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Extensible Markup Language (XML) 1.0 (Fifth Edition).html 265 KB
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<h1><a name="title" id="title" data-ss1529144233="1">Extensible Markup Language (XML) 1.0 (Fifth Edition)</a></h1><a name="title" id="title" data-ss1529144233="1">
  </a><h2><a name="title" id="title" data-ss1529144233="1"></a><a name="w3c-doctype" id="w3c-doctype" data-ss1529144233="1">W3C Recommendation 26 November 2008</a></h2><a name="w3c-doctype" id="w3c-doctype" data-ss1529144233="1">
    <div id="notice-20130207" style="border: solid black 1px; padding: 0.5em; background: #FFB;">
      <p><strong>Note:</strong> On 7 February 2013, this specification was modified in place to replace broken links to RFC4646 and RFC4647.</p>
    </div>
    </a><dl><a name="w3c-doctype" id="w3c-doctype" data-ss1529144233="1"><dt>This version:</dt></a><dd><a name="w3c-doctype" id="w3c-doctype" data-ss1529144233="1">
			</a><a href="http://www.w3.org/TR/2008/REC-xml-20081126/" data-ss1529144233="1">http://www.w3.org/TR/2008/REC-xml-20081126/</a>
		</dd><dt>Latest version:</dt><dd>
			<a href="http://www.w3.org/TR/xml/" data-ss1529144233="1">http://www.w3.org/TR/xml/</a>
		</dd><dt>Previous versions:</dt><dd>
   <a href="http://www.w3.org/TR/2008/PER-xml-20080205/" data-ss1529144233="1">http://www.w3.org/TR/2008/PER-xml-20080205/</a>
  <br>
   <a href="http://www.w3.org/TR/2006/REC-xml-20060816/" data-ss1529144233="1">http://www.w3.org/TR/2006/REC-xml-20060816/</a>
		</dd><dt>Editors:</dt><dd>Tim Bray, Textuality and Netscape <a href="mailto:tbray@textuality.com" rel="noreferrer" data-ss1529144233="1">&lt;tbray@textuality.com&gt;</a></dd><dd>Jean Paoli, Microsoft <a href="mailto:jeanpa@microsoft.com" rel="noreferrer" data-ss1529144233="1">&lt;jeanpa@microsoft.com&gt;</a></dd><dd>C. M. Sperberg-McQueen, W3C <a href="mailto:cmsmcq@w3.org" data-ss1529144233="1">&lt;cmsmcq@w3.org&gt;</a></dd><dd>Eve Maler, Sun Microsystems, Inc. <a href="mailto:elm@east.sun.com" rel="noreferrer" data-ss1529144233="1">&lt;eve.maler@east.sun.com&gt;</a></dd><dd>François Yergeau</dd></dl><p>Please refer to the <a href="http://www.w3.org/XML/xml-V10-5e-errata" data-ss1529144233="1"><strong>errata</strong></a> for this document, which may
      include some normative corrections.</p><p>The <a href="http://www.w3.org/XML/xml-V10-4e-errata" data-ss1529144233="1">previous errata</a> for this document, are also available.</p><p>See also <a href="http://www.w3.org/2003/03/Translations/byTechnology?technology=xml" data-ss1529144233="1"><strong>translations</strong></a>.</p><p>This document is also available in these non-normative formats: <a href="https://www.w3.org/TR/REC-xml/REC-xml-20081126.xml" data-ss1529144233="1">XML</a> and&nbsp;<a href="https://www.w3.org/TR/REC-xml/REC-xml-20081126-review.html" data-ss1529144233="1">XHTML with color-coded revision indicators</a>.</p><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright" data-ss1529144233="1">Copyright</a>&nbsp;©&nbsp;2008&nbsp;<a href="http://www.w3.org/" data-ss1529144233="1"><acronym title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup> (<a href="http://www.csail.mit.edu/" rel="noreferrer" data-ss1529144233="1"><acronym title="Massachusetts Institute of Technology">MIT</acronym></a>, <a href="http://www.ercim.org/" rel="noreferrer" data-ss1529144233="1"><acronym title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></a>, <a href="http://www.keio.ac.jp/" rel="noreferrer" data-ss1529144233="1">Keio</a>), All Rights Reserved. W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer" data-ss1529144233="1">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks" data-ss1529144233="1">trademark</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-documents" data-ss1529144233="1">document use</a> rules apply.</p></div><hr><div>
<h2><a name="abstract" id="abstract" data-ss1529144233="1">Abstract</a></h2><p><a name="abstract" id="abstract" data-ss1529144233="1">The Extensible Markup Language (XML) is a subset of SGML that is completely
described in this document. Its goal is to enable generic SGML to be served,
received, and processed on the Web in the way that is now possible with HTML.
XML has been designed for ease of implementation and for interoperability
with both SGML and HTML.</a></p></div><div><a name="abstract" id="abstract" data-ss1529144233="1">
</a><h2><a name="abstract" id="abstract" data-ss1529144233="1"></a><a name="status" id="status" data-ss1529144233="1">Status of this Document</a></h2><p><a name="status" id="status" data-ss1529144233="1"><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 </em></a><em><a href="http://www.w3.org/TR/" data-ss1529144233="1">W3C technical reports index</a> at
				http://www.w3.org/TR/.</em></p><p>This document specifies a syntax created by subsetting an existing, widely
				used international text processing standard (Standard Generalized Markup Language,
				ISO 8879:1986(E) as amended and corrected) for use on the World Wide Web.
				It is a product of the <a href="http://www.w3.org/XML/Core/" data-ss1529144233="1">XML Core Working Group</a>
				as part of the <a href="http://www.w3.org/XML/Activity" data-ss1529144233="1">XML Activity</a>.
				The English version of this specification is the only normative version. However,
				for translations of this document, see <a href="http://www.w3.org/2003/03/Translations/byTechnology?technology=xml" data-ss1529144233="1">http://www.w3.org/2003/03/Translations/byTechnology?technology=xml</a>.</p><p>This document is a <a href="http://www.w3.org/2005/10/Process-20051014/tr.html#q74" data-ss1529144233="1">W3C Recommendation</a>. This fifth edition is <em>not</em> a new version of XML. As a convenience to readers,
				it incorporates the changes dictated by the accumulated errata (available at
				<a href="http://www.w3.org/XML/xml-V10-4e-errata" data-ss1529144233="1">http://www.w3.org/XML/xml-V10-4e-errata</a>) to the <a href="http://www.w3.org/TR/2006/REC-xml-20060816/" data-ss1529144233="1">Fourth
				Edition of XML 1.0, dated 16 August 2006</a>.  In particular, erratum <a href="http://www.w3.org/XML/xml-V10-4e-errata#E09" data-ss1529144233="1">[E09]</a>
				relaxes the restrictions on element and attribute names, thereby providing in XML 1.0 the major end user benefit
				currently achievable only by using XML
1.1.  As a consequence, many possible
 documents which were not well-formed according to previous editions of this
 specification are now well-formed, and previously invalid documents
using the newly-allowed name characters in, for example, ID
attributes, are now valid.</p><p>This edition supersedes the previous <a href="http://www.w3.org/TR/2006/REC-xml-20060816/" data-ss1529144233="1">W3C Recommendation
				of 16 August 2006</a>.</p><p>Please report errors in this document to
the public <a href="mailto:xml-editor@w3.org" data-ss1529144233="1">xml-editor@w3.org</a> mail list; public
				<a href="http://lists.w3.org/Archives/Public/xml-editor/" data-ss1529144233="1">archives</a> are available. For the convenience of readers,
				an <a href="https://www.w3.org/TR/REC-xml/REC-xml-20081126-review.html" data-ss1529144233="1">XHTML version with color-coded revision indicators</a> is
				also provided; this version highlights each change due to an erratum published in the
				<a href="http://www.w3.org/XML/xml-V10-4e-errata" data-ss1529144233="1">errata
list</a> for the previous edition, together with a link to the particular
				erratum in that list. Most of the
errata in the list provide a rationale for the change.  The errata
list for this fifth edition is available at <a href="http://www.w3.org/XML/xml-V10-5e-errata" data-ss1529144233="1">http://www.w3.org/XML/xml-V10-5e-errata</a>.</p><p>An implementation report is available at <a href="http://www.w3.org/XML/2008/01/xml10-5e-implementation.html" data-ss1529144233="1">http://www.w3.org/XML/2008/01/xml10-5e-implementation.html</a>.
				A <a href="http://www.w3.org/XML/Test/" data-ss1529144233="1">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>W3C maintains a <a href="http://www.w3.org/2002/08/xmlcore-IPR-statements" rel="disclosure" data-ss1529144233="1">public list of
				any patent disclosures</a> made in connection with the deliverables of
				the group; that page also includes instructions for disclosing a patent.
