error.</p><p>
817xyz"</pre></div></td><td rowspan="1" colspan="1"><div class="exampleInner"><pre>x y z</pre></div></td><td rowspan="1" colspan="1"><div class="exampleInner"><pre>#x20 #x20 x y z</pre></div></td></tr><tr><td rowspan="1" colspan="1"><div class="exampleInner"><pre>a="&amp;d;&amp;d;A&amp;a;<span>&amp;#x20;</span>&amp;a;B&amp;da;"</pre></div></td><td rowspan="1" colspan="1"><div class="exampleInner"><pre>A #x20 B</pre></div></td><td rowspan="1" colspan="1"><div class="exampleInner"><pre>#x20 #x20 A #x20 <span>#x20</span> #x20 B #x20 #x20</pre></div></td></tr><tr><td rowspan="1" colspan="1"><div class="exampleInner"><pre>a= 817 [<a name="dt-eldecl" id="dt-eldecl" title="Element Type declaration">Definition</a>: An <b>element
818"&amp;#xd;&amp;#xd;A&amp;#xa;&amp;#xa;B&amp;#xd;&amp;#xa;"</pre></div></td><td rowspan="1" colspan="1"><div class="exampleInner"><pre>#xD #xD A #xA #xA B #xD #xA</pre></div></td><td rowspan="1" colspan="1"><div class="exampleInner"><pre>#xD #xD A #xA #xA B #xD #xA</pre></div></td></tr></tbody></table><p>Note that the last example is invalid (but well-formed) if <code>a</code> 818type declaration</b> takes the form:]
819is declared to be of type <b>NMTOKENS</b>.</p></div></div><div class="div2"> <h3><a name="sec-condition-sect" id="sec-condition-sect" />3.4 Conditional Sections</h3><p>[<a name="dt-cond-section" id="dt-cond-section" title="conditional section">Definition</a>: <b>Conditional 819 </p> <h5><a name="IDAYPIS" id="IDAYPIS"/>Element Type Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-elementdecl" id="NT-elementdecl"/>[45]   </td><td><code>elementdecl</code></td><td>   ::=   </td><td><code>'&lt;!ELEMENT' <a href="#NT-S">S</a>
820sections</b> are portions of the <a title="Document Type Declaration" href="#dt-doctype">document type 820 <a href="#NT-Name">Name</a>
821declaration external subset</a> <span>or 821 <a href="#NT-S">S</a>
822of external parameter entities </span>which are included in, or excluded from, 822 <a href="#NT-contentspec">contentspec</a>
823the logical structure of the DTD based on the keyword which governs them.]</p> <h5><a name="IDAMHDU" id="IDAMHDU" />Conditional Section</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-conditionalSect" id="NT-conditionalSect" />[61]   </td><td><code>conditionalSect</code></td><td>   ::=   </td><td><code><a href="#NT-includeSect">includeSect</a> | <a href="#NT-ignoreSect">ignoreSect</a></code></td></tr><tr valign="baseline"><td><a name="NT-includeSect" id="NT-includeSect" />[62]   </td><td><code>includeSect</code></td><td>   ::=   </td><td><code>'&lt;![' S? 'INCLUDE' S? '[' <a href="#NT-extSubsetDecl">extSubsetDecl</a> 823 <a href="#NT-S">S</a>?
824']]&gt;' </code></td><td><a href="#condsec-nesting">[VC: Proper Conditional Section/PE Nesting]</a></td></tr><tr valign="baseline"><td><a name="NT-ignoreSect" id="NT-ignoreSect" />[63]   </td><td><code>ignoreSect</code></td><td>   ::=   </td><td><code>'&lt;![' S? 'IGNORE' S? '[' <a href="#NT-ignoreSectContents">ignoreSectContents</a>* 824'&gt;'</code></td><td><a href="#EDUnique">[VC: Unique Element Type Declaration]</a></td></tr><tr valign="baseline"><td><a name="NT-contentspec" id="NT-contentspec"/>[46]   </td><td><code>contentspec</code></td><td>   ::=   </td><td><code>'EMPTY' | 'ANY' | <a href="#NT-Mixed">Mixed</a>
825']]&gt;'</code></td><td><a href="#condsec-nesting">[VC: Proper Conditional Section/PE Nesting]</a></td></tr><tr valign="baseline"><td><a name="NT-ignoreSectContents" id="NT-ignoreSectContents" />[64]   </td><td><code>ignoreSectContents</code></td><td>   ::=   </td><td><code><a href="#NT-Ignore">Ignore</a> ('&lt;![' <a href="#NT-ignoreSectContents">ignoreSectContents</a> ']]&gt;' <a href="#NT-Ignore">Ignore</a>)*</code></td></tr><tr valign="baseline"><td><a name="NT-Ignore" id="NT-Ignore" />[65]   </td><td><code>Ignore</code></td><td>   ::=   </td><td><code><a href="#NT-Char">Char</a>* - (<a href="#NT-Char">Char</a>* 825| <a href="#NT-children">children</a>
826('&lt;![' | ']]&gt;') <a href="#NT-Char">Char</a>*) </code></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="condsec-nesting" id="condsec-nesting" /><b>Validity constraint: Proper Conditional Section/PE Nesting</b></p><p>If any of the "<code>&lt;![</code>", 826 </code></td></tr></tbody></table><p>where the <a href="#NT-Name">Name</a> gives the element type being declared.</p><div class="constraint"><p class="prefix"><a name="EDUnique" id="EDUnique"/><b>Validity constraint: Unique Element Type Declaration</b></p><p>An element type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be declared more than once.</p></div><p>Examples of element type declarations:</p><div class="exampleInner"><pre>&lt;!ELEMENT br EMPTY&gt;
827"<code>[</code>", or "<code>]]&gt;</code>" of a conditional section is contained 827&lt;!ELEMENT p (#PCDATA|emph)* &gt;
828in the replacement text for a parameter-entity reference, all of them <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> 828&lt;!ELEMENT %name.para; %content.para; &gt;
829be contained in the same replacement text.</p></div><p>Like the internal and external DTD subsets, a conditional section may contain 829&lt;!ELEMENT container ANY&gt;</pre></div><div class="div3"> <h4><a name="sec-element-content" id="sec-element-content"/>3.2.1 Element Content</h4><p>
830one or more complete declarations, comments, processing instructions, or nested 830 [<a name="dt-elemcontent" id="dt-elemcontent" title="Element content">Definition</a>: An element <a title="Start-Tag" href="#dt-stag">type</a> has <b>element content</b> when elements
831conditional sections, intermingled with white space.</p><p>If the keyword of the conditional section is <b>INCLUDE</b>, then the 831of that type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> contain only <a title="Parent/Child" href="#dt-parentchild">child</a>
832contents of the conditional section <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be considered</span> part of the DTD. If the keyword of 832elements (no character data), optionally separated by white space (characters
833the conditional section is <b>IGNORE</b>, then the contents of the conditional 833matching the nonterminal <a href="#NT-S">S</a>).]
834section <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be considered as</span> not logically part of the DTD. 834 [<a name="dt-content-model" id="dt-content-model" title="Content model">Definition</a>: In this case, the constraint includes a <b>content
835If a conditional section with a keyword of <b>INCLUDE</b> occurs within 835model</b>, a simple grammar governing the allowed types of the
836a larger conditional section with a keyword of <b>IGNORE</b>, both the outer 836child elements and the order in which they are allowed to appear.]
837and the inner conditional sections <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be</span> ignored. The contents 837The grammar is built on content particles (<a href="#NT-cp">cp</a>s), which
838of an ignored conditional section <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be</span> parsed by ignoring all characters after 838consist of names, choice lists of content particles, or sequence lists of
839the "<code>[</code>" following the keyword, except conditional section starts 839content particles:</p> <h5><a name="IDATTIS" id="IDATTIS"/>Element-content Models</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-children" id="NT-children"/>[47]   </td><td><code>children</code></td><td>   ::=   </td><td><code>(<a href="#NT-choice">choice</a> | <a href="#NT-seq">seq</a>)
840"<code>&lt;![</code>" and ends "<code>]]&gt;</code>", until the matching conditional 840('?' | '*' | '+')?</code></td></tr><tr valign="baseline"><td><a name="NT-cp" id="NT-cp"/>[48]   </td><td><code>cp</code></td><td>   ::=   </td><td><code>(<a href="#NT-Name">Name</a> | <a href="#NT-choice">choice</a>
841section end is found. Parameter entity references <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be</span> recognized in this 841| <a href="#NT-seq">seq</a>) ('?' | '*' | '+')?</code></td></tr><tr valign="baseline"><td><a name="NT-choice" id="NT-choice"/>[49]   </td><td><code>choice</code></td><td>   ::=   </td><td><code>'(' <a href="#NT-S">S</a>? <a href="#NT-cp">cp</a> ( <a href="#NT-S">S</a>? '|' <a href="#NT-S">S</a>? <a href="#NT-cp">cp</a> )+ <a href="#NT-S">S</a>? ')'</code></td><td><a href="#vc-PEinGroup">[VC: Proper Group/PE Nesting]</a></td></tr><tr valign="baseline"><td><a name="NT-seq" id="NT-seq"/>[50]   </td><td><code>seq</code></td><td>   ::=   </td><td><code>'(' <a href="#NT-S">S</a>? <a href="#NT-cp">cp</a> ( <a href="#NT-S">S</a>? ',' <a href="#NT-S">S</a>? <a href="#NT-cp">cp</a> )* <a href="#NT-S">S</a>? ')'</code></td><td><a href="#vc-PEinGroup">[VC: Proper Group/PE Nesting]</a></td></tr></tbody></table><p>where each <a href="#NT-Name">Name</a> is the type of an element which
842process.</p><p>If the keyword of the conditional section is a parameter-entity reference, 842<span>may</span> appear as a <a title="Parent/Child" href="#dt-parentchild">child</a>. Any content
843the parameter entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be replaced by its content before the processor 843particle in a choice list <span>may</span> appear in the <a title="Element content" href="#dt-elemcontent">element
844decides whether to include or ignore the conditional section.</p><p>An example:</p><div class="exampleInner"><pre>&lt;!ENTITY % draft 'INCLUDE' &gt; 844content</a> at the location where the choice list appears in the grammar;
845&lt;!ENTITY % final 'IGNORE' &gt; 845content particles occurring in a sequence list <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> each appear in the <a title="Element content" href="#dt-elemcontent">element content</a> in the order given in the list.
846&lt;![%draft;[ 846The optional character following a name or list governs whether the element
847&lt;!ELEMENT book (comments*, title, body, supplements?)&gt; 847or the content particles in the list may occur one or more (<code>+</code>),
848]]&gt; 848zero or more (<code>*</code>), or zero or one times (<code>?</code>). The
849&lt;![%final;[ 849absence of such an operator means that the element or content particle <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
850&lt;!ELEMENT book (title, body, supplements?)&gt; 850appear exactly once. This syntax and meaning are identical to those used in
851]]&gt;</pre></div></div></div><div class="div1"> <h2><a name="sec-physical-struct" id="sec-physical-struct" />4 Physical Structures</h2><p>[<a name="dt-entity" id="dt-entity" title="Entity">Definition</a>: An XML document may consist of one 851the productions in this specification.</p><p>The content of an element matches a content model if and only if it is
852or many storage units. These 852possible to trace out a path through the content model, obeying the sequence,
853are called <b>entities</b>; they all have <b>content</b> and are 853choice, and repetition operators and matching each element in the content
854all (except for the <a title="Document Entity" href="#dt-docent">document entity</a> and 854against an element type in the content model. <a title="For Compatibility" href="#dt-compat">For
855the <a title="Document Type Declaration" href="#dt-doctype">external DTD subset</a>) identified by 855compatibility</a>, it is an error if the content model
856entity <b>name</b>.] Each XML document has one entity 856allows an element to match more than one occurrence of an element type in the
857called the <a title="Document Entity" href="#dt-docent">document entity</a>, which serves 857content model. For more information, see <a href="#determinism"><b>D Deterministic Content Models</b></a>.</p><div class="constraint"><p class="prefix"><a name="vc-PEinGroup" id="vc-PEinGroup"/><b>Validity constraint: Proper Group/PE Nesting</b></p><p>Parameter-entity <a title="Replacement Text" href="#dt-repltext">replacement text</a>
858as the starting point for the <a title="XML Processor" href="#dt-xml-proc">XML processor</a> 858 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be properly nested with parenthesized
859and may contain the whole document.</p><p>Entities may be either parsed or unparsed. [<a name="dt-parsedent" id="dt-parsedent" title="Text Entity">Definition</a>: The contents of a <b>parsed 859groups. That is to say, if either of the opening or closing parentheses in
860entity</b> are referred to as its <a title="Replacement Text" href="#dt-repltext">replacement 860a <a href="#NT-choice">choice</a>, <a href="#NT-seq">seq</a>, or <a href="#NT-Mixed">Mixed</a>
861text</a>; this <a title="Text" href="#dt-text">text</a> is considered an 861construct is contained in the replacement text for a <a title="Parameter-entity reference" href="#dt-PERef">parameter
862integral part of the document.]</p><p>[<a name="dt-unparsed" id="dt-unparsed" title="Unparsed Entity">Definition</a>: An <b>unparsed entity</b> 862entity</a>, both <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be contained in the same replacement text.</p><p>
863is a resource whose contents may or may not be <a title="Text" href="#dt-text">text</a>, 863 <a title="For interoperability" href="#dt-interop">For interoperability</a>, if a parameter-entity reference
864and if text, may 864appears in a <a href="#NT-choice">choice</a>, <a href="#NT-seq">seq</a>, or <a href="#NT-Mixed">Mixed</a> construct, its replacement text <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> contain at
865be other than XML. Each unparsed entity has an associated <a title="Notation" href="#dt-notation">notation</a>, identified by name. Beyond a requirement 865least one non-blank character, and neither the first nor last non-blank character
866that an XML processor make the identifiers for the entity and notation available 866of the replacement text <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be a connector (<code>|</code> or <code>,</code>).</p></div><p>Examples of element-content models:</p><div class="exampleInner"><pre>&lt;!ELEMENT spec (front, body, back?)&gt;
867to the application, XML places no constraints on the contents of unparsed 867&lt;!ELEMENT div1 (head, (p | list | note)*, div2*)&gt;
868entities.]</p><p>Parsed entities are invoked by name using entity references; unparsed entities 868&lt;!ELEMENT dictionary-body (%div.mix; | %dict.mix;)*&gt;</pre></div></div><div class="div3"> <h4><a name="sec-mixed-content" id="sec-mixed-content"/>3.2.2 Mixed Content</h4><p>
869by name, given in the value of <b>ENTITY</b> or <b>ENTITIES</b> attributes.</p><p>[<a name="gen-entity" id="gen-entity" title="general entity">Definition</a>: <b>General entities</b> 869 [<a name="dt-mixed" id="dt-mixed" title="Mixed Content">Definition</a>: An element <a title="Start-Tag" href="#dt-stag">type</a>
870are entities for use within the document content. In this specification, general 870has <b>mixed content</b> when elements of that type <span>may</span> contain character
871entities are sometimes referred to with the unqualified term <em>entity</em> 871data, optionally interspersed with <a title="Parent/Child" href="#dt-parentchild">child</a>
872when this leads to no ambiguity.] [<a name="dt-PE" id="dt-PE" title="Parameter entity">Definition</a>: <b>Parameter 872elements.] In this case, the types of the child elements <span>may</span> be constrained,
873entities</b> are parsed entities for use within the DTD.] 873but not their order or their number of occurrences:</p> <h5><a name="IDAC2IS" id="IDAC2IS"/>Mixed-content Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-Mixed" id="NT-Mixed"/>[51]   </td><td><code>Mixed</code></td><td>   ::=   </td><td><code>'(' <a href="#NT-S">S</a>? '#PCDATA' (<a href="#NT-S">S</a>?
874These two types of entities use different forms of reference and are recognized 874'|' <a href="#NT-S">S</a>? <a href="#NT-Name">Name</a>)* <a href="#NT-S">S</a>?
875in different contexts. Furthermore, they occupy different namespaces; a parameter 875')*' </code></td></tr><tr valign="baseline"><td/><td/><td/><td><code>| '(' <a href="#NT-S">S</a>? '#PCDATA' <a href="#NT-S">S</a>? ')' </code></td><td><a href="#vc-PEinGroup">[VC: Proper Group/PE Nesting]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#vc-MixedChildrenUnique">[VC: No Duplicate Types]</a></td></tr></tbody></table><p>where the <a href="#NT-Name">Name</a>s give the types of elements that
876entity and a general entity with the same name are two distinct entities.</p><div class="div2"> <h3><a name="sec-references" id="sec-references" />4.1 Character and Entity References</h3><p>[<a name="dt-charref" id="dt-charref" title="Character Reference">Definition</a>: A <b>character 876may appear as children. The
877reference</b> refers to a specific character in the ISO/IEC 10646 character 877keyword <b>#PCDATA</b> derives historically from the term "parsed
878set, for example one not directly accessible from available input devices.]</p> <h5><a name="IDAFYDU" id="IDAFYDU" />Character Reference</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-CharRef" id="NT-CharRef" />[66]   </td><td><code>CharRef</code></td><td>   ::=   </td><td><code>'&amp;#' [0-9]+ ';' </code></td></tr><tr valign="baseline"><td /><td /><td /><td><code>| '&amp;#x' [0-9a-fA-F]+ ';'</code></td><td><a href="#wf-Legalchar">[WFC: Legal Character]</a></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="wf-Legalchar" id="wf-Legalchar" /><b>Well-formedness constraint: Legal Character</b></p><p>Characters referred 878character data."
879to using character references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the production for <a href="#NT-Char">Char</a>.</p></div><p>If the character reference begins with "<code>&amp;#x</code>", 879 </p><div class="constraint"><p class="prefix"><a name="vc-MixedChildrenUnique" id="vc-MixedChildrenUnique"/><b>Validity constraint: No Duplicate Types</b></p><p>The
880the digits and letters up to the terminating <code>;</code> provide a hexadecimal 880same name <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear more than once in a single mixed-content declaration.</p></div><p>Examples of mixed content declarations:</p><div class="exampleInner"><pre>&lt;!ELEMENT p (#PCDATA|a|ul|b|i|em)*&gt;
881representation of the character's code point in ISO/IEC 10646. If it begins 881&lt;!ELEMENT p (#PCDATA | %font; | %phrase; | %special; | %form;)* &gt;
882just with "<code>&amp;#</code>", the digits up to the terminating <code>;</code> 882&lt;!ELEMENT b (#PCDATA)&gt;</pre></div></div></div><div class="div2"> <h3><a name="attdecls" id="attdecls"/>3.3 Attribute-List Declarations</h3><p>
883provide a decimal representation of the character's code point.</p><p>[<a name="dt-entref" id="dt-entref" title="Entity Reference">Definition</a>: An <b>entity reference</b> 883 <a title="Attribute" href="#dt-attr">Attributes</a> are used to associate name-value
884refers to the content of a named entity.] [<a name="dt-GERef" id="dt-GERef" title="General Entity Reference">Definition</a>: References to parsed general entities use 884pairs with <a title="Element" href="#dt-element">elements</a>. Attribute specifications
885ampersand (<code>&amp;</code>) and semicolon (<code>;</code>) as delimiters.] [<a name="dt-PERef" id="dt-PERef" title="Parameter-entity reference">Definition</a>: <b>Parameter-entity references</b> 885<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear outside of <a title="Start-Tag" href="#dt-stag">start-tags</a> and <a title="empty-element tag" href="#dt-eetag">empty-element tags</a>; thus, the productions used to
886use percent-sign (<code>%</code>) and semicolon (<code>;</code>) as delimiters.]</p> <h5><a name="IDAS0DU" id="IDAS0DU" />Entity Reference</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-Reference" id="NT-Reference" />[67]   </td><td><code>Reference</code></td><td>   ::=   </td><td><code><a href="#NT-EntityRef">EntityRef</a> | <a href="#NT-CharRef">CharRef</a></code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-EntityRef" id="NT-EntityRef" />[68]   </td><td><code>EntityRef</code></td><td>   ::=   </td><td><code>'&amp;' <a href="#NT-Name">Name</a> ';'</code></td><td><a href="#wf-entdeclared">[WFC: Entity Declared]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#vc-entdeclared">[VC: Entity Declared]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#textent">[WFC: Parsed Entity]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#norecursion">[WFC: No Recursion]</a></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PEReference" id="NT-PEReference" />[69]   </td><td><code>PEReference</code></td><td>   ::=   </td><td><code>'%' <a href="#NT-Name">Name</a> ';'</code></td><td><a href="#vc-entdeclared">[VC: Entity Declared]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#norecursion">[WFC: No Recursion]</a></td></tr><tr valign="baseline"><td /><td /><td /><td /><td><a href="#indtd">[WFC: In DTD]</a></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="wf-entdeclared" id="wf-entdeclared" /><b>Well-formedness constraint: Entity Declared</b></p><p>In a document 886recognize them appear in <a href="#sec-starttags"><b>3.1 Start-Tags, End-Tags, and Empty-Element Tags</b></a>. Attribute-list declarations
887without any DTD, a document with only an internal DTD subset which contains 887<span>may</span> be used:</p><ul><li><p>To define the set of attributes pertaining to a given element type.</p></li><li><p>To establish type constraints for these attributes.</p></li><li><p>To provide <a title="Attribute Default" href="#dt-default">default values</a> for
888no parameter entity references, or a document with "<code>standalone='yes'</code>", for 888attributes.</p></li></ul><p>
889an entity reference that does not occur within the external subset or a parameter 889 [<a name="dt-attdecl" id="dt-attdecl" title="Attribute-List Declaration">Definition</a>:
890entity, the <a href="#NT-Name">Name</a> given in the entity reference <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> <a title="match" href="#dt-match">match</a> that in an <a href="#sec-entity-decl"><cite>entity 890 <b>Attribute-list
891declaration</cite></a> that does not occur within the external subset or a 891declarations</b> specify the name, data type, and default value (if any)
892parameter entity, except that well-formed documents need not declare 892of each attribute associated with a given element type:]
893any of the following entities: <code>amp</code>, 893 </p> <h5><a name="IDAUAJS" id="IDAUAJS"/>Attribute-list Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-AttlistDecl" id="NT-AttlistDecl"/>[52]   </td><td><code>AttlistDecl</code></td><td>   ::=   </td><td><code>'&lt;!ATTLIST' <a href="#NT-S">S</a>
894<code>lt</code>, 894 <a href="#NT-Name">Name</a>
895<code>gt</code>, 895 <a href="#NT-AttDef">AttDef</a>* <a href="#NT-S">S</a>? '&gt;'</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-AttDef" id="NT-AttDef"/>[53]   </td><td><code>AttDef</code></td><td>   ::=   </td><td><code>
896<code>apos</code>, 896 <a href="#NT-S">S</a>
897<code>quot</code>. The 897 <a href="#NT-Name">Name</a>
898declaration of a general entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> precede any reference to it which appears 898 <a href="#NT-S">S</a>
899in a default value in an attribute-list declaration.</p><p><span>Note 899 <a href="#NT-AttType">AttType</a>
900that non-validating processors are <a href="#include-if-valid"><cite>not 900 <a href="#NT-S">S</a>
901obligated to</cite></a> to read and process entity declarations occurring in parameter entities or in 901 <a href="#NT-DefaultDecl">DefaultDecl</a>
902the external subset</span>; for such documents, 902 </code></td></tr></tbody></table><p>The <a href="#NT-Name">Name</a> in the <a href="#NT-AttlistDecl">AttlistDecl</a>
903the rule that an entity must be declared is a well-formedness constraint only 903rule is the type of an element. At user option, an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> issue
904if <a href="#sec-rmd"><cite>standalone='yes'</cite></a>.</p></div><div class="constraint"><p class="prefix"><a name="vc-entdeclared" id="vc-entdeclared" /><b>Validity constraint: Entity Declared</b></p><p>In a document with 904a warning if attributes are declared for an element type not itself declared,
905an external subset or external parameter entities with "<code>standalone='no'</code>", 905but this is not an error. The <a href="#NT-Name">Name</a> in the <a href="#NT-AttDef">AttDef</a>
906the <a href="#NT-Name">Name</a> given in the entity reference <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> <a title="match" href="#dt-match">match</a> that in an <a href="#sec-entity-decl"><cite>entity 906rule is the name of the attribute.</p><p>When more than one <a href="#NT-AttlistDecl">AttlistDecl</a> is provided
907declaration</cite></a>. For interoperability, valid documents <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> declare 907for a given element type, the contents of all those provided are merged. When
908the entities <code>amp</code>, 908more than one definition is provided for the same attribute of a given element
909<code>lt</code>, 909type, the first declaration is binding and later declarations are ignored. <a title="For interoperability" href="#dt-interop">For interoperability,</a> writers of DTDs <span>may</span> choose
910<code>gt</code>, 910to provide at most one attribute-list declaration for a given element type,
911<code>apos</code>, 911at most one attribute definition for a given attribute name in an attribute-list
912<code>quot</code>, in the form specified in <a href="#sec-predefined-ent"><b>4.6 Predefined Entities</b></a>. 912declaration, and at least one attribute definition in each attribute-list
913The declaration of a parameter entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> precede any reference to it. Similarly, 913declaration. For interoperability, an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> at user option
914the declaration of a general entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> precede any attribute-list 914issue a warning when more than one attribute-list declaration is provided
915declaration containing a default value with a direct or indirect reference 915for a given element type, or more than one attribute definition is provided
916to that general entity.</p></div><div class="constraint"><p class="prefix"><a name="textent" id="textent" /><b>Well-formedness constraint: Parsed Entity</b></p><p>An entity reference <em class="rfc2119" title="Keyword in RFC 2119 context">MUST 916for a given attribute, but this is not an error.</p><div class="div3"> <h4><a name="sec-attribute-types" id="sec-attribute-types"/>3.3.1 Attribute Types</h4><p>XML attribute types are of three kinds: a string type, a set of tokenized
917NOT</em> contain the name of an <a title="Unparsed Entity" href="#dt-unparsed">unparsed entity</a>. 917types, and enumerated types. The string type may take any literal string as
918Unparsed entities may be referred to only in <a title="Attribute Value" href="#dt-attrval">attribute 918a value; the tokenized types
919values</a> declared to be of type <b>ENTITY</b> or <b>ENTITIES</b>.</p></div><div class="constraint"><p class="prefix"><a name="norecursion" id="norecursion" /><b>Well-formedness constraint: No Recursion</b></p><p>A parsed entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> contain a recursive reference to itself, either directly or indirectly.</p></div><div class="constraint"><p class="prefix"><a name="indtd" id="indtd" /><b>Well-formedness constraint: In DTD</b></p><p>Parameter-entity references <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear outside</span> 919 <span>
920the <a title="Document Type Declaration" href="#dt-doctype">DTD</a>.</p></div><p>Examples of character and entity references:</p><div class="exampleInner"><pre>Type &lt;key&gt;less-than&lt;/key&gt; (&amp;#x3C;) to save options. 920 are more constrained</span>.