				An individual who has actual knowledge of a patent which the individual
				believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential" data-ss1529144233="1">Essential
				Claim(s)</a> must disclose the information in accordance with 
				<a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure" data-ss1529144233="1">section 6 of the W3C Patent Policy</a>.</p></div><div class="toc">
<h2><a name="contents" id="contents" data-ss1529144233="1">Table of Contents</a></h2><p class="toc"><a name="contents" id="contents" data-ss1529144233="1">1 </a><a href="#sec-intro" data-ss1529144233="1">Introduction</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;1.1 <a href="#sec-origin-goals" data-ss1529144233="1">Origin and Goals</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;1.2 <a href="#sec-terminology" data-ss1529144233="1">Terminology</a><br>
2 <a href="#sec-documents" data-ss1529144233="1">Documents</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;2.1 <a href="#sec-well-formed" data-ss1529144233="1">Well-Formed XML Documents</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;2.2 <a href="#charsets" data-ss1529144233="1">Characters</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;2.3 <a href="#sec-common-syn" data-ss1529144233="1">Common Syntactic Constructs</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;2.4 <a href="#syntax" data-ss1529144233="1">Character Data and Markup</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;2.5 <a href="#sec-comments" data-ss1529144233="1">Comments</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;2.6 <a href="#sec-pi" data-ss1529144233="1">Processing Instructions</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;2.7 <a href="#sec-cdata-sect" data-ss1529144233="1">CDATA Sections</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;2.8 <a href="#sec-prolog-dtd" data-ss1529144233="1">Prolog and Document Type Declaration</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;2.9 <a href="#sec-rmd" data-ss1529144233="1">Standalone Document Declaration</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;2.10 <a href="#sec-white-space" data-ss1529144233="1">White Space Handling</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;2.11 <a href="#sec-line-ends" data-ss1529144233="1">End-of-Line Handling</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;2.12 <a href="#sec-lang-tag" data-ss1529144233="1">Language Identification</a><br>
3 <a href="#sec-logical-struct" data-ss1529144233="1">Logical Structures</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;3.1 <a href="#sec-starttags" data-ss1529144233="1">Start-Tags, End-Tags, and Empty-Element Tags</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;3.2 <a href="#elemdecls" data-ss1529144233="1">Element Type Declarations</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3.2.1 <a href="#sec-element-content" data-ss1529144233="1">Element Content</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3.2.2 <a href="#sec-mixed-content" data-ss1529144233="1">Mixed Content</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;3.3 <a href="#attdecls" data-ss1529144233="1">Attribute-List Declarations</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3.3.1 <a href="#sec-attribute-types" data-ss1529144233="1">Attribute Types</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3.3.2 <a href="#sec-attr-defaults" data-ss1529144233="1">Attribute Defaults</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3.3.3 <a href="#AVNormalize" data-ss1529144233="1">Attribute-Value Normalization</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;3.4 <a href="#sec-condition-sect" data-ss1529144233="1">Conditional Sections</a><br>
4 <a href="#sec-physical-struct" data-ss1529144233="1">Physical Structures</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;4.1 <a href="#sec-references" data-ss1529144233="1">Character and Entity References</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;4.2 <a href="#sec-entity-decl" data-ss1529144233="1">Entity Declarations</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.2.1 <a href="#sec-internal-ent" data-ss1529144233="1">Internal Entities</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.2.2 <a href="#sec-external-ent" data-ss1529144233="1">External Entities</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;4.3 <a href="#TextEntities" data-ss1529144233="1">Parsed Entities</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.3.1 <a href="#sec-TextDecl" data-ss1529144233="1">The Text Declaration</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.3.2 <a href="#wf-entities" data-ss1529144233="1">Well-Formed Parsed Entities</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.3.3 <a href="#charencoding" data-ss1529144233="1">Character Encoding in Entities</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;4.4 <a href="#entproc" data-ss1529144233="1">XML Processor Treatment of Entities and References</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.4.1 <a href="#not-recognized" data-ss1529144233="1">Not Recognized</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.4.2 <a href="#included" data-ss1529144233="1">Included</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.4.3 <a href="#include-if-valid" data-ss1529144233="1">Included If Validating</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.4.4 <a href="#forbidden" data-ss1529144233="1">Forbidden</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.4.5 <a href="#inliteral" data-ss1529144233="1">Included in Literal</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.4.6 <a href="#notify" data-ss1529144233="1">Notify</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.4.7 <a href="#bypass" data-ss1529144233="1">Bypassed</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.4.8 <a href="#as-PE" data-ss1529144233="1">Included as PE</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4.4.9 <a href="#error" data-ss1529144233="1">Error</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;4.5 <a href="#intern-replacement" data-ss1529144233="1">Construction of Entity Replacement Text</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;4.6 <a href="#sec-predefined-ent" data-ss1529144233="1">Predefined Entities</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;4.7 <a href="#Notations" data-ss1529144233="1">Notation Declarations</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;4.8 <a href="#sec-doc-entity" data-ss1529144233="1">Document Entity</a><br>
5 <a href="#sec-conformance" data-ss1529144233="1">Conformance</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;5.1 <a href="#proc-types" data-ss1529144233="1">Validating and Non-Validating Processors</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;5.2 <a href="#safe-behavior" data-ss1529144233="1">Using XML Processors</a><br>
6 <a href="#sec-notation" data-ss1529144233="1">Notation</a><br>
</p>
<h3><a name="appendices" id="appendices" data-ss1529144233="1">Appendices</a></h3><p class="toc"><a name="appendices" id="appendices" data-ss1529144233="1">A </a><a href="#sec-bibliography" data-ss1529144233="1">References</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;A.1 <a href="#sec-existing-stds" data-ss1529144233="1">Normative References</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;A.2 <a href="#null" data-ss1529144233="1">Other References</a><br>
B <a href="#CharClasses" data-ss1529144233="1">Character Classes</a><br>
C <a href="#sec-xml-and-sgml" data-ss1529144233="1">XML and SGML</a> (Non-Normative)<br>
D <a href="#sec-entexpand" data-ss1529144233="1">Expansion of Entity and Character References</a> (Non-Normative)<br>
E <a href="#determinism" data-ss1529144233="1">Deterministic Content Models</a> (Non-Normative)<br>
F <a href="#sec-guessing" data-ss1529144233="1">Autodetection of Character Encodings</a> (Non-Normative)<br>
&nbsp;&nbsp;&nbsp;&nbsp;F.1 <a href="#sec-guessing-no-ext-info" data-ss1529144233="1">Detection Without External Encoding Information</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;F.2 <a href="#sec-guessing-with-ext-info" data-ss1529144233="1">Priorities in the Presence of External Encoding Information</a><br>
G <a href="#sec-xml-wg" data-ss1529144233="1">W3C XML Working Group</a> (Non-Normative)<br>
H <a href="#sec-core-wg" data-ss1529144233="1">W3C XML Core Working Group</a> (Non-Normative)<br>
I <a href="#prod-notes" data-ss1529144233="1">Production Notes</a> (Non-Normative)<br>
J <a href="#sec-suggested-names" data-ss1529144233="1">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" data-ss1529144233="1">1 Introduction</a></h2><p><a name="sec-intro" id="sec-intro" data-ss1529144233="1">Extensible Markup Language, abbreviated XML, describes a class of data
objects called </a><a title="XML Document" href="#dt-xml-doc" data-ss1529144233="1">XML documents</a> and partially
describes the behavior of computer programs which process them. XML is an
application profile or restricted form of SGML, the Standard Generalized Markup
Language <a href="#ISO8879" data-ss1529144233="1">[ISO 8879]</a>. By construction, XML documents are conforming
SGML documents.</p><p>XML documents are made up of storage units called <a title="Entity" href="#dt-entity" data-ss1529144233="1">entities</a>,
which contain either parsed or unparsed data. Parsed data is made up of <a title="Character" href="#dt-character" data-ss1529144233="1">characters</a>, some of which form <a title="Character Data" href="#dt-chardata" data-ss1529144233="1">character
data</a>, and some of which form <a title="Markup" href="#dt-markup" data-ss1529144233="1">markup</a>.
Markup encodes a description of the document's storage layout and logical
structure. XML provides a mechanism to impose constraints on the storage layout
and logical structure.</p><p>
				[<a name="dt-xml-proc" id="dt-xml-proc" title="XML Processor" data-ss1529144233="1">Definition</a>: A software module called
an <b>XML processor</b> is used to read XML documents and provide access
to their content and structure.]
				[<a name="dt-app" id="dt-app" title="Application" data-ss1529144233="1">Definition</a>: It
is assumed that an XML processor is doing its work on behalf of another module,
called the <b>application</b>.] This specification describes
the required behavior of an XML processor in terms of how it must read XML
data and the information it must provide to the application.</p><div class="div2">
<h3><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">1.1 Origin and Goals</a></h3><p><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">XML was developed by an XML Working Group (originally known as the SGML
Editorial Review Board) formed under the auspices of the World Wide Web Consortium
(W3C) in 1996. It was chaired by Jon Bosak of Sun Microsystems with the active
participation of an XML Special Interest Group (previously known as the SGML
Working Group) also organized by the W3C. The membership of the XML Working
Group is given in an appendix. Dan Connolly served as the Working Group's contact with
the W3C.</a></p><p><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">The design goals for XML are:</a></p><ol class="enumar"><li><p><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">XML shall be straightforwardly usable over the Internet.</a></p></li><li><p><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">XML shall support a wide variety of applications.</a></p></li><li><p><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">XML shall be compatible with SGML.</a></p></li><li><p><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">It shall be easy to write programs which process XML documents.</a></p></li><li><p><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">The number of optional features in XML is to be kept to the absolute
minimum, ideally zero.</a></p></li><li><p><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">XML documents should be human-legible and reasonably clear.</a></p></li><li><p><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">The XML design should be prepared quickly.</a></p></li><li><p><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">The design of XML shall be formal and concise.</a></p></li><li><p><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">XML documents shall be easy to create.</a></p></li><li><p><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">Terseness in XML markup is of minimal importance.</a></p></li></ol><p><a name="sec-origin-goals" id="sec-origin-goals" data-ss1529144233="1">This specification, together with associated standards (Unicode </a><a href="#Unicode" data-ss1529144233="1">[Unicode]</a>
					and ISO/IEC 10646 <a href="#ISO10646" data-ss1529144233="1">[ISO/IEC 10646]</a> for characters, Internet <span>BCP 47</span>
					<a href="#RFC1766" data-ss1529144233="1">[IETF BCP 47]</a> <span>and the Language Subtag Registry <a href="#IANA-LANGCODES" data-ss1529144233="1">[IANA-LANGCODES]</a></span> for language
					identification tags), provides
all the information necessary to understand XML Version 1.0 and
construct computer programs to process it.</p><p>This version of the XML specification may be distributed freely, as long as
all text and legal notices remain intact.</p></div><div class="div2">
<h3><a name="sec-terminology" id="sec-terminology" data-ss1529144233="1">1.2 Terminology</a></h3><p><a name="sec-terminology" id="sec-terminology" data-ss1529144233="1">The terminology used to describe XML documents is defined in the body of
this 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><a href="#rfc2119" data-ss1529144233="1">[IETF RFC 2119]</a>. In addition, the terms defined
in the following list are used in building
those 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" data-ss1529144233="1">Definition</a>:
 A violation of the rules of this specification;
results 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
and <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" data-ss1529144233="1">Definition</a>: An error which a conforming <a title="XML Processor" href="#dt-xml-proc" data-ss1529144233="1">XML processor</a>
										<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> detect and report to the application.
After encountering a fatal error, the processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> continue processing the
data to search for further errors and <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> report such errors to the application.
In order to support correction of errors, the processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> make unprocessed
data from the document (with intermingled character data and markup) available
to the application. Once a fatal error is detected, however, the processor
<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
data and information about the document's logical structure to the application
in 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" data-ss1529144233="1">Definition</a>: Conforming software
<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;
if it does, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> provide users a means to enable or disable the behavior
described.]
								</p></dd><dt class="label">validity constraint</dt><dd><p>
									[<a name="dt-vc" id="dt-vc" title="Validity constraint" data-ss1529144233="1">Definition</a>: A rule which applies to
all <a title="Validity" href="#dt-valid" data-ss1529144233="1">valid</a> XML documents. Violations of validity
constraints 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" data-ss1529144233="1">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" data-ss1529144233="1">Definition</a>: A rule which applies
to all <a title="Well-Formed" href="#dt-wellformed" data-ss1529144233="1">well-formed</a> XML documents. Violations
of well-formedness constraints are <a title="Fatal Error" href="#dt-fatal" data-ss1529144233="1">fatal errors</a>.]
								</p></dd><dt class="label">match</dt><dd><p>
									[<a name="dt-match" id="dt-match" title="match" data-ss1529144233="1">Definition</a>: (Of strings or names:) Two strings
or names being compared are identical. Characters with multiple possible
representations in ISO/IEC 10646 (e.g. characters with both precomposed and
base+diacritic forms) match only if they have the same representation in both
strings. No
case folding is performed. (Of strings and rules in the grammar:) A string
matches a grammatical production if it belongs to the language generated by
that production. (Of content and content models:) An element matches its declaration
when it conforms in the fashion described in the constraint <b>[VC: <a href="#elementvalid" data-ss1529144233="1">Element Valid</a>]</b>.]
								</p></dd><dt class="label">for compatibility</dt><dd><p>
									[<a name="dt-compat" id="dt-compat" title="For Compatibility" data-ss1529144233="1">Definition</a>: Marks
a sentence describing a feature of XML included solely to ensure
that 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" data-ss1529144233="1">Definition</a>: Marks
a sentence describing a non-binding recommendation included to increase
the chances that XML documents can be processed by the existing installed
base of SGML processors which predate the WebSGML Adaptations Annex to ISO 8879.]
								</p></dd></dl><p>
				</p></div></div><div class="div1">
<h2><a name="sec-documents" id="sec-documents" data-ss1529144233="1">2 Documents</a></h2><p><a name="sec-documents" id="sec-documents" data-ss1529144233="1">
				[</a><a name="dt-xml-doc" id="dt-xml-doc" title="XML Document" data-ss1529144233="1">Definition</a>:  A data object is an <b>XML
document</b> if it is <a title="Well-Formed" href="#dt-wellformed" data-ss1529144233="1">well-formed</a>,
as defined in this specification. In addition, the XML document is
<a title="Validity" href="#dt-valid" data-ss1529144233="1">valid</a> if it meets certain further constraints.]
			</p><p>Each XML document has both a logical and a physical structure. Physically,
the document is composed of units called <a title="Entity" href="#dt-entity" data-ss1529144233="1">entities</a>.
An entity may
				<a title="Entity Reference" href="#dt-entref" data-ss1529144233="1">refer</a> to other entities to
cause their inclusion in the document. A document begins in a "root"
or <a title="Document Entity" href="#dt-docent" data-ss1529144233="1">document entity</a>. Logically, the document
is composed of declarations, elements, comments, character references, and
processing instructions, all of which are indicated in the document by explicit
markup. The logical and physical structures <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> nest properly, as described
in <a href="#wf-entities" data-ss1529144233="1"><b>4.3.2 Well-Formed Parsed Entities</b></a>.</p><div class="div2">
<h3><a name="sec-well-formed" id="sec-well-formed" data-ss1529144233="1">2.1 Well-Formed XML Documents</a></h3><p><a name="sec-well-formed" id="sec-well-formed" data-ss1529144233="1">
					[</a><a name="dt-wellformed" id="dt-wellformed" title="Well-Formed" data-ss1529144233="1">Definition</a>:  A textual object is a <b>well-formed</b>
XML document if:]
				</p><ol class="enumar"><li><p>Taken as a whole, it matches the production labeled <a href="#NT-document" data-ss1529144233="1">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" data-ss1529144233="1">parsed entities</a>
which is referenced directly or indirectly within the document is <a title="Well-Formed" href="#dt-wellformed" data-ss1529144233="1">well-formed</a>.</p></li></ol>
<h5><a name="document" id="document" data-ss1529144233="1">Document</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-document" id="NT-document" data-ss1529144233="1">[1]&nbsp;&nbsp;&nbsp;</a></td><td><code>document</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
							<a href="#NT-prolog" data-ss1529144233="1">prolog</a>
							<a href="#NT-element" data-ss1529144233="1">element</a>
							<a href="#NT-Misc" data-ss1529144233="1">Misc</a>*</code></td></tr></tbody></table><p><a name="document" id="document" data-ss1529144233="1">Matching the </a><a href="#NT-document" data-ss1529144233="1">document</a> production implies that:</p><ol class="enumar"><li><p>It contains one or more <a title="Element" href="#dt-element" data-ss1529144233="1">elements</a>.</p></li><li><p>
							[<a name="dt-root" id="dt-root" title="Root Element" data-ss1529144233="1">Definition</a>: There is exactly one element,
called the <b>root</b>, or document element, no part of which appears
in the <a title="Content" href="#dt-content" data-ss1529144233="1">content</a> of any other element.] For
all other elements, if the <a title="Start-Tag" href="#dt-stag" data-ss1529144233="1">start-tag</a> is in
the content of another element, the <a title="End Tag" href="#dt-etag" data-ss1529144233="1">end-tag</a>
is in the content of the same element. More simply stated, the elements,
delimited by start- and end-tags, nest properly within each other.</p></li></ol><p>
					[<a name="dt-parentchild" id="dt-parentchild" title="Parent/Child" data-ss1529144233="1">Definition</a>: As a consequence of this,
for each non-root element <code>C</code> in the document, there is one other element <code>P</code>
in the document such that <code>C</code> is in the content of <code>P</code>, but
is not in the content of any other element that is in the content of <code>P</code>. <code>P</code>
is referred to as the <b>parent</b> of <code>C</code>, and <code>C</code> as
a <b>child</b> of <code>P</code>.]
				</p></div><div class="div2">
<h3><a name="charsets" id="charsets" data-ss1529144233="1">2.2 Characters</a></h3><p><a name="charsets" id="charsets" data-ss1529144233="1">
					[</a><a name="dt-text" id="dt-text" title="Text" data-ss1529144233="1">Definition</a>: A parsed entity contains <b>text</b>,
a sequence of <a title="Character" href="#dt-character" data-ss1529144233="1">characters</a>, which may
represent markup or character data.]
					[<a name="dt-character" id="dt-character" title="Character" data-ss1529144233="1">Definition</a>: A <b>character</b>
is an atomic unit of text as specified by ISO/IEC 10646:2000 <a href="#ISO10646" data-ss1529144233="1">[ISO/IEC 10646]</a>. Legal characters are tab, carriage
return, line feed, and the legal characters
of Unicode and ISO/IEC 10646. The
versions of these standards cited in <a href="#sec-existing-stds" data-ss1529144233="1"><b>A.1 Normative References</b></a> were
current at the time this document was prepared. New characters may be added
to these standards by amendments or new editions. Consequently, XML processors
<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> accept any character in the range specified for <a href="#NT-Char" data-ss1529144233="1">Char</a>.
]
				</p>
<h5><a name="char32" id="char32" data-ss1529144233="1">Character Range</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-Char" id="NT-Char" data-ss1529144233="1">[2]&nbsp;&nbsp;&nbsp;</a></td><td><code>Char</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>#x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD] | [#x10000-#x10FFFF]</code></td><td><i>/* any Unicode character, excluding the surrogate blocks, FFFE, and FFFF. */</i></td></tr></tbody></table><p><a name="char32" id="char32" data-ss1529144233="1">The mechanism for encoding character code points into bit patterns may
vary 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
encodings of Unicode <span></span></a><a href="#Unicode" data-ss1529144233="1">[Unicode]</a>;
the mechanisms for signaling which of the two is in use,
or for bringing other encodings into play, are discussed later, in <a href="#charencoding" data-ss1529144233="1"><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
"compatibility characters", as defined
in section <span>2.3</span> of <a href="#Unicode" data-ss1529144233="1">[Unicode]</a>. The characters defined in the following ranges are also
discouraged. They are either control characters or permanently undefined Unicode
characters:</p><div class="exampleInner"><pre>[#x7F-#x84], [#x86-#x9F], [#xFDD0-#xFD<span>E</span>F],
[#x1FFFE-#x1FFFF], [#x2FFFE-#x2FFFF], [#x3FFFE-#x3FFFF],
[#x4FFFE-#x4FFFF], [#x5FFFE-#x5FFFF], [#x6FFFE-#x6FFFF],
[#x7FFFE-#x7FFFF], [#x8FFFE-#x8FFFF], [#x9FFFE-#x9FFFF],
[#xAFFFE-#xAFFFF], [#xBFFFE-#xBFFFF], [#xCFFFE-#xCFFFF],
[#xDFFFE-#xDFFFF], [#xEFFFE-#xEFFFF], [#xFFFFE-#xFFFFF],
[#x10FFFE-#x10FFFF].</pre></div></div></div><div class="div2">
<h3><a name="sec-common-syn" id="sec-common-syn" data-ss1529144233="1">2.3 Common Syntactic Constructs</a></h3><p><a name="sec-common-syn" id="sec-common-syn" data-ss1529144233="1">This section defines some symbols used widely in the grammar.</a></p><p><a name="sec-common-syn" id="sec-common-syn" data-ss1529144233="1">
					</a><a href="#NT-S" data-ss1529144233="1">S</a> (white space) consists of one or more space (#x20)
characters, carriage returns, line feeds, or tabs.</p>
<h5><a name="white" id="white" data-ss1529144233="1">White Space</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-S" id="NT-S" data-ss1529144233="1">[3]&nbsp;&nbsp;&nbsp;</a></td><td><code>S</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>(#x20 | #x9 | #xD | #xA)+</code></td></tr></tbody></table><div class="note"><p class="prefix"><a name="white" id="white" data-ss1529144233="1"><b>Note:</b></a></p><p><a name="white" id="white" data-ss1529144233="1">The presence of #xD in the above production is
	maintained purely for backward compatibility with the
	</a><a href="http://www.w3.org/TR/1998/REC-xml-19980210" data-ss1529144233="1">First Edition</a>.