921This document was prepared on &amp;docdate; and 921The validity constraints noted in the grammar are applied after the attribute
922is classified &amp;security-level;.</pre></div><p>Example of a parameter-entity reference:</p><div class="exampleInner"><pre>&lt;!-- declare the parameter entity "ISOLat2"... --&gt; 922value has been normalized as described in <a href="#AVNormalize"><b>3.3.3 Attribute-Value Normalization</b></a>.</p> <h5><a name="IDAVEJS" id="IDAVEJS"/>Attribute Types</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-AttType" id="NT-AttType"/>[54]   </td><td><code>AttType</code></td><td>   ::=   </td><td><code>
923&lt;!ENTITY % ISOLat2 923 <a href="#NT-StringType">StringType</a> | <a href="#NT-TokenizedType">TokenizedType</a>
924SYSTEM "http://www.xml.com/iso/isolat2-xml.entities" &gt; 924| <a href="#NT-EnumeratedType">EnumeratedType</a>
925&lt;!-- ... now reference it. --&gt; 925 </code></td></tr><tr valign="baseline"><td><a name="NT-StringType" id="NT-StringType"/>[55]   </td><td><code>StringType</code></td><td>   ::=   </td><td><code>'CDATA'</code></td></tr><tr valign="baseline"><td><a name="NT-TokenizedType" id="NT-TokenizedType"/>[56]   </td><td><code>TokenizedType</code></td><td>   ::=   </td><td><code>'ID'</code></td><td><a href="#id">[VC: ID]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#one-id-per-el">[VC: One ID per Element Type]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#id-default">[VC: ID Attribute Default]</a></td></tr><tr valign="baseline"><td/><td/><td/><td><code>| 'IDREF'</code></td><td><a href="#idref">[VC: IDREF]</a></td></tr><tr valign="baseline"><td/><td/><td/><td><code>| 'IDREFS'</code></td><td><a href="#idref">[VC: IDREF]</a></td></tr><tr valign="baseline"><td/><td/><td/><td><code>| 'ENTITY'</code></td><td><a href="#entname">[VC: Entity Name]</a></td></tr><tr valign="baseline"><td/><td/><td/><td><code>| 'ENTITIES'</code></td><td><a href="#entname">[VC: Entity Name]</a></td></tr><tr valign="baseline"><td/><td/><td/><td><code>| 'NMTOKEN'</code></td><td><a href="#nmtok">[VC: Name Token]</a></td></tr><tr valign="baseline"><td/><td/><td/><td><code>| 'NMTOKENS'</code></td><td><a href="#nmtok">[VC: Name Token]</a></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="id" id="id"/><b>Validity constraint: ID</b></p><p>Values of type <b>ID</b>
926%ISOLat2;</pre></div></div><div class="div2"> <h3><a name="sec-entity-decl" id="sec-entity-decl" />4.2 Entity Declarations</h3><p>[<a name="dt-entdecl" id="dt-entdecl" title="entity declaration">Definition</a>: Entities are declared 926 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the <a href="#NT-Name">Name</a> production. A name <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear more than once
927thus:]</p> <h5><a name="IDAECEU" id="IDAECEU" />Entity Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EntityDecl" id="NT-EntityDecl" />[70]   </td><td><code>EntityDecl</code></td><td>   ::=   </td><td><code><a href="#NT-GEDecl">GEDecl</a> | <a href="#NT-PEDecl">PEDecl</a></code></td></tr><tr valign="baseline"><td><a name="NT-GEDecl" id="NT-GEDecl" />[71]   </td><td><code>GEDecl</code></td><td>   ::=   </td><td><code>'&lt;!ENTITY' <a href="#NT-S">S</a> <a href="#NT-Name">Name</a> <a href="#NT-S">S</a> <a href="#NT-EntityDef">EntityDef</a> <a href="#NT-S">S</a>? 927in an XML document as a value of this type; i.e., ID values <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> uniquely
928'&gt;'</code></td></tr><tr valign="baseline"><td><a name="NT-PEDecl" id="NT-PEDecl" />[72]   </td><td><code>PEDecl</code></td><td>   ::=   </td><td><code>'&lt;!ENTITY' <a href="#NT-S">S</a> '%' <a href="#NT-S">S</a> <a href="#NT-Name">Name</a> <a href="#NT-S">S</a> <a href="#NT-PEDef">PEDef</a> <a href="#NT-S">S</a>? '&gt;'</code></td></tr><tr valign="baseline"><td><a name="NT-EntityDef" id="NT-EntityDef" />[73]   </td><td><code>EntityDef</code></td><td>   ::=   </td><td><code><a href="#NT-EntityValue">EntityValue</a>| (<a href="#NT-ExternalID">ExternalID</a> <a href="#NT-NDataDecl">NDataDecl</a>?)</code></td></tr><tr valign="baseline"><td><a name="NT-PEDef" id="NT-PEDef" />[74]   </td><td><code>PEDef</code></td><td>   ::=   </td><td><code><a href="#NT-EntityValue">EntityValue</a> | <a href="#NT-ExternalID">ExternalID</a></code></td></tr></tbody></table><p>The <a href="#NT-Name">Name</a> identifies the entity in an <a title="Entity Reference" href="#dt-entref">entity 928identify the elements which bear them.</p></div><div class="constraint"><p class="prefix"><a name="one-id-per-el" id="one-id-per-el"/><b>Validity constraint: One ID per Element Type</b></p><p>An element type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> have more than one ID attribute specified.</p></div><div class="constraint"><p class="prefix"><a name="id-default" id="id-default"/><b>Validity constraint: ID Attribute Default</b></p><p>An ID attribute
929reference</a> or, in the case of an unparsed entity, in the value of 929<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> have a declared default of <b>#IMPLIED</b> or <b>#REQUIRED</b>.</p></div><div class="constraint"><p class="prefix"><a name="idref" id="idref"/><b>Validity constraint: IDREF</b></p><p>Values of type <b>IDREF</b>
930an <b>ENTITY</b> or <b>ENTITIES</b> attribute. If the same entity is declared 930 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
931more than once, the first declaration encountered is binding; at user option, 931match the <a href="#NT-Name">Name</a> production, and values of type <b>IDREFS</b>
932an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> issue a warning if entities are declared multiple times.</p><div class="div3"> <h4><a name="sec-internal-ent" id="sec-internal-ent" />4.2.1 Internal Entities</h4><p>[<a name="dt-internent" id="dt-internent" title="Internal Entity Replacement Text">Definition</a>: If the 932 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match <a href="#NT-Names">Names</a>; each <a href="#NT-Name">Name</a>
933entity definition is an <a href="#NT-EntityValue">EntityValue</a>, the defined 933 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the value of an ID attribute on some element in the XML document;
934entity is called an <b>internal entity</b>. There is no separate physical 934i.e. <b>IDREF</b> values <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the value of some ID attribute.</p></div><div class="constraint"><p class="prefix"><a name="entname" id="entname"/><b>Validity constraint: Entity Name</b></p><p>Values of type <b>ENTITY</b>
935storage object, and the content of the entity is given in the declaration.] 935 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the <a href="#NT-Name">Name</a> production, values of type <b>ENTITIES</b>
936Note that some processing of entity and character references in the <a title="Literal Entity Value" href="#dt-litentval">literal entity value</a> may be required to produce 936 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match <a href="#NT-Names">Names</a>; each <a href="#NT-Name">Name</a>
937the correct <a title="Replacement Text" href="#dt-repltext">replacement text</a>: see <a href="#intern-replacement"><b>4.5 Construction of Entity Replacement Text</b></a>.</p><p>An internal entity is a <a title="Text Entity" href="#dt-parsedent">parsed entity</a>.</p><p>Example of an internal entity declaration:</p><div class="exampleInner"><pre>&lt;!ENTITY Pub-Status "This is a pre-release of the 937 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the name of an <a title="Unparsed Entity" href="#dt-unparsed">unparsed entity</a>
938specification."&gt;</pre></div></div><div class="div3"> <h4><a name="sec-external-ent" id="sec-external-ent" />4.2.2 External Entities</h4><p>[<a name="dt-extent" id="dt-extent" title="External Entity">Definition</a>: If the entity is not internal, 938declared in the <a title="Document Type Declaration" href="#dt-doctype">DTD</a>.</p></div><div class="constraint"><p class="prefix"><a name="nmtok" id="nmtok"/><b>Validity constraint: Name Token</b></p><p>Values of type <b>NMTOKEN</b>
939it is an <b>external entity</b>, declared as follows:]</p> <h5><a name="IDAUIEU" id="IDAUIEU" />External Entity Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-ExternalID" id="NT-ExternalID" />[75]   </td><td><code>ExternalID</code></td><td>   ::=   </td><td><code>'SYSTEM' <a href="#NT-S">S</a> <a href="#NT-SystemLiteral">SystemLiteral</a></code></td></tr><tr valign="baseline"><td /><td /><td /><td><code>| 'PUBLIC' <a href="#NT-S">S</a> <a href="#NT-PubidLiteral">PubidLiteral</a> <a href="#NT-S">S</a> <a href="#NT-SystemLiteral">SystemLiteral</a></code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-NDataDecl" id="NT-NDataDecl" />[76]   </td><td><code>NDataDecl</code></td><td>   ::=   </td><td><code><a href="#NT-S">S</a> 'NDATA' <a href="#NT-S">S</a> <a href="#NT-Name">Name</a></code></td><td><a href="#not-declared">[VC: Notation Declared]</a></td></tr></tbody></table><p>If the <a href="#NT-NDataDecl">NDataDecl</a> is present, this is a general <a title="Unparsed Entity" href="#dt-unparsed">unparsed entity</a>; otherwise it is a parsed entity.</p><div class="constraint"><p class="prefix"><a name="not-declared" id="not-declared" /><b>Validity constraint: Notation Declared</b></p><p>The <a href="#NT-Name">Name</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the declared name of a <a title="Notation" href="#dt-notation">notation</a>.</p></div><p>[<a name="dt-sysid" id="dt-sysid" title="System Identifier">Definition</a>: The <a href="#NT-SystemLiteral">SystemLiteral</a> is called the entity's <b>system 939 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the <a href="#NT-Nmtoken">Nmtoken</a> production; values of type <b>NMTOKENS</b>
940identifier</b>. It is <span>meant to be 940 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match <a href="#NT-Nmtokens">Nmtokens</a>.</p></div><p>
941converted to</span> a URI reference 941 [<a name="dt-enumerated" id="dt-enumerated" title="Enumerated Attribute&#xA;Values">Definition</a>:
942(as defined in <a href="#rfc2396">[IETF RFC 2396]</a>, updated by <a href="#rfc2732">[IETF RFC 2732]</a>), 942 <b>Enumerated attributes</b>
943<span>as part of the 943
944process of dereferencing it</span> to obtain input for the XML processor to construct the 944 <span>have a list of allowed
945entity's replacement text.] It is an error for a fragment identifier 945values in their declaration</span>
946(beginning with a <code>#</code> character) to be part of a system identifier. 946 ]. <span>They <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> take one of those values. </span>There are two kinds of enumerated<span> attribute</span> types:</p> <h5><a name="IDAANJS" id="IDAANJS"/>Enumerated Attribute Types</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EnumeratedType" id="NT-EnumeratedType"/>[57]   </td><td><code>EnumeratedType</code></td><td>   ::=   </td><td><code>
947Unless otherwise provided by information outside the scope of this specification 947 <a href="#NT-NotationType">NotationType</a>
948(e.g. a special XML element type defined by a particular DTD, or a processing 948| <a href="#NT-Enumeration">Enumeration</a>
949instruction defined by a particular application specification), relative URIs 949 </code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-NotationType" id="NT-NotationType"/>[58]   </td><td><code>NotationType</code></td><td>   ::=   </td><td><code>'NOTATION' <a href="#NT-S">S</a> '(' <a href="#NT-S">S</a>? <a href="#NT-Name">Name</a> (<a href="#NT-S">S</a>? '|' <a href="#NT-S">S</a>? <a href="#NT-Name">Name</a>)* <a href="#NT-S">S</a>? ')' </code></td><td><a href="#notatn">[VC: Notation Attributes]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#OneNotationPer">[VC: One Notation Per Element Type]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#NoNotationEmpty">[VC: No Notation on Empty Element]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#NoDuplicateTokens">[VC: No Duplicate
950are relative to the location of the resource within which the entity declaration 950Tokens]</a></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Enumeration" id="NT-Enumeration"/>[59]   </td><td><code>Enumeration</code></td><td>   ::=   </td><td><code>'(' <a href="#NT-S">S</a>? <a href="#NT-Nmtoken">Nmtoken</a>
951occurs. <span>This is defined to 951(<a href="#NT-S">S</a>? '|' <a href="#NT-S">S</a>? <a href="#NT-Nmtoken">Nmtoken</a>)* <a href="#NT-S">S</a>? ')'</code></td><td><a href="#enum">[VC: Enumeration]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#NoDuplicateTokens">[VC: No Duplicate
952be the external entity containing the '&lt;' which starts the declaration, at the 952Tokens]</a></td></tr></tbody></table><p>A <b>NOTATION</b> attribute identifies a <a title="Notation" href="#dt-notation">notation</a>,
953point when it is parsed as a declaration.</span> 953declared in the DTD with associated system and/or public identifiers, to be
954A URI might thus be relative to the <a title="Document Entity" href="#dt-docent">document 954used in interpreting the element to which the attribute is attached.</p><div class="constraint"><p class="prefix"><a name="notatn" id="notatn"/><b>Validity constraint: Notation Attributes</b></p><p>Values of this type
955entity</a>, to the entity containing the <a title="Document Type Declaration" href="#dt-doctype">external 955<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match one of the <a href="#Notations"><cite>notation</cite></a> names
956DTD subset</a>, or to some other <a title="External Entity" href="#dt-extent">external parameter 956included in the declaration; all notation names in the declaration <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be
957entity</a>. <span>Attempts to 957declared.</p></div><div class="constraint"><p class="prefix"><a name="OneNotationPer" id="OneNotationPer"/><b>Validity constraint: One Notation Per Element Type</b></p><p>An element type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> have more than one <b>NOTATION</b>
958retrieve the resource identified by a URI <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be redirected at the parser 958attribute specified.</p></div><div class="constraint"><p class="prefix"><a name="NoNotationEmpty" id="NoNotationEmpty"/><b>Validity constraint: No Notation on Empty Element</b></p><p>
959level (for example, in an entity resolver) or below (at the protocol level, 959 <a title="For Compatibility" href="#dt-compat">For compatibility</a>,
960for example, via an HTTP <code>Location:</code> header). In the absence of additional 960an attribute of type <b>NOTATION</b>
961information outside the scope of this specification within the resource, 961 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be declared on an element
962the base URI of a resource is always the URI of the actual resource returned. 962declared <b>EMPTY</b>.</p></div><div class="constraint"><p class="prefix"><a name="NoDuplicateTokens" id="NoDuplicateTokens"/><b>Validity constraint: No Duplicate
963In other words, it is the URI of the resource retrieved after all redirection 963Tokens</b></p><p>The notation names in a single <a href="#NT-NotationType">NotationType</a>
964has occurred.</span></p><p>System 964attribute declaration, as well as the <a href="#NT-Nmtoken">NmToken</a>s in a single
965identifiers (and other XML strings meant to be used as URI references) <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> contain 965<a href="#NT-Enumeration">Enumeration</a> attribute declaration, <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> all be distinct.</p></div><div class="constraint"><p class="prefix"><a name="enum" id="enum"/><b>Validity constraint: Enumeration</b></p><p>Values of this type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match
966characters that, according to <a href="#rfc2396">[IETF RFC 2396]</a> and <a href="#rfc2732">[IETF RFC 2732]</a>, 966one of the <a href="#NT-Nmtoken">Nmtoken</a> tokens in the declaration.</p></div><p>
967must be escaped before a URI can be used to retrieve the referenced resource. The 967 <a title="For interoperability" href="#dt-interop">For interoperability,</a> the same <a href="#NT-Nmtoken">Nmtoken</a>
968characters to be escaped are the control characters #x0 to #x1F and #x7F (most of 968 <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD NOT</em> occur more than once in the enumerated
969which cannot appear in XML), space #x20, the delimiters '&lt;' #x3C, '&gt;' #x3E and 969attribute types of a single element type.</p></div><div class="div3"> <h4><a name="sec-attr-defaults" id="sec-attr-defaults"/>3.3.2 Attribute Defaults</h4><p>An <a title="Attribute-List Declaration" href="#dt-attdecl">attribute declaration</a> provides information
970'"' #x22, the <em>unwise</em> characters '{' #x7B, '}' #x7D, '|' #x7C, '\' #x5C, '^' #x5E and 970on whether the attribute's presence is <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>, and if not, how an XML processor
971'`' #x60, as well as all characters above #x7F. Since escaping is not always a fully 971is to react if a declared attribute is absent in a document.</p> <h5><a name="IDAGUJS" id="IDAGUJS"/>Attribute Defaults</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-DefaultDecl" id="NT-DefaultDecl"/>[60]   </td><td><code>DefaultDecl</code></td><td>   ::=   </td><td><code>'#REQUIRED' | '#IMPLIED' </code></td></tr><tr valign="baseline"><td/><td/><td/><td><code>| (('#FIXED' <a href="#NT-S">S</a>)? <a href="#NT-AttValue">AttValue</a>)</code></td><td><a href="#RequiredAttr">[VC: Required Attribute]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#defattrvalid">[VC: Attribute Default Value Syntactically Correct]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#CleanAttrVals">[WFC: No &lt; in Attribute Values]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#FixedAttr">[VC: Fixed Attribute Default]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#NoExternalRefs">[WFC: No External Entity References]</a></td></tr></tbody></table><p>In an attribute declaration, <b>#REQUIRED</b> means that the attribute
972reversible process, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be performed only when absolutely necessary and as late 972<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> always be provided, <b>#IMPLIED</b> that no default value is provided.
973as possible in a processing chain. In particular, neither the process of converting 973
974a relative URI to an absolute one nor the process of passing a URI reference to a 974 [<a name="dt-default" id="dt-default" title="Attribute Default">Definition</a>: If
975process or software component responsible for dereferencing it <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> trigger escaping. 975the declaration is neither <b>#REQUIRED</b> nor <b>#IMPLIED</b>, then
976When escaping does occur, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be performed as follows:</p><ol type="1"><li><p>Each 976the <a href="#NT-AttValue">AttValue</a> value contains the declared <b>default</b>
977character <span>to be escaped</span> 977value; the <b>#FIXED</b> keyword states that the attribute <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> always have
978is <span>represented in</span> 978the default value.
979UTF-8 <span><a href="#Unicode">[Unicode]</a></span> 979When an XML processor encounters
980as one or more bytes.</p></li><li><p><span>The resulting bytes</span> 980an element
981are escaped with 981without a specification for an attribute for which it has read a default
982the URI escaping mechanism (that is, converted to <code>%</code><var>HH</var>, 982value declaration, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> report the attribute with the declared default
983where HH is the hexadecimal notation of the byte value).</p></li><li><p>The original character is replaced by the resulting character sequence.</p></li></ol><p>[<a name="dt-pubid" id="dt-pubid" title="Public identifier">Definition</a>: In addition to a system 983value to the application.]
984identifier, an external identifier <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> include a <b>public identifier</b>.] 984 </p><div class="constraint"><p class="prefix"><a name="RequiredAttr" id="RequiredAttr"/><b>Validity constraint: Required Attribute</b></p><p>If the default
985An XML processor attempting to retrieve the entity's content <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> use 985declaration is the keyword <b>#REQUIRED</b>, then the attribute <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be
986<span>any combination of 986specified for all elements of the type in the attribute-list declaration.</p></div><div class="constraint"><p class="prefix"><a name="defattrvalid" id="defattrvalid"/><b>Validity constraint: Attribute Default Value Syntactically Correct</b></p><p>The declared default value <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> meet the syntactic
987the public and system identifiers as well as additional information outside the 987constraints of the declared attribute type.<span>
988scope of this specification</span> to try to generate an alternative URI reference. 988 That is, the default value of an attribute:</span>
989If the processor is unable to do so, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> use the URI 989 </p><ul><li><p>
990reference specified in the system literal. Before a match is attempted, 990 of type IDREF or ENTITY must match the <a href="#NT-Name">Name</a> production;</p></li><li><p>
991all strings of white space in the public identifier <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be normalized to 991 of type IDREFS or ENTITIES must match the <a href="#NT-Names">Names</a> production;</p></li><li><p>
992single space characters (#x20), and leading and trailing white space <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> 992 of type NMTOKEN must match the <a href="#NT-Nmtoken">Nmtoken</a> production;</p></li><li><p>
993be removed.</p><p>Examples of external entity declarations:</p><div class="exampleInner"><pre>&lt;!ENTITY open-hatch 993 of type NMTOKENS must match the <a href="#NT-Nmtokens">Nmtokens</a> production;</p></li><li><p>
994SYSTEM "http://www.textuality.com/boilerplate/OpenHatch.xml"&gt; 994 of an <a href="#NT-EnumeratedType">enumerated type</a> (either a <a href="#NT-NotationType">NOTATION</a> type or an <a href="#NT-Enumeration">enumeration</a>) must match one of the enumerated values.</p></li></ul><p>Note that only the
995&lt;!ENTITY open-hatch 995syntactic constraints of the type are required here; other constraints (e.g.
996PUBLIC "-//Textuality//TEXT Standard open-hatch boilerplate//EN" 996that the value be the name of a declared unparsed entity, for an attribute of
997"http://www.textuality.com/boilerplate/OpenHatch.xml"&gt; 997type ENTITY)
998&lt;!ENTITY hatch-pic 998 <span>
999SYSTEM "../grafix/OpenHatch.gif" 999 will be reported by a validating
1000NDATA gif &gt;</pre></div></div></div><div class="div2"> <h3><a name="TextEntities" id="TextEntities" />4.3 Parsed Entities</h3><div class="div3"> <h4><a name="sec-TextDecl" id="sec-TextDecl" />4.3.1 The Text Declaration</h4><p>External parsed entities <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> each begin with a <b>text declaration</b>.</p> <h5><a name="IDAUPEU" id="IDAUPEU" />Text Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-TextDecl" id="NT-TextDecl" />[77]   </td><td><code>TextDecl</code></td><td>   ::=   </td><td><code>'&lt;?xml' <a href="#NT-VersionInfo">VersionInfo</a>? <a href="#NT-EncodingDecl">EncodingDecl</a> <a href="#NT-S">S</a>? '?&gt;'</code></td></tr></tbody></table><p>The text declaration <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be provided literally, not by reference 1000parser only if an element without a specification for this attribute
1001to a parsed entity. <span class="mustard">The</span> text declaration 1001actually occurs</span>.</p></div><div class="constraint"><p class="prefix"><a name="FixedAttr" id="FixedAttr"/><b>Validity constraint: Fixed Attribute Default</b></p><p>If an attribute
1002<span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em></span> appear at any 1002has a default value declared with the <b>#FIXED</b> keyword, instances of
1003position other than the beginning of an external parsed entity. The text declaration 1003that attribute <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the default value.</p></div><p>Examples of attribute-list declarations:</p><div class="exampleInner"><pre>&lt;!ATTLIST termdef
1004in an external parsed entity is not considered part of its <a title="Replacement Text" href="#dt-repltext">replacement text</a>.</p></div><div class="div3"> <h4><a name="wf-entities" id="wf-entities" />4.3.2 Well-Formed Parsed Entities</h4><p>The document entity is well-formed if it matches the production labeled <a href="#NT-document">document</a>. An external general parsed entity is well-formed 1004id ID #REQUIRED
1005if it matches the production labeled <a href="#NT-extParsedEnt">extParsedEnt</a>. All 1005name CDATA #IMPLIED&gt;
1006external parameter entities are well-formed by definition.</p> <h5><a name="IDA2REU" id="IDA2REU" />Well-Formed External Parsed Entity</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-extParsedEnt" id="NT-extParsedEnt" />[78]   </td><td><code>extParsedEnt</code></td><td>   ::=   </td><td><code><a href="#NT-TextDecl">TextDecl</a>? <a href="#NT-content">content</a> - <a href="#NT-Char">Char</a>* <a href="#NT-RestrictedChar">RestrictedChar</a> <a href="#NT-Char">Char</a>*</code></td></tr></tbody></table><p>An internal general parsed entity is well-formed if its replacement text 1006&lt;!ATTLIST list
1007matches the production labeled <a href="#NT-content">content</a>. All internal 1007type (bullets|ordered|glossary) "ordered"&gt;
1008parameter entities are well-formed by definition.</p><p>A consequence of well-formedness in <span>general</span> 1008&lt;!ATTLIST form
1009entities is that the logical and physical 1009method CDATA #FIXED "POST"&gt;</pre></div></div><div class="div3"> <h4><a name="AVNormalize" id="AVNormalize"/>3.3.3 Attribute-Value Normalization</h4><p>Before the value of an attribute is passed to the application or checked
1010structures in an XML document are properly nested; no <a title="Start-Tag" href="#dt-stag">start-tag</a>, <a title="End Tag" href="#dt-etag">end-tag</a>, <a title="Empty" href="#dt-empty">empty-element tag</a>, <a title="Element" href="#dt-element">element</a>, <a title="Comment" href="#dt-comment">comment</a>, <a title="Processing instruction" href="#dt-pi">processing instruction</a>, <a title="Character Reference" href="#dt-charref">character 1010for validity, the XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> normalize the attribute value by applying
1011reference</a>, or <a title="Entity Reference" href="#dt-entref">entity reference</a> 1011the algorithm below, or by using some other method such that the value passed
1012can begin in one entity and end in another.</p></div><div class="div3"> <h4><a name="charencoding" id="charencoding" />4.3.3 Character Encoding in Entities</h4><p>Each external parsed entity in an XML document <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> use a different encoding 1012to the application is the same as that produced by the algorithm.</p><ol class="enumar"><li><p>All line breaks <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> have been normalized on input to #xA as described
1013for its characters. All XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be able to read entities in both 1013in <a href="#sec-line-ends"><b>2.11 End-of-Line Handling</b></a>, so the rest of this algorithm operates
1014the UTF-8 and UTF-16 encodings. The terms "UTF-8" 1014on text normalized in this way.</p></li><li><p>Begin with a normalized value consisting of the empty string.</p></li><li><p>For each character, entity reference, or character reference in the
1015and "UTF-16" in this specification do not apply to character 1015unnormalized attribute value, beginning with the first and continuing to the
1016encodings with any other labels, even if the encodings or labels are very 1016last, do the following:</p><ul><li><p>For a character reference, append the referenced character to the
1017similar to UTF-8 or UTF-16.</p><p>Entities encoded in UTF-16 <span><em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em></span> <span>and entities 1017normalized value.</p></li><li><p>For an entity reference, recursively apply step 3 of this algorithm
1018encoded in UTF-8 <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em></span> begin with the Byte Order Mark described in 1018to the replacement text of the entity.</p></li><li><p>For a white space character (#x20, #xD, #xA, #x9), append a space
1019ISO/IEC 10646 <a href="#ISO10646">[ISO/IEC 10646]</a> or Unicode <a href="#Unicode">[Unicode]</a> 1019character (#x20) to the normalized value.</p></li><li><p>For another character, append the character to the normalized value.</p></li></ul></li></ol><p>If the attribute type is not CDATA, then the XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> further
1020(the ZERO WIDTH NO-BREAK SPACE character, #xFEFF). This is an encoding signature, 1020process the normalized attribute value by discarding any leading and trailing
1021not part of either the markup or the character data of the XML document. XML 1021space (#x20) characters, and by replacing sequences of space (#x20) characters
1022processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be able to use this character to differentiate between UTF-8 1022by a single space (#x20) character.</p><p>Note that if the unnormalized attribute value contains a character reference
1023and UTF-16 encoded documents.</p><p>Although an XML processor is required to read only entities in the UTF-8 1023to a white space character other than space (#x20), the normalized value contains
1024and UTF-16 encodings, it is recognized that other encodings are used around 1024the referenced character itself (#xD, #xA or #x9). This contrasts with the
1025the world, and it may be desired for XML processors to read entities that 1025case where the unnormalized value contains a white space character (not a
1026use them. In 1026reference), which is replaced with a space character (#x20) in the normalized
1027the absence of external character encoding information (such as MIME headers), 1027value and also contrasts with the case where the unnormalized value contains
1028parsed entities which are stored in an encoding other than UTF-8 or UTF-16 1028an entity reference whose replacement text contains a white space character;
1029<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> begin with a text declaration (see <a href="#sec-TextDecl"><b>4.3.1 The Text Declaration</b></a>) containing 1029being recursively processed, the white space character is replaced with a
1030an encoding declaration:</p> <h5><a name="IDARVEU" id="IDARVEU" />Encoding Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EncodingDecl" id="NT-EncodingDecl" />[80]   </td><td><code>EncodingDecl</code></td><td>   ::=   </td><td><code><a href="#NT-S">S</a> 'encoding' <a href="#NT-Eq">Eq</a> 1030space character (#x20) in the normalized value.</p><p>All attributes for which no declaration has been read <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be treated
1031('"' <a href="#NT-EncName">EncName</a> '"' | "'" <a href="#NT-EncName">EncName</a> 1031by a non-validating processor as if declared <b>CDATA</b>.</p><p>It
1032"'" ) </code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-EncName" id="NT-EncName" />[81]   </td><td><code>EncName</code></td><td>   ::=   </td><td><code>[A-Za-z] ([A-Za-z0-9._] | '-')*</code></td><td><i>/* Encoding 1032is an error if an
1033name contains only Latin characters */</i></td></tr></tbody></table><p>In the <a title="Document Entity" href="#dt-docent">document entity</a>, the encoding 1033<a title="Attribute Value" href="#dt-attrval">attribute
1034declaration is part of the <a title="XML Declaration" href="#dt-xmldecl">XML declaration</a>. 1034value</a> contains a <a title="Entity Reference" href="#dt-entref">reference</a> to an
1035The <a href="#NT-EncName">EncName</a> is the name of the encoding used.</p><p>In an encoding declaration, the values "<code>UTF-8</code>", "<code>UTF-16</code>", 1035entity for which no declaration has been read.</p><p>Following are examples of attribute normalization. Given the following
1036"<code>ISO-10646-UCS-2</code>", and "<code>ISO-10646-UCS-4</code>" <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be used 1036declarations:</p><div class="exampleInner"><pre>&lt;!ENTITY d "&amp;#xD;"&gt;
1037for the various encodings and transformations of Unicode / ISO/IEC 10646, 1037&lt;!ENTITY a "&amp;#xA;"&gt;
1038the values "<code>ISO-8859-1</code>", "<code>ISO-8859-2</code>", 1038&lt;!ENTITY da "&amp;#xD;&amp;#xA;"&gt;</pre></div><p>the attribute specifications in the left column below would be normalized
1039... "<code>ISO-8859-</code><var>n</var>" (where <var>n</var> 1039to the character sequences of the middle column if the attribute <code>a</code>
1040is the part number) <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be used for the parts of ISO 8859, and 1040is declared <b>NMTOKENS</b> and to those of the right columns if <code>a</code>
1041the values "<code>ISO-2022-JP</code>", "<code>Shift_JIS</code>", 1041is declared <b>CDATA</b>.</p><table border="1" frame="border" summary="Attribute normalization summary"><thead><tr><th>Attribute specification</th><th>a is NMTOKENS</th><th>a is CDATA</th></tr></thead><tbody><tr><td>
1042and "<code>EUC-JP</code>" <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be used for the various encoded 1042 <div class="exampleInner"><pre>a="
1043forms of JIS X-0208-1997. It 1043xyz"</pre></div>
1044is <em class="rfc2119" title="Keyword in RFC 2119 context">RECOMMENDED</em> that character encodings registered (as <em>charset</em>s) 1044 </td><td>
1045with the Internet Assigned Numbers Authority <a href="#IANA">[IANA-CHARSETS]</a>, 1045 <div class="exampleInner"><pre>x y z</pre></div>
1046other than those just listed, be referred to using their registered names; 1046 </td><td>
1047other encodings <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> use names starting with an "x-" prefix. 1047 <div class="exampleInner"><pre>#x20 #x20 x y z</pre></div>
1048XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> match character encoding names in a case-insensitive 1048 </td></tr><tr><td>
1049way and <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> either interpret an IANA-registered name as the encoding registered 1049 <div class="exampleInner"><pre>a="&amp;d;&amp;d;A&amp;a;&amp;#x20;&amp;a;B&amp;da;"</pre></div>
1050at IANA for that name or treat it as unknown (processors are, of course, not 1050 </td><td>
1051required to support all IANA-registered encodings).</p><p>In the absence of information provided by an external transport protocol 1051 <div class="exampleInner"><pre>A #x20 B</pre></div>
1052(e.g. HTTP or MIME), it is a <a title="Fatal Error" href="#dt-fatal">fatal error</a> for 1052 </td><td>
1053an entity including an encoding declaration to be presented to the XML processor 1053 <div class="exampleInner"><pre>#x20 #x20 A #x20 #x20 #x20 B #x20 #x20</pre></div>
1054in an encoding other than that named in the declaration, or for an entity which 1054 </td></tr><tr><td>
1055begins with neither a Byte Order Mark 1055 <div class="exampleInner"><pre>a=
1056nor an encoding declaration to use an encoding other than UTF-8. Note that 1056"&amp;#xd;&amp;#xd;A&amp;#xa;&amp;#xa;B&amp;#xd;&amp;#xa;"</pre></div>
1057since ASCII is a subset of UTF-8, ordinary ASCII entities do not strictly 1057 </td><td>
1058need an encoding declaration.</p><p>It is a <a title="Fatal Error" href="#dt-fatal">fatal error</a> for a <a href="#NT-TextDecl">TextDecl</a> to occur other 1058 <div class="exampleInner"><pre>#xD #xD A #xA #xA B #xD #xA</pre></div>
1059than at the beginning of an external entity.</p><p>It is a <a title="Fatal Error" href="#dt-fatal">fatal error</a> when an XML processor 1059 </td><td>
1060encounters an entity with an encoding that it is unable to process. It 1060 <div class="exampleInner"><pre>#xD #xD A #xA #xA B #xD #xA</pre></div>
1061is a <a title="Fatal Error" href="#dt-fatal">fatal error</a> if an XML entity is determined (via default, encoding declaration, 1061 </td></tr></tbody></table><p>Note that the last example is invalid (but well-formed) if <code>a</code>
1062or higher-level protocol) to be in a certain encoding but contains <span>byte</span> 1062is declared to be of type <b>NMTOKENS</b>.</p></div></div><div class="div2"> <h3><a name="sec-condition-sect" id="sec-condition-sect"/>3.4 Conditional Sections</h3><p>
1063sequences that are not legal in that encoding. <span>Specifically, it is a 1063 [<a name="dt-cond-section" id="dt-cond-section" title="conditional section">Definition</a>:
1064fatal error if an entity encoded in UTF-8 contains any irregular code unit sequences, 1064 <b>Conditional
1065as defined in Unicode <a href="#Unicode">[Unicode]</a>.</span> <span>Unless an encoding 1065sections</b> are portions of the <a title="Document Type Declaration" href="#dt-doctype">document type
1066is determined by a higher-level protocol, </span>it is also a <a title="Fatal Error" href="#dt-fatal">fatal error</a> if an XML entity 1066declaration external subset</a> or
1067contains no encoding declaration and its content is not legal UTF-8 or UTF-16.</p><p>Examples of text declarations containing encoding declarations:</p><div class="exampleInner"><pre>&lt;?xml encoding='UTF-8'?&gt; 1067of external parameter entities which are included in, or excluded from,
1068&lt;?xml encoding='EUC-JP'?&gt;</pre></div></div><div class="div3"> <h4><a name="sec-version-info" id="sec-version-info" />4.3.4 Version Information in Entities</h4><p>Each entity, including the <a title="Document Entity" href="#dt-docent">document entity</a>, 1068the logical structure of the DTD based on the keyword which governs them.]