	As explained in <a href="#sec-line-ends" data-ss1529144233="1"><b>2.11 End-of-Line Handling</b></a>,
	all #xD characters literally present in an XML document
	are either removed or replaced by #xA characters before
	any other processing is done. The only way to get a #xD character to match this production is to
  use a character reference in an entity value literal.</p></div><p>An <a href="#NT-Nmtoken" data-ss1529144233="1">Nmtoken</a> (name token) is any mixture of name
characters.</p><p>[<a name="dt-name" id="dt-name" title="Name" data-ss1529144233="1">Definition</a>: A <a href="#NT-Name" data-ss1529144233="1">Name</a> is an <a href="#NT-Nmtoken" data-ss1529144233="1">Nmtoken</a> with a restricted set of initial characters.]  Disallowed initial characters for <a href="#NT-Name" data-ss1529144233="1">Names</a> include digits, diacritics, the full stop and the hyphen.</p><p>Names beginning with the string "<code>xml</code>",
or with any string which would match <code>(('X'|'x') ('M'|'m') ('L'|'l'))</code>,
are reserved for standardization in this or future versions of this specification.</p><div class="note"><p class="prefix"><b>Note:</b></p><p>The
Namespaces in XML Recommendation <a href="#xml-names" data-ss1529144233="1">[XML Names]</a> assigns a meaning
to names containing colon characters. Therefore, authors should not use the
colon in XML names except for namespace purposes, but XML processors must
accept the colon as a name character.</p></div><p>The first character of a <a href="#NT-Name" data-ss1529144233="1">Name</a> <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be a <a href="#NT-NameStartChar" data-ss1529144233="1">NameStartChar</a>, and any
					other characters <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be <a href="#NT-NameChar" data-ss1529144233="1">NameChars</a>; this mechanism is used to
					prevent names from beginning with European (ASCII) digits or with
					basic combining characters. Almost all characters are permitted in
					names, except those which either are or reasonably could be used as
					delimiters. The intention is to be inclusive rather than exclusive,
					so that writing systems not yet encoded in Unicode can be used in
					XML names. See <a href="#sec-suggested-names" data-ss1529144233="1"><b>J Suggestions for XML Names</b></a> for suggestions on the creation of
					names.</p><p>Document authors are encouraged to use names which are
					meaningful words or combinations of words in natural languages, and
					to avoid symbolic or white space characters in names. Note that
					COLON, HYPHEN-MINUS, FULL STOP (period), LOW LINE (underscore), and
					MIDDLE DOT are explicitly permitted.</p><p>The ASCII symbols and punctuation marks, along with a fairly
					large group of Unicode symbol characters, are excluded from names
					because they are more useful as delimiters in contexts where XML
					names are used outside XML documents; providing this group gives
					those contexts hard guarantees about what <em>cannot</em> be part of
					an XML name. The character #x037E, GREEK QUESTION MARK, is excluded
					because when normalized it becomes a semicolon, which could change
					the meaning of entity references.</p>
<h5><a name="d0e804" id="d0e804" data-ss1529144233="1">Names and Tokens</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-NameStartChar" id="NT-NameStartChar" data-ss1529144233="1">[4]&nbsp;&nbsp;&nbsp;</a></td><td><code>NameStartChar</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</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" data-ss1529144233="1">[4a]&nbsp;&nbsp;&nbsp;</a></td><td><code>NameChar</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code><a href="#NT-NameStartChar" data-ss1529144233="1">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" data-ss1529144233="1">[5]&nbsp;&nbsp;&nbsp;</a></td><td><code>Name</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code><a href="#NT-NameStartChar" data-ss1529144233="1">NameStartChar</a> (<a href="#NT-NameChar" data-ss1529144233="1">NameChar</a>)*</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Names" id="NT-Names" data-ss1529144233="1">[6]&nbsp;&nbsp;&nbsp;</a></td><td><code>Names</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code><a href="#NT-Name" data-ss1529144233="1">Name</a> (#x20 <a href="#NT-Name" data-ss1529144233="1">Name</a>)*</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Nmtoken" id="NT-Nmtoken" data-ss1529144233="1">[7]&nbsp;&nbsp;&nbsp;</a></td><td><code>Nmtoken</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>(<a href="#NT-NameChar" data-ss1529144233="1">NameChar</a>)+</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Nmtokens" id="NT-Nmtokens" data-ss1529144233="1">[8]&nbsp;&nbsp;&nbsp;</a></td><td><code>Nmtokens</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code><a href="#NT-Nmtoken" data-ss1529144233="1">Nmtoken</a> (#x20 <a href="#NT-Nmtoken" data-ss1529144233="1">Nmtoken</a>)*</code></td></tr></tbody></table><div class="note"><p class="prefix"><a name="d0e804" id="d0e804" data-ss1529144233="1"><b>Note:</b></a></p><p><a name="d0e804" id="d0e804" data-ss1529144233="1">The </a><a href="#NT-Names" data-ss1529144233="1">Names</a>
and <a href="#NT-Nmtokens" data-ss1529144233="1">Nmtokens</a> productions are used to define the validity
of tokenized attribute values after normalization (see <a href="#sec-attribute-types" data-ss1529144233="1"><b>3.3.1 Attribute Types</b></a>).</p></div><p>Literal data is any quoted string not containing the quotation mark used
as a delimiter for that string. Literals are used for specifying the content
of internal entities (<a href="#NT-EntityValue" data-ss1529144233="1">EntityValue</a>), the values
of attributes (<a href="#NT-AttValue" data-ss1529144233="1">AttValue</a>), and external identifiers
(<a href="#NT-SystemLiteral" data-ss1529144233="1">SystemLiteral</a>). Note that a <a href="#NT-SystemLiteral" data-ss1529144233="1">SystemLiteral</a>
can be parsed without scanning for markup.</p>
<h5><a name="d0e888" id="d0e888" data-ss1529144233="1">Literals</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EntityValue" id="NT-EntityValue" data-ss1529144233="1">[9]&nbsp;&nbsp;&nbsp;</a></td><td><code>EntityValue</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'"' ([^%&amp;"] | <a href="#NT-PEReference" data-ss1529144233="1">PEReference</a>
| <a href="#NT-Reference" data-ss1529144233="1">Reference</a>)* '"' </code></td></tr><tr valign="baseline"><td></td><td></td><td></td><td><code>|&nbsp; "'" ([^%&amp;'] | <a href="#NT-PEReference" data-ss1529144233="1">PEReference</a> | <a href="#NT-Reference" data-ss1529144233="1">Reference</a>)* "'"</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-AttValue" id="NT-AttValue" data-ss1529144233="1">[10]&nbsp;&nbsp;&nbsp;</a></td><td><code>AttValue</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'"' ([^&lt;&amp;"] | <a href="#NT-Reference" data-ss1529144233="1">Reference</a>)*
'"' </code></td></tr><tr valign="baseline"><td></td><td></td><td></td><td><code>|&nbsp; "'" ([^&lt;&amp;'] | <a href="#NT-Reference" data-ss1529144233="1">Reference</a>)*
"'"</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-SystemLiteral" id="NT-SystemLiteral" data-ss1529144233="1">[11]&nbsp;&nbsp;&nbsp;</a></td><td><code>SystemLiteral</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>('"' [^"]* '"') |&nbsp;("'" [^']* "'") </code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PubidLiteral" id="NT-PubidLiteral" data-ss1529144233="1">[12]&nbsp;&nbsp;&nbsp;</a></td><td><code>PubidLiteral</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'"' <a href="#NT-PubidChar" data-ss1529144233="1">PubidChar</a>* '"'
| "'" (<a href="#NT-PubidChar" data-ss1529144233="1">PubidChar</a> - "'")* "'"</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PubidChar" id="NT-PubidChar" data-ss1529144233="1">[13]&nbsp;&nbsp;&nbsp;</a></td><td><code>PubidChar</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>#x20 | #xD | #xA |&nbsp;[a-zA-Z0-9] |&nbsp;[-'()+,./:=?;!*#@$_%]</code></td></tr></tbody></table><div class="note"><p class="prefix"><a name="d0e888" id="d0e888" data-ss1529144233="1"><b>Note:</b></a></p><p><a name="d0e888" id="d0e888" data-ss1529144233="1">Although
the </a><a href="#NT-EntityValue" data-ss1529144233="1">EntityValue</a> production allows the definition
of a general entity consisting of a single explicit <code>&lt;</code> in the literal
(e.g., <code>&lt;!ENTITY mylt "&lt;"&gt;</code>), it is strongly advised to avoid
this practice since any reference to that entity will cause a well-formedness
error.</p></div></div><div class="div2">
<h3><a name="syntax" id="syntax" data-ss1529144233="1">2.4 Character Data and Markup</a></h3><p><a name="syntax" id="syntax" data-ss1529144233="1">
					</a><a title="Text" href="#dt-text" data-ss1529144233="1">Text</a> consists of intermingled <a title="Character Data" href="#dt-chardata" data-ss1529144233="1">character data</a> and markup. [<a name="dt-markup" id="dt-markup" title="Markup" data-ss1529144233="1">Definition</a>: 
						<b>Markup</b> takes the form of <a title="Start-Tag" href="#dt-stag" data-ss1529144233="1">start-tags</a>, <a title="End Tag" href="#dt-etag" data-ss1529144233="1">end-tags</a>, <a title="Empty" href="#dt-empty" data-ss1529144233="1">empty-element tags</a>, <a title="Entity Reference" href="#dt-entref" data-ss1529144233="1">entity references</a>, <a title="Character Reference" href="#dt-charref" data-ss1529144233="1">character
references</a>, <a title="Comment" href="#dt-comment" data-ss1529144233="1">comments</a>, <a title="CDATA Section" href="#dt-cdsection" data-ss1529144233="1">CDATA section</a> delimiters, <a title="Document Type Declaration" href="#dt-doctype" data-ss1529144233="1">document
type declarations</a>, <a title="Processing instruction" href="#dt-pi" data-ss1529144233="1">processing instructions</a>, <a href="#NT-XMLDecl" data-ss1529144233="1">XML declarations</a>, <a href="#NT-TextDecl" data-ss1529144233="1">text declarations</a>,
and any white space that is at the top level of the document entity (that
is, outside the document element and not inside any other markup).]
				</p><p>
					[<a name="dt-chardata" id="dt-chardata" title="Character Data" data-ss1529144233="1">Definition</a>: All text that is not markup
constitutes the <b>character data</b> of the document.]
				</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
in their literal form, except when used as markup delimiters, or
within a <a title="Comment" href="#dt-comment" data-ss1529144233="1">comment</a>, a <a title="Processing instruction" href="#dt-pi" data-ss1529144233="1">processing
instruction</a>, or a <a title="CDATA Section" href="#dt-cdsection" data-ss1529144233="1">CDATA section</a>.

If they are needed elsewhere, they <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be <a title="escape" href="#dt-escape" data-ss1529144233="1">escaped</a>
using either <a title="Character Reference" href="#dt-charref" data-ss1529144233="1">numeric character references</a>
or the strings "
						<code>&amp;amp;</code>
					" and "
						<code>&amp;lt;</code>
					"
respectively. The right angle bracket (&gt;) may be represented using the string "
						<code>&amp;gt;</code>
					",
and <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>, <a title="For Compatibility" href="#dt-compat" data-ss1529144233="1">for compatibility</a>, be escaped
using either "
						<code>&amp;gt;</code>
					" or a character reference when it
appears in the string "
						<code>]]&gt;</code>
					" in content, when
that string is not marking the end of a <a title="CDATA Section" href="#dt-cdsection" data-ss1529144233="1">CDATA
section</a>.</p><p>In the content of elements, character data is any string of characters
which does not contain the start-delimiter of any markup and does not include the CDATA-section-close
delimiter, "
						<code>]]&gt;</code>
					". In a CDATA section,
character data is any string of characters not including the CDATA-section-close
delimiter, "
						<code>]]&gt;</code>
					".</p><p>To allow attribute values to contain both single and double quotes, the
apostrophe or single-quote character (') may be represented as "
						<code>&amp;apos;</code>
					",
and the double-quote character (") as "
						<code>&amp;quot;</code>
					".</p>
<h5><a name="d0e1106" id="d0e1106" data-ss1529144233="1">Character Data</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-CharData" id="NT-CharData" data-ss1529144233="1">[14]&nbsp;&nbsp;&nbsp;</a></td><td><code>CharData</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>[^&lt;&amp;]* - ([^&lt;&amp;]* ']]&gt;' [^&lt;&amp;]*)</code></td></tr></tbody></table></div><div class="div2"><a name="d0e1106" id="d0e1106" data-ss1529144233="1">
</a><h3><a name="d0e1106" id="d0e1106" data-ss1529144233="1"></a><a name="sec-comments" id="sec-comments" data-ss1529144233="1">2.5 Comments</a></h3><p><a name="sec-comments" id="sec-comments" data-ss1529144233="1">
					[</a><a name="dt-comment" id="dt-comment" title="Comment" data-ss1529144233="1">Definition</a>: 
						<b>Comments</b> may appear
anywhere in a document outside other <a title="Markup" href="#dt-markup" data-ss1529144233="1">markup</a>;
in addition, they may appear within the document type declaration at places
allowed by the grammar. They are not part of the document's <a title="Character Data" href="#dt-chardata" data-ss1529144233="1">character
data</a>; an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em>, but need not, make it possible for an
application to retrieve the text of comments. <a title="For Compatibility" href="#dt-compat" data-ss1529144233="1">For
compatibility</a>, the string "
							<code>--</code>
						" (double-hyphen)
<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> occur within comments.] Parameter
entity references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be recognized within comments.</p>
<h5><a name="d0e1149" id="d0e1149" data-ss1529144233="1">Comments</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-Comment" id="NT-Comment" data-ss1529144233="1">[15]&nbsp;&nbsp;&nbsp;</a></td><td><code>Comment</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;!--' ((<a href="#NT-Char" data-ss1529144233="1">Char</a> - '-') | ('-'
(<a href="#NT-Char" data-ss1529144233="1">Char</a> - '-')))* '--&gt;'</code></td></tr></tbody></table><p><a name="d0e1149" id="d0e1149" data-ss1529144233="1">An example of a comment:</a></p><div class="exampleInner"><pre><a name="d0e1149" id="d0e1149" data-ss1529144233="1">&lt;!-- declarations for &lt;head&gt; &amp; &lt;body&gt; --&gt;</a></pre></div><p><a name="d0e1149" id="d0e1149" data-ss1529144233="1">Note
that the grammar does not allow a comment ending in <code>---&gt;</code>. The
following example is <em>not</em> well-formed.</a></p><div class="exampleInner"><pre><a name="d0e1149" id="d0e1149" data-ss1529144233="1">&lt;!-- B+, B, or B---&gt;</a></pre></div></div><div class="div2"><a name="d0e1149" id="d0e1149" data-ss1529144233="1">
</a><h3><a name="d0e1149" id="d0e1149" data-ss1529144233="1"></a><a name="sec-pi" id="sec-pi" data-ss1529144233="1">2.6 Processing Instructions</a></h3><p><a name="sec-pi" id="sec-pi" data-ss1529144233="1">
					[</a><a name="dt-pi" id="dt-pi" title="Processing instruction" data-ss1529144233="1">Definition</a>: 
						<b>Processing instructions</b>
(PIs) allow documents to contain instructions for applications.]
				</p>
<h5><a name="d0e1188" id="d0e1188" data-ss1529144233="1">Processing Instructions</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-PI" id="NT-PI" data-ss1529144233="1">[16]&nbsp;&nbsp;&nbsp;</a></td><td><code>PI</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;?' <a href="#NT-PITarget" data-ss1529144233="1">PITarget</a> (<a href="#NT-S" data-ss1529144233="1">S</a>
(<a href="#NT-Char" data-ss1529144233="1">Char</a>* - (<a href="#NT-Char" data-ss1529144233="1">Char</a>* '?&gt;' <a href="#NT-Char" data-ss1529144233="1">Char</a>*)))? '?&gt;'</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PITarget" id="NT-PITarget" data-ss1529144233="1">[17]&nbsp;&nbsp;&nbsp;</a></td><td><code>PITarget</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
							<a href="#NT-Name" data-ss1529144233="1">Name</a> - (('X' | 'x') ('M' |
'm') ('L' | 'l'))</code></td></tr></tbody></table><p><a name="d0e1188" id="d0e1188" data-ss1529144233="1">PIs are not part of the document's </a><a title="Character Data" href="#dt-chardata" data-ss1529144233="1">character
data</a>, but <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be passed through to the application. The PI begins
with a target (<a href="#NT-PITarget" data-ss1529144233="1">PITarget</a>) used to identify the application
to which the instruction is directed. The target names "
						<code>XML</code>
					", "
						<code>xml</code>
					",
and so on are reserved for standardization in this or future versions of this
specification. The XML <a title="Notation" href="#dt-notation" data-ss1529144233="1">Notation</a> mechanism
may be used for formal declaration of PI targets. Parameter
entity 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" data-ss1529144233="1">2.7 CDATA Sections</a></h3><p><a name="sec-cdata-sect" id="sec-cdata-sect" data-ss1529144233="1">
					[</a><a name="dt-cdsection" id="dt-cdsection" title="CDATA Section" data-ss1529144233="1">Definition</a>: 
						<b>CDATA sections</b> may occur anywhere character data may occur; they are used to escape blocks
of text containing characters which would otherwise be recognized as markup.
CDATA sections begin with the string "
							<code>&lt;![CDATA[</code>
						"
and end with the string "
							<code>]]&gt;</code>
						":]
				</p>
<h5><a name="d0e1271" id="d0e1271" data-ss1529144233="1">CDATA Sections</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-CDSect" id="NT-CDSect" data-ss1529144233="1">[18]&nbsp;&nbsp;&nbsp;</a></td><td><code>CDSect</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
							<a href="#NT-CDStart" data-ss1529144233="1">CDStart</a>
							<a href="#NT-CData" data-ss1529144233="1">CData</a>
							<a href="#NT-CDEnd" data-ss1529144233="1">CDEnd</a>
						</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-CDStart" id="NT-CDStart" data-ss1529144233="1">[19]&nbsp;&nbsp;&nbsp;</a></td><td><code>CDStart</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;![CDATA['</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-CData" id="NT-CData" data-ss1529144233="1">[20]&nbsp;&nbsp;&nbsp;</a></td><td><code>CData</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>(<a href="#NT-Char" data-ss1529144233="1">Char</a>* - (<a href="#NT-Char" data-ss1529144233="1">Char</a>*
']]&gt;' <a href="#NT-Char" data-ss1529144233="1">Char</a>*)) </code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-CDEnd" id="NT-CDEnd" data-ss1529144233="1">[21]&nbsp;&nbsp;&nbsp;</a></td><td><code>CDEnd</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>']]&gt;'</code></td></tr></tbody></table><p><a name="d0e1271" id="d0e1271" data-ss1529144233="1">Within a CDATA section, only the </a><a href="#NT-CDEnd" data-ss1529144233="1">CDEnd</a> string is
recognized as markup, so that left angle brackets and ampersands may occur
in their literal form; they need not (and cannot) be escaped using "
						<code>&amp;lt;</code>
					"
and "
						<code>&amp;amp;</code>
					". CDATA sections cannot nest.</p><p>An example of a CDATA section, in which "
						<code>&lt;greeting&gt;</code>
					"
and "
						<code>&lt;/greeting&gt;</code>
					" are recognized as <a title="Character Data" href="#dt-chardata" data-ss1529144233="1">character data</a>, not <a title="Markup" href="#dt-markup" data-ss1529144233="1">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" data-ss1529144233="1">2.8 Prolog and Document Type Declaration</a></h3><p><a name="sec-prolog-dtd" id="sec-prolog-dtd" data-ss1529144233="1">
					[</a><a name="dt-xmldecl" id="dt-xmldecl" title="XML Declaration" data-ss1529144233="1">Definition</a>: XML documents <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em>
begin with an <b>XML declaration</b> which specifies the version of
XML being used.] For example, the following is a complete XML document, <a title="Well-Formed" href="#dt-wellformed" data-ss1529144233="1">well-formed</a> but not <a title="Validity" href="#dt-valid" data-ss1529144233="1">valid</a>:</p><div class="exampleInner"><pre>&lt;?xml version="1.0"?&gt;
&lt;greeting&gt;Hello, world!&lt;/greeting&gt; </pre></div><p>and so is this:</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
logical structure and to associate attribute
name-value pairs with its logical structures. XML provides a mechanism, the
<a title="Document Type Declaration" href="#dt-doctype" data-ss1529144233="1">document
type declaration</a>, to define constraints on the logical structure
and to support the use of predefined storage units. [<a name="dt-valid" id="dt-valid" title="Validity" data-ss1529144233="1">Definition</a>: An XML document is <b>valid</b> if it has an associated
document type declaration and if the document complies with the constraints
expressed 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" data-ss1529144233="1">element</a>
in the document.</p>
<h5><a name="xmldoc" id="xmldoc" data-ss1529144233="1">Prolog</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-prolog" id="NT-prolog" data-ss1529144233="1">[22]&nbsp;&nbsp;&nbsp;</a></td><td><code>prolog</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-XMLDecl" data-ss1529144233="1">XMLDecl</a>? <a href="#NT-Misc" data-ss1529144233="1">Misc</a>*
(<a href="#NT-doctypedecl" data-ss1529144233="1">doctypedecl</a>
								<a href="#NT-Misc" data-ss1529144233="1">Misc</a>*)?</code></td></tr><tr valign="baseline"><td><a name="NT-XMLDecl" id="NT-XMLDecl" data-ss1529144233="1">[23]&nbsp;&nbsp;&nbsp;</a></td><td><code>XMLDecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;?xml' <a href="#NT-VersionInfo" data-ss1529144233="1">VersionInfo</a>
								<a href="#NT-EncodingDecl" data-ss1529144233="1">EncodingDecl</a>? <a href="#NT-SDDecl" data-ss1529144233="1">SDDecl</a>? <a href="#NT-S" data-ss1529144233="1">S</a>? '?&gt;'</code></td></tr><tr valign="baseline"><td><a name="NT-VersionInfo" id="NT-VersionInfo" data-ss1529144233="1">[24]&nbsp;&nbsp;&nbsp;</a></td><td><code>VersionInfo</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-S" data-ss1529144233="1">S</a> 'version' <a href="#NT-Eq" data-ss1529144233="1">Eq</a>
("'" <a href="#NT-VersionNum" data-ss1529144233="1">VersionNum</a> "'" | '"' <a href="#NT-VersionNum" data-ss1529144233="1">VersionNum</a>
'"')</code></td></tr><tr valign="baseline"><td><a name="NT-Eq" id="NT-Eq" data-ss1529144233="1">[25]&nbsp;&nbsp;&nbsp;</a></td><td><code>Eq</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-S" data-ss1529144233="1">S</a>? '=' <a href="#NT-S" data-ss1529144233="1">S</a>?</code></td></tr><tr valign="baseline"><td><a name="NT-VersionNum" id="NT-VersionNum" data-ss1529144233="1">[26]&nbsp;&nbsp;&nbsp;</a></td><td><code>VersionNum</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'1.' [0-9]+</code></td></tr><tr valign="baseline"><td><a name="NT-Misc" id="NT-Misc" data-ss1529144233="1">[27]&nbsp;&nbsp;&nbsp;</a></td><td><code>Misc</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-Comment" data-ss1529144233="1">Comment</a> | <a href="#NT-PI" data-ss1529144233="1">PI</a>
| <a href="#NT-S" data-ss1529144233="1">S</a>
							</code></td></tr></tbody></table><p><a name="xmldoc" id="xmldoc" data-ss1529144233="1">Even though the </a><a href="#NT-VersionNum" data-ss1529144233="1">VersionNum</a> production matches
					any version number of the form '1.x', XML 1.0 documents <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD NOT</em> specify a version number other than '1.0'.</p><div class="note"><p class="prefix"><b>Note:</b></p><p>When an XML 1.0 processor encounters a document that specifies
						a 1.x version number other than '1.0', it will process it as
						a 1.0 document.  This means that an XML 1.0 processor will accept
						1.x documents provided they do not use any non-1.0 features.</p></div><p>
					[<a name="dt-doctype" id="dt-doctype" title="Document Type Declaration" data-ss1529144233="1">Definition</a>: The XML <b>document
type declaration</b> contains or points to <a title="markup declaration" href="#dt-markupdecl" data-ss1529144233="1">markup
declarations</a> that provide a grammar for a class of documents. This
grammar is known as a document type definition, or <b>DTD</b>. The document
type declaration can point to an external subset (a special kind of <a title="External Entity" href="#dt-extent" data-ss1529144233="1">external entity</a>) containing markup declarations,
or can contain the markup declarations directly in an internal subset, or
can 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" data-ss1529144233="1">Definition</a>:  A <b>markup declaration</b>
is an <a title="Element Type declaration" href="#dt-eldecl" data-ss1529144233="1">element type declaration</a>, an <a title="Attribute-List Declaration" href="#dt-attdecl" data-ss1529144233="1">attribute-list declaration</a>, an <a title="entity declaration" href="#dt-entdecl" data-ss1529144233="1">entity
declaration</a>, or a <a title="Notation Declaration" href="#dt-notdecl" data-ss1529144233="1">notation declaration</a>.]