1069can be separately 1069 </p> <h5><a name="IDA1AKS" id="IDA1AKS"/>Conditional Section</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-conditionalSect" id="NT-conditionalSect"/>[61]   </td><td><code>conditionalSect</code></td><td>   ::=   </td><td><code>
1070declared as XML 1.0 or XML 1.1. The version declaration appearing 1070 <a href="#NT-includeSect">includeSect</a> | <a href="#NT-ignoreSect">ignoreSect</a>
1071in the document entity determines the version of the document as a 1071 </code></td></tr><tr valign="baseline"><td><a name="NT-includeSect" id="NT-includeSect"/>[62]   </td><td><code>includeSect</code></td><td>   ::=   </td><td><code>'&lt;![' <a href="#NT-S">S</a>? 'INCLUDE' <a href="#NT-S">S</a>? '[' <a href="#NT-extSubsetDecl">extSubsetDecl</a>
1072whole. An XML 1.1 document may invoke XML 1.0 external entities, so 1072']]&gt;' </code></td><td><a href="#condsec-nesting">[VC: Proper Conditional Section/PE Nesting]</a></td></tr><tr valign="baseline"><td><a name="NT-ignoreSect" id="NT-ignoreSect"/>[63]   </td><td><code>ignoreSect</code></td><td>   ::=   </td><td><code>'&lt;![' <a href="#NT-S">S</a>? 'IGNORE' <a href="#NT-S">S</a>? '[' <a href="#NT-ignoreSectContents">ignoreSectContents</a>*
1073that otherwise duplicated versions of external entities, 1073']]&gt;'</code></td><td><a href="#condsec-nesting">[VC: Proper Conditional Section/PE Nesting]</a></td></tr><tr valign="baseline"><td><a name="NT-ignoreSectContents" id="NT-ignoreSectContents"/>[64]   </td><td><code>ignoreSectContents</code></td><td>   ::=   </td><td><code>
1074particularly DTD external subsets, need not be maintained. However, 1074 <a href="#NT-Ignore">Ignore</a> ('&lt;![' <a href="#NT-ignoreSectContents">ignoreSectContents</a> ']]&gt;' <a href="#NT-Ignore">Ignore</a>)*</code></td></tr><tr valign="baseline"><td><a name="NT-Ignore" id="NT-Ignore"/>[65]   </td><td><code>Ignore</code></td><td>   ::=   </td><td><code>
1075in such a case the rules of XML 1.1 are applied to the entire 1075 <a href="#NT-Char">Char</a>* - (<a href="#NT-Char">Char</a>*
1076document.</p><p> If an entity (including the document entity) is not labeled 1076('&lt;![' | ']]&gt;') <a href="#NT-Char">Char</a>*) </code></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="condsec-nesting" id="condsec-nesting"/><b>Validity constraint: Proper Conditional Section/PE Nesting</b></p><p>If any of the "<code>&lt;![</code>",
1077with a version number, it is treated as if labeled as version 1077"<code>[</code>", or "<code>]]&gt;</code>" of a conditional section is contained
10781.0.</p></div></div><div class="div2"> <h3><a name="entproc" id="entproc" />4.4 XML Processor Treatment of Entities and References</h3><p>The table below summarizes the contexts in which character references, 1078in the replacement text for a parameter-entity reference, all of them <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
1079entity references, and invocations of unparsed entities might appear and the 1079be contained in the same replacement text.</p></div><p>Like the internal and external DTD subsets, a conditional section may contain
1080<em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> behavior of an <a title="XML Processor" href="#dt-xml-proc">XML processor</a> 1080one or more complete declarations, comments, processing instructions, or nested
1081in each case. The labels in the leftmost column describe the recognition context: </p><dl><dt class="label">Reference in Content</dt><dd><p>as a reference anywhere after the <a title="Start-Tag" href="#dt-stag">start-tag</a> 1081conditional sections, intermingled with white space.</p><p>If the keyword of the conditional section is <b>INCLUDE</b>, then the
1082and before the <a title="End Tag" href="#dt-etag">end-tag</a> of an element; corresponds 1082contents of the conditional section <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be
1083to the nonterminal <a href="#NT-content">content</a>.</p></dd><dt class="label">Reference in Attribute Value</dt><dd><p>as a reference within either the value of an attribute in a <a title="Start-Tag" href="#dt-stag">start-tag</a>, 1083 <span>processed as</span>
1084or a default value in an <a title="Attribute-List Declaration" href="#dt-attdecl">attribute declaration</a>; 1084part of the DTD. If the keyword of
1085corresponds to the nonterminal <a href="#NT-AttValue">AttValue</a>.</p></dd><dt class="label">Occurs as Attribute Value</dt><dd><p>as a <a href="#NT-Name">Name</a>, not a reference, appearing either as 1085the conditional section is <b>IGNORE</b>, then the contents of the conditional
1086the value of an attribute which has been declared as type <b>ENTITY</b>, 1086section <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
1087or as one of the space-separated tokens in the value of an attribute which 1087
1088has been declared as type <b>ENTITIES</b>.</p></dd><dt class="label">Reference in Entity Value</dt><dd><p>as a reference within a parameter or internal entity's <a title="Literal Entity Value" href="#dt-litentval">literal 1088 <span>
1089entity value</a> in the entity's declaration; corresponds to the nonterminal <a href="#NT-EntityValue">EntityValue</a>.</p></dd><dt class="label">Reference in DTD</dt><dd><p>as a reference within either the internal or external subsets of the <a title="Document Type Declaration" href="#dt-doctype">DTD</a>, but outside of an <a href="#NT-EntityValue">EntityValue</a>, <a href="#NT-AttValue">AttValue</a>, <a href="#NT-PI">PI</a>, <a href="#NT-Comment">Comment</a>, <a href="#NT-SystemLiteral">SystemLiteral</a>, <a href="#NT-PubidLiteral">PubidLiteral</a>, 1089 <em class="rfc2119" title="Keyword in RFC 2119 context">NOT</em> be processed as</span> part of the DTD.
1090or the contents of an ignored conditional section (see <a href="#sec-condition-sect"><b>3.4 Conditional Sections</b></a>).</p><p>.</p></dd></dl><p></p><table border="1" frame="border" cellpadding="7" summary="Entity type/reference matrix"><tbody align="center"><tr><td rowspan="2" colspan="1"></td><td colspan="4" align="center" valign="bottom" rowspan="1">Entity 1090If a conditional section with a keyword of <b>INCLUDE</b> occurs within
1091Type</td><td rowspan="2" align="center" colspan="1">Character</td></tr><tr align="center" valign="bottom"><td rowspan="1" colspan="1">Parameter</td><td rowspan="1" colspan="1">Internal General</td><td rowspan="1" colspan="1">External Parsed 1091a larger conditional section with a keyword of <b>IGNORE</b>, both the outer
1092General</td><td rowspan="1" colspan="1">Unparsed</td></tr><tr align="center" valign="middle"><td align="right" rowspan="1" colspan="1">Reference 1092and the inner conditional sections <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be ignored. The contents
1093in Content</td><td rowspan="1" colspan="1"><a href="#not-recognized"><cite>Not recognized</cite></a></td><td rowspan="1" colspan="1"><a href="#included"><cite>Included</cite></a></td><td rowspan="1" colspan="1"><a href="#include-if-valid"><cite>Included 1093of an ignored conditional section <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be parsed by ignoring all characters after
1094if validating</cite></a></td><td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td><td rowspan="1" colspan="1"><a href="#included"><cite>Included</cite></a></td></tr><tr align="center" valign="middle"><td align="right" rowspan="1" colspan="1">Reference in Attribute Value</td><td rowspan="1" colspan="1"><a href="#not-recognized"><cite>Not recognized</cite></a></td><td rowspan="1" colspan="1"><a href="#inliteral"><cite>Included 1094the "<code>[</code>" following the keyword, except conditional section starts
1095in literal</cite></a></td><td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td><td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td><td rowspan="1" colspan="1"><a href="#included"><cite>Included</cite></a></td></tr><tr align="center" valign="middle"><td align="right" rowspan="1" colspan="1">Occurs as Attribute 1095"<code>&lt;![</code>" and ends "<code>]]&gt;</code>", until the matching conditional
1096Value</td><td rowspan="1" colspan="1"><a href="#not-recognized"><cite>Not recognized</cite></a></td><td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td><td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td><td rowspan="1" colspan="1"><a href="#notify"><cite>Notify</cite></a></td><td rowspan="1" colspan="1"><a href="#not-recognized"><cite>Not recognized</cite></a></td></tr><tr align="center" valign="middle"><td align="right" rowspan="1" colspan="1">Reference in EntityValue</td><td rowspan="1" colspan="1"><a href="#inliteral"><cite>Included in literal</cite></a></td><td rowspan="1" colspan="1"><a href="#bypass"><cite>Bypassed</cite></a></td><td rowspan="1" colspan="1"><a href="#bypass"><cite>Bypassed</cite></a></td><td rowspan="1" colspan="1"><a href="#error"><cite><span>Error</span></cite></a></td><td rowspan="1" colspan="1"><a href="#included"><cite>Included</cite></a></td></tr><tr align="center" valign="middle"><td align="right" rowspan="1" colspan="1">Reference in DTD</td><td rowspan="1" colspan="1"><a href="#as-PE"><cite>Included as PE</cite></a></td><td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td><td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td><td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td><td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td></tr></tbody></table><div class="div3"> <h4><a name="not-recognized" id="not-recognized" />4.4.1 Not Recognized</h4><p>Outside the DTD, the <code>%</code> character has no special significance; 1096section end is found. Parameter entity references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be recognized in this
1097thus, what would be parameter entity references in the DTD are not recognized 1097process.</p><p>If the keyword of the conditional section is a parameter-entity reference,
1098as markup in <a href="#NT-content">content</a>. Similarly, the names of unparsed 1098the parameter entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be replaced by its content before the processor
1099entities are not recognized except when they appear in the value of an appropriately 1099decides whether to include or ignore the conditional section.</p><p>An example:</p><div class="exampleInner"><pre>&lt;!ENTITY % draft 'INCLUDE' &gt;
1100declared attribute.</p></div><div class="div3"> <h4><a name="included" id="included" />4.4.2 Included</h4><p>[<a name="dt-include" id="dt-include" title="Include">Definition</a>: An entity is <b>included</b> 1100&lt;!ENTITY % final 'IGNORE' &gt;
1101when its <a title="Replacement Text" href="#dt-repltext">replacement text</a> is retrieved 1101&lt;![%draft;[
1102and processed, in place of the reference itself, as though it were part of 1102&lt;!ELEMENT book (comments*, title, body, supplements?)&gt;
1103the document at the location the reference was recognized.] The replacement 1103]]&gt;
1104text <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> contain both <a title="Character Data" href="#dt-chardata">character data</a> 1104&lt;![%final;[
1105and (except for parameter entities) <a title="Markup" href="#dt-markup">markup</a>, 1105&lt;!ELEMENT book (title, body, supplements?)&gt;
1106which <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be recognized in the usual way. (The string "<code>AT&amp;amp;T;</code>" 1106]]&gt;</pre></div></div></div><div class="div1"> <h2><a name="sec-physical-struct" id="sec-physical-struct"/>4 Physical Structures</h2><p>
1107expands to "<code>AT&amp;T;</code>" and the remaining ampersand 1107 [<a name="dt-entity" id="dt-entity" title="Entity">Definition</a>: An XML document may consist of one
1108is not recognized as an entity-reference delimiter.) A character reference 1108or many storage units. These
1109is <b>included</b> when the indicated character is processed in place 1109are called <b>entities</b>; they all have <b>content</b> and are
1110of the reference itself. </p></div><div class="div3"> <h4><a name="include-if-valid" id="include-if-valid" />4.4.3 Included If Validating</h4><p>When an XML processor recognizes a reference to a parsed entity, in order 1110all (except for the <a title="Document Entity" href="#dt-docent">document entity</a> and
1111to <a title="Validity" href="#dt-valid">validate</a> the document, the processor 1111the <a title="Document Type Declaration" href="#dt-doctype">external DTD subset</a>) identified by
1112<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> <a title="Include" href="#dt-include">include</a> its replacement text. If 1112entity <b>name</b>.] Each XML document has one entity
1113the entity is external, and the processor is not attempting to validate the 1113called the <a title="Document Entity" href="#dt-docent">document entity</a>, which serves
1114XML document, the processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em>, but need 1114as the starting point for the <a title="XML Processor" href="#dt-xml-proc">XML processor</a>
1115not, include the entity's replacement text. If a non-validating processor 1115and may contain the whole document.</p><p>Entities may be either parsed or unparsed. [<a name="dt-parsedent" id="dt-parsedent" title="Text Entity">Definition</a>: The contents of a <b>parsed
1116does not include the replacement text, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> inform the application that 1116entity</b> are referred to as its <a title="Replacement Text" href="#dt-repltext">replacement
1117it recognized, but did not read, the entity.</p><p>This rule is based on the recognition that the automatic inclusion provided 1117text</a>; this <a title="Text" href="#dt-text">text</a> is considered an
1118by the SGML and XML entity mechanism, primarily designed to support modularity 1118integral part of the document.]
1119in authoring, is not necessarily appropriate for other applications, in particular 1119 </p><p>
1120document browsing. Browsers, for example, when encountering an external parsed 1120 [<a name="dt-unparsed" id="dt-unparsed" title="Unparsed Entity">Definition</a>: An <b>unparsed entity</b>
1121entity reference, might choose to provide a visual indication of the entity's 1121is a resource whose contents may or may not be <a title="Text" href="#dt-text">text</a>,
1122presence and retrieve it for display only on demand.</p></div><div class="div3"> <h4><a name="forbidden" id="forbidden" />4.4.4 Forbidden</h4><p>The following are forbidden, and constitute <a title="Fatal Error" href="#dt-fatal">fatal 1122and if text, may
1123errors</a>:</p><ul><li><p>the appearance of a reference to an <a title="Unparsed Entity" href="#dt-unparsed">unparsed 1123be other than XML. Each unparsed entity has an associated <a title="Notation" href="#dt-notation">notation</a>, identified by name. Beyond a requirement
1124entity</a><span>, except in the 1124that an XML processor make the identifiers for the entity and notation available
1125<a href="#NT-EntityValue">EntityValue</a> in an entity declaration</span>.</p></li><li><p>the appearance of any character or general-entity reference in the 1125to the application, XML places no constraints on the contents of unparsed
1126DTD except within an <a href="#NT-EntityValue">EntityValue</a> or <a href="#NT-AttValue">AttValue</a>.</p></li><li><p>a reference to an external entity in an attribute value.</p></li></ul></div><div class="div3"> <h4><a name="inliteral" id="inliteral" />4.4.5 Included in Literal</h4><p>When an <a title="Entity Reference" href="#dt-entref">entity reference</a> appears in 1126entities.]
1127an attribute value, or a parameter entity reference appears in a literal entity 1127 </p><p>Parsed entities are invoked by name using entity references; unparsed entities
1128value, its <a title="Replacement Text" href="#dt-repltext">replacement text</a> <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be</span> processed 1128by name, given in the value of <b>ENTITY</b> or <b>ENTITIES</b> attributes.</p><p>
1129in place of the reference itself as though it were part of the document at 1129 [<a name="gen-entity" id="gen-entity" title="general entity">Definition</a>:
1130the location the reference was recognized, except that a single or double 1130 <b>General entities</b>
1131quote character in the replacement text <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> always be</span> treated as a normal data 1131are entities for use within the document content. In this specification, general
1132character and <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em></span> terminate the literal. For example, this is well-formed:</p><div class="exampleInner"><pre>&lt;!ENTITY % YN '"Yes"' &gt; 1132entities are sometimes referred to with the unqualified term <em>entity</em>
1133&lt;!ENTITY WhatHeSaid "He said %YN;" &gt;</pre></div><p>while this is not:</p><div class="exampleInner"><pre>&lt;!ENTITY EndAttr "27'" &gt; 1133when this leads to no ambiguity.]
1134&lt;element attribute='a-&amp;EndAttr;&gt;</pre></div></div><div class="div3"> <h4><a name="notify" id="notify" />4.4.6 Notify</h4><p>When the name of an <a title="Unparsed Entity" href="#dt-unparsed">unparsed entity</a> 1134 [<a name="dt-PE" id="dt-PE" title="Parameter entity">Definition</a>:
1135appears as a token in the value of an attribute of declared type <b>ENTITY</b> 1135 <b>Parameter
1136or <b>ENTITIES</b>, a validating processor <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> inform the application of 1136entities</b> are parsed entities for use within the DTD.]
1137the <a title="System Identifier" href="#dt-sysid">system</a> and <a title="Public identifier" href="#dt-pubid">public</a> 1137These two types of entities use different forms of reference and are recognized
1138(if any) identifiers for both the entity and its associated <a title="Notation" href="#dt-notation">notation</a>.</p></div><div class="div3"> <h4><a name="bypass" id="bypass" />4.4.7 Bypassed</h4><p>When a general entity reference appears in the <a href="#NT-EntityValue">EntityValue</a> 1138in different contexts. Furthermore, they occupy different namespaces; a parameter
1139in an entity declaration, it <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be</span> bypassed and left as is.</p></div><div class="div3"> <h4><a name="as-PE" id="as-PE" />4.4.8 Included as PE</h4><p>Just as with external parsed entities, parameter entities need only be <a href="#include-if-valid"><cite>included if validating</cite></a>. When a parameter-entity 1139entity and a general entity with the same name are two distinct entities.</p><div class="div2"> <h3><a name="sec-references" id="sec-references"/>4.1 Character and Entity References</h3><p>
1140reference is recognized in the DTD and included, its <a title="Replacement Text" href="#dt-repltext">replacement 1140 [<a name="dt-charref" id="dt-charref" title="Character Reference">Definition</a>: A <b>character
1141text</a> <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be</span> enlarged by the attachment of one leading and one following 1141reference</b> refers to a specific character in the ISO/IEC 10646 character
1142space (#x20) character; the intent is to constrain the replacement text of 1142set, for example one not directly accessible from available input devices.]
1143parameter entities to contain an integral number of grammatical tokens in 1143 </p> <h5><a name="IDAOKKS" id="IDAOKKS"/>Character Reference</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-CharRef" id="NT-CharRef"/>[66]   </td><td><code>CharRef</code></td><td>   ::=   </td><td><code>'&amp;#' [0-9]+ ';' </code></td></tr><tr valign="baseline"><td/><td/><td/><td><code>| '&amp;#x' [0-9a-fA-F]+ ';'</code></td><td><a href="#wf-Legalchar">[WFC: Legal Character]</a></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="wf-Legalchar" id="wf-Legalchar"/><b>Well-formedness constraint: Legal Character</b></p><p>Characters referred
1144the DTD. This 1144to using character references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the production for <a href="#NT-Char">Char</a>.</p></div><p>If the character reference begins with "<code>&amp;#x</code>",
1145behavior <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em></span> apply to parameter entity references within entity values; 1145the digits and letters up to the terminating <code>;</code> provide a hexadecimal
1146these are described in <a href="#inliteral"><b>4.4.5 Included in Literal</b></a>.</p></div><div class="div3"> <h4><a name="error" id="error" />4.4.9 Error</h4><p>It is an <a title="Error" href="#dt-error">error</a> for a reference to 1146representation of the character's code point in ISO/IEC 10646. If it begins
1147an unparsed entity to appear in the <a href="#NT-EntityValue">EntityValue</a> in an 1147just with "<code>&amp;#</code>", the digits up to the terminating <code>;</code>
1148entity declaration.</p></div></div><div class="div2"> <h3><a name="intern-replacement" id="intern-replacement" />4.5 Construction of Entity Replacement Text</h3><p>In discussing the treatment of entities, it is useful to distinguish 1148provide a decimal representation of the character's code point.</p><p>
1149two forms of the entity's value. 1149 [<a name="dt-entref" id="dt-entref" title="Entity Reference">Definition</a>: An <b>entity reference</b>
1150[<a name="dt-litentval" id="dt-litentval" title="Literal Entity Value">Definition</a>: <span>For an 1150refers to the content of a named entity.]
1151internal entity, </span>the <b>literal 1151 [<a name="dt-GERef" id="dt-GERef" title="General Entity Reference">Definition</a>: References to parsed general entities use
1152entity value</b> is the quoted string actually present in the entity declaration, 1152ampersand (<code>&amp;</code>) and semicolon (<code>;</code>) as delimiters.]
1153corresponding to the non-terminal <a href="#NT-EntityValue">EntityValue</a>.] [<a name="dt-extlitentval" id="dt-extlitentval" title="Literal Entity Value">Definition</a>: For an external entity, the <b>literal 1153 [<a name="dt-PERef" id="dt-PERef" title="Parameter-entity reference">Definition</a>:
1154entity value</b> is the exact text contained in the entity.] [<a name="dt-repltext" id="dt-repltext" title="Replacement Text">Definition</a>: <span>For an 1154 <b>Parameter-entity references</b>
1155internal entity, </span>the <b>replacement text</b> 1155use percent-sign (<code>%</code>) and semicolon (<code>;</code>) as delimiters.]
1156is the content of the entity, after replacement of character references and 1156 </p> <h5><a name="IDA1MKS" id="IDA1MKS"/>Entity Reference</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-Reference" id="NT-Reference"/>[67]   </td><td><code>Reference</code></td><td>   ::=   </td><td><code>
1157parameter-entity references.] [<a name="dt-extrepltext" id="dt-extrepltext" title="Replacement Text">Definition</a>: For 1157 <a href="#NT-EntityRef">EntityRef</a> | <a href="#NT-CharRef">CharRef</a>
1158an external entity, the <b>replacement text</b> is the content of the entity, 1158 </code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-EntityRef" id="NT-EntityRef"/>[68]   </td><td><code>EntityRef</code></td><td>   ::=   </td><td><code>'&amp;' <a href="#NT-Name">Name</a> ';'</code></td><td><a href="#wf-entdeclared">[WFC: Entity Declared]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#vc-entdeclared">[VC: Entity Declared]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#textent">[WFC: Parsed Entity]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#norecursion">[WFC: No Recursion]</a></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PEReference" id="NT-PEReference"/>[69]   </td><td><code>PEReference</code></td><td>   ::=   </td><td><code>'%' <a href="#NT-Name">Name</a> ';'</code></td><td><a href="#vc-entdeclared">[VC: Entity Declared]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#norecursion">[WFC: No Recursion]</a></td></tr><tr valign="baseline"><td/><td/><td/><td/><td><a href="#indtd">[WFC: In DTD]</a></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="wf-entdeclared" id="wf-entdeclared"/><b>Well-formedness constraint: Entity Declared</b></p><p>In a document
1159after stripping the text declaration (leaving any surrounding white space) if there 1159without any DTD, a document with only an internal DTD subset which contains
1160is one but without any replacement of character references or parameter-entity 1160no parameter entity references, or a document with "<code>standalone='yes'</code>", for
1161references.]</p><p>The literal entity value as given in an internal entity declaration (<a href="#NT-EntityValue">EntityValue</a>) <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> contain character, parameter-entity, 1161an entity reference that does not occur within the external subset or a parameter
1162and general-entity references. Such references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be contained entirely 1162entity, the <a href="#NT-Name">Name</a> given in the entity reference <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
1163within the literal entity value. The actual replacement text that is <a title="Include" href="#dt-include">included</a><span> (or <a title="" href="#inliteral">included in literal</a>)</span> as described above 1163 <a title="match" href="#dt-match">match</a> that in an <a href="#sec-entity-decl"><cite>entity
1164<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> contain the <em>replacement 1164declaration</cite></a> that does not occur within the external subset or a
1165text</em> of any parameter entities referred to, and <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> contain the character 1165parameter entity, except that well-formed documents need not declare
1166referred to, in place of any character references in the literal entity value; 1166any of the following entities: <code>amp</code>,
1167however, general-entity references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be left as-is, unexpanded. For example, 1167<code>lt</code>,
1168given the following declarations:</p><div class="exampleInner"><pre>&lt;!ENTITY % pub "&amp;#xc9;ditions Gallimard" &gt; 1168<code>gt</code>,
1169&lt;!ENTITY rights "All rights reserved" &gt; 1169<code>apos</code>,
1170&lt;!ENTITY book "La Peste: Albert Camus, 1170<code>quot</code>. The
1171&amp;#xA9; 1947 %pub;. &amp;rights;" &gt;</pre></div><p>then the replacement text for the entity "<code>book</code>" 1171declaration of a general entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> precede any reference to it which appears
1172is:</p><div class="exampleInner"><pre>La Peste: Albert Camus, 1172in a default value in an attribute-list declaration.</p><p>Note
1173© 1947 Éditions Gallimard. &amp;rights;</pre></div><p>The general-entity reference "<code>&amp;rights;</code>" would 1173that non-validating processors are <a href="#include-if-valid"><cite>not
1174be expanded should the reference "<code>&amp;book;</code>" appear 1174obligated to</cite></a> to read and process entity declarations occurring in parameter entities or in
1175in the document's content or an attribute value.</p><p>These simple rules may have complex interactions; for a detailed discussion 1175the external subset; for such documents,
1176of a difficult example, see <a href="#sec-entexpand"><b>C Expansion of Entity and Character References</b></a>.</p></div><div class="div2"> <h3><a name="sec-predefined-ent" id="sec-predefined-ent" />4.6 Predefined Entities</h3><p>[<a name="dt-escape" id="dt-escape" title="escape">Definition</a>: Entity and character references <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> 1176the rule that an entity must be declared is a well-formedness constraint only
1177both be used to <b>escape</b> the left angle bracket, ampersand, and 1177if <a href="#sec-rmd"><cite>standalone='yes'</cite></a>.</p></div><div class="constraint"><p class="prefix"><a name="vc-entdeclared" id="vc-entdeclared"/><b>Validity constraint: Entity Declared</b></p><p>In a document with an external subset or parameter
1178other delimiters. A set of general entities (<code>amp</code>, 1178 <span>
1179<code>lt</code>, 1179 entity references</span> with
1180<code>gt</code>, 1180 "<code>standalone='no'</code>",
1181<code>apos</code>, 1181the <a href="#NT-Name">Name</a> given in the entity reference <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
1182<code>quot</code>) is specified for 1182 <a title="match" href="#dt-match">match</a> that in an <a href="#sec-entity-decl"><cite>entity
1183this purpose. Numeric character references <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> also be used; they are expanded 1183declaration</cite></a>. For interoperability, valid documents <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> declare
1184immediately when recognized and <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be treated as character data, so the 1184the entities <code>amp</code>,
1185numeric character references "<code>&amp;#60;</code>" and "<code>&amp;#38;</code>" <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be used to escape <code>&lt;</code> and <code>&amp;</code> when they occur 1185<code>lt</code>,
1186in character data.]</p><p>All XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> recognize these entities whether they are declared 1186<code>gt</code>,
1187or not. <a title="For interoperability" href="#dt-interop">For interoperability</a>, valid XML 1187<code>apos</code>,
1188documents <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> declare these entities, like any others, before using them. If 1188<code>quot</code>, in the form specified in <a href="#sec-predefined-ent"><b>4.6 Predefined Entities</b></a>.
1189the entities <code>lt</code> or <code>amp</code> are declared, they <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be 1189The declaration of a parameter entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> precede any reference to it. Similarly,
1190declared as internal entities whose replacement text is a character reference 1190the declaration of a general entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> precede any attribute-list
1191to the respective 1191declaration containing a default value with a direct or indirect reference
1192character (less-than sign or ampersand) being escaped; the double 1192to that general entity.</p></div><div class="constraint"><p class="prefix"><a name="textent" id="textent"/><b>Well-formedness constraint: Parsed Entity</b></p><p>An entity reference <em class="rfc2119" title="Keyword in RFC 2119 context">MUST
1193escaping is <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> for these entities so that references to them produce 1193NOT</em> contain the name of an <a title="Unparsed Entity" href="#dt-unparsed">unparsed entity</a>.
1194a well-formed result. If the entities <code>gt</code>, <code>apos</code>, 1194Unparsed entities may be referred to only in <a title="Attribute Value" href="#dt-attrval">attribute
1195or <code>quot</code> are declared, they <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be declared as internal entities 1195values</a> declared to be of type <b>ENTITY</b> or <b>ENTITIES</b>.</p></div><div class="constraint"><p class="prefix"><a name="norecursion" id="norecursion"/><b>Well-formedness constraint: No Recursion</b></p><p>A parsed entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> contain a recursive reference to itself, either directly or indirectly.</p></div><div class="constraint"><p class="prefix"><a name="indtd" id="indtd"/><b>Well-formedness constraint: In DTD</b></p><p>Parameter-entity references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear outside
1196whose replacement text is the single character being escaped (or a character 1196the <a title="Document Type Declaration" href="#dt-doctype">DTD</a>.</p></div><p>Examples of character and entity references:</p><div class="exampleInner"><pre>Type &lt;key&gt;less-than&lt;/key&gt; (&amp;#x3C;) to save options.
1197reference to that character; the double escaping here is <span class="mustard"><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em></span> but harmless). 1197This document was prepared on &amp;docdate; and
1198For example:</p><div class="exampleInner"><pre>&lt;!ENTITY lt "&amp;#38;#60;"&gt; 1198is classified &amp;security-level;.</pre></div><p>Example of a parameter-entity reference:</p><div class="exampleInner"><pre>&lt;!-- declare the parameter entity "ISOLat2"... --&gt;
1199&lt;!ENTITY gt "&amp;#62;"&gt; 1199&lt;!ENTITY % ISOLat2
1200&lt;!ENTITY amp "&amp;#38;#38;"&gt; 1200SYSTEM "http://www.xml.com/iso/isolat2-xml.entities" &gt;
1201&lt;!ENTITY apos "&amp;#39;"&gt; 1201&lt;!-- ... now reference it. --&gt;
1202&lt;!ENTITY quot "&amp;#34;"&gt;</pre></div></div><div class="div2"> <h3><a name="Notations" id="Notations" />4.7 Notation Declarations</h3><p>[<a name="dt-notation" id="dt-notation" title="Notation">Definition</a>: <b>Notations</b> identify 1202%ISOLat2;</pre></div></div><div class="div2"> <h3><a name="sec-entity-decl" id="sec-entity-decl"/>4.2 Entity Declarations</h3><p>
1203by name the format of <a title="External Entity" href="#dt-extent">unparsed entities</a>, 1203 [<a name="dt-entdecl" id="dt-entdecl" title="entity declaration">Definition</a>: Entities are declared
1204the format of elements which bear a notation attribute, or the application 1204thus:]
1205to which a <a title="Processing instruction" href="#dt-pi">processing instruction</a> is addressed.]</p><p>[<a name="dt-notdecl" id="dt-notdecl" title="Notation Declaration">Definition</a>: <b>Notation declarations</b> 1205 </p> <h5><a name="IDABVKS" id="IDABVKS"/>Entity Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EntityDecl" id="NT-EntityDecl"/>[70]   </td><td><code>EntityDecl</code></td><td>   ::=   </td><td><code>
1206provide a name for the notation, for use in entity and attribute-list declarations 1206 <a href="#NT-GEDecl">GEDecl</a>
1207and in attribute specifications, and an external identifier for the notation 1207 | <a href="#NT-PEDecl">PEDecl</a>
1208which may allow an XML processor or its client application to locate a helper 1208 </code></td></tr><tr valign="baseline"><td><a name="NT-GEDecl" id="NT-GEDecl"/>[71]   </td><td><code>GEDecl</code></td><td>   ::=   </td><td><code>'&lt;!ENTITY' <a href="#NT-S">S</a>
1209application capable of processing data in the given notation.]</p> <h5><a name="IDAYTFU" id="IDAYTFU" />Notation Declarations</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-NotationDecl" id="NT-NotationDecl" />[82]   </td><td><code>NotationDecl</code></td><td>   ::=   </td><td><code>'&lt;!NOTATION' <a href="#NT-S">S</a> <a href="#NT-Name">Name</a> <a href="#NT-S">S</a> (<a href="#NT-ExternalID">ExternalID</a> | <a href="#NT-PublicID">PublicID</a>) <a href="#NT-S">S</a>? '&gt;'</code></td><td><a href="#UniqueNotationName">[VC: Unique Notation Name]</a></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PublicID" id="NT-PublicID" />[83]   </td><td><code>PublicID</code></td><td>   ::=   </td><td><code>'PUBLIC' <a href="#NT-S">S</a> <a href="#NT-PubidLiteral">PubidLiteral</a></code></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="UniqueNotationName" id="UniqueNotationName" /><b>Validity constraint: Unique Notation Name</b></p><p><span class="mustard">A given <a href="#NT-Name">Name</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be declared in more than one notation declaration.</span></p></div><p>XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> provide applications with the name and external identifier(s) 1209 <a href="#NT-Name">Name</a>
1210of any notation declared and referred to in an attribute value, attribute 1210 <a href="#NT-S">S</a>
1211definition, or entity declaration. They <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> additionally resolve the external 1211 <a href="#NT-EntityDef">EntityDef</a>
1212identifier into the <a title="System Identifier" href="#dt-sysid">system identifier</a>, file 1212 <a href="#NT-S">S</a>?
1213name, or other information needed to allow the application to call a processor 1213'&gt;'</code></td></tr><tr valign="baseline"><td><a name="NT-PEDecl" id="NT-PEDecl"/>[72]   </td><td><code>PEDecl</code></td><td>   ::=   </td><td><code>'&lt;!ENTITY' <a href="#NT-S">S</a> '%' <a href="#NT-S">S</a>
1214for data in the notation described. (It is not an error, however, for XML 1214 <a href="#NT-Name">Name</a>
1215documents to declare and refer to notations for which notation-specific applications 1215 <a href="#NT-S">S</a>
1216are not available on the system where the XML processor or application is 1216 <a href="#NT-PEDef">PEDef</a>
1217running.)</p></div><div class="div2"> <h3><a name="sec-doc-entity" id="sec-doc-entity" />4.8 Document Entity</h3><p>[<a name="dt-docent" id="dt-docent" title="Document Entity">Definition</a>: The <b>document entity</b> 1217 <a href="#NT-S">S</a>? '&gt;'</code></td></tr><tr valign="baseline"><td><a name="NT-EntityDef" id="NT-EntityDef"/>[73]   </td><td><code>EntityDef</code></td><td>   ::=   </td><td><code>
1218serves as the root of the entity tree and a starting-point for an <a title="XML Processor" href="#dt-xml-proc">XML processor</a>.] This specification does 1218 <a href="#NT-EntityValue">EntityValue</a>
1219not specify how the document entity is to be located by an XML processor; 1219 | (<a href="#NT-ExternalID">ExternalID</a>
1220unlike other entities, the document entity has no name and might well appear 1220 <a href="#NT-NDataDecl">NDataDecl</a>?)</code></td></tr><tr valign="baseline"><td><a name="NT-PEDef" id="NT-PEDef"/>[74]   </td><td><code>PEDef</code></td><td>   ::=   </td><td><code>
1221on a processor input stream without any identification at all.</p></div></div><div class="div1"> <h2><a name="sec-conformance" id="sec-conformance" />5 Conformance</h2><div class="div2"> <h3><a name="proc-types" id="proc-types" />5.1 Validating and Non-Validating Processors</h3><p>Conforming <a title="XML Processor" href="#dt-xml-proc">XML processors</a> fall into 1221 <a href="#NT-EntityValue">EntityValue</a> | <a href="#NT-ExternalID">ExternalID</a>
1222two classes: validating and non-validating.</p><p>Validating and non-validating processors alike <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> report violations of 1222 </code></td></tr></tbody></table><p>The <a href="#NT-Name">Name</a> identifies the entity in an <a title="Entity Reference" href="#dt-entref">entity
1223this specification's well-formedness constraints in the content of the <a title="Document Entity" href="#dt-docent">document entity</a> and any other <a title="Text Entity" href="#dt-parsedent">parsed 1223reference</a> or, in the case of an unparsed entity, in the value of
1224entities</a> that they read.</p><p>[<a name="dt-validating" id="dt-validating" title="Validating Processor">Definition</a>: <b>Validating 1224an <b>ENTITY</b> or <b>ENTITIES</b> attribute. If the same entity is declared
1225processors</b> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>, 1225more than once, the first declaration encountered is binding; at user option,
1226at user option, report violations of the constraints expressed by 1226an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> issue a warning if entities are declared multiple times.</p><div class="div3"> <h4><a name="sec-internal-ent" id="sec-internal-ent"/>4.2.1 Internal Entities</h4><p>
1227the declarations in the <a title="Document Type Declaration" href="#dt-doctype">DTD</a>, and failures 1227 [<a name="dt-internent" id="dt-internent" title="Internal Entity Replacement Text">Definition</a>: If the
1228to fulfill the validity constraints given in this specification.] 1228entity definition is an <a href="#NT-EntityValue">EntityValue</a>, the defined
1229To accomplish this, validating XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> read and process the entire 1229entity is called an <b>internal entity</b>. There is no separate physical
1230DTD and all external parsed entities referenced in the document.</p><p>Non-validating processors are <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> to check only the <a title="Document Entity" href="#dt-docent">document 1230storage object, and the content of the entity is given in the declaration.]
1231entity</a>, including the entire internal DTD subset, for well-formedness. [<a name="dt-use-mdecl" id="dt-use-mdecl" title="Process Declarations">Definition</a>: While they are not required 1231Note that some processing of entity and character references in the <a title="Literal Entity Value" href="#dt-litentval">literal entity value</a> may be required to produce
1232to check the document for validity, they are <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> to <b>process</b> 1232the correct <a title="Replacement Text" href="#dt-repltext">replacement text</a>: see <a href="#intern-replacement"><b>4.5 Construction of Entity Replacement Text</b></a>.</p><p>An internal entity is a <a title="Text Entity" href="#dt-parsedent">parsed entity</a>.</p><p>Example of an internal entity declaration:</p><div class="exampleInner"><pre>&lt;!ENTITY Pub-Status "This is a pre-release of the
1233all the declarations they read in the internal DTD subset and in any parameter 1233specification."&gt;</pre></div></div><div class="div3"> <h4><a name="sec-external-ent" id="sec-external-ent"/>4.2.2 External Entities</h4><p>
1234entity that they read, up to the first reference to a parameter entity that 1234 [<a name="dt-extent" id="dt-extent" title="External Entity">Definition</a>: If the entity is not internal,
1235they do <em>not</em> read; that is to say, they <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> use the information 1235it is an <b>external entity</b>, declared as follows:]
1236in those declarations to <a href="#AVNormalize"><cite>normalize</cite></a> 1236 </p> <h5><a name="IDAX1KS" id="IDAX1KS"/>External Entity Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-ExternalID" id="NT-ExternalID"/>[75]   </td><td><code>ExternalID</code></td><td>   ::=   </td><td><code>'SYSTEM' <a href="#NT-S">S</a>
1237attribute values, <a href="#included"><cite>include</cite></a> the replacement 1237 <a href="#NT-SystemLiteral">SystemLiteral</a>
1238text of internal entities, and supply <a href="#sec-attr-defaults"><cite>default 1238 </code></td></tr><tr valign="baseline"><td/><td/><td/><td><code>| 'PUBLIC' <a href="#NT-S">S</a>
1239attribute values</cite></a>.] Except when <code>standalone="yes"</code>, they 1239 <a href="#NT-PubidLiteral">PubidLiteral</a>
1240<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> <a title="Process Declarations" href="#dt-use-mdecl">process</a> <a title="entity declaration" href="#dt-entdecl">entity 1240 <a href="#NT-S">S</a>
1241declarations</a> or <a title="Attribute-List Declaration" href="#dt-attdecl">attribute-list declarations</a> 1241 <a href="#NT-SystemLiteral">SystemLiteral</a>
1242encountered after a reference to a parameter entity that is not read, since 1242 </code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-NDataDecl" id="NT-NDataDecl"/>[76]   </td><td><code>NDataDecl</code></td><td>   ::=   </td><td><code>
1243the entity may have contained overriding declarations<span>; when <code>standalone="yes"</code>, processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> 1243 <a href="#NT-S">S</a> 'NDATA' <a href="#NT-S">S</a>
1244process these declarations</span>.</p><p>Note 1244 <a href="#NT-Name">Name</a>
1245that when processing invalid documents with a non-validating 1245 </code></td><td><a href="#not-declared">[VC: Notation Declared]</a></td></tr></tbody></table><p>If the <a href="#NT-NDataDecl">NDataDecl</a> is present, this is a general <a title="Unparsed Entity" href="#dt-unparsed">unparsed entity</a>; otherwise it is a parsed entity.</p><div class="constraint"><p class="prefix"><a name="not-declared" id="not-declared"/><b>Validity constraint: Notation Declared</b></p><p>The <a href="#NT-Name">Name</a>
1246processor the application may not be presented with consistent 1246 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the declared name of a <a title="Notation" href="#dt-notation">notation</a>.</p></div><p>
1247information. For example, several requirements for uniqueness 1247 [<a name="dt-sysid" id="dt-sysid" title="System Identifier">Definition</a>: The <a href="#NT-SystemLiteral">SystemLiteral</a> is called the entity's <b>system
1248within the document may not be met, including more than one element 1248identifier</b>. It is meant to be
1249with the same id, duplicate declarations of elements or notations 1249converted to a URI reference
1250with the same name, etc. In these cases the behavior of the parser 1250(as defined in <a href="#rfc3986">[IETF RFC 3986]</a>),
1251with respect to reporting such information to the application is 1251as part of the
1252undefined.</p><p>XML 1.1 processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be able to process both XML 1.0 1252process of dereferencing it to obtain input for the XML processor to construct the
1253and XML 1.1 documents. Programs which generate XML <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> 1253entity's replacement text.] It is an error for a fragment identifier
1254generate XML 1.0, unless one of the specific features of XML 1.1 is required.</p></div><div class="div2"> <h3><a name="safe-behavior" id="safe-behavior" />5.2 Using XML Processors</h3><p>The behavior of a validating XML processor is highly predictable; it must 1254(beginning with a <code>#</code> character) to be part of a system identifier.
1255read every piece of a document and report all well-formedness and validity 1255Unless otherwise provided by information outside the scope of this specification
1256violations. Less is required of a non-validating processor; it need not read 1256(e.g. a special XML element type defined by a particular DTD, or a processing
1257any part of the document other than the document entity. This has two effects 1257instruction defined by a particular application specification), relative URIs
1258that may be important to users of XML processors:</p><ul><li><p>Certain well-formedness errors, specifically those that require reading 1258are relative to the location of the resource within which the entity declaration
1259external entities, <span>may fail to</span> be detected by a non-validating processor. Examples 1259occurs. This is defined to
1260include the constraints entitled <a href="#wf-entdeclared"><cite>Entity Declared</cite></a>, <a href="#textent"><cite>Parsed Entity</cite></a>, and <a href="#norecursion"><cite>No 1260be the external entity containing the '&lt;' which starts the declaration, at the
1261Recursion</cite></a>, as well as some of the cases described as <a href="#forbidden"><cite>forbidden</cite></a> in <a href="#entproc"><b>4.4 XML Processor Treatment of Entities and References</b></a>.</p></li><li><p>The information passed from the processor to the application may 1261point when it is parsed as a declaration.
1262vary, depending on whether the processor reads parameter and external entities. 1262A URI might thus be relative to the <a title="Document Entity" href="#dt-docent">document
1263For example, a non-validating processor <span>may fail to</span> <a href="#AVNormalize"><cite>normalize</cite></a> 1263entity</a>, to the entity containing the <a title="Document Type Declaration" href="#dt-doctype">external
1264attribute values, <a href="#included"><cite>include</cite></a> the replacement 1264DTD subset</a>, or to some other <a title="External Entity" href="#dt-extent">external parameter
1265text of internal entities, or supply <a href="#sec-attr-defaults"><cite>default 1265entity</a>. Attempts to
1266attribute values</cite></a>, where doing so depends on having read declarations 1266retrieve the resource identified by a URI <span>may</span> be redirected at the parser
1267in external or parameter entities.</p></li></ul><p>For maximum reliability in interoperating between different XML processors, 1267level (for example, in an entity resolver) or below (at the protocol level,
1268applications which use non-validating processors <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD NOT</em> rely on any behaviors 1268for example, via an HTTP <code>Location:</code> header). In the absence of additional
1269not required of such processors. Applications which require DTD facilities 1269information outside the scope of this specification within the resource,
1270not related to validation (such 1270the base URI of a resource is always the URI of the actual resource returned.
1271as the declaration of default attributes and internal entities that are 1271In other words, it is the URI of the resource retrieved after all redirection
1272or may be specified in 1272has occurred.</p><p>System
1273external entities <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> use validating XML processors.</p></div></div><div class="div1"> <h2><a name="sec-notation" id="sec-notation" />6 Notation</h2><p>The formal grammar of XML is given in this specification using a simple 1273identifiers (and other XML strings meant to be used as URI references) <span>may</span> contain
1274Extended Backus-Naur Form (EBNF) notation. Each rule in the grammar defines 1274characters that, according to <a href="#rfc3986">[IETF RFC 3986]</a>,
1275one symbol, in the form</p><div class="exampleInner"><pre>symbol ::= expression</pre></div><p>Symbols are written with an initial capital letter if they are the 1275must be escaped before a URI can be used to retrieve the referenced resource. The
1276start symbol of a regular language, otherwise with an initial lowercase 1276characters to be escaped are the control characters #x0 to #x1F and #x7F (most of
1277letter. Literal strings are quoted.</p><p>Within the expression on the right-hand side of a rule, the following expressions 1277which cannot appear in XML), space #x20, the delimiters '&lt;' #x3C, '&gt;' #x3E and
1278are used to match strings of one or more characters: </p><dl><dt class="label"><code>#xN</code></dt><dd><p>where <code>N</code> is a hexadecimal integer, the expression matches the character 1278'"' #x22, the <em>unwise</em> characters '{' #x7B, '}' #x7D, '|' #x7C, '\' #x5C, '^' #x5E and
1279<span>whose</span><span> number 1279'`' #x60, as well as all characters above #x7F. Since escaping is not always a fully
1280(code point) in</span> ISO/IEC 10646 <span>is <code>N</code></span>. The number of leading zeros in the <code>#xN</code> 1280reversible process, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be performed only when absolutely necessary and as late
1281form is insignificant.</p></dd><dt class="label"><code>[a-zA-Z]</code>, <code>[#xN-#xN]</code></dt><dd><p>matches any <a href="#NT-Char">Char</a> with a value in the range(s) indicated (inclusive).</p></dd><dt class="label"><code>[abc]</code>, <code>[#xN#xN#xN]</code></dt><dd><p>matches any <a href="#NT-Char">Char</a> with a value among the characters 1281as possible in a processing chain. In particular, neither the process of converting
1282enumerated. Enumerations and ranges can be mixed in one set of brackets.</p></dd><dt class="label"><code>[^a-z]</code>, <code>[^#xN-#xN]</code></dt><dd><p>matches any <a href="#NT-Char">Char</a> with a value <em>outside</em> the range 1282a relative URI to an absolute one nor the process of passing a URI reference to a
1283indicated.</p></dd><dt class="label"><code>[^abc]</code>, <code>[^#xN#xN#xN]</code></dt><dd><p>matches any <a href="#NT-Char">Char</a> with a value not among the characters given. Enumerations 1283process or software component responsible for dereferencing it <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> trigger escaping.
1284and ranges of forbidden values can be mixed in one set of brackets.</p></dd><dt class="label"><code>"string"</code></dt><dd><p>matches a literal string <a title="match" href="#dt-match">matching</a> that 1284When escaping does occur, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be performed as follows:</p><ol class="enumar"><li><p>Each character to be escaped is represented in
1285given inside the double quotes.</p></dd><dt class="label"><code>'string'</code></dt><dd><p>matches a literal string <a title="match" href="#dt-match">matching</a> that 1285UTF-8 <a href="#Unicode">[Unicode]</a>
1286given inside the single quotes.</p></dd></dl><p> These symbols may be combined to match more complex patterns as follows, 1286as one or more bytes.</p></li><li><p>The resulting bytes are escaped with
1287where <code>A</code> and <code>B</code> represent simple expressions: </p><dl><dt class="label">(<code>expression</code>)</dt><dd><p><code>expression</code> is treated as a unit and may be combined as described 1287the URI escaping mechanism (that is, converted to <code>%</code><var>HH</var>,
1288in this list.</p></dd><dt class="label"><code>A?</code></dt><dd><p>matches <code>A</code> or nothing; optional <code>A</code>.</p></dd><dt class="label"><code>A B</code></dt><dd><p>matches <code>A</code> followed by <code>B</code>. This 1288where HH is the hexadecimal notation of the byte value).</p></li><li><p>The original character is replaced by the resulting character sequence.</p></li></ol><p>
1289operator has higher precedence than alternation; thus <code>A B | C D</code> 1289 [<a name="dt-pubid" id="dt-pubid" title="Public identifier">Definition</a>: In addition to a system
1290is identical to <code>(A B) | (C D)</code>.</p></dd><dt class="label"><code>A | B</code></dt><dd><p>matches <code>A</code> or <code>B</code>.</p></dd><dt class="label"><code>A - B</code></dt><dd><p>matches any string that matches <code>A</code> but does not match <code>B</code>.</p></dd><dt class="label"><code>A+</code></dt><dd><p>matches one or more occurrences of <code>A</code>. Concatenation 1290identifier, an external identifier <span>may</span> include a <b>public identifier</b>.]
1291has higher precedence than alternation; thus <code>A+ | B+</code> is identical 1291An XML processor attempting to retrieve the entity's content <span>may</span> use
1292to <code>(A+) | (B+)</code>.</p></dd><dt class="label"><code>A*</code></dt><dd><p>matches zero or more occurrences of <code>A</code>. Concatenation 1292any combination of
1293has higher precedence than alternation; thus <code>A* | B*</code> is identical 1293the public and system identifiers as well as additional information outside the
1294to <code>(A*) | (B*)</code>.</p></dd></dl><p> Other notations used in the productions are: </p><dl><dt class="label"><code>/* ... */</code></dt><dd><p>comment.</p></dd><dt class="label"><code>[ wfc: ... ]</code></dt><dd><p>well-formedness constraint; this identifies by name a constraint on <a title="Well-Formed" href="#dt-wellformed">well-formed</a> documents associated with a production.</p></dd><dt class="label"><code>[ vc: ... ]</code></dt><dd><p>validity constraint; this identifies by name a constraint on <a title="Validity" href="#dt-valid">valid</a> 1294scope of this specification to try to generate an alternative URI reference.