These declarations may be contained in whole or in part within <a title="Parameter entity" href="#dt-PE" data-ss1529144233="1">parameter
entities</a>, as described in the well-formedness and validity constraints
below. For further
information, see <a href="#sec-physical-struct" data-ss1529144233="1"><b>4 Physical Structures</b></a>.</p>
<h5><a name="dtd" id="dtd" data-ss1529144233="1">Document Type Definition</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-doctypedecl" id="NT-doctypedecl" data-ss1529144233="1">[28]&nbsp;&nbsp;&nbsp;</a></td><td><code>doctypedecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;!DOCTYPE' <a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-Name" data-ss1529144233="1">Name</a>
(<a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-ExternalID" data-ss1529144233="1">ExternalID</a>)? <a href="#NT-S" data-ss1529144233="1">S</a>?
('[' <a href="#NT-intSubset" data-ss1529144233="1">intSubset</a> ']' <a href="#NT-S" data-ss1529144233="1">S</a>?)? '&gt;'</code></td><td><a href="#vc-roottype" data-ss1529144233="1">[VC: Root Element Type]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#ExtSubset" data-ss1529144233="1">[WFC: External Subset]</a></td></tr><tr valign="baseline"><td><a name="NT-DeclSep" id="NT-DeclSep" data-ss1529144233="1">[28a]&nbsp;&nbsp;&nbsp;</a></td><td><code>DeclSep</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-PEReference" data-ss1529144233="1">PEReference</a> | <a href="#NT-S" data-ss1529144233="1">S</a>
							</code></td><td><a href="#PE-between-Decls" data-ss1529144233="1">[WFC: PE Between Declarations]</a></td></tr><tr valign="baseline"><td><a name="NT-intSubset" id="NT-intSubset" data-ss1529144233="1">[28b]&nbsp;&nbsp;&nbsp;</a></td><td><code>intSubset</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>(<a href="#NT-markupdecl" data-ss1529144233="1">markupdecl</a> | <a href="#NT-DeclSep" data-ss1529144233="1">DeclSep</a>)*</code></td></tr><tr valign="baseline"><td><a name="NT-markupdecl" id="NT-markupdecl" data-ss1529144233="1">[29]&nbsp;&nbsp;&nbsp;</a></td><td><code>markupdecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-elementdecl" data-ss1529144233="1">elementdecl</a> | <a href="#NT-AttlistDecl" data-ss1529144233="1">AttlistDecl</a> | <a href="#NT-EntityDecl" data-ss1529144233="1">EntityDecl</a>
| <a href="#NT-NotationDecl" data-ss1529144233="1">NotationDecl</a> | <a href="#NT-PI" data-ss1529144233="1">PI</a> | <a href="#NT-Comment" data-ss1529144233="1">Comment</a>
							</code></td><td><a href="#vc-PEinMarkupDecl" data-ss1529144233="1">[VC: Proper Declaration/PE Nesting]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#wfc-PEinInternalSubset" data-ss1529144233="1">[WFC: PEs in Internal Subset]</a></td></tr></tbody></table><p><a name="dtd" id="dtd" data-ss1529144233="1">Note
that it is possible to construct a well-formed document containing a </a><a href="#NT-doctypedecl" data-ss1529144233="1">doctypedecl</a>
that neither points to an external subset nor contains an internal subset.</p><p>The markup declarations may be made up in whole or in part of the <a title="Replacement Text" href="#dt-repltext" data-ss1529144233="1">replacement text</a> of <a title="Parameter entity" href="#dt-PE" data-ss1529144233="1">parameter
entities</a>. The productions later in this specification for individual
nonterminals (<a href="#NT-elementdecl" data-ss1529144233="1">elementdecl</a>, <a href="#NT-AttlistDecl" data-ss1529144233="1">AttlistDecl</a>,
and so on) describe the declarations <em>after</em> all the parameter
entities have been <a title="Include" href="#dt-include" data-ss1529144233="1">included</a>.</p><p>Parameter
entity references are recognized anywhere in the DTD (internal and external
subsets and external parameter entities), except in literals, processing instructions,
comments, and the contents of ignored conditional sections (see <a href="#sec-condition-sect" data-ss1529144233="1"><b>3.4 Conditional Sections</b></a>).
They are also recognized in entity value literals. The use of parameter entities
in the internal subset is restricted as described below.</p><div class="constraint"><p class="prefix"><a name="vc-roottype" id="vc-roottype" data-ss1529144233="1"><b>Validity constraint: Root Element Type</b></a></p><p><a name="vc-roottype" id="vc-roottype" data-ss1529144233="1">The </a><a href="#NT-Name" data-ss1529144233="1">Name</a>
in 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" data-ss1529144233="1">root element</a>.</p></div><div class="constraint"><p class="prefix"><a name="vc-PEinMarkupDecl" id="vc-PEinMarkupDecl" data-ss1529144233="1"><b>Validity constraint: Proper Declaration/PE Nesting</b></a></p><p><a name="vc-PEinMarkupDecl" id="vc-PEinMarkupDecl" data-ss1529144233="1">Parameter-entity </a><a title="Replacement Text" href="#dt-repltext" data-ss1529144233="1">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
the first character or the last character of a markup declaration (<a href="#NT-markupdecl" data-ss1529144233="1">markupdecl</a>
above) is contained in the replacement text for a <a title="Parameter-entity reference" href="#dt-PERef" data-ss1529144233="1">parameter-entity
reference</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" data-ss1529144233="1"><b>Well-formedness constraint: PEs in Internal Subset</b></a></p><p><a name="wfc-PEinInternalSubset" id="wfc-PEinInternalSubset" data-ss1529144233="1">In
the internal DTD subset, </a><a title="Parameter-entity reference" href="#dt-PERef" data-ss1529144233="1">parameter-entity references</a>
						<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> occur within markup declarations; they may occur where markup declarations can occur.
(This does not apply to references that occur in external parameter entities
or to the external subset.)</p></div><div class="constraint"><p class="prefix"><a name="ExtSubset" id="ExtSubset" data-ss1529144233="1"><b>Well-formedness constraint: External Subset</b></a></p><p><a name="ExtSubset" id="ExtSubset" data-ss1529144233="1">The external subset, if any, <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the production for </a><a href="#NT-extSubset" data-ss1529144233="1">extSubset</a>.</p></div><div class="constraint"><p class="prefix"><a name="PE-between-Decls" id="PE-between-Decls" data-ss1529144233="1"><b>Well-formedness constraint: PE Between Declarations</b></a></p><p><a name="PE-between-Decls" id="PE-between-Decls" data-ss1529144233="1">The replacement text of a parameter entity reference
in a </a><a href="#NT-DeclSep" data-ss1529144233="1">DeclSep</a>
						<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the production <a href="#NT-extSubsetDecl" data-ss1529144233="1">extSubsetDecl</a>.</p></div><p>Like the internal subset, the external subset and any external parameter
entities referenced
in a <a href="#NT-DeclSep" data-ss1529144233="1">DeclSep</a>
					<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> consist of a series of
complete markup declarations of the types allowed by the non-terminal symbol <a href="#NT-markupdecl" data-ss1529144233="1">markupdecl</a>, interspersed with white space or <a title="Parameter-entity reference" href="#dt-PERef" data-ss1529144233="1">parameter-entity references</a>. However, portions of
the contents of the external subset or of these
external parameter entities may conditionally be ignored by using the <a title="conditional section" href="#dt-cond-section" data-ss1529144233="1">conditional section</a> construct; this is not
allowed in the internal subset but is
allowed in external parameter entities referenced in the internal subset.</p>
<h5><a name="ext-Subset" id="ext-Subset" data-ss1529144233="1">External Subset</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-extSubset" id="NT-extSubset" data-ss1529144233="1">[30]&nbsp;&nbsp;&nbsp;</a></td><td><code>extSubset</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-TextDecl" data-ss1529144233="1">TextDecl</a>? <a href="#NT-extSubsetDecl" data-ss1529144233="1">extSubsetDecl</a>
							</code></td></tr><tr valign="baseline"><td><a name="NT-extSubsetDecl" id="NT-extSubsetDecl" data-ss1529144233="1">[31]&nbsp;&nbsp;&nbsp;</a></td><td><code>extSubsetDecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>( <a href="#NT-markupdecl" data-ss1529144233="1">markupdecl</a> | <a href="#NT-conditionalSect" data-ss1529144233="1">conditionalSect</a> | <a href="#NT-DeclSep" data-ss1529144233="1">DeclSep</a>)*</code></td></tr></tbody></table><p><a name="ext-Subset" id="ext-Subset" data-ss1529144233="1">The external subset and external parameter entities also differ from the
internal subset in that in them, </a><a title="Parameter-entity reference" href="#dt-PERef" data-ss1529144233="1">parameter-entity
references</a> are permitted <em>within</em> markup declarations,
not 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="1.0"?&gt;
&lt;!DOCTYPE greeting SYSTEM "hello.dtd"&gt;
&lt;greeting&gt;Hello, world!&lt;/greeting&gt; </pre></div><p>The <a title="System Identifier" href="#dt-sysid" data-ss1529144233="1">system identifier</a>
					"
						<code>hello.dtd</code>
					"
gives 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="1.0" encoding="UTF-8" ?&gt;
&lt;!DOCTYPE greeting [
  &lt;!ELEMENT greeting (#PCDATA)&gt;
]&gt;
&lt;greeting&gt;Hello, world!&lt;/greeting&gt;</pre></div><p>If both the external and internal subsets are used, the internal subset
<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be considered to occur before the external subset. 
This has the effect that entity and attribute-list declarations in the internal
subset take precedence over those in the external subset.</p></div><div class="div2">
<h3><a name="sec-rmd" id="sec-rmd" data-ss1529144233="1">2.9 Standalone Document Declaration</a></h3><p><a name="sec-rmd" id="sec-rmd" data-ss1529144233="1">Markup declarations can affect the content of the document, as passed from
an </a><a title="XML Processor" href="#dt-xml-proc" data-ss1529144233="1">XML processor</a> to an application; examples
are attribute defaults and entity declarations. The standalone document declaration,
which may appear as a component of the XML declaration, signals whether or
not there are such declarations which appear external to the <a title="Document Entity" href="#dt-docent" data-ss1529144233="1">document
entity</a>
or in parameter entities. [<a name="dt-extmkpdecl" id="dt-extmkpdecl" title="External Markup Declaration" data-ss1529144233="1">Definition</a>: An <b>external
markup declaration</b> is defined as a markup declaration occurring in
the external subset or in a parameter entity (external or internal, the latter
being included because non-validating processors are not required to read
them).]