1295documents associated with a production.</p></dd></dl><p></p></div></div><div class="back"><div class="div1"> <h2><a name="sec-bibliography" id="sec-bibliography" />A References</h2><div class="div2"> <h3><a name="sec-existing-stds" id="sec-existing-stds" />A.1 Normative References</h3><dl><dt class="label"><a name="IANA" id="IANA" />IANA-CHARSETS</dt><dd>(Internet 1295If the processor is unable to do so, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> use the URI
1296Assigned Numbers Authority) <a href="http://www.iana.org/assignments/character-sets"><cite>Official Names for Character Sets</cite></a>, 1296reference specified in the system literal. Before a match is attempted,
1297ed. Keld Simonsen et al. (See http://www.iana.org/assignments/character-sets.)</dd><dt class="label"><a name="rfc2119" id="rfc2119" />IETF RFC 2119</dt><dd>IETF 1297all strings of white space in the public identifier <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be normalized to
1298(Internet Engineering Task Force). <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>RFC 2119: Key words for use in RFCs to Indicate Requirement Levels</cite></a>. 1298single space characters (#x20), and leading and trailing white space <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
1299Scott Bradner, 1997. (See http://www.ietf.org/rfc/rfc2119.txt.)</dd><dt class="label"><a name="rfc2396" id="rfc2396" />IETF RFC 2396</dt><dd>IETF 1299be removed.</p><p>Examples of external entity declarations:</p><div class="exampleInner"><pre>&lt;!ENTITY open-hatch
1300(Internet Engineering Task Force). <a href="http://www.ietf.org/rfc/rfc2396.txt"><cite>RFC 2396: Uniform Resource Identifiers 1300SYSTEM "http://www.textuality.com/boilerplate/OpenHatch.xml"&gt;
1301(URI): Generic Syntax</cite></a>. T. Berners-Lee, R. Fielding, L. Masinter. 1301&lt;!ENTITY open-hatch
13021998. (See http://www.ietf.org/rfc/rfc2396.txt.)</dd><dt class="label"><a name="rfc2732" id="rfc2732" />IETF RFC 2732</dt><dd>IETF 1302PUBLIC "-//Textuality//TEXT Standard open-hatch boilerplate//EN"
1303(Internet Engineering Task Force). <a href="http://www.ietf.org/rfc/rfc2732.txt"><cite>RFC 2732: Format for Literal 1303"http://www.textuality.com/boilerplate/OpenHatch.xml"&gt;
1304IPv6 Addresses in URL's</cite></a>. R. Hinden, B. Carpenter, L. Masinter. 1304&lt;!ENTITY hatch-pic
13051999. (See http://www.ietf.org/rfc/rfc2732.txt.)</dd><dt class="label"><a name="RFC1766" id="RFC1766" />IETF RFC 3066</dt><dd>IETF 1305SYSTEM "../grafix/OpenHatch.gif"
1306(Internet Engineering Task Force). <a href="http://www.ietf.org/rfc/rfc3066.txt"><cite>RFC 3066: Tags for the Identification 1306NDATA gif &gt;</pre></div></div></div><div class="div2"> <h3><a name="TextEntities" id="TextEntities"/>4.3 Parsed Entities</h3><div class="div3"> <h4><a name="sec-TextDecl" id="sec-TextDecl"/>4.3.1 The Text Declaration</h4><p>External parsed entities <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> each begin with a <b>text declaration</b>.</p> <h5><a name="IDAGDLS" id="IDAGDLS"/>Text Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-TextDecl" id="NT-TextDecl"/>[77]   </td><td><code>TextDecl</code></td><td>   ::=   </td><td><code>'&lt;?xml' <a href="#NT-VersionInfo">VersionInfo</a>? <a href="#NT-EncodingDecl">EncodingDecl</a>
1307of Languages</cite></a>, ed. H. Alvestrand. 2001. (See http://www.ietf.org/rfc/rfc3066.txt.)</dd><dt class="label"><a name="ISO10646" id="ISO10646" />ISO/IEC 10646</dt><dd><span>ISO (International 1307 <a href="#NT-S">S</a>? '?&gt;'</code></td></tr></tbody></table><p>The text declaration <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be provided literally, not by reference
1308Organization for Standardization). <cite>ISO/IEC 10646-1:2000. Information 1308to a parsed entity. The text declaration
1309technology — Universal Multiple-Octet Coded Character Set (UCS) — 1309<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear at any
1310Part 1: Architecture and Basic Multilingual Plane</cite> and <cite>ISO/IEC 10646-2:2001. 1310position other than the beginning of an external parsed entity. The text declaration
1311Information technology — Universal Multiple-Octet Coded Character Set (UCS) — Part 2: 1311in an external parsed entity is not considered part of its <a title="Replacement Text" href="#dt-repltext">replacement text</a>.</p></div><div class="div3"> <h4><a name="wf-entities" id="wf-entities"/>4.3.2 Well-Formed Parsed Entities</h4><p>The document entity is well-formed if it matches the production labeled <a href="#NT-document">document</a>. An external general parsed entity is well-formed
1312Supplementary Planes</cite>, as, from time to time, amended, replaced by a new edition or 1312if it matches the production labeled <a href="#NT-extParsedEnt">extParsedEnt</a>. All
1313expanded by the addition of new parts. [Geneva]: International Organization for Standardization. 1313external parameter entities are well-formed by definition.</p><div class="note"><p class="prefix"><b>Note:</b></p><p>
1314(See <a href="http://www.iso.ch">http://www.iso.ch</a> for the latest version.)</span></dd><dt class="label"><a name="Unicode" id="Unicode" />Unicode</dt><dd>The Unicode Consortium. <em>The Unicode 1314 Only parsed entities that are referenced directly or indirectly within the document are required to be well-formed.</p></div> <h5><a name="IDAKFLS" id="IDAKFLS"/>Well-Formed External Parsed Entity</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-extParsedEnt" id="NT-extParsedEnt"/>[78]   </td><td><code>extParsedEnt</code></td><td>   ::=   </td><td><code>
1315Standard, Version 4.0.</em> Reading, Mass.: Addison-Wesley, 1315 <span>
13162003, 1316 (</span>
1317as updated from time to time by the publication of new versions. (See 1317 <a href="#NT-TextDecl">TextDecl</a>? <a href="#NT-content">content</a>
1318<a href="http://www.unicode.org/unicode/standard/versions"> 1318 <span>
1319http://www.unicode.org/unicode/standard/versions</a> for the latest version 1319 )</span> - <span>
1320and additional information on versions of the standard and of the Unicode 1320 (</span>
1321Character Database).</dd><dt class="label"><a name="XML1.0" />XML-1.0</dt><dd>W3C. <a href="http://www.w3.org/TR/REC-xml"><cite>Extensible Markup Language (XML) 1.0 (Third 1321 <a href="#NT-Char">Char</a>* <a href="#NT-RestrictedChar">RestrictedChar</a>
1322Edition)</cite></a>. Tim Bray, Jean Paoli, C.M. Sperberg-McQueen, Eve Maler, François Yergeau 1322 <a href="#NT-Char">Char</a>*<span>
1323(editors) (See http://www.w3.org/TR/REC-xml.)</dd></dl></div><div class="div2"> <h3><a name="null" id="null" />A.2 Other References</h3><dl><dt class="label"><a name="Aho" id="Aho" />Aho/Ullman</dt><dd>Aho, Alfred V., Ravi Sethi, and Jeffrey D. 1323 )</span>
1324Ullman. <cite>Compilers: Principles, Techniques, and Tools</cite>. 1324 </code></td></tr></tbody></table><p>An internal general parsed entity is well-formed if its replacement text
1325Reading: Addison-Wesley, 1986, rpt. corr. 1988.</dd><dt class="label"><a name="ABK" id="ABK" />Brüggemann-Klein</dt><dd>Brüggemann-Klein, 1325matches the production labeled <a href="#NT-content">content</a>. All internal
1326Anne. <a href="ftp://ftp.informatik.uni-freiburg.de/documents/papers/brueggem/habil.ps"><cite>Formal Models in Document Processing</cite></a>. Habilitationsschrift. Faculty 1326parameter entities are well-formed by definition.</p><p>A consequence of well-formedness in general
1327of Mathematics at the University of Freiburg, 1993. (See ftp://ftp.informatik.uni-freiburg.de/documents/papers/brueggem/habil.ps.)</dd><dt class="label"><a name="ABKDW" id="ABKDW" />Brüggemann-Klein and Wood</dt><dd>Brüggemann-Klein, 1327entities is that the logical and physical
1328Anne, and Derick Wood. <cite>Deterministic Regular Languages</cite>. 1328structures in an XML document are properly nested; no <a title="Start-Tag" href="#dt-stag">start-tag</a>, <a title="End Tag" href="#dt-etag">end-tag</a>, <a title="Empty" href="#dt-empty">empty-element tag</a>, <a title="Element" href="#dt-element">element</a>, <a title="Comment" href="#dt-comment">comment</a>, <a title="Processing instruction" href="#dt-pi">processing instruction</a>, <a title="Character Reference" href="#dt-charref">character
1329Universität Freiburg, Institut für Informatik, Bericht 38, Oktober 1991. Extended 1329reference</a>, or <a title="Entity Reference" href="#dt-entref">entity reference</a>
1330abstract in A. Finkel, M. Jantzen, Hrsg., STACS 1992, S. 173-184. Springer-Verlag, 1330can begin in one entity and end in another.</p></div><div class="div3"> <h4><a name="charencoding" id="charencoding"/>4.3.3 Character Encoding in Entities</h4><p>Each external parsed entity in an XML document <span>may</span> use a different encoding
1331Berlin 1992. Lecture Notes in Computer Science 577. Full version titled <cite>One-Unambiguous 1331for its characters. All XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be able to read entities in both
1332Regular Languages</cite> in Information and Computation 140 (2): 229-253, 1332the UTF-8 and UTF-16 encodings. The terms "UTF-8"
1333February 1998.</dd><dt class="label"><a name="Charmod" />Charmod</dt><dd>W3C Working Draft. 1333and "UTF-16" in this specification do not apply to character
1334 1334encodings with any other labels, even if the encodings or labels are very
1335<a href="http://www.w3.org/TR/2003/WD-charmod-20030822/"><cite>Character Model for the World Wide Web 1.0</cite></a>. 1335similar to UTF-8 or UTF-16.</p><p>Entities encoded in UTF-16 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> and entities
1336 1336encoded in UTF-8 <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> begin with the Byte Order Mark described in
1337Martin J. Dürst, François Yergeau, Richard Ishida, Misha Wolf, Tex Texin. (See http://www.w3.org/TR/2003/WD-charmod-20030822/.)</dd><dt class="label"><a name="Clark" id="Clark" />Clark</dt><dd>James Clark. 1337ISO/IEC 10646 <a href="#ISO10646">[ISO/IEC 10646]</a> or Unicode <a href="#Unicode">[Unicode]</a>
1338<a href="http://www.w3.org/TR/NOTE-sgml-xml-971215"><cite>Comparison of SGML and XML</cite></a>. (See http://www.w3.org/TR/NOTE-sgml-xml-971215.)</dd><dt class="label"><a name="IANA-LANGCODES" id="IANA-LANGCODES" />IANA-LANGCODES</dt><dd>(Internet 1338(the ZERO WIDTH NO-BREAK SPACE character, #xFEFF). This is an encoding signature,
1339Assigned Numbers Authority) <a href="http://www.iana.org/assignments/language-tags"><cite>Registry of Language Tags</cite></a>, 1339not part of either the markup or the character data of the XML document. XML
1340ed. Keld Simonsen et al. (See http://www.iana.org/assignments/language-tags.)</dd><dt class="label"><a name="RFC2141" id="RFC2141" />IETF RFC 2141</dt><dd>IETF 1340processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be able to use this character to differentiate between UTF-8
1341(Internet Engineering Task Force). <a href="http://www.ietf.org/rfc/rfc2141.txt"><cite>RFC 2141: URN Syntax</cite></a>, ed. 1341and UTF-16 encoded documents.</p><p>Although an XML processor is required to read only entities in the UTF-8
1342R. Moats. 1997. (See http://www.ietf.org/rfc/rfc2141.txt.)</dd><dt class="label"><a name="rfc2376" id="rfc2376" />IETF RFC 3023</dt><dd>IETF 1342and UTF-16 encodings, it is recognized that other encodings are used around
1343(Internet Engineering Task Force). <a href="http://www.ietf.org/rfc/rfc3023.txt"><cite>RFC 3023: XML Media Types</cite></a>. 1343the world, and it may be desired for XML processors to read entities that
1344eds. M. Murata, S. St.Laurent, D. Kohn. 2001. (See http://www.ietf.org/rfc/rfc3023.txt.)</dd><dt class="label"><a name="rfc2781" id="rfc2781" />IETF RFC 2781</dt><dd>IETF 1344use them. In
1345(Internet Engineering Task Force). <a href="http://www.ietf.org/rfc/rfc2781.txt"><cite>RFC 2781: UTF-16, an encoding 1345the absence of external character encoding information (such as MIME headers),
1346of ISO 10646</cite></a>, ed. P. Hoffman, F. Yergeau. 2000. (See http://www.ietf.org/rfc/rfc2781.txt.)</dd><dt class="label"><a name="ISO639" id="ISO639" />ISO 639</dt><dd>(International Organization for Standardization). 1346parsed entities which are stored in an encoding other than UTF-8 or UTF-16
1347<cite>ISO 639:1988 (E). 1347<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> begin with a text declaration (see <a href="#sec-TextDecl"><b>4.3.1 The Text Declaration</b></a>) containing
1348Code for the representation of names of languages.</cite> [Geneva]: International 1348an encoding declaration:</p> <h5><a name="IDABKLS" id="IDABKLS"/>Encoding Declaration</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EncodingDecl" id="NT-EncodingDecl"/>[80]   </td><td><code>EncodingDecl</code></td><td>   ::=   </td><td><code>
1349Organization for Standardization, 1988.</dd><dt class="label"><a name="ISO3166" id="ISO3166" />ISO 3166</dt><dd>(International Organization for Standardization). 1349 <a href="#NT-S">S</a> 'encoding' <a href="#NT-Eq">Eq</a>
1350<cite>ISO 3166-1:1997 1350('"' <a href="#NT-EncName">EncName</a> '"' | "'" <a href="#NT-EncName">EncName</a>
1351(E). Codes for the representation of names of countries and their subdivisions — 1351"'" ) </code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-EncName" id="NT-EncName"/>[81]   </td><td><code>EncName</code></td><td>   ::=   </td><td><code>[A-Za-z] ([A-Za-z0-9._] | '-')*</code></td><td><i>/* Encoding
1352Part 1: Country codes</cite> [Geneva]: International Organization for 1352name contains only Latin characters */</i></td></tr></tbody></table><p>In the <a title="Document Entity" href="#dt-docent">document entity</a>, the encoding
1353Standardization, 1997.</dd><dt class="label"><a name="ISO8879" id="ISO8879" />ISO 8879</dt><dd>ISO (International Organization for Standardization). <cite>ISO 1353declaration is part of the <a title="XML Declaration" href="#dt-xmldecl">XML declaration</a>.
13548879:1986(E). Information processing — Text and Office Systems — 1354The <a href="#NT-EncName">EncName</a> is the name of the encoding used.</p><p>In an encoding declaration, the values "<code>UTF-8</code>", "<code>UTF-16</code>",
1355Standard Generalized Markup Language (SGML).</cite> First edition — 1355"<code>ISO-10646-UCS-2</code>", and "<code>ISO-10646-UCS-4</code>"
13561986-10-15. [Geneva]: International Organization for Standardization, 1986. </dd><dt class="label"><a name="ISO10744" id="ISO10744" />ISO/IEC 10744</dt><dd>ISO (International Organization for 1356 <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be used
1357Standardization). <cite>ISO/IEC 10744-1992 (E). Information technology — 1357for the various encodings and transformations of Unicode / ISO/IEC 10646,
1358Hypermedia/Time-based Structuring Language (HyTime). </cite> [Geneva]: 1358the values "<code>ISO-8859-1</code>", "<code>ISO-8859-2</code>",
1359International Organization for Standardization, 1992. <em>Extended Facilities 1359... "<code>ISO-8859-</code><var>n</var>" (where <var>n</var>
1360Annexe.</em> [Geneva]: International Organization for Standardization, 1996. </dd><dt class="label"><a name="websgml" id="websgml" />WEBSGML</dt><dd>ISO 1360is the part number) <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be used for the parts of ISO 8859, and
1361(International Organization for Standardization). <a href="http://www.sgmlsource.com/8879/n0029.htm"><cite>ISO 8879:1986 1361the values "<code>ISO-2022-JP</code>", "<code>Shift_JIS</code>",
1362TC2. Information technology — Document Description and Processing Languages</cite></a>. 1362and "<code>EUC-JP</code>"
1363[Geneva]: International Organization for Standardization, 1998. (See http://www.sgmlsource.com/8879/n0029.htm.)</dd><dt class="label"><a name="xml-names" id="xml-names" />XML Names</dt><dd>Tim Bray, 1363 <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be used for the various encoded
1364Dave Hollander, and Andrew Layman, editors. <a href="http://www.w3.org/TR/REC-xml-names/"><cite>Namespaces in XML</cite></a>. 1364forms of JIS X-0208-1997. It
1365Textuality, Hewlett-Packard, and Microsoft. World Wide Web Consortium, 1999. (See http://www.w3.org/TR/REC-xml-names/.)</dd></dl></div></div><div class="div1"> <h2><a name="sec-CharNorm" id="sec-CharNorm" />B Definitions for Character Normalization</h2><p>This appendix contains the necessary definitions for character normalization. 1365is <em class="rfc2119" title="Keyword in RFC 2119 context">RECOMMENDED</em> that character encodings registered (as <em>charset</em>s)
1366For additional background information and examples, see <a href="#Charmod">[Charmod]</a>.</p><p> 1366with the Internet Assigned Numbers Authority <a href="#IANA">[IANA-CHARSETS]</a>,
1367[<a name="dt-Uni-encform" id="dt-Uni-encform" title="Unicode encoding form">Definition</a>: Text is said to be 1367other than those just listed, be referred to using their registered names;
1368in a <b>Unicode encoding form</b> if it is encoded in 1368other encodings <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> use names starting with an "x-" prefix.
1369UTF-8, UTF-16 or UTF-32.]</p><p> 1369XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> match character encoding names in a case-insensitive
1370[<a name="dt-legacyenc" id="dt-legacyenc" title="legacy encoding">Definition</a>: <b>Legacy encoding</b> 1370way and <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> either interpret an IANA-registered name as the encoding registered
1371is taken to mean any character encoding not based on Unicode.]</p><p> 1371at IANA for that name or treat it as unknown (processors are, of course, not
1372[<a name="dt-normtransc" id="dt-normtransc" title="normalizing transcoder">Definition</a>: A 1372required to support all IANA-registered encodings).</p><p>In the absence of information provided by an external transport protocol
1373<b>normalizing transcoder</b> is a transcoder that converts from a 1373(e.g. HTTP or MIME), it is a <a title="Fatal Error" href="#dt-fatal">fatal error</a> for
1374<a title="legacy encoding" href="#dt-legacyenc">legacy encoding</a> to a 1374an entity including an encoding declaration to be presented to the XML processor
1375<a title="Unicode encoding form" href="#dt-Uni-encform">Unicode encoding form</a> and 1375in an encoding other than that named in the declaration, or for an entity which
1376ensures that the result is in Unicode Normalization Form C 1376begins with neither a Byte Order Mark
1377(see UAX #15 <a href="#Unicode">[Unicode]</a>).]</p><p>[<a name="dt-charesc" id="dt-charesc" title="character escape">Definition</a>: A <b>character escape</b> 1377nor an encoding declaration to use an encoding other than UTF-8. Note that
1378is a syntactic device defined in a markup or programming language that allows 1378since ASCII is a subset of UTF-8, ordinary ASCII entities do not strictly
1379one or more of:]</p><ol type="1"><li><p>expressing syntax-significant characters while disregarding 1379need an encoding declaration.</p><p>It is a <a title="Fatal Error" href="#dt-fatal">fatal error</a> for a <a href="#NT-TextDecl">TextDecl</a> to occur other
1380their significance in the syntax of the language, or</p></li><li><p>expressing characters not representable in the character encoding 1380than at the beginning of an external entity.</p><p>It is a <a title="Fatal Error" href="#dt-fatal">fatal error</a> when an XML processor
1381chosen for an instance of the language, or</p></li><li><p>expressing characters in general, without use of the corresponding 1381encounters an entity with an encoding that it is unable to process. It
1382character codes.</p></li></ol><p> 1382is a <a title="Fatal Error" href="#dt-fatal">fatal error</a> if an XML entity is determined (via default, encoding declaration,
1383[<a name="dt-certified" id="dt-certified" title="certified">Definition</a>: <b>Certified</b> text 1383or higher-level protocol) to be in a certain encoding but contains byte
1384is text which satisfies at least one of the following conditions:]</p><ol type="1"><li><p>it has been confirmed through inspection that the text 1384sequences that are not legal in that encoding. Specifically, it is a
1385is in normalized form</p></li><li><p>the source text-processing component is identified 1385fatal error if an entity encoded in UTF-8 contains any irregular code unit sequences,
1386and is known to produce only normalized text.</p></li></ol><p> 1386as defined in Unicode <a href="#Unicode">[Unicode]</a>. Unless an encoding
1387[<a name="dt-uninorm" id="dt-uninorm" title="Unicode-normalized">Definition</a>: Text is, for the purposes of 1387is determined by a higher-level protocol, it is also a <a title="Fatal Error" href="#dt-fatal">fatal error</a> if an XML entity
1388this specification, <b>Unicode-normalized</b> if it is in a 1388contains no encoding declaration and its content is not legal UTF-8 or UTF-16.</p><p>Examples of text declarations containing encoding declarations:</p><div class="exampleInner"><pre>&lt;?xml encoding='UTF-8'?&gt;
1389<a title="Unicode encoding form" href="#dt-Uni-encform">Unicode encoding form</a> and is in 1389&lt;?xml encoding='EUC-JP'?&gt;</pre></div></div><div class="div3"> <h4><a name="sec-version-info" id="sec-version-info"/>4.3.4 Version Information in Entities</h4><p>Each entity, including the <a title="Document Entity" href="#dt-docent">document entity</a>,
1390Unicode Normalization Form C, according to a version of Unicode Standard Annex #15: 1390can be separately
1391Unicode Normalization Forms <a href="#Unicode">[Unicode]</a> at least as recent as the 1391declared as XML 1.0 or XML 1.1. The version declaration appearing
1392oldest version of the Unicode Standard that contains all the characters 1392in the document entity determines the version of the document as a
1393actually present in the text, but no earlier 1393whole. An XML 1.1 document may invoke XML 1.0 external entities, so
1394than version 3.2.]</p><p> 1394that otherwise duplicated versions of external entities,
1395[<a name="dt-inclnorm" id="dt-inclnorm" title="include-normalized">Definition</a>: Text is 1395particularly DTD external subsets, need not be maintained. However,
1396<b>include-normalized</b> if:]</p><ol type="1"><li><p>the text is <a title="Unicode-normalized" href="#dt-uninorm">Unicode-normalized</a> 1396in such a case the rules of XML 1.1 are applied to the entire
1397and does not contain any <a title="character escape" href="#dt-charesc">character escapes</a> 1397document.</p><p> If an entity (including the document entity) is not labeled
1398or <a title="Include" href="#dt-include">includes</a> whose expansion would 1398with a version number, it is treated as if labeled as version
1399cause the text to become no longer <a title="Unicode-normalized" href="#dt-uninorm">Unicode-normalized</a>; 13991.0.</p></div></div><div class="div2"> <h3><a name="entproc" id="entproc"/>4.4 XML Processor Treatment of Entities and References</h3><p>The table below summarizes the contexts in which character references,
1400or</p></li><li><p>the text is in a <a title="legacy encoding" href="#dt-legacyenc">legacy encoding</a> and, if it were transcoded 1400entity references, and invocations of unparsed entities might appear and the
1401to a <a title="Unicode encoding form" href="#dt-Uni-encform">Unicode encoding form</a> by a 1401<em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> behavior of an <a title="XML Processor" href="#dt-xml-proc">XML processor</a>
1402<a title="normalizing transcoder" href="#dt-normtransc">normalizing transcoder</a>, the resulting 1402in each case. The labels in the leftmost column describe the recognition context: </p><dl><dt class="label">Reference in Content</dt><dd><p>as a reference anywhere after the <a title="Start-Tag" href="#dt-stag">start-tag</a>
1403text would satisfy clause 1 above.</p></li></ol><p> 1403and before the <a title="End Tag" href="#dt-etag">end-tag</a> of an element; corresponds
1404[<a name="dt-compchar" id="dt-compchar" title="composing character">Definition</a>: A <b>composing character</b> 1404to the nonterminal <a href="#NT-content">content</a>.</p></dd><dt class="label">Reference in Attribute Value</dt><dd><p>as a reference within either the value of an attribute in a <a title="Start-Tag" href="#dt-stag">start-tag</a>,
1405is a character that is one or both of the following:]</p><ol type="1"><li><p>the second character in the canonical decomposition mapping of 1405or a default value in an <a title="Attribute-List Declaration" href="#dt-attdecl">attribute declaration</a>;
1406some primary composite (as defined in D3 of UAX #15 <a href="#Unicode">[Unicode]</a>), or</p></li><li><p>of non-zero canonical combining class (as defined in Unicode 1406corresponds to the nonterminal <a href="#NT-AttValue">AttValue</a>.</p></dd><dt class="label">Occurs as Attribute Value</dt><dd><p>as a <a href="#NT-Name">Name</a>, not a reference, appearing either as
1407<a href="#Unicode">[Unicode]</a>).</p></li></ol><p> 1407the value of an attribute which has been declared as type <b>ENTITY</b>,
1408[<a name="dt-fullnorm" id="dt-fullnorm" title="fully normalized">Definition</a>: Text is 1408or as one of the space-separated tokens in the value of an attribute which
1409<b>fully-normalized</b> if:]</p><ol type="1"><li><p>the text is in a <a title="Unicode encoding form" href="#dt-Uni-encform">Unicode encoding 1409has been declared as type <b>ENTITIES</b>.</p></dd><dt class="label">Reference in Entity Value</dt><dd><p>as a reference within a parameter or internal entity's <a title="Literal Entity Value" href="#dt-litentval">literal
1410form</a>, is <a title="include-normalized" href="#dt-inclnorm">include-normalized</a> and 1410entity value</a> in the entity's declaration; corresponds to the nonterminal <a href="#NT-EntityValue">EntityValue</a>.</p></dd><dt class="label">Reference in DTD</dt><dd><p>as a reference within either the internal or external subsets of the <a title="Document Type Declaration" href="#dt-doctype">DTD</a>, but outside of an <a href="#NT-EntityValue">EntityValue</a>, <a href="#NT-AttValue">AttValue</a>, <a href="#NT-PI">PI</a>, <a href="#NT-Comment">Comment</a>, <a href="#NT-SystemLiteral">SystemLiteral</a>, <a href="#NT-PubidLiteral">PubidLiteral</a>,
1411none of the <a title="" href="#dt-relconst"><span>relevant</span> 1411or the contents of an ignored conditional section (see <a href="#sec-condition-sect"><b>3.4 Conditional Sections</b></a>).</p><p>.</p></dd></dl><p>
1412constructs</a> comprising the text begin with a 1412 </p><table border="1" frame="border" cellpadding="7" summary="Entity type/reference matrix"><tbody align="center"><tr><td rowspan="2"></td><td colspan="4" align="center" valign="bottom">Entity
1413<a title="composing character" href="#dt-compchar">composing character</a> or a 1413Type</td><td rowspan="2" align="center">Character</td></tr><tr align="center" valign="bottom"><td>Parameter</td><td>Internal General</td><td>External Parsed
1414character escape representing a 1414General</td><td>Unparsed</td></tr><tr align="center" valign="middle"><td align="right">Reference
1415<a title="composing character" href="#dt-compchar">composing character</a>; or</p></li><li><p>the text is in a <a title="legacy encoding" href="#dt-legacyenc">legacy encoding</a> and, 1415in Content</td><td>
1416if it were transcoded to a <a title="Unicode encoding form" href="#dt-Uni-encform">Unicode encoding form</a> 1416 <a href="#not-recognized"><cite>Not recognized</cite></a>
1417by a <a title="normalizing transcoder" href="#dt-normtransc">normalizing transcoder</a>, the resulting text 1417 </td><td>
1418would satisfy clause 1 above.</p></li></ol></div><div class="div1"> <h2><a name="sec-entexpand" id="sec-entexpand" />C Expansion of Entity and Character References (Non-Normative)</h2><p>This appendix contains some examples illustrating the sequence of entity- 1418 <a href="#included"><cite>Included</cite></a>
1419and character-reference recognition and expansion, as specified in <a href="#entproc"><b>4.4 XML Processor Treatment of Entities and References</b></a>.</p><p>If the DTD contains the declaration</p><div class="exampleInner"><pre>&lt;!ENTITY example "&lt;p&gt;An ampersand (&amp;#38;#38;) may be escaped 1419 </td><td>
1420numerically (&amp;#38;#38;#38;) or with a general entity 1420 <a href="#include-if-valid"><cite>Included
1421(&amp;amp;amp;).&lt;/p&gt;" &gt;</pre></div><p>then the XML processor will recognize the character references when it 1421if validating</cite></a>
1422parses the entity declaration, and resolve them before storing the following 1422 </td><td>
1423string as the value of the entity "<code>example</code>":</p><div class="exampleInner"><pre>&lt;p&gt;An ampersand (&amp;#38;) may be escaped 1423 <a href="#forbidden"><cite>Forbidden</cite></a>
1424numerically (&amp;#38;#38;) or with a general entity 1424 </td><td>
1425(&amp;amp;amp;).&lt;/p&gt;</pre></div><p>A reference in the document to "<code>&amp;example;</code>" 1425 <a href="#included"><cite>Included</cite></a>
1426will cause the text to be reparsed, at which time the start- and end-tags 1426 </td></tr><tr align="center" valign="middle"><td align="right">Reference in Attribute Value</td><td>
1427of the <code>p</code> element will be recognized and the three references will 1427 <a href="#not-recognized"><cite>Not recognized</cite></a>
1428be recognized and expanded, resulting in a <code>p</code> element with the following 1428 </td><td>
1429content (all data, no delimiters or markup):</p><div class="exampleInner"><pre>An ampersand (&amp;) may be escaped 1429 <a href="#inliteral"><cite>Included
1430numerically (&amp;#38;) or with a general entity 1430in literal</cite></a>
1431(&amp;amp;).</pre></div><p>A more complex example will illustrate the rules and their effects fully. 1431 </td><td>
1432In the following example, the line numbers are solely for reference.</p><div class="exampleInner"><pre>1 &lt;?xml version='1.0'?&gt; 1432 <a href="#forbidden"><cite>Forbidden</cite></a>
14332 &lt;!DOCTYPE test [ 1433 </td><td>
14343 &lt;!ELEMENT test (#PCDATA) &gt; 1434 <a href="#forbidden"><cite>Forbidden</cite></a>
14354 &lt;!ENTITY % xx '&amp;#37;zz;'&gt; 1435 </td><td>
14365 &lt;!ENTITY % zz '&amp;#60;!ENTITY tricky "error-prone" &gt;' &gt; 1436 <a href="#included"><cite>Included</cite></a>
14376 %xx; 1437 </td></tr><tr align="center" valign="middle"><td align="right">Occurs as Attribute
14387 ]&gt; 1438Value</td><td>
14398 &lt;test&gt;This sample shows a &amp;tricky; method.&lt;/test&gt;</pre></div><p>This produces the following:</p><ul><li><p>in line 4, the reference to character 37 is expanded immediately, 1439 <a href="#not-recognized"><cite>Not recognized</cite></a>
1440and the parameter entity "<code>xx</code>" is stored in the symbol 1440 </td><td>
1441table with the value "<code>%zz;</code>". Since the replacement 1441 <a href="#forbidden"><cite>Forbidden</cite></a>
1442text is not rescanned, the reference to parameter entity "<code>zz</code>" 1442 </td><td>
1443is not recognized. (And it would be an error if it were, since "<code>zz</code>" 1443 <a href="#forbidden"><cite>Forbidden</cite></a>
1444is not yet declared.)</p></li><li><p>in line 5, the character reference "<code>&amp;#60;</code>" 1444 </td><td>
1445is expanded immediately and the parameter entity "<code>zz</code>" 1445 <a href="#notify"><cite>Notify</cite></a>
1446is stored with the replacement text "<code>&lt;!ENTITY tricky "error-prone" 1446 </td><td>
1447&gt;</code>", which is a well-formed entity declaration.</p></li><li><p>in line 6, the reference to "<code>xx</code>" is recognized, 1447 <a href="#not-recognized"><cite>Not recognized</cite></a>
1448and the replacement text of "<code>xx</code>" (namely "<code>%zz;</code>") 1448 </td></tr><tr align="center" valign="middle"><td align="right">Reference in EntityValue</td><td>
1449is parsed. The reference to "<code>zz</code>" is recognized in 1449 <a href="#inliteral"><cite>Included in literal</cite></a>
1450its turn, and its replacement text ("<code>&lt;!ENTITY tricky "error-prone" 1450 </td><td>
1451&gt;</code>") is parsed. The general entity "<code>tricky</code>" 1451 <a href="#bypass"><cite>Bypassed</cite></a>
1452has now been declared, with the replacement text "<code>error-prone</code>".</p></li><li><p>in line 8, the reference to the general entity "<code>tricky</code>" 1452 </td><td>
1453is recognized, and it is expanded, so the full content of the <code>test</code> 1453 <a href="#bypass"><cite>Bypassed</cite></a>
1454element is the self-describing (and ungrammatical) string <em>This sample 1454 </td><td>
1455shows a error-prone method.</em></p></li></ul></div><div class="div1"> <h2><a name="determinism" id="determinism" />D Deterministic Content Models (Non-Normative)</h2><p>As 1455 <a href="#error"><cite>Error</cite></a>
1456noted in <a href="#sec-element-content"><b>3.2.1 Element Content</b></a>, it is required that content 1456 </td><td>
1457models in element type declarations be deterministic. This requirement is <a title="For Compatibility" href="#dt-compat">for compatibility</a> with SGML (which calls deterministic 1457 <a href="#included"><cite>Included</cite></a>
1458content models "unambiguous"); XML processors built 1458 </td></tr><tr align="center" valign="middle"><td align="right">Reference in DTD</td><td>
1459using SGML systems may flag non-deterministic content models as errors.</p><p>For example, the content model <code>((b, c) | (b, d))</code> is non-deterministic, 1459 <a href="#as-PE"><cite>Included as PE</cite></a>
1460because given an initial <code>b</code> the XML processor 1460 </td><td>
1461cannot know which <code>b</code> in the model is being matched without looking 1461 <a href="#forbidden"><cite>Forbidden</cite></a>
1462ahead to see which element follows the <code>b</code>. In this case, the two references 1462 </td><td>
1463to <code>b</code> can be collapsed into a single reference, making the model read <code>(b, 1463 <a href="#forbidden"><cite>Forbidden</cite></a>
1464(c | d))</code>. An initial <code>b</code> now clearly matches only a single name 1464 </td><td>
1465in the content model. The processor doesn't need to look ahead to see what follows; either <code>c</code> or <code>d</code> 1465 <a href="#forbidden"><cite>Forbidden</cite></a>
1466would be accepted.</p><p>More formally: a finite state automaton may be constructed from the content 1466 </td><td>
1467model using the standard algorithms, e.g. algorithm 3.5 in section 3.9 of 1467 <a href="#forbidden"><cite>Forbidden</cite></a>
1468Aho, Sethi, and Ullman <a href="#Aho">[Aho/Ullman]</a>. In many such algorithms, a follow 1468 </td></tr></tbody></table><div class="div3"> <h4><a name="not-recognized" id="not-recognized"/>4.4.1 Not Recognized</h4><p>Outside the DTD, the <code>%</code> character has no special significance;
1469set is constructed for each position in the regular expression (i.e., each 1469thus, what would be parameter entity references in the DTD are not recognized
1470leaf node in the syntax tree for the regular expression); if any position 1470as markup in <a href="#NT-content">content</a>. Similarly, the names of unparsed
1471has a follow set in which more than one following position is labeled with 1471entities are not recognized except when they appear in the value of an appropriately
1472the same element type name, then the content model is in error and may be 1472declared attribute.</p></div><div class="div3"> <h4><a name="included" id="included"/>4.4.2 Included</h4><p>
1473reported as an error.</p><p>Algorithms exist which allow many but not all non-deterministic content 1473 [<a name="dt-include" id="dt-include" title="Include">Definition</a>: An entity is <b>included</b>
1474models to be reduced automatically to equivalent deterministic models; see 1474when its <a title="Replacement Text" href="#dt-repltext">replacement text</a> is retrieved
1475Brüggemann-Klein 1991 <a href="#ABK">[Brüggemann-Klein]</a>.</p></div><div class="div1"> <h2><a name="sec-guessing" id="sec-guessing" />E Autodetection of Character Encodings (Non-Normative)</h2><p>The XML encoding declaration functions as an internal label on each entity, 1475and processed, in place of the reference itself, as though it were part of
1476indicating which character encoding is in use. Before an XML processor can 1476the document at the location the reference was recognized.] The replacement
1477read the internal label, however, it apparently has to know what character 1477text <span>may</span> contain both <a title="Character Data" href="#dt-chardata">character data</a>
1478encoding is in use — which is what the internal label is trying to indicate. 1478and (except for parameter entities) <a title="Markup" href="#dt-markup">markup</a>,
1479In the general case, this is a hopeless situation. It is not entirely hopeless 1479which <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be recognized in the usual way. (The string "<code>AT&amp;amp;T;</code>"
1480in XML, however, because XML limits the general case in two ways: each implementation 1480expands to "<code>AT&amp;T;</code>" and the remaining ampersand
1481is assumed to support only a finite set of character encodings, and the XML 1481is not recognized as an entity-reference delimiter.) A character reference
1482encoding declaration is restricted in position and content in order to make 1482is <b>included</b> when the indicated character is processed in place
1483it feasible to autodetect the character encoding in use in each entity in 1483of the reference itself. </p></div><div class="div3"> <h4><a name="include-if-valid" id="include-if-valid"/>4.4.3 Included If Validating</h4><p>When an XML processor recognizes a reference to a parsed entity, in order
1484normal cases. Also, in many cases other sources of information are available 1484to <a title="Validity" href="#dt-valid">validate</a> the document, the processor
1485in addition to the XML data stream itself. Two cases may be distinguished, 1485<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
1486depending on whether the XML entity is presented to the processor without, 1486 <a title="Include" href="#dt-include">include</a> its replacement text. If
1487or with, any accompanying (external) information. We consider the first case 1487the entity is external, and the processor is not attempting to validate the
1488first.</p><div class="div2"> <h3><a name="sec-guessing-no-ext-info" id="sec-guessing-no-ext-info" />E.1 Detection Without External Encoding Information</h3><p>Because each XML entity not accompanied by external 1488XML document, the processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em>, but need
1489encoding information and not in UTF-8 or UTF-16 encoding must 1489not, include the entity's replacement text. If a non-validating processor
1490begin with an XML encoding declaration, in which the first characters must 1490does not include the replacement text, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> inform the application that
1491be '<code>&lt;?xml</code>', any conforming processor can detect, after two 1491it recognized, but did not read, the entity.</p><p>This rule is based on the recognition that the automatic inclusion provided
1492to four octets of input, which of the following cases apply. In reading this 1492by the SGML and XML entity mechanism, primarily designed to support modularity
1493list, it may help to know that in UCS-4, '&lt;' is "<code>#x0000003C</code>" 1493in authoring, is not necessarily appropriate for other applications, in particular
1494and '?' is "<code>#x0000003F</code>", and the Byte Order Mark 1494document browsing. Browsers, for example, when encountering an external parsed
1495required of UTF-16 data streams is "<code>#xFEFF</code>". The notation 1495entity reference, might choose to provide a visual indication of the entity's
1496<var>##</var> is used to denote any byte value except that two consecutive 1496presence and retrieve it for display only on demand.</p></div><div class="div3"> <h4><a name="forbidden" id="forbidden"/>4.4.4 Forbidden</h4><p>The following are forbidden, and constitute <a title="Fatal Error" href="#dt-fatal">fatal
1497<var>##</var>s cannot be both 00.</p><p>With a Byte Order Mark:</p><table border="1" frame="border" summary="Encoding detection summary"><tbody><tr><td rowspan="1" colspan="1"><code>00 00 FE 1497errors</a>:</p><ul><li><p>the appearance of a reference to an <a title="Unparsed Entity" href="#dt-unparsed">unparsed
1498FF</code></td><td rowspan="1" colspan="1">UCS-4, big-endian machine (1234 order)</td></tr><tr><td rowspan="1" colspan="1"><code>FF 1498entity</a>, except in the
1499FE 00 00</code></td><td rowspan="1" colspan="1">UCS-4, little-endian machine (4321 order)</td></tr><tr><td rowspan="1" colspan="1"><code>00 00 FF FE</code></td><td rowspan="1" colspan="1">UCS-4, unusual octet order (2143)</td></tr><tr><td rowspan="1" colspan="1"><code>FE FF 00 00</code></td><td rowspan="1" colspan="1">UCS-4, unusual octet order (3412)</td></tr><tr><td rowspan="1" colspan="1"><code>FE FF ## ##</code></td><td rowspan="1" colspan="1">UTF-16, big-endian</td></tr><tr><td rowspan="1" colspan="1"><code>FF FE ## ##</code></td><td rowspan="1" colspan="1">UTF-16, little-endian</td></tr><tr><td rowspan="1" colspan="1"><code>EF BB BF</code></td><td rowspan="1" colspan="1">UTF-8</td></tr></tbody></table><p>Without a Byte Order Mark:</p><table border="1" frame="border" summary="Encoding detection summary"><tbody><tr><td rowspan="1" colspan="1"><code>00 00 00 3C</code></td><td rowspan="4" colspan="1">UCS-4 or other encoding with a 32-bit code unit and ASCII 1499<a href="#NT-EntityValue">EntityValue</a> in an entity declaration.</p></li><li><p>the appearance of any character or general-entity reference in the
1500characters encoded as ASCII values, in respectively big-endian (1234), little-endian 1500DTD except within an <a href="#NT-EntityValue">EntityValue</a> or <a href="#NT-AttValue">AttValue</a>.</p></li><li><p>a reference to an external entity in an attribute value.</p></li></ul></div><div class="div3"> <h4><a name="inliteral" id="inliteral"/>4.4.5 Included in Literal</h4><p>When an <a title="Entity Reference" href="#dt-entref">entity reference</a> appears in
1501(4321) and two unusual byte orders (2143 and 3412). The encoding declaration 1501an attribute value, or a parameter entity reference appears in a literal entity
1502must be read to determine which of UCS-4 or other supported 32-bit encodings 1502value, its <a title="Replacement Text" href="#dt-repltext">replacement text</a>
1503applies.</td></tr><tr><td rowspan="1" colspan="1"><code>3C 00 00 00</code></td></tr><tr><td rowspan="1" colspan="1"><code>00 00 3C 00</code></td></tr><tr><td rowspan="1" colspan="1"><code>00 3C 00 00</code></td></tr><tr><td rowspan="1" colspan="1"><code>00 3C 00 3F</code></td><td rowspan="1" colspan="1">UTF-16BE or big-endian ISO-10646-UCS-2 1503 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be processed
1504or other encoding with a 16-bit code unit in big-endian order and ASCII characters 1504in place of the reference itself as though it were part of the document at
1505encoded as ASCII values (the encoding declaration must be read to determine 1505the location the reference was recognized, except that a single or double
1506which)</td></tr><tr><td rowspan="1" colspan="1"><code>3C 00 3F 00</code></td><td rowspan="1" colspan="1">UTF-16LE or little-endian 1506quote character in the replacement text <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> always be treated as a normal data
1507ISO-10646-UCS-2 or other encoding with a 16-bit code unit in little-endian 1507character and <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> terminate the literal. For example, this is well-formed:</p><div class="exampleInner"><pre>&lt;!ENTITY % YN '"Yes"' &gt;
1508order and ASCII characters encoded as ASCII values (the encoding declaration 1508&lt;!ENTITY WhatHeSaid "He said %YN;" &gt;</pre></div><p>while this is not:</p><div class="exampleInner"><pre>&lt;!ENTITY EndAttr "27'" &gt;
1509must be read to determine which)</td></tr><tr><td rowspan="1" colspan="1"><code>3C 3F 78 6D</code></td><td rowspan="1" colspan="1">UTF-8, ISO 646, ASCII, some part of ISO 8859, Shift-JIS, EUC, or any other 1509&lt;element attribute='a-&amp;EndAttr;&gt;</pre></div></div><div class="div3"> <h4><a name="notify" id="notify"/>4.4.6 Notify</h4><p>When the name of an <a title="Unparsed Entity" href="#dt-unparsed">unparsed entity</a>
15107-bit, 8-bit, or mixed-width encoding which ensures that the characters of 1510appears as a token in the value of an attribute of declared type <b>ENTITY</b>
1511ASCII have their normal positions, width, and values; the actual encoding 1511or <b>ENTITIES</b>, a validating processor <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> inform the application of
1512declaration must be read to detect which of these applies, but since all of 1512the <a title="System Identifier" href="#dt-sysid">system</a> and <a title="Public identifier" href="#dt-pubid">public</a>
1513these encodings use the same bit patterns for the relevant ASCII characters, 1513(if any) identifiers for both the entity and its associated <a title="Notation" href="#dt-notation">notation</a>.</p></div><div class="div3"> <h4><a name="bypass" id="bypass"/>4.4.7 Bypassed</h4><p>When a general entity reference appears in the <a href="#NT-EntityValue">EntityValue</a>
1514the encoding declaration itself may be read reliably</td></tr><tr><td rowspan="1" colspan="1"><code>4C 1514in an entity declaration, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be bypassed and left as is.</p></div><div class="div3"> <h4><a name="as-PE" id="as-PE"/>4.4.8 Included as PE</h4><p>Just as with external parsed entities, parameter entities need only be <a href="#include-if-valid"><cite>included if validating</cite></a>. When a parameter-entity
15156F A7 94</code></td><td rowspan="1" colspan="1">EBCDIC (in some flavor; the full encoding declaration 1515reference is recognized in the DTD and included, its <a title="Replacement Text" href="#dt-repltext">replacement
1516must be read to tell which code page is in use)</td></tr><tr><td rowspan="1" colspan="1">Other</td><td rowspan="1" colspan="1">UTF-8 without an encoding declaration, or else the data stream is mislabeled 1516text</a>
1517(lacking a required encoding declaration), corrupt, fragmentary, or enclosed 1517 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be enlarged by the attachment of one leading and one following
1518in a wrapper of some kind</td></tr></tbody></table><div class="note"><p class="prefix"><b>Note:</b></p><p>In cases above which do not require reading the encoding declaration to 1518space (#x20) character; the intent is to constrain the replacement text of
1519determine the encoding, section 4.3.3 still requires that the encoding declaration, 1519parameter entities to contain an integral number of grammatical tokens in
1520if present, be read and that the encoding name be checked to match the actual 1520the DTD. This
1521encoding of the entity. Also, it is possible that new character encodings 1521behavior <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> apply to parameter entity references within entity values;
1522will be invented that will make it necessary to use the encoding declaration 1522these are described in <a href="#inliteral"><b>4.4.5 Included in Literal</b></a>.</p></div><div class="div3"> <h4><a name="error" id="error"/>4.4.9 Error</h4><p>It is an <a title="Error" href="#dt-error">error</a> for a reference to
1523to determine the encoding, in cases where this is not required at present.</p></div><p>This level of autodetection is enough to read the XML encoding declaration 1523an unparsed entity to appear in the <a href="#NT-EntityValue">EntityValue</a> in an
1524and parse the character-encoding identifier, which is still necessary to distinguish 1524entity declaration.</p></div></div><div class="div2"> <h3><a name="intern-replacement" id="intern-replacement"/>4.5 Construction of Entity Replacement Text</h3><p>In discussing the treatment of entities, it is useful to distinguish
1525the individual members of each family of encodings (e.g. to tell UTF-8 from 1525two forms of the entity's value.
15268859, and the parts of 8859 from each other, or to distinguish the specific 1526[<a name="dt-litentval" id="dt-litentval" title="Literal Entity Value">Definition</a>: For an
1527EBCDIC code page in use, and so on).</p><p>Because the contents of the encoding declaration are restricted to characters 1527internal entity, the <b>literal
1528from the ASCII repertoire (however encoded), 1528entity value</b> is the quoted string actually present in the entity declaration,
1529a processor can reliably read the entire encoding declaration as soon as it 1529corresponding to the non-terminal <a href="#NT-EntityValue">EntityValue</a>.]
1530has detected which family of encodings is in use. Since in practice, all widely 1530 [<a name="dt-extlitentval" id="dt-extlitentval" title="Literal Entity Value">Definition</a>: For an external entity, the <b>literal
1531used character encodings fall into one of the categories above, the XML encoding 1531entity value</b> is the exact text contained in the entity.]
1532declaration allows reasonably reliable in-band labeling of character encodings, 1532 [<a name="dt-repltext" id="dt-repltext" title="Replacement Text">Definition</a>: For an
1533even when external sources of information at the operating-system or transport-protocol 1533internal entity, the <b>replacement text</b>
1534level are unreliable. Character encodings such as UTF-7 1534is the content of the entity, after replacement of character references and
1535that make overloaded usage of ASCII-valued bytes may fail to be reliably detected.</p><p>Once the processor has detected the character encoding in use, it can act 1535parameter-entity references.]
1536appropriately, whether by invoking a separate input routine for each case, 1536 [<a name="dt-extrepltext" id="dt-extrepltext" title="Replacement Text">Definition</a>: For
1537or by calling the proper conversion function on each character of input.</p><p>Like any self-labeling system, the XML encoding declaration will not work 1537an external entity, the <b>replacement text</b> is the content of the entity,
1538if any software changes the entity's character set or encoding without updating 1538after stripping the text declaration (leaving any surrounding white space) if there
1539the encoding declaration. Implementors of character-encoding routines should 1539is one but without any replacement of character references or parameter-entity
1540be careful to ensure the accuracy of the internal and external information 1540references.]
1541used to label the entity.</p></div><div class="div2"> <h3><a name="sec-guessing-with-ext-info" id="sec-guessing-with-ext-info" />E.2 Priorities in the Presence of External Encoding Information</h3><p>The second possible case occurs when the XML entity is accompanied by encoding 1541 </p><p>The literal entity value as given in an internal entity declaration (<a href="#NT-EntityValue">EntityValue</a>) <span>may</span> contain character, parameter-entity,
1542information, as in some file systems and some network protocols. When multiple 1542and general-entity references. Such references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be contained entirely
1543sources of information are available, their relative priority and the preferred 1543within the literal entity value. The actual replacement text that is <a title="Include" href="#dt-include">included</a> (or <a title="" href="#inliteral">included in literal</a>) as described above
1544method of handling conflict should be specified as part of the higher-level 1544<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> contain the <em>replacement
1545protocol used to deliver XML. In particular, please refer 1545text</em> of any parameter entities referred to, and <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> contain the character
1546to <a href="#rfc2376">[IETF RFC 3023]</a> or its successor, which defines the <code>text/xml</code> 1546referred to, in place of any character references in the literal entity value;
1547and <code>application/xml</code> MIME types and provides some useful guidance. 1547however, general-entity references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be left as-is, unexpanded. For example,
1548In the interests of interoperability, however, the following rule is recommended.</p><ul><li><p>If an XML entity is in a file, the Byte-Order Mark and encoding declaration are used 1548given the following declarations:</p><div class="exampleInner"><pre>&lt;!ENTITY % pub "&amp;#xc9;ditions Gallimard" &gt;
1549(if present) to determine the character encoding.</p></li></ul></div></div><div class="div1"> <h2><a name="sec-xml-wg" id="sec-xml-wg" />F W3C XML Working Group (Non-Normative)</h2><p>This specification was prepared and approved for publication by the W3C 1549&lt;!ENTITY rights "All rights reserved" &gt;
1550XML Working Group (WG). WG approval of this specification does not necessarily 1550&lt;!ENTITY book "La Peste: Albert Camus,
1551imply that all WG participants voted for its approval. The current and former members 1551&amp;#xA9; 1947 %pub;. &amp;rights;" &gt;</pre></div><p>then the replacement text for the entity "<code>book</code>"
1552in the XML WG are:</p><ul><li>Jon Bosak, Sun (<i>Chair</i>) </li><li>James Clark (<i>Technical Lead</i>) </li><li>Tim Bray, Textuality and Netscape (<i>XML Co-editor</i>) </li><li>Jean Paoli, Microsoft (<i>XML 1552is:</p><div class="exampleInner"><pre>La Peste: Albert Camus,
1553Co-editor</i>) </li><li>C. M. Sperberg-McQueen, U. of Ill. (<i>XML Co-editor</i>) </li><li>Dan Connolly, W3C (<i>W3C Liaison</i>) </li><li>Paula Angerstein, Texcel</li><li>Steve DeRose, INSO</li><li>Dave Hollander, HP</li><li>Eliot Kimber, ISOGEN</li><li>Eve Maler, ArborText</li><li>Tom Magliery, NCSA</li><li>Murray Maloney, SoftQuad, Grif 1553© 1947 Éditions Gallimard. &amp;rights;</pre></div><p>The general-entity reference "<code>&amp;rights;</code>" would
1554SA, Muzmo and Veo Systems</li><li>MURATA Makoto (FAMILY Given), Fuji 1554be expanded should the reference "<code>&amp;book;</code>" appear
1555Xerox Information Systems</li><li>Joel Nava, Adobe</li><li>Conleth O'Connell, Vignette</li><li>Peter Sharpe, SoftQuad</li><li>John Tigue, DataChannel</li></ul></div><div class="div1"> <h2><a name="sec-core-wg" id="sec-core-wg" />G W3C XML Core <span>Working</span> Group (Non-Normative)</h2><p>The present edition of this specification was prepared by the W3C XML Core 1555in the document's content or an attribute value.</p><p>These simple rules may have complex interactions; for a detailed discussion
1556Working Group (WG). The participants in the WG at the time of publication of this 1556of a difficult example, see <a href="#sec-entexpand"><b>C Expansion of Entity and Character References</b></a>.</p></div><div class="div2"> <h3><a name="sec-predefined-ent" id="sec-predefined-ent"/>4.6 Predefined Entities</h3><p>
1557edition were:</p><ul><li>Leonid Arbouzov, Sun Microsystems</li><li>Mary Brady</li><li>John Cowan (<i>XML 1.1 First Edition Editor</i>) </li><li>John Evdemon, Microsoft</li><li>Andrew Fang, Arbortext</li><li>Paul Grosso, Arbortext (<i>Co-Chair</i>) </li><li>Arnaud Le Hors, IBM</li><li>Dmitry Lenkov, Oracle</li><li>Anjana Manian, Oracle</li><li>Glenn Marcy, IBM</li><li>Jonathan Marsh, Microsoft</li><li>Sandra Martinez, NIST</li><li>Liam Quin, W3C (<i>Staff Contact</i>) </li><li>Lew Shannon</li><li>Richard Tobin, University of Edinburgh</li><li>Daniel Veillard</li><li>Norman Walsh, Sun Microsystems (<i>Co-Chair</i>) </li><li>François Yergeau</li></ul></div><div class="div1"> <h2><a name="prod-notes" id="prod-notes" />H Production Notes (Non-Normative)</h2><p>This edition was encoded in a 1557 [<a name="dt-escape" id="dt-escape" title="escape">Definition</a>: Entity and character references <span>may</span>
1558slightly modified version of the 1558both be used to <b>escape</b> the left angle bracket, ampersand, and
1559<a href="http://www.w3.org/2002/xmlspec/dtd/2.5/xmlspec.dtd">XMLspec DTD, 2.5</a>. 1559other delimiters. A set of general entities (<code>amp</code>,
1560The XHTML versions were produced with a combination of the 1560<code>lt</code>,
1561<a href="http://www.w3.org/2002/xmlspec/xhtml/1.9/xmlspec.xsl">xmlspec.xsl</a>, 1561<code>gt</code>,
1562<a href="http://www.w3.org/2002/xmlspec/xhtml/1.9/diffspec.xsl">diffspec.xsl</a>, 1562<code>apos</code>,
1563and <a href="REC-xml-3e.xsl">REC-xml-3e.xsl</a> 1563<code>quot</code>) is specified for
1564XSLT stylesheets.</p></div><div class="div1"> <h2><a name="sec-suggested-names" id="sec-suggested-names" />I Suggestions for XML Names (Non-Normative)</h2><p>The following suggestions define what is believed to be best 1564this purpose. Numeric character references <span>may</span> also be used; they are expanded
1565practice in the construction of XML names used as element names, 1565immediately when recognized and <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be treated as character data, so the
1566attribute names, processing instruction targets, entity names, 1566numeric character references "<code>&amp;#60;</code>" and "<code>&amp;#38;</code>" <span>may</span> be used to escape <code>&lt;</code> and <code>&amp;</code> when they occur
1567notation names, and the values of attributes of type ID, and are 1567in character data.]
1568intended as guidance for document authors and schema designers. 1568 </p><p>All XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> recognize these entities whether they are declared
1569All references to Unicode are understood with respect to 1569or not. <a title="For interoperability" href="#dt-interop">For interoperability</a>, valid XML
1570a particular version of the Unicode Standard greater than or equal 1570documents <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> declare these entities, like any others, before using them. If
1571to 3.0; which version should be used is left to the discretion of 1571the entities <code>lt</code> or <code>amp</code> are declared, they <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be
1572the document author or schema designer.</p><p>The first two suggestions are directly derived from the rules 1572declared as internal entities whose replacement text is a character reference
1573given for identifiers in the Unicode Standard, version 3.0, and 1573to the respective
1574exclude all control characters, enclosing nonspacing marks, 1574character (less-than sign or ampersand) being escaped; the double
1575non-decimal numbers, private-use characters, punctuation characters 1575escaping is <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> for these entities so that references to them produce
1576(with the noted exceptions), symbol characters, unassigned 1576a well-formed result. If the entities <code>gt</code>, <code>apos</code>,
1577codepoints, and white space characters. The other suggestions 1577or <code>quot</code> are declared, they <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be declared as internal entities
1578are mostly derived from <a href="#XML1.0">[XML-1.0]</a> Appendix B.</p><ol type="1"><li><p>The first character of any name should have a Unicode General 1578whose replacement text is the single character being escaped (or a character
1579Category of Ll, Lu, Lo, Lm, Lt, or Nl, or else be '_' #x5F.</p></li><li><p>Characters other than the first should have a Unicode General 1579reference to that character; the double escaping here is <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> but harmless).