				</p>
<h5><a name="fulldtd" id="fulldtd" data-ss1529144233="1">Standalone Document Declaration</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-SDDecl" id="NT-SDDecl" data-ss1529144233="1">[32]&nbsp;&nbsp;&nbsp;</a></td><td><code>SDDecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-S" data-ss1529144233="1">S</a> 'standalone' <a href="#NT-Eq" data-ss1529144233="1">Eq</a>
(("'" ('yes' | 'no') "'") | ('"' ('yes' | 'no') '"')) </code></td><td><a href="#vc-check-rmd" data-ss1529144233="1">[VC: Standalone Document Declaration]</a></td></tr></tbody></table><p><a name="fulldtd" id="fulldtd" data-ss1529144233="1">In a standalone document declaration, the value "yes" indicates
that there are no </a><a title="External Markup Declaration" href="#dt-extmkpdecl" data-ss1529144233="1">external markup declarations</a> which
affect the information passed from the XML processor to the application. The
value "no" indicates that there are or may be such external
markup declarations. Note that the standalone document declaration only denotes
the presence of external <em>declarations</em>; the presence, in a document,
of references to external <em>entities</em>, when those entities are internally
declared, does not change its standalone status.</p><p>If there are no external markup declarations, the standalone document declaration
has no meaning. If there are external markup declarations but there is no
standalone document declaration, the value "no" is assumed.</p><p>Any XML document for which <code>standalone="no"</code> holds can be converted
algorithmically to a standalone document, which may be desirable for some
network delivery applications.</p><div class="constraint"><p class="prefix"><a name="vc-check-rmd" id="vc-check-rmd" data-ss1529144233="1"><b>Validity constraint: Standalone Document Declaration</b></a></p><p><a name="vc-check-rmd" id="vc-check-rmd" data-ss1529144233="1">The
standalone document declaration <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> have the value "no" if
any external markup declarations contain declarations of:</a></p><ul><li><p><a name="vc-check-rmd" id="vc-check-rmd" data-ss1529144233="1">attributes with </a><a title="Attribute Default" href="#dt-default" data-ss1529144233="1">default</a> values,
if elements to which these attributes apply appear in the document without
specifications of values for these attributes, or</p></li><li><p>entities (other than <code>amp</code>,
<code>lt</code>,
<code>gt</code>,
<code>apos</code>,
<code>quot</code>), if <a title="Entity Reference" href="#dt-entref" data-ss1529144233="1">references</a>
to those entities appear in the document, or</p></li><li><p>attributes with
tokenized types, where the
attribute appears in the document with a value such that
<a href="#AVNormalize" data-ss1529144233="1"><cite>normalization</cite></a>
will produce a different value from that which would be produced
in the absence of the declaration, or</p></li><li><p>element types with <a title="Element content" href="#dt-elemcontent" data-ss1529144233="1">element content</a>,
if 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="1.0" standalone='yes'?&gt;</pre></div></div><div class="div2">
<h3><a name="sec-white-space" id="sec-white-space" data-ss1529144233="1">2.10 White Space Handling</a></h3><p><a name="sec-white-space" id="sec-white-space" data-ss1529144233="1">In editing XML documents, it is often convenient to use "white space"
(spaces, tabs, and blank lines)
to set apart the markup for greater readability. Such white space is typically
not intended for inclusion in the delivered version of the document. On the
other hand, "significant" white space that should be preserved
in the delivered version is common, for example in poetry and source code.</a></p><p><a name="sec-white-space" id="sec-white-space" data-ss1529144233="1">An </a><a title="XML Processor" href="#dt-xml-proc" data-ss1529144233="1">XML processor</a>
					<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> always pass
all characters in a document that are not markup through to the application.
A <a title="Validating Processor" href="#dt-validating" data-ss1529144233="1"> validating XML processor</a>
					<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> also
inform the application which of these characters constitute white space appearing
in <a title="Element content" href="#dt-elemcontent" data-ss1529144233="1">element content</a>.</p><p>A special <a title="Attribute" href="#dt-attr" data-ss1529144233="1">attribute</a> named <code>xml:space</code> may be attached to an element to signal an intention that in that element,
white space should be preserved by applications. In 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" data-ss1529144233="1">declared</a>
if 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 Values" href="#dt-enumerated" data-ss1529144233="1">enumerated
type</a> whose values
are one or both of "default" and "preserve".
For example:</p><div class="exampleInner"><pre>&lt;!ATTLIST poem  xml:space (default|preserve) 'preserve'&gt;

&lt;!ATTLIST pre xml:space (preserve) #FIXED 'preserve'&gt;</pre></div><p>The value "default" signals that applications' default white-space
processing modes are acceptable for this element; the value "preserve"
indicates the intent that applications preserve all the white space. This
declared intent is considered to apply to all elements within the content
of the element where it is specified, unless overridden with
another 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" data-ss1529144233="1">root element</a> of any document is considered
to have signaled no intentions as regards application space handling, unless
it provides a value for this attribute or the attribute is declared with a
default value.</p></div><div class="div2">
<h3><a name="sec-line-ends" id="sec-line-ends" data-ss1529144233="1">2.11 End-of-Line Handling</a></h3><p><a name="sec-line-ends" id="sec-line-ends" data-ss1529144233="1">XML </a><a title="Text Entity" href="#dt-parsedent" data-ss1529144233="1">parsed entities</a> are often stored
in computer files which, for editing convenience, are organized into lines.
These lines are typically separated by some combination of the characters
CARRIAGE RETURN (#xD) and LINE FEED (#xA).</p><p>To
simplify the tasks of <a title="Application" href="#dt-app" data-ss1529144233="1">applications</a>, the
<a title="XML Processor" href="#dt-xml-proc" data-ss1529144233="1">XML
processor</a>
					<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> behave as if it normalized all line breaks in external parsed
entities (including the document entity) on input, before parsing, by translating
both the two-character sequence #xD #xA and any #xD that is not followed by
#xA to a single #xA character.</p></div><div class="div2">
<h3><a name="sec-lang-tag" id="sec-lang-tag" data-ss1529144233="1">2.12 Language Identification</a></h3><p><a name="sec-lang-tag" id="sec-lang-tag" data-ss1529144233="1">In document processing, it is often useful to identify the natural or formal
language in which the content is written. A special </a><a title="Attribute" href="#dt-attr" data-ss1529144233="1">attribute</a>
named <code>xml:lang</code> may be inserted in documents to specify the language
used in the contents and attribute values of any element in an XML document.
In 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" data-ss1529144233="1">declared</a>
if it is used. The
values of the attribute are language identifiers as defined by <a href="#RFC1766" data-ss1529144233="1">[IETF BCP 47]</a>, <cite>Tags
for the Identification of Languages</cite>; in addition, the empty string may 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;
&lt;p xml:lang="en-GB"&gt;What colour is it?&lt;/p&gt;
&lt;p xml:lang="en-US"&gt;What color is it?&lt;/p&gt;
&lt;sp who="Faust" desc='leise' xml:lang="de"&gt;
  &lt;l&gt;Habe nun, ach! Philosophie,&lt;/l&gt;
  &lt;l&gt;Juristerei, und Medizin&lt;/l&gt;
  &lt;l&gt;und leider auch Theologie&lt;/l&gt;
  &lt;l&gt;durchaus studiert mit heißem Bemüh'n.&lt;/l&gt;
&lt;/sp&gt;</pre></div><p>The language specified by <code>xml:lang</code> applies to the element where it is specified
		 (including the values of its attributes), and  to all elements in its content unless
     overridden with another instance of <code>xml:lang</code>. 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. Applications determine which of an element's attribute values
     and which parts of its character content, if any, are treated as language-dependent values described by <code>xml:lang</code>. </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
  MIME). When available, this information may be used by XML applications, but the more local
  information provided by <code>xml:lang</code> should be considered to override it.
</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 may also be given, if appropriate. In a collection
of French poems for English students, with glosses and notes in English, the <code>xml:lang</code>
attribute might be declared this way:</p><div class="exampleInner"><pre>&lt;!ATTLIST poem   xml:lang CDATA 'fr'&gt;
&lt;!ATTLIST gloss  xml:lang CDATA 'en'&gt;
&lt;!ATTLIST note   xml:lang CDATA 'en'&gt;</pre></div></div></div><div class="div1">
<h2><a name="sec-logical-struct" id="sec-logical-struct" data-ss1529144233="1">3 Logical Structures</a></h2><p><a name="sec-logical-struct" id="sec-logical-struct" data-ss1529144233="1">
				[</a><a name="dt-element" id="dt-element" title="Element" data-ss1529144233="1">Definition</a>: Each <a title="XML Document" href="#dt-xml-doc" data-ss1529144233="1">XML
document</a> contains one or more <b>elements</b>, the boundaries
of which are either delimited by <a title="Start-Tag" href="#dt-stag" data-ss1529144233="1">start-tags</a>
and <a title="End Tag" href="#dt-etag" data-ss1529144233="1">end-tags</a>, or, for <a title="Empty" href="#dt-empty" data-ss1529144233="1">empty</a>
elements, by an <a title="empty-element tag" href="#dt-eetag" data-ss1529144233="1">empty-element tag</a>. Each
element has a type, identified by name, sometimes called its "generic
identifier" (GI), and may have a set of attribute specifications.]
Each attribute specification has a <a title="Attribute Name" href="#dt-attrname" data-ss1529144233="1">name</a>
and a <a title="Attribute Value" href="#dt-attrval" data-ss1529144233="1">value</a>.</p>
<h5><a name="d0e2130" id="d0e2130" data-ss1529144233="1">Element</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-element" id="NT-element" data-ss1529144233="1">[39]&nbsp;&nbsp;&nbsp;</a></td><td><code>element</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
						<a href="#NT-EmptyElemTag" data-ss1529144233="1">EmptyElemTag</a>
					</code></td></tr><tr valign="baseline"><td></td><td></td><td></td><td><code>| <a href="#NT-STag" data-ss1529144233="1">STag</a>
						<a href="#NT-content" data-ss1529144233="1">content</a>
						<a href="#NT-ETag" data-ss1529144233="1">ETag</a>
					</code></td><td><a href="#GIMatch" data-ss1529144233="1">[WFC: Element Type Match]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#elementvalid" data-ss1529144233="1">[VC: Element Valid]</a></td></tr></tbody></table><p><a name="d0e2130" id="d0e2130" data-ss1529144233="1">This specification does not constrain the
			application semantics, use, or (beyond syntax)
names of the element types and attributes, except that names beginning with
a match to <code>(('X'|'x')('M'|'m')('L'|'l'))</code> are reserved for standardization
in this or future versions of this specification.</a></p><div class="constraint"><p class="prefix"><a name="GIMatch" id="GIMatch" data-ss1529144233="1"><b>Well-formedness constraint: Element Type Match</b></a></p><p><a name="GIMatch" id="GIMatch" data-ss1529144233="1">The </a><a href="#NT-Name" data-ss1529144233="1">Name</a>
in 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" data-ss1529144233="1"><b>Validity constraint: Element Valid</b></a></p><p><a name="elementvalid" id="elementvalid" data-ss1529144233="1">An element is valid
if there is a declaration matching </a><a href="#NT-elementdecl" data-ss1529144233="1">elementdecl</a>
where the <a href="#NT-Name" data-ss1529144233="1">Name</a> matches the element type, and one of
the 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" data-ss1529144233="1">content</a> (not even entity
references, comments, PIs or white space).</p></li><li><p>The declaration matches <a href="#NT-children" data-ss1529144233="1">children</a> and the
sequence of <a title="Parent/Child" href="#dt-parentchild" data-ss1529144233="1">child elements</a> belongs
to the language generated by the regular expression in the content model,
with optional white space, comments and
PIs (i.e. markup matching production [27] <a href="#NT-Misc" data-ss1529144233="1">Misc</a>) between the
start-tag and the first child element, between child elements, or between
the last child element and the end-tag. Note that a CDATA section containing
only white space or a reference
to an entity whose replacement text is character references expanding to white
space do not
match the nonterminal <a href="#NT-S" data-ss1529144233="1">S</a>, and
hence cannot appear in these positions; however, a
reference to an internal entity with a literal value consisting of character
references expanding to white space does match <a href="#NT-S" data-ss1529144233="1">S</a>, since its
replacement text is the white space resulting from expansion of the character
references.</p></li><li><p>The declaration matches <a href="#NT-Mixed" data-ss1529144233="1">Mixed</a>, and the content
(after replacing
any entity references with their replacement text) consists of
<a title="Character Data" href="#dt-chardata" data-ss1529144233="1">character data</a>
(including <a title="CDATA Section" href="#dt-cdsection" data-ss1529144233="1">CDATA sections</a>),
<a title="Comment" href="#dt-comment" data-ss1529144233="1">comments</a>, <a title="Processing instruction" href="#dt-pi" data-ss1529144233="1">PIs</a> and <a title="Parent/Child" href="#dt-parentchild" data-ss1529144233="1">child elements</a> whose types match names in the
content model.</p></li><li><p>The declaration matches <b>ANY</b>, and the content (after replacing
any entity references with their replacement text)
consists of character data, <a title="CDATA Section" href="#dt-cdsection" data-ss1529144233="1">CDATA
sections</a>, <a title="Comment" href="#dt-comment" data-ss1529144233="1">comments</a>, <a title="Processing instruction" href="#dt-pi" data-ss1529144233="1">PIs</a>
 and <a title="Parent/Child" href="#dt-parentchild" data-ss1529144233="1">child elements</a>
whose types have been declared.</p></li></ol></div><div class="div2">
<h3><a name="sec-starttags" id="sec-starttags" data-ss1529144233="1">3.1 Start-Tags, End-Tags, and Empty-Element Tags</a></h3><p><a name="sec-starttags" id="sec-starttags" data-ss1529144233="1">
					[</a><a name="dt-stag" id="dt-stag" title="Start-Tag" data-ss1529144233="1">Definition</a>: The beginning of every non-empty
XML element is marked by a <b>start-tag</b>.]