1580Category of Ll, Lu, Lo, Lm, Lt, Mc, Mn, Nl, Nd, Pc, or Cf, or else 1580For example:</p><div class="exampleInner"><pre>&lt;!ENTITY lt "&amp;#38;#60;"&gt;
1581be one of the following: '-' #x2D, '.' #x2E, ':' #x3A or 1581&lt;!ENTITY gt "&amp;#62;"&gt;
1582'·' #xB7 (middle dot). Since Cf characters are not 1582&lt;!ENTITY amp "&amp;#38;#38;"&gt;
1583directly visible, they should be employed with caution and only 1583&lt;!ENTITY apos "&amp;#39;"&gt;
1584when necessary, to avoid creating names which are distinct to XML 1584&lt;!ENTITY quot "&amp;#34;"&gt;</pre></div></div><div class="div2"> <h3><a name="Notations" id="Notations"/>4.7 Notation Declarations</h3><p>
1585processors but look the same to human beings.</p></li><li><p>Ideographic characters which have a canonical decomposition 1585 [<a name="dt-notation" id="dt-notation" title="Notation">Definition</a>:
1586(including those in the ranges [#xF900-#xFAFF] and 1586 <b>Notations</b> identify
1587[#x2F800-#x2FFFD], with 12 exceptions) should not be used in names. 1587by name the format of <a title="Unparsed Entity" href="#dt-unparsed">unparsed entities</a>,
1588</p></li><li><p>Characters which have a compatibility decomposition (those with 1588the format of elements which bear a notation attribute, or the application
1589a "compatibility formatting tag" in field 5 of the Unicode 1589to which a <a title="Processing instruction" href="#dt-pi">processing instruction</a> is addressed.]
1590Character Database -- marked by field 5 beginning with a "&lt;") 1590 </p><p>
1591should not be used in names. This suggestion does not apply 1591 [<a name="dt-notdecl" id="dt-notdecl" title="Notation Declaration">Definition</a>:
1592to #x0E33 THAI CHARACTER SARA AM or #x0EB3 LAO CHARACTER AM, which 1592 <b>Notation declarations</b>
1593despite their compatibility decompositions are in regular use in 1593provide a name for the notation, for use in entity and attribute-list declarations
1594those scripts.</p></li><li><p>Combining characters meant for use with symbols only (including 1594and in attribute specifications, and an external identifier for the notation
1595those in the ranges [#x20D0-#x20EF] and [#x1D165-#x1D1AD]) should 1595which may allow an XML processor or its client application to locate a helper
1596not be used in names.</p></li><li><p>The interlinear annotation characters ([#xFFF9-#xFFFB) should 1596application capable of processing data in the given notation.]
1597not be used in names.</p></li><li><p>Variation selector characters should not be used in names.</p></li><li><p>Names which are nonsensical, unpronounceable, hard to read, or 1597 </p> <h5><a name="IDANRMS" id="IDANRMS"/>Notation Declarations</h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-NotationDecl" id="NT-NotationDecl"/>[82]   </td><td><code>NotationDecl</code></td><td>   ::=   </td><td><code>'&lt;!NOTATION' <a href="#NT-S">S</a>
1598easily confusable with other names should not be employed.</p></li></ol></div></div></body></html> 1598 <a href="#NT-Name">Name</a>
1599 <a href="#NT-S">S</a> (<a href="#NT-ExternalID">ExternalID</a> | <a href="#NT-PublicID">PublicID</a>) <a href="#NT-S">S</a>? '&gt;'</code></td><td><a href="#UniqueNotationName">[VC: Unique Notation Name]</a></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PublicID" id="NT-PublicID"/>[83]   </td><td><code>PublicID</code></td><td>   ::=   </td><td><code>'PUBLIC' <a href="#NT-S">S</a>
1600 <a href="#NT-PubidLiteral">PubidLiteral</a>
1601 </code></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="UniqueNotationName" id="UniqueNotationName"/><b>Validity constraint: Unique Notation Name</b></p><p>A given <a href="#NT-Name">Name</a>
1602 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be declared in more than one notation declaration.</p></div><p>XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> provide applications with the name and external identifier(s)
1603of any notation declared and referred to in an attribute value, attribute
1604definition, or entity declaration. They <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> additionally resolve the external
1605identifier into the <a title="System Identifier" href="#dt-sysid">system identifier</a>, file
1606name, or other information needed to allow the application to call a processor
1607for data in the notation described. (It is not an error, however, for XML
1608documents to declare and refer to notations for which notation-specific applications
1609are not available on the system where the XML processor or application is
1610running.)</p></div><div class="div2"> <h3><a name="sec-doc-entity" id="sec-doc-entity"/>4.8 Document Entity</h3><p>
1611 [<a name="dt-docent" id="dt-docent" title="Document Entity">Definition</a>: The <b>document entity</b>
1612serves as the root of the entity tree and a starting-point for an <a title="XML Processor" href="#dt-xml-proc">XML processor</a>.] This specification does
1613not specify how the document entity is to be located by an XML processor;
1614unlike other entities, the document entity has no name and might well appear
1615on a processor input stream without any identification at all.</p></div></div><div class="div1"> <h2><a name="sec-conformance" id="sec-conformance"/>5 Conformance</h2><div class="div2"> <h3><a name="proc-types" id="proc-types"/>5.1 Validating and Non-Validating Processors</h3><p>Conforming <a title="XML Processor" href="#dt-xml-proc">XML processors</a> fall into
1616two classes: validating and non-validating.</p><p>Validating and non-validating processors alike <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> report violations of
1617this specification's well-formedness constraints in the content of the <a title="Document Entity" href="#dt-docent">document entity</a> and any other <a title="Text Entity" href="#dt-parsedent">parsed
1618entities</a> that they read.</p><p>
1619 [<a name="dt-validating" id="dt-validating" title="Validating Processor">Definition</a>:
1620 <b>Validating
1621processors</b>
1622 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>,
1623at user option, report violations of the constraints expressed by
1624the declarations in the <a title="Document Type Declaration" href="#dt-doctype">DTD</a>, and failures
1625to fulfill the validity constraints given in this specification.]
1626To accomplish this, validating XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> read and process the entire
1627DTD and all external parsed entities referenced in the document.</p><p>Non-validating processors are <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> to check only the <a title="Document Entity" href="#dt-docent">document
1628entity</a>, including the entire internal DTD subset, for well-formedness. [<a name="dt-use-mdecl" id="dt-use-mdecl" title="Process Declarations">Definition</a>: While they are not required
1629to check the document for validity, they are <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> to <b>process</b>
1630all the declarations they read in the internal DTD subset and in any parameter
1631entity that they read, up to the first reference to a parameter entity that
1632they do <em>not</em> read; that is to say, they <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> use the information
1633in those declarations to <a href="#AVNormalize"><cite>normalize</cite></a>
1634attribute values, <a href="#included"><cite>include</cite></a> the replacement
1635text of internal entities, and supply <a href="#sec-attr-defaults"><cite>default
1636attribute values</cite></a>.] Except when <code>standalone="yes"</code>, they
1637<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em>
1638 <a title="Process Declarations" href="#dt-use-mdecl">process</a>
1639 <a title="entity declaration" href="#dt-entdecl">entity
1640declarations</a> or <a title="Attribute-List Declaration" href="#dt-attdecl">attribute-list declarations</a>
1641encountered after a reference to a parameter entity that is not read, since
1642the entity may have contained overriding declarations; when <code>standalone="yes"</code>, processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
1643process these declarations.</p><p>Note
1644that when processing invalid documents with a non-validating
1645processor the application may not be presented with consistent
1646information. For example, several requirements for uniqueness
1647within the document may not be met, including more than one element
1648with the same id, duplicate declarations of elements or notations
1649with the same name, etc. In these cases the behavior of the parser
1650with respect to reporting such information to the application is
1651undefined.</p><p>XML 1.1 processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be able to process both XML 1.0
1652and XML 1.1 documents. Programs which generate XML <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em>
1653generate XML 1.0, unless one of the specific features of XML 1.1 is required.</p></div><div class="div2"> <h3><a name="safe-behavior" id="safe-behavior"/>5.2 Using XML Processors</h3><p>The behavior of a validating XML processor is highly predictable; it must
1654read every piece of a document and report all well-formedness and validity
1655violations. Less is required of a non-validating processor; it need not read
1656any part of the document other than the document entity. This has two effects
1657that may be important to users of XML processors:</p><ul><li><p>Certain well-formedness errors, specifically those that require reading
1658external entities, may fail to be detected by a non-validating processor. Examples
1659include the constraints entitled <a href="#wf-entdeclared"><cite>Entity Declared</cite></a>, <a href="#textent"><cite>Parsed Entity</cite></a>, and <a href="#norecursion"><cite>No
1660Recursion</cite></a>, as well as some of the cases described as <a href="#forbidden"><cite>forbidden</cite></a> in <a href="#entproc"><b>4.4 XML Processor Treatment of Entities and References</b></a>.</p></li><li><p>The information passed from the processor to the application may
1661vary, depending on whether the processor reads parameter and external entities.
1662For example, a non-validating processor may fail to <a href="#AVNormalize"><cite>normalize</cite></a>
1663attribute values, <a href="#included"><cite>include</cite></a> the replacement
1664text of internal entities, or supply <a href="#sec-attr-defaults"><cite>default
1665attribute values</cite></a>, where doing so depends on having read declarations
1666in external or parameter entities.</p></li></ul><p>For maximum reliability in interoperating between different XML processors,
1667applications which use non-validating processors <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD NOT</em> rely on any behaviors
1668not required of such processors. Applications which require DTD facilities
1669not related to validation (such
1670as the declaration of default attributes and internal entities that are
1671or may be specified in
1672external entities<span>
1673 )</span>
1674 <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> use validating XML processors.</p></div></div><div class="div1"> <h2><a name="sec-notation" id="sec-notation"/>6 Notation</h2><p>The formal grammar of XML is given in this specification using a simple
1675Extended Backus-Naur Form (EBNF) notation. Each rule in the grammar defines
1676one symbol, in the form</p><div class="exampleInner"><pre>symbol ::= expression</pre></div><p>Symbols are written with an initial capital letter if they are the
1677start symbol of a regular language, otherwise with an initial lowercase
1678letter. Literal strings are quoted.</p><p>Within the expression on the right-hand side of a rule, the following expressions
1679are used to match strings of one or more characters: </p><dl><dt class="label">
1680 <code>#xN</code>
1681 </dt><dd><p>where <code>N</code> is a hexadecimal integer, the expression matches the character
1682whose number
1683(code point) in ISO/IEC 10646 is <code>N</code>. The number of leading zeros in the <code>#xN</code>
1684form is insignificant.</p></dd><dt class="label">
1685 <code>[a-zA-Z]</code>, <code>[#xN-#xN]</code>
1686 </dt><dd><p>matches any <a href="#NT-Char">Char</a> with a value in the range(s) indicated (inclusive).</p></dd><dt class="label">
1687 <code>[abc]</code>, <code>[#xN#xN#xN]</code>
1688 </dt><dd><p>matches any <a href="#NT-Char">Char</a> with a value among the characters
1689enumerated. Enumerations and ranges can be mixed in one set of brackets.</p></dd><dt class="label">
1690 <code>[^a-z]</code>, <code>[^#xN-#xN]</code>
1691 </dt><dd><p>matches any <a href="#NT-Char">Char</a> with a value <em>outside</em> the range
1692indicated.</p></dd><dt class="label">
1693 <code>[^abc]</code>, <code>[^#xN#xN#xN]</code>
1694 </dt><dd><p>matches any <a href="#NT-Char">Char</a> with a value not among the characters given. Enumerations
1695and ranges of forbidden values can be mixed in one set of brackets.</p></dd><dt class="label">
1696 <code>"string"</code>
1697 </dt><dd><p>matches a literal string <a title="match" href="#dt-match">matching</a> that
1698given inside the double quotes.</p></dd><dt class="label">
1699 <code>'string'</code>
1700 </dt><dd><p>matches a literal string <a title="match" href="#dt-match">matching</a> that
1701given inside the single quotes.</p></dd></dl><p> These symbols may be combined to match more complex patterns as follows,
1702where <code>A</code> and <code>B</code> represent simple expressions: </p><dl><dt class="label">(<code>expression</code>)</dt><dd><p>
1703 <code>expression</code> is treated as a unit and may be combined as described
1704in this list.</p></dd><dt class="label">
1705 <code>A?</code>
1706 </dt><dd><p>matches <code>A</code> or nothing; optional <code>A</code>.</p></dd><dt class="label">
1707 <code>A B</code>
1708 </dt><dd><p>matches <code>A</code> followed by <code>B</code>. This
1709operator has higher precedence than alternation; thus <code>A B | C D</code>
1710is identical to <code>(A B) | (C D)</code>.</p></dd><dt class="label">
1711 <code>A | B</code>
1712 </dt><dd><p>matches <code>A</code> or <code>B</code>.</p></dd><dt class="label">
1713 <code>A - B</code>
1714 </dt><dd><p>matches any string that matches <code>A</code> but does not match <code>B</code>.</p></dd><dt class="label">
1715 <code>A+</code>
1716 </dt><dd><p>matches one or more occurrences of <code>A</code>. Concatenation
1717has higher precedence than alternation; thus <code>A+ | B+</code> is identical
1718to <code>(A+) | (B+)</code>.</p></dd><dt class="label">
1719 <code>A*</code>
1720 </dt><dd><p>matches zero or more occurrences of <code>A</code>. Concatenation
1721has higher precedence than alternation; thus <code>A* | B*</code> is identical
1722to <code>(A*) | (B*)</code>.</p></dd></dl><p> Other notations used in the productions are: </p><dl><dt class="label">
1723 <code>/* ... */</code>
1724 </dt><dd><p>comment.</p></dd><dt class="label">
1725 <code>[ wfc: ... ]</code>
1726 </dt><dd><p>well-formedness constraint; this identifies by name a constraint on <a title="Well-Formed" href="#dt-wellformed">well-formed</a> documents associated with a production.</p></dd><dt class="label">
1727 <code>[ vc: ... ]</code>
1728 </dt><dd><p>validity constraint; this identifies by name a constraint on <a title="Validity" href="#dt-valid">valid</a>
1729documents associated with a production.</p></dd></dl><p>
1730 </p></div></div><div class="back"><div class="div1"> <h2><a name="sec-bibliography" id="sec-bibliography"/>A References</h2><div class="div2"> <h3><a name="sec-existing-stds" id="sec-existing-stds"/>A.1 Normative References</h3><dl><dt class="label"><a name="IANA" id="IANA"/>IANA-CHARSETS</dt><dd>(Internet
1731Assigned Numbers Authority) <a href="http://www.iana.org/assignments/character-sets"><cite>Official Names for Character Sets</cite></a>,
1732ed. Keld Simonsen et al. (See http://www.iana.org/assignments/character-sets.)</dd><dt class="label"><a name="rfc2119" id="rfc2119"/>IETF RFC 2119</dt><dd>IETF
1733(Internet Engineering Task Force). <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>RFC 2119: Key words for use in RFCs to Indicate Requirement Levels</cite></a>.
1734Scott Bradner, 1997. (See http://www.ietf.org/rfc/rfc2119.txt.)</dd><dt class="label"><a name="RFC1766" id="RFC1766"/>IETF RFC 3066</dt><dd>IETF
1735(Internet Engineering Task Force). <a href="http://www.ietf.org/rfc/rfc3066.txt"><cite>RFC 3066: Tags for the Identification
1736of Languages</cite></a>, ed. H. Alvestrand. 2001. (See http://www.ietf.org/rfc/rfc3066.txt.)</dd><dt class="label"><a name="rfc3986"/>IETF RFC 3986</dt><dd>IETF (Internet Engineering Task Force). <a href="http://www.ietf.org/rfc/rfc3986.txt"><cite>RFC 3986: Uniform Resource Identifier (URI): Generic Syntax</cite></a>. T. Berners-Lee, R. Fielding, L. Masinter. 2005. (See http://www.ietf.org/rfc/rfc3986.txt.)</dd><dt class="label"><a name="ISO10646" id="ISO10646"/>ISO/IEC 10646</dt><dd>ISO (International
1737Organization for Standardization). <cite>ISO/IEC 10646-1:2000. Information
1738technology — Universal Multiple-Octet Coded Character Set (UCS) —
1739Part 1: Architecture and Basic Multilingual Plane</cite> and <cite>ISO/IEC 10646-2:2001.
1740Information technology — Universal Multiple-Octet Coded Character Set (UCS) — Part 2:
1741Supplementary Planes</cite>, as, from time to time, amended, replaced by a new edition or
1742expanded by the addition of new parts. [Geneva]: International Organization for Standardization.
1743(See <a href="http://www.iso.ch">http://www.iso.ch</a> for the latest version.)</dd><dt class="label"><a name="Unicode" id="Unicode"/>Unicode</dt><dd>The Unicode Consortium. <em>The Unicode
1744Standard, Version 4.0.</em> Reading, Mass.: Addison-Wesley,
17452003,
1746as updated from time to time by the publication of new versions. (See
1747<a href="http://www.unicode.org/unicode/standard/versions">
1748http://www.unicode.org/unicode/standard/versions</a> for the latest version
1749and additional information on versions of the standard and of the Unicode
1750Character Database).</dd><dt class="label"><a name="XML1.0" id="XML1.0"/>XML-1.0</dt><dd>W3C. <a href="http://www.w3.org/TR/xml"><cite>Extensible Markup Language (XML) 1.0 (Fourth
1751Edition)</cite></a>. Tim Bray, Jean Paoli, C.M. Sperberg-McQueen, Eve Maler, François Yergeau
1752(editors) (See http://www.w3.org/TR/xml.)</dd></dl></div><div class="div2"> <h3><a name="null" id="null"/>A.2 Other References</h3><dl><dt class="label"><a name="Aho" id="Aho"/>Aho/Ullman</dt><dd>Aho, Alfred V., Ravi Sethi, and Jeffrey D.
1753Ullman. <cite>Compilers: Principles, Techniques, and Tools</cite>.
1754Reading: Addison-Wesley, 1986, rpt. corr. 1988.</dd><dt class="label"><a name="ABK" id="ABK"/>Brüggemann-Klein</dt><dd>Brüggemann-Klein,
1755Anne. <a href="ftp://ftp.informatik.uni-freiburg.de/documents/papers/brueggem/habil.ps"><cite>Formal Models in Document Processing</cite></a>. Habilitationsschrift. Faculty
1756of Mathematics at the University of Freiburg, 1993. (See ftp://ftp.informatik.uni-freiburg.de/documents/papers/brueggem/habil.ps.)</dd><dt class="label"><a name="ABKDW" id="ABKDW"/>Brüggemann-Klein and Wood</dt><dd>Brüggemann-Klein,
1757Anne, and Derick Wood. <cite>Deterministic Regular Languages</cite>.
1758Universität Freiburg, Institut für Informatik, Bericht 38, Oktober 1991. Extended
1759abstract in A. Finkel, M. Jantzen, Hrsg., STACS 1992, S. 173-184. Springer-Verlag,
1760Berlin 1992. Lecture Notes in Computer Science 577. Full version titled <cite>One-Unambiguous
1761Regular Languages</cite> in Information and Computation 140 (2): 229-253,
1762February 1998.</dd><dt class="label"><a name="Charmod" id="Charmod"/>Charmod</dt><dd>W3C Working Draft.
1763<a href="http://www.w3.org/TR/2003/WD-charmod-20030822/"><cite>Character Model for the World Wide Web 1.0</cite></a>.
1764Martin J. Dürst, François Yergeau, Richard Ishida, Misha Wolf, Tex Texin. (See http://www.w3.org/TR/2003/WD-charmod-20030822/.)</dd><dt class="label"><a name="Clark" id="Clark"/>Clark</dt><dd>James Clark.
1765<a href="http://www.w3.org/TR/NOTE-sgml-xml-971215"><cite>Comparison of SGML and XML</cite></a>. (See http://www.w3.org/TR/NOTE-sgml-xml-971215.)</dd><dt class="label"><a name="IANA-LANGCODES" id="IANA-LANGCODES"/>IANA-LANGCODES</dt><dd>(Internet
1766Assigned Numbers Authority) <a href="http://www.iana.org/assignments/language-tags"><cite>Registry of Language Tags</cite></a>,
1767ed. Keld Simonsen et al. (See http://www.iana.org/assignments/language-tags.)</dd><dt class="label"><a name="RFC2141" id="RFC2141"/>IETF RFC 2141</dt><dd>IETF
1768(Internet Engineering Task Force). <a href="http://www.ietf.org/rfc/rfc2141.txt"><cite>RFC 2141: URN Syntax</cite></a>, ed.
1769R. Moats. 1997. (See http://www.ietf.org/rfc/rfc2141.txt.)</dd><dt class="label"><a name="rfc2376" id="rfc2376"/>IETF RFC 3023</dt><dd>IETF
1770(Internet Engineering Task Force). <a href="http://www.ietf.org/rfc/rfc3023.txt"><cite>RFC 3023: XML Media Types</cite></a>.
1771eds. M. Murata, S. St.Laurent, D. Kohn. 2001. (See http://www.ietf.org/rfc/rfc3023.txt.)</dd><dt class="label"><a name="rfc2781" id="rfc2781"/>IETF RFC 2781</dt><dd>IETF
1772(Internet Engineering Task Force). <a href="http://www.ietf.org/rfc/rfc2781.txt"><cite>RFC 2781: UTF-16, an encoding
1773of ISO 10646</cite></a>, ed. P. Hoffman, F. Yergeau. 2000. (See http://www.ietf.org/rfc/rfc2781.txt.)</dd><dt class="label"><a name="ISO639" id="ISO639"/>ISO 639</dt><dd>(International Organization for Standardization).
1774<cite>ISO 639:1988 (E).
1775Code for the representation of names of languages.</cite> [Geneva]: International
1776Organization for Standardization, 1988.</dd><dt class="label"><a name="ISO3166" id="ISO3166"/>ISO 3166</dt><dd>(International Organization for Standardization).
1777<cite>ISO 3166-1:1997
1778(E). Codes for the representation of names of countries and their subdivisions —
1779Part 1: Country codes</cite> [Geneva]: International Organization for
1780Standardization, 1997.</dd><dt class="label"><a name="ISO8879" id="ISO8879"/>ISO 8879</dt><dd>ISO (International Organization for Standardization). <cite>ISO
17818879:1986(E). Information processing — Text and Office Systems —
1782Standard Generalized Markup Language (SGML).</cite> First edition —
17831986-10-15. [Geneva]: International Organization for Standardization, 1986. </dd><dt class="label"><a name="ISO10744" id="ISO10744"/>ISO/IEC 10744</dt><dd>ISO (International Organization for
1784Standardization). <cite>ISO/IEC 10744-1992 (E). Information technology —
1785Hypermedia/Time-based Structuring Language (HyTime). </cite> [Geneva]:
1786International Organization for Standardization, 1992. <em>Extended Facilities
1787Annexe.</em> [Geneva]: International Organization for Standardization, 1996. </dd><dt class="label"><a name="websgml" id="websgml"/>WEBSGML</dt><dd>ISO
1788(International Organization for Standardization). <a href="http://www.sgmlsource.com/8879/n0029.htm"><cite>ISO 8879:1986
1789TC2. Information technology — Document Description and Processing Languages</cite></a>.
1790[Geneva]: International Organization for Standardization, 1998. (See http://www.sgmlsource.com/8879/n0029.htm.)</dd><dt class="label"><a name="xml-names" id="xml-names"/>XML Names</dt><dd>Tim Bray,
1791Dave Hollander, and Andrew Layman, editors. <a href="http://www.w3.org/TR/REC-xml-names/"><cite>Namespaces in XML</cite></a>.
1792Textuality, Hewlett-Packard, and Microsoft. World Wide Web Consortium, 1999. (See http://www.w3.org/TR/REC-xml-names/.)</dd></dl></div></div><div class="div1"> <h2><a name="sec-CharNorm" id="sec-CharNorm"/>B Definitions for Character Normalization</h2><p>This appendix contains the necessary definitions for character normalization.
1793For additional background information and examples, see <a href="#Charmod">[Charmod]</a>.</p><p>
1794
1795 [<a name="dt-Uni-encform" id="dt-Uni-encform" title="Unicode encoding form">Definition</a>: Text is said to be
1796in a <b>Unicode encoding form</b> if it is encoded in
1797UTF-8, UTF-16 or UTF-32.]
1798 </p><p>
1799
1800 [<a name="dt-legacyenc" id="dt-legacyenc" title="legacy encoding">Definition</a>:
1801 <b>Legacy encoding</b>
1802is taken to mean any character encoding not based on Unicode.]
1803 </p><p>
1804
1805 [<a name="dt-normtransc" id="dt-normtransc" title="normalizing transcoder">Definition</a>: A
1806<b>normalizing transcoder</b> is a transcoder that converts from a
1807<a title="legacy encoding" href="#dt-legacyenc">legacy encoding</a> to a
1808<a title="Unicode encoding form" href="#dt-Uni-encform">Unicode encoding form</a> and
1809ensures that the result is in Unicode Normalization Form C
1810(see UAX #15 <a href="#Unicode">[Unicode]</a>).]
1811 </p><p>
1812 [<a name="dt-charesc" id="dt-charesc" title="character escape">Definition</a>: A <b>character escape</b>
1813is a syntactic device defined in a markup or programming language that allows
1814one or more of:]
1815 </p><ol class="enumar"><li><p>expressing syntax-significant characters while disregarding
1816their significance in the syntax of the language, or</p></li><li><p>expressing characters not representable in the character encoding
1817chosen for an instance of the language, or</p></li><li><p>expressing characters in general, without use of the corresponding
1818character codes.</p></li></ol><p>
1819
1820 [<a name="dt-certified" id="dt-certified" title="certified">Definition</a>:
1821 <b>Certified</b> text
1822is text which satisfies at least one of the following conditions:]
1823 </p><ol class="enumar"><li><p>it has been confirmed through inspection that the text
1824is in normalized form</p></li><li><p>the source text-processing component is identified
1825and is known to produce only normalized text.</p></li></ol><p>
1826
1827 [<a name="dt-uninorm" id="dt-uninorm" title="Unicode-normalized">Definition</a>: Text is, for the purposes of
1828this specification, <b>Unicode-normalized</b> if it is in a
1829<a title="Unicode encoding form" href="#dt-Uni-encform">Unicode encoding form</a> and is in
1830Unicode Normalization Form C, according to a version of Unicode Standard Annex #15:
1831Unicode Normalization Forms <a href="#Unicode">[Unicode]</a> at least as recent as the
1832oldest version of the Unicode Standard that contains all the characters
1833actually present in the text, but no earlier
1834than version 3.2.]
1835 </p><p>
1836
1837 [<a name="dt-inclnorm" id="dt-inclnorm" title="include-normalized">Definition</a>: Text is
1838<b>include-normalized</b> if:]
1839 </p><ol class="enumar"><li><p>the text is <a title="Unicode-normalized" href="#dt-uninorm">Unicode-normalized</a>
1840and does not contain any <a title="character escape" href="#dt-charesc">character escapes</a>
1841or <a title="Include" href="#dt-include">includes</a> whose expansion would
1842cause the text to become no longer <a title="Unicode-normalized" href="#dt-uninorm">Unicode-normalized</a>;
1843or</p></li><li><p>the text is in a <a title="legacy encoding" href="#dt-legacyenc">legacy encoding</a> and, if it were transcoded
1844to a <a title="Unicode encoding form" href="#dt-Uni-encform">Unicode encoding form</a> by a
1845<a title="normalizing transcoder" href="#dt-normtransc">normalizing transcoder</a>, the resulting
1846text would satisfy clause 1 above.</p></li></ol><p>
1847
1848 [<a name="dt-compchar" id="dt-compchar" title="composing character">Definition</a>: A <b>composing character</b>
1849is a character that is one or both of the following:]
1850 </p><ol class="enumar"><li><p>the second character in the canonical decomposition mapping of
1851some primary composite (as defined in D3 of UAX #15 <a href="#Unicode">[Unicode]</a>), or</p></li><li><p>of non-zero canonical combining class (as defined in Unicode
1852<a href="#Unicode">[Unicode]</a>).</p></li></ol><p>
1853
1854 [<a name="dt-fullnorm" id="dt-fullnorm" title="fully normalized">Definition</a>: Text is
1855<b>fully-normalized</b> if:]
1856 </p><ol class="enumar"><li><p>the text is in a <a title="Unicode encoding form" href="#dt-Uni-encform">Unicode encoding
1857form</a>, is <a title="include-normalized" href="#dt-inclnorm">include-normalized</a> and
1858none of the <a title="" href="#dt-relconst">relevant
1859constructs</a> comprising the text begin with a
1860<a title="composing character" href="#dt-compchar">composing character</a> or a
1861character escape representing a
1862<a title="composing character" href="#dt-compchar">composing character</a>; or</p></li><li><p>the text is in a <a title="legacy encoding" href="#dt-legacyenc">legacy encoding</a> and,
1863if it were transcoded to a <a title="Unicode encoding form" href="#dt-Uni-encform">Unicode encoding form</a>
1864by a <a title="normalizing transcoder" href="#dt-normtransc">normalizing transcoder</a>, the resulting text
1865would satisfy clause 1 above.</p></li></ol></div><div class="div1"> <h2><a name="sec-entexpand" id="sec-entexpand"/>C Expansion of Entity and Character References (Non-Normative)</h2><p>This appendix contains some examples illustrating the sequence of entity-
1866and character-reference recognition and expansion, as specified in <a href="#entproc"><b>4.4 XML Processor Treatment of Entities and References</b></a>.</p><p>If the DTD contains the declaration</p><div class="exampleInner"><pre>&lt;!ENTITY example "&lt;p&gt;An ampersand (&amp;#38;#38;) may be escaped
1867numerically (&amp;#38;#38;#38;) or with a general entity
1868(&amp;amp;amp;).&lt;/p&gt;" &gt;</pre></div><p>then the XML processor will recognize the character references when it
1869parses the entity declaration, and resolve them before storing the following
1870string as the value of the entity "<code>example</code>":</p><div class="exampleInner"><pre>&lt;p&gt;An ampersand (&amp;#38;) may be escaped
1871numerically (&amp;#38;#38;) or with a general entity
1872(&amp;amp;amp;).&lt;/p&gt;</pre></div><p>A reference in the document to "<code>&amp;example;</code>"
1873will cause the text to be reparsed, at which time the start- and end-tags
1874of the <code>p</code> element will be recognized and the three references will
1875be recognized and expanded, resulting in a <code>p</code> element with the following
1876content (all data, no delimiters or markup):</p><div class="exampleInner"><pre>An ampersand (&amp;) may be escaped
1877numerically (&amp;#38;) or with a general entity
1878(&amp;amp;).</pre></div><p>A more complex example will illustrate the rules and their effects fully.
1879In the following example, the line numbers are solely for reference.</p><div class="exampleInner"><pre>1 &lt;?xml version='1.<span>1</span>'?&gt;
18802 &lt;!DOCTYPE test [
18813 &lt;!ELEMENT test (#PCDATA) &gt;
18824 &lt;!ENTITY % xx '&amp;#37;zz;'&gt;
18835 &lt;!ENTITY % zz '&amp;#60;!ENTITY tricky "error-prone" &gt;' &gt;
18846 %xx;
18857 ]&gt;
18868 &lt;test&gt;This sample shows a &amp;tricky; method.&lt;/test&gt;</pre></div><p>This produces the following:</p><ul><li><p>in line 4, the reference to character 37 is expanded immediately,
1887and the parameter entity "<code>xx</code>" is stored in the symbol
1888table with the value "<code>%zz;</code>". Since the replacement
1889text is not rescanned, the reference to parameter entity "<code>zz</code>"
1890is not recognized. (And it would be an error if it were, since "<code>zz</code>"
1891is not yet declared.)</p></li><li><p>in line 5, the character reference "<code>&amp;#60;</code>"
1892is expanded immediately and the parameter entity "<code>zz</code>"
1893is stored with the replacement text "<code>&lt;!ENTITY tricky "error-prone"&gt;</code>", which is a well-formed entity declaration.</p></li><li><p>in line 6, the reference to "<code>xx</code>" is recognized,
1894and the replacement text of "<code>xx</code>" (namely "<code>%zz;</code>")
1895is parsed. The reference to "<code>zz</code>" is recognized in
1896its turn, and its replacement text ("<code>&lt;!ENTITY tricky "error-prone"&gt;</code>") is parsed. The general entity "<code>tricky</code>"
1897has now been declared, with the replacement text "<code>error-prone</code>".</p></li><li><p>in line 8, the reference to the general entity "<code>tricky</code>"
1898is recognized, and it is expanded, so the full content of the <code>test</code>
1899element is the self-describing (and ungrammatical) string <em>This sample
1900shows a error-prone method.</em>
1901 </p></li></ul></div><div class="div1"> <h2><a name="determinism" id="determinism"/>D Deterministic Content Models (Non-Normative)</h2><p>As
1902noted in <a href="#sec-element-content"><b>3.2.1 Element Content</b></a>, it is required that content
1903models in element type declarations be deterministic. This requirement is <a title="For Compatibility" href="#dt-compat">for compatibility</a> with SGML (which calls deterministic
1904content models "unambiguous"); XML processors built
1905using SGML systems may flag non-deterministic content models as errors.</p><p>For example, the content model <code>((b, c) | (b, d))</code> is non-deterministic,
1906because given an initial <code>b</code> the XML processor
1907cannot know which <code>b</code> in the model is being matched without looking
1908ahead to see which element follows the <code>b</code>. In this case, the two references
1909to <code>b</code> can be collapsed into a single reference, making the model read <code>(b,
1910(c | d))</code>. An initial <code>b</code> now clearly matches only a single name
1911in the content model. The processor doesn't need to look ahead to see what follows; either <code>c</code> or <code>d</code>
1912would be accepted.</p><p>More formally: a finite state automaton may be constructed from the content
1913model using the standard algorithms, e.g. algorithm 3.5 in section 3.9 of
1914Aho, Sethi, and Ullman <a href="#Aho">[Aho/Ullman]</a>. In many such algorithms, a follow
1915set is constructed for each position in the regular expression (i.e., each
1916leaf node in the syntax tree for the regular expression); if any position
1917has a follow set in which more than one following position is labeled with
1918the same element type name, then the content model is in error and may be
1919reported as an error.</p><p>Algorithms exist which allow many but not all non-deterministic content
1920models to be reduced automatically to equivalent deterministic models; see
1921Brüggemann-Klein 1991 <a href="#ABK">[Brüggemann-Klein]</a>.</p></div><div class="div1"> <h2><a name="sec-guessing" id="sec-guessing"/>E Autodetection of Character Encodings (Non-Normative)</h2><p>The XML encoding declaration functions as an internal label on each entity,
1922indicating which character encoding is in use. Before an XML processor can
1923read the internal label, however, it apparently has to know what character
1924encoding is in use — which is what the internal label is trying to indicate.
1925In the general case, this is a hopeless situation. It is not entirely hopeless
1926in XML, however, because XML limits the general case in two ways: each implementation
1927is assumed to support only a finite set of character encodings, and the XML
1928encoding declaration is restricted in position and content in order to make
1929it feasible to autodetect the character encoding in use in each entity in
1930normal cases. Also, in many cases other sources of information are available
1931in addition to the XML data stream itself. Two cases may be distinguished,
1932depending on whether the XML entity is presented to the processor without,
1933or with, any accompanying (external) information. We consider the first case
1934first.</p><div class="div2"> <h3><a name="sec-guessing-no-ext-info" id="sec-guessing-no-ext-info"/>E.1 Detection Without External Encoding Information</h3><p>Because each XML entity not accompanied by external
1935encoding information and not in UTF-8 or UTF-16 encoding must
1936begin with an XML encoding declaration, in which the first characters must
1937be '<code>&lt;?xml</code>', any conforming processor can detect, after two
1938to four octets of input, which of the following cases apply. In reading this
1939list, it may help to know that in UCS-4, '&lt;' is "<code>#x0000003C</code>"
1940and '?' is "<code>#x0000003F</code>", and the Byte Order Mark
1941required of UTF-16 data streams is "<code>#xFEFF</code>". The notation
1942<var>##</var> is used to denote any byte value except that two consecutive
1943<var>##</var>s cannot be both 00.</p><p>With a Byte Order Mark:</p><table border="1" frame="border" summary="Encoding detection summary"><tbody><tr><td>
1944 <code>00 00 FE
1945FF</code>
1946 </td><td>UCS-4, big-endian machine (1234 order)</td></tr><tr><td>
1947 <code>FF
1948FE 00 00</code>
1949 </td><td>UCS-4, little-endian machine (4321 order)</td></tr><tr><td>
1950 <code>00 00 FF FE</code>
1951 </td><td>UCS-4, unusual octet order (2143)</td></tr><tr><td>
1952 <code>FE FF 00 00</code>
1953 </td><td>UCS-4, unusual octet order (3412)</td></tr><tr><td>
1954 <code>FE FF ## ##</code>
1955 </td><td>UTF-16, big-endian</td></tr><tr><td>
1956 <code>FF FE ## ##</code>
1957 </td><td>UTF-16, little-endian</td></tr><tr><td>
1958 <code>EF BB BF</code>
1959 </td><td>UTF-8</td></tr></tbody></table><p>Without a Byte Order Mark:</p><table border="1" frame="border" summary="Encoding detection summary"><tbody><tr><td>
1960 <code>00 00 00 3C</code>
1961 </td><td rowspan="4">UCS-4 or other encoding with a 32-bit code unit and ASCII
1962characters encoded as ASCII values, in respectively big-endian (1234), little-endian
1963(4321) and two unusual byte orders (2143 and 3412). The encoding declaration
1964must be read to determine which of UCS-4 or other supported 32-bit encodings
1965applies.</td></tr><tr><td>
1966 <code>3C 00 00 00</code>
1967 </td></tr><tr><td>
1968 <code>00 00 3C 00</code>
1969 </td></tr><tr><td>
1970 <code>00 3C 00 00</code>
1971 </td></tr><tr><td>
1972 <code>00 3C 00 3F</code>
1973 </td><td>UTF-16BE or big-endian ISO-10646-UCS-2
1974or other encoding with a 16-bit code unit in big-endian order and ASCII characters
1975encoded as ASCII values (the encoding declaration must be read to determine
1976which)</td></tr><tr><td>
1977 <code>3C 00 3F 00</code>
1978 </td><td>UTF-16LE or little-endian
1979ISO-10646-UCS-2 or other encoding with a 16-bit code unit in little-endian
1980order and ASCII characters encoded as ASCII values (the encoding declaration
1981must be read to determine which)</td></tr><tr><td>
1982 <code>3C 3F 78 6D</code>
1983 </td><td>UTF-8, ISO 646, ASCII, some part of ISO 8859, Shift-JIS, EUC, or any other
19847-bit, 8-bit, or mixed-width encoding which ensures that the characters of
1985ASCII have their normal positions, width, and values; the actual encoding
1986declaration must be read to detect which of these applies, but since all of
1987these encodings use the same bit patterns for the relevant ASCII characters,
1988the encoding declaration itself may be read reliably</td></tr><tr><td>
1989 <code>4C
19906F A7 94</code>
1991 </td><td>EBCDIC (in some flavor; the full encoding declaration
1992must be read to tell which code page is in use)</td></tr><tr><td>Other</td><td>UTF-8 without an encoding declaration, or else the data stream is mislabeled
1993(lacking a required encoding declaration), corrupt, fragmentary, or enclosed
1994in a wrapper of some kind</td></tr></tbody></table><div class="note"><p class="prefix"><b>Note:</b></p><p>In cases above which do not require reading the encoding declaration to
1995determine the encoding, section 4.3.3 still requires that the encoding declaration,
1996if present, be read and that the encoding name be checked to match the actual
1997encoding of the entity. Also, it is possible that new character encodings
1998will be invented that will make it necessary to use the encoding declaration
1999to determine the encoding, in cases where this is not required at present.</p></div><p>This level of autodetection is enough to read the XML encoding declaration
2000and parse the character-encoding identifier, which is still necessary to distinguish
2001the individual members of each family of encodings (e.g. to tell UTF-8 from
20028859, and the parts of 8859 from each other, or to distinguish the specific
2003EBCDIC code page in use, and so on).</p><p>Because the contents of the encoding declaration are restricted to characters
2004from the ASCII repertoire (however encoded),
2005a processor can reliably read the entire encoding declaration as soon as it
2006has detected which family of encodings is in use. Since in practice, all widely
2007used character encodings fall into one of the categories above, the XML encoding
2008declaration allows reasonably reliable in-band labeling of character encodings,
2009even when external sources of information at the operating-system or transport-protocol
2010level are unreliable. Character encodings such as UTF-7
2011that make overloaded usage of ASCII-valued bytes may fail to be reliably detected.</p><p>Once the processor has detected the character encoding in use, it can act
2012appropriately, whether by invoking a separate input routine for each case,
2013or by calling the proper conversion function on each character of input.</p><p>Like any self-labeling system, the XML encoding declaration will not work
2014if any software changes the entity's character set or encoding without updating
2015the encoding declaration. Implementors of character-encoding routines should
2016be careful to ensure the accuracy of the internal and external information
2017used to label the entity.</p></div><div class="div2"> <h3><a name="sec-guessing-with-ext-info" id="sec-guessing-with-ext-info"/>E.2 Priorities in the Presence of External Encoding Information</h3><p>The second possible case occurs when the XML entity is accompanied by encoding
2018information, as in some file systems and some network protocols. When multiple
2019sources of information are available, their relative priority and the preferred
2020method of handling conflict should be specified as part of the higher-level
2021protocol used to deliver XML. In particular, please refer
2022to <a href="#rfc2376">[IETF RFC 3023]</a> or its successor, which defines the <code>text/xml</code>
2023and <code>application/xml</code> MIME types and provides some useful guidance.
2024In the interests of interoperability, however, the following rule is recommended.</p><ul><li><p>If an XML entity is in a file, the Byte-Order Mark and encoding declaration are used
2025(if present) to determine the character encoding.</p></li></ul></div></div><div class="div1"> <h2><a name="sec-xml-wg" id="sec-xml-wg"/>F W3C XML Working Group (Non-Normative)</h2><p>This specification was prepared and approved for publication by the W3C
2026XML Working Group (WG). WG approval of this specification does not necessarily
2027imply that all WG participants voted for its approval. The current and former members
2028in the XML WG are:</p><ul><li>Jon Bosak, Sun (<i>Chair</i>) </li><li>James Clark (<i>Technical Lead</i>) </li><li>Tim Bray, Textuality and Netscape (<i>XML Co-editor</i>) </li><li>Jean Paoli, Microsoft (<i>XML
2029Co-editor</i>) </li><li>C. M. Sperberg-McQueen, U. of Ill. (<i>XML Co-editor</i>) </li><li>Dan Connolly, W3C (<i>W3C Liaison</i>) </li><li>Paula Angerstein, Texcel</li><li>Steve DeRose, INSO</li><li>Dave Hollander, HP</li><li>Eliot Kimber, ISOGEN</li><li>Eve Maler, ArborText</li><li>Tom Magliery, NCSA</li><li>Murray Maloney, SoftQuad, Grif
2030SA, Muzmo and Veo Systems</li><li>MURATA Makoto (FAMILY Given), Fuji
2031Xerox Information Systems</li><li>Joel Nava, Adobe</li><li>Conleth O'Connell, Vignette</li><li>Peter Sharpe, SoftQuad</li><li>John Tigue, DataChannel</li></ul></div><div class="div1"> <h2><a name="sec-core-wg" id="sec-core-wg"/>G W3C XML Core Working Group (Non-Normative)</h2><p>The <span>second</span> edition of this specification was prepared by the W3C XML Core
2032Working Group (WG). The participants in the WG at the time of publication of this
2033edition were:</p><ul><li>Leonid Arbouzov, Sun Microsystems</li><li>John Cowan</li><li>Andrew Fang, PTC-Arbortext</li><li>Paul Grosso, PTC-Arbortext (<i>Co-Chair</i>) </li><li>Konrad Lanz, A-SIT</li><li>Philippe Le Hégaret, W3C (<i>Staff Contact</i>) </li><li>Glenn Marcy, IBM</li><li>Sandra Martinez, NIST</li><li>Ravindrakumar R, CDAC</li><li>Lew Shannon</li><li>Henry Thompson, W3C (<i>Staff Contact</i>) </li><li>Richard Tobin, University of Edinburgh</li><li>Daniel Veillard</li><li>Norman Walsh, Sun Microsystems (<i>Co-Chair</i>) </li><li>François Yergeau</li></ul></div><div class="div1"> <h2><a name="prod-notes" id="prod-notes"/>H Production Notes (Non-Normative)</h2><p>This edition was encoded in a
2034slightly modified version of the
2035<a href="http://www.w3.org/2002/xmlspec/dtd/2.10/xmlspec.dtd">XMLspec DTD, 2.10</a>.
2036The XHTML versions were produced with a combination of the
2037<a href="http://www.w3.org/2002/xmlspec/xhtml/1.13/xmlspec.xsl">xmlspec.xsl</a>,
2038<a href="http://www.w3.org/2002/xmlspec/xhtml/1.13/diffspec.xsl">diffspec.xsl</a>,
2039and <a href="REC-xml.xsl">REC-xml.xsl</a>
2040XSLT stylesheets.</p></div><div class="div1"> <h2><a name="sec-suggested-names" id="sec-suggested-names"/>I Suggestions for XML Names (Non-Normative)</h2><p>The following suggestions define what is believed to be best
2041practice in the construction of XML names used as element names,
2042attribute names, processing instruction targets, entity names,
2043notation names, and the values of attributes of type ID, and are
2044intended as guidance for document authors and schema designers.
2045All references to Unicode are understood with respect to
2046a particular version of the Unicode Standard greater than or equal
2047to 3.0; which version should be used is left to the discretion of
2048the document author or schema designer.</p><p>The first two suggestions are directly derived from the rules
2049given for identifiers in the Unicode Standard, version 3.0, and
2050exclude all control characters, enclosing nonspacing marks,
2051non-decimal numbers, private-use characters, punctuation characters
2052(with the noted exceptions), symbol characters, unassigned
2053codepoints, and white space characters. The other suggestions
2054are mostly derived from <a href="#XML1.0">[XML-1.0]</a> Appendix B.</p><ol class="enumar"><li><p>The first character of any name should have a Unicode General
2055Category of Ll, Lu, Lo, Lm, Lt, or Nl, or else be '_' #x5F.</p></li><li><p>Characters other than the first should have a Unicode General
2056Category of Ll, Lu, Lo, Lm, Lt, Mc, Mn, Nl, Nd, Pc, or Cf, or else
2057be one of the following: '-' #x2D, '.' #x2E, ':' #x3A or
2058'·' #xB7 (middle dot). Since Cf characters are not
2059directly visible, they should be employed with caution and only
2060when necessary, to avoid creating names which are distinct to XML
2061processors but look the same to human beings.</p></li><li><p>Ideographic characters which have a canonical decomposition
2062(including those in the ranges [#xF900-#xFAFF] and
2063[#x2F800-#x2FFFD], with 12 exceptions) should not be used in names.
2064</p></li><li><p>Characters which have a compatibility decomposition (those with
2065a "compatibility formatting tag" in field 5 of the Unicode
2066Character Database -- marked by field 5 beginning with a "&lt;")
2067should not be used in names. This suggestion does not apply
2068to #x0E33 THAI CHARACTER SARA AM or #x0EB3 LAO CHARACTER AM, which
2069despite their compatibility decompositions are in regular use in
2070those scripts.</p></li><li><p>Combining characters meant for use with symbols only (including
2071those in the ranges [#x20D0-#x20EF] and [#x1D165-#x1D1AD]) should
2072not be used in names.</p></li><li><p>The interlinear annotation characters ([#xFFF9-#xFFFB<span>
2073 ]</span>) should
2074not be used in names.</p></li><li><p>Variation selector characters should not be used in names.</p></li><li><p>Names which are nonsensical, unpronounceable, hard to read, or
2075easily confusable with other names should not be employed.</p></li></ol></div></div></body></html>
diff --git a/misc/xml-grammar b/misc/xml-grammar
new file mode 100644
index 0000000..023e166
--- /dev/null
+++ b/misc/xml-grammar
@@ -0,0 +1,7 @@
1document ::= prolog element misc*
2
3prolog ::= XMLDecl misc* (doctypedecl misc*)?
4
5XMLDecl ::= '<?xml' VersionInfo EncodingDecl? SDDecl? ws? '?>'
6
7VersionInfo ::= ws
diff --git a/src/fstring.h b/src/fstring.h
index 8b22160..fb4bf55 100644
--- a/src/fstring.h
+++ b/src/fstring.h
@@ -187,7 +187,26 @@ namespace Bu
187 append( &cData, 1 ); 187 append( &cData, 1 );
188 } 188 }
189 } 189 }
190 190
191 /**
192 * Append another FString to this one.
193 *@param sData (MyType &) The FString to append.
194 */
195 void append( const MyType & sData )
196 {
197 append( sData.getStr(), sData.getSize() );
198 }
199
200 /**
201 * Append another FString to this one.
202 *@param sData (MyType &) The FString to append.
203 *@param nLen How much data to append.
204 */
205 void append( const MyType & sData, long nLen )
206 {
207 append( sData.getStr(), nLen );
208 }
209
191 /** 210 /**
192 * Prepend another FString to this one. 211 * Prepend another FString to this one.
193 *@param sData (MyType &) The FString to prepend. 212 *@param sData (MyType &) The FString to prepend.
diff --git a/src/unit/xml.cpp b/src/unit/xml.cpp
new file mode 100644
index 0000000..e845cc1
--- /dev/null
+++ b/src/unit/xml.cpp
@@ -0,0 +1,39 @@
1/*
2 * Copyright (C) 2007-2008 Xagasoft, All rights reserved.
3 *
4 * This file is part of the libbu++ library and is released under the
5 * terms of the license contained in the file LICENSE.
6 */
7
8#include "bu/fstring.h"
9#include "bu/unitsuite.h"
10#include "bu/xmlreader.h"
11#include "bu/membuf.h"
12
13class Unit : public Bu::UnitSuite
14{
15public:
16 Unit()
17 {
18 setName("Xml");
19 addTest( Unit::declaration );
20 }
21
22 virtual ~Unit()
23 {
24 }
25
26 void declaration()
27 {
28 Bu::FString sXml("<?xml ?> <hi />");
29 Bu::MemBuf buf( sXml );
30 Bu::XmlReader xr( buf );
31 }
32
33};
34
35int main( int argc, char *argv[] )
36{
37 return Unit().run( argc, argv );
38}
39
diff --git a/src/xmlreader.cpp b/src/xmlreader.cpp
new file mode 100644
index 0000000..9d299e6
--- /dev/null
+++ b/src/xmlreader.cpp
@@ -0,0 +1,165 @@
1#include "bu/xmlreader.h"
2#include "bu/stream.h"
3#include "bu/exceptions.h"
4
5Bu::XmlReader::XmlReader( Stream &rInput ) :
6 rInput( rInput ),
7 iCurToken( 0 ),
8 iNextToken( 0 ),
9 bIgnoreWS( true )
10{
11 nextToken();
12 stDocument();
13}
14
15Bu::XmlReader::~XmlReader()
16{
17}
18
19void Bu::XmlReader::fillBuffer()
20{
21 if( rInput.isEOS() )
22 return;
23 char buf[1024];
24 int iSize = rInput.read( buf, 1024 );
25 sBuf.append( buf, iSize );
26}
27
28void Bu::XmlReader::cleanupBuffer( int iUsed )
29{
30 for( int j = 0; j < iUsed; j++ )
31 {
32 if( sBuf[j] == '\n' )
33 {
34 spNextToken.iLine++;
35 spNextToken.iChar = 1;
36 }
37 else
38 {
39 spNextToken.iChar++;
40 }
41 }
42
43 printf("--Deleting %d bytes from front of buffer.\n", iUsed );
44 sBuf.trimFront( iUsed );
45}
46
47int Bu::XmlReader::nextToken()
48{
49 fillBuffer();
50
51 int iUsed = 1;
52
53 iCurToken = iNextToken;
54 spCurToken = spNextToken;
55
56 switch( sBuf[0] )
57 {
58 case '<':
59 if( !strncmp( sBuf.getStr(), "<?xml", 5 ) )
60 {
61 iNextToken = tokXmlDeclHead;
62 iUsed = 5;
63 }
64 else
65 {
66 iNextToken = '<';
67 }
68 break;
69
70 case '?':
71 if( sBuf[1] == '>' )
72 {
73 iNextToken = tokXmlDeclEnd;
74 iUsed = 2;
75 }
76 else
77 {
78 iNextToken = '?';
79 }
80 break;
81
82 case ' ':
83 case '\t':
84 case '\n':
85 case '\r':
86 for( int j = 1;; j++ )
87 {
88 if( j == sBuf.getSize() )
89 {
90 if( rInput.isEOS() )
91 error("Reached end of input while waiting for whitespace to end.");
92
93 fillBuffer();
94 }
95 if( sBuf[j] == ' ' || sBuf[j] == '\t' ||
96 sBuf[j] == '\n' || sBuf[j] == '\r' )
97 iUsed++;
98 else
99 break;
100 }
101 sStr.clear();
102 sStr.append( sBuf, iUsed );
103 iNextToken = tokWS;
104 break;
105
106 case '=':
107 iNextToken = sBuf[0];
108 break;
109
110 default:
111 if( (sBuf[0] >= 'a' && sBuf[0] <= 'z') ||
112 (sBuf[0] >= 'A' && sBuf[0] <= 'Z') )
113 {
114 for( int j = 1;; j++ )
115 {
116 if( j == sBuf.getSize() )
117 {
118 if( rInput.isEOS() )
119 error("Reached end of input while waiting for a string to end.");
120
121 fillBuffer();
122 }
123 if( (sBuf[j] >= 'a' && sBuf[j] <= 'z') ||
124 (sBuf[j] >= 'A' && sBuf[j] <= 'Z') )
125 iUsed++;
126 else
127 break;
128 }
129 sStr.clear();
130 sStr.append( sBuf, iUsed );
131 iNextToken = tokIdent;
132 }
133 }
134
135 cleanupBuffer( iUsed );
136
137 return iCurToken;
138}
139
140void Bu::XmlReader::error( const char *sMessage )
141{
142 throw Bu::XmlException("%d:%d: %s",
143 spCurToken.iLine, spCurToken.iChar, sMessage );
144}
145
146void Bu::XmlReader::stDocument()
147{
148 stProlog();
149}
150
151void Bu::XmlReader::stProlog()
152{
153 stXmlDecl();
154}
155
156void Bu::XmlReader::stXmlDecl()
157{
158 if( nextToken() != tokXmlDeclHead )
159 error("You must begin your xml file with a declaration: <?xml ... ?>");
160 if( nextToken() != tokIdent )
161 error("A version comes first!");
162 if( sStr != "version" )
163 error("No, a version!");
164}
165
diff --git a/src/xmlreader.h b/src/xmlreader.h
new file mode 100644
index 0000000..375dfe3
--- /dev/null
+++ b/src/xmlreader.h
@@ -0,0 +1,54 @@
1#ifndef BU_XML_READER_H
2#define BU_XML_READER_H
3
4#include "bu/fstring.h"
5
6namespace Bu
7{
8 class Stream;
9
10 class XmlReader
11 {
12 public:
13 XmlReader( Stream &rInput );
14 virtual ~XmlReader();
15
16 private:
17 Stream &rInput;
18 int iCurToken;
19 int iNextToken;
20 Bu::FString sBuf;
21 Bu::FString sStr;
22 bool bIgnoreWS;
23 typedef struct StreamPos
24 {
25 StreamPos() : iLine( 1 ), iChar( 1 ) { }
26 int iLine;
27 int iChar;
28 } StreamPos;
29 StreamPos spCurToken;
30 StreamPos spNextToken;
31
32
33 enum
34 {
35 tokXmlDeclHead = 0x100,
36 tokXmlDeclEnd,
37 tokWS,
38 tokIdent,
39 tokString
40 };
41
42 void fillBuffer();
43 void cleanupBuffer( int iUsed );
44 int nextToken();
45
46 void stDocument();
47 void stProlog();
48 void stXmlDecl();
49
50 void error( const char *sMessage );
51 };
52};
53
54#endif