				</p>
<h5><a name="d0e2259" id="d0e2259" data-ss1529144233="1">Start-tag</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-STag" id="NT-STag" data-ss1529144233="1">[40]&nbsp;&nbsp;&nbsp;</a></td><td><code>STag</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;' <a href="#NT-Name" data-ss1529144233="1">Name</a> (<a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-Attribute" data-ss1529144233="1">Attribute</a>)* <a href="#NT-S" data-ss1529144233="1">S</a>? '&gt;'</code></td><td><a href="#uniqattspec" data-ss1529144233="1">[WFC: Unique Att Spec]</a></td></tr><tr valign="baseline"><td><a name="NT-Attribute" id="NT-Attribute" data-ss1529144233="1">[41]&nbsp;&nbsp;&nbsp;</a></td><td><code>Attribute</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-Name" data-ss1529144233="1">Name</a>
								<a href="#NT-Eq" data-ss1529144233="1">Eq</a>
								<a href="#NT-AttValue" data-ss1529144233="1">AttValue</a>
							</code></td><td><a href="#ValueType" data-ss1529144233="1">[VC: Attribute Value Type]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#NoExternalRefs" data-ss1529144233="1">[WFC: No External Entity References]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#CleanAttrVals" data-ss1529144233="1">[WFC: No &lt; in Attribute Values]</a></td></tr></tbody></table><p><a name="d0e2259" id="d0e2259" data-ss1529144233="1">The </a><a href="#NT-Name" data-ss1529144233="1">Name</a> in the start- and end-tags gives the element's <b>type</b>. [<a name="dt-attr" id="dt-attr" title="Attribute" data-ss1529144233="1">Definition</a>:  The <a href="#NT-Name" data-ss1529144233="1">Name</a>-<a href="#NT-AttValue" data-ss1529144233="1">AttValue</a>
pairs are referred to as the <b>attribute specifications</b> of the
element], [<a name="dt-attrname" id="dt-attrname" title="Attribute Name" data-ss1529144233="1">Definition</a>: with the <a href="#NT-Name" data-ss1529144233="1">Name</a> in each pair referred to as the <b>attribute name</b>
					]
and [<a name="dt-attrval" id="dt-attrval" title="Attribute Value" data-ss1529144233="1">Definition</a>: the content of the <a href="#NT-AttValue" data-ss1529144233="1">AttValue</a> (the text between the <code>'</code> or <code>"</code>
delimiters) as the <b>attribute value</b>.] Note
that the order of attribute specifications in a start-tag or empty-element
tag is not significant.</p><div class="constraint"><p class="prefix"><a name="uniqattspec" id="uniqattspec" data-ss1529144233="1"><b>Well-formedness constraint: Unique Att Spec</b></a></p><p><a name="uniqattspec" id="uniqattspec" data-ss1529144233="1">An attribute name
<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.</a></p></div><div class="constraint"><p class="prefix"><a name="ValueType" id="ValueType" data-ss1529144233="1"><b>Validity constraint: Attribute Value Type</b></a></p><p><a name="ValueType" id="ValueType" data-ss1529144233="1">The attribute <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
have been declared; the value <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be of the type declared for it. (For attribute
types, see </a><a href="#attdecls" data-ss1529144233="1"><b>3.3 Attribute-List Declarations</b></a>.)</p></div><div class="constraint"><p class="prefix"><a name="NoExternalRefs" id="NoExternalRefs" data-ss1529144233="1"><b>Well-formedness constraint: No External Entity References</b></a></p><p><a name="NoExternalRefs" id="NoExternalRefs" data-ss1529144233="1">Attribute
values <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> contain direct or indirect entity references to external entities.</a></p></div><div class="constraint"><p class="prefix"><a name="CleanAttrVals" id="CleanAttrVals" data-ss1529144233="1"><b>Well-formedness constraint: No <code>&lt;</code> in Attribute Values</b></a></p><p><a name="CleanAttrVals" id="CleanAttrVals" data-ss1529144233="1">The </a><a title="Replacement Text" href="#dt-repltext" data-ss1529144233="1">replacement text</a> of any entity
referred 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" data-ss1529144233="1">Definition</a>: The end of every element that begins
with 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
that echoes the element's type as given in the start-tag:]
				</p>
<h5><a name="d0e2403" id="d0e2403" data-ss1529144233="1">End-tag</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-ETag" id="NT-ETag" data-ss1529144233="1">[42]&nbsp;&nbsp;&nbsp;</a></td><td><code>ETag</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;/' <a href="#NT-Name" data-ss1529144233="1">Name</a>
								<a href="#NT-S" data-ss1529144233="1">S</a>?
'&gt;'</code></td></tr></tbody></table><p><a name="d0e2403" id="d0e2403" data-ss1529144233="1">An example of an end-tag:</a></p><div class="exampleInner"><pre><a name="d0e2403" id="d0e2403" data-ss1529144233="1">&lt;/termdef&gt;</a></pre></div><p><a name="d0e2403" id="d0e2403" data-ss1529144233="1">
					[</a><a name="dt-content" id="dt-content" title="Content" data-ss1529144233="1">Definition</a>: The <a title="Text" href="#dt-text" data-ss1529144233="1">text</a>
between the start-tag and end-tag is called the element's <b>content</b>:]
				</p>
<h5><a name="d0e2433" id="d0e2433" data-ss1529144233="1">Content of Elements</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-content" id="NT-content" data-ss1529144233="1">[43]&nbsp;&nbsp;&nbsp;</a></td><td><code>content</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-CharData" data-ss1529144233="1">CharData</a>? ((<a href="#NT-element" data-ss1529144233="1">element</a>
| <a href="#NT-Reference" data-ss1529144233="1">Reference</a> | <a href="#NT-CDSect" data-ss1529144233="1">CDSect</a>
| <a href="#NT-PI" data-ss1529144233="1">PI</a> | <a href="#NT-Comment" data-ss1529144233="1">Comment</a>) <a href="#NT-CharData" data-ss1529144233="1">CharData</a>?)*</code></td></tr></tbody></table><p><a name="d0e2433" id="d0e2433" data-ss1529144233="1">
					[</a><a name="dt-empty" id="dt-empty" title="Empty" data-ss1529144233="1">Definition</a>: An element
with no <a href="#NT-content" data-ss1529144233="1">content</a> is said to be <b>empty</b>.] The representation
of an empty element is either a start-tag immediately followed by an end-tag,
or an empty-element tag. [<a name="dt-eetag" id="dt-eetag" title="empty-element tag" data-ss1529144233="1">Definition</a>: An <b>empty-element
tag</b> takes a special form:]
				</p>
<h5><a name="d0e2480" id="d0e2480" data-ss1529144233="1">Tags for Empty Elements</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EmptyElemTag" id="NT-EmptyElemTag" data-ss1529144233="1">[44]&nbsp;&nbsp;&nbsp;</a></td><td><code>EmptyElemTag</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;' <a href="#NT-Name" data-ss1529144233="1">Name</a> (<a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-Attribute" data-ss1529144233="1">Attribute</a>)* <a href="#NT-S" data-ss1529144233="1">S</a>? '/&gt;'</code></td><td><a href="#uniqattspec" data-ss1529144233="1">[WFC: Unique Att Spec]</a></td></tr></tbody></table><p><a name="d0e2480" id="d0e2480" data-ss1529144233="1">Empty-element tags may be used for any element which has no content, whether
or not it is declared using the keyword <b>EMPTY</b>. </a><a title="For interoperability" href="#dt-interop" data-ss1529144233="1">For
interoperability</a>, the empty-element tag <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em>
be used, and <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> only be used, for elements which are declared
EMPTY.</p><p>Examples of empty elements:</p><div class="exampleInner"><pre>&lt;IMG align="left"
 src="http://www.w3.org/Icons/WWW/w3c_home" /&gt;
&lt;br&gt;&lt;/br&gt;
&lt;br/&gt;</pre></div></div><div class="div2">
<h3><a name="elemdecls" id="elemdecls" data-ss1529144233="1">3.2 Element Type Declarations</a></h3><p><a name="elemdecls" id="elemdecls" data-ss1529144233="1">The </a><a title="Element" href="#dt-element" data-ss1529144233="1">element</a> structure of an <a title="XML Document" href="#dt-xml-doc" data-ss1529144233="1">XML document</a> may, for <a title="Validity" href="#dt-valid" data-ss1529144233="1">validation</a>
purposes, be constrained using element type and attribute-list declarations.
An element type declaration constrains the element's <a title="Content" href="#dt-content" data-ss1529144233="1">content</a>.</p><p>Element type declarations often constrain which element types can appear
as <a title="Parent/Child" href="#dt-parentchild" data-ss1529144233="1">children</a> of the element. At user
option, an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> issue a warning when a declaration mentions an
element 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" data-ss1529144233="1">Definition</a>: An <b>element
type declaration</b> takes the form:]
				</p>
<h5><a name="d0e2553" id="d0e2553" data-ss1529144233="1">Element Type Declaration</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-elementdecl" id="NT-elementdecl" data-ss1529144233="1">[45]&nbsp;&nbsp;&nbsp;</a></td><td><code>elementdecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;!ELEMENT' <a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-Name" data-ss1529144233="1">Name</a>
								<a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-contentspec" data-ss1529144233="1">contentspec</a>
								<a href="#NT-S" data-ss1529144233="1">S</a>?
'&gt;'</code></td><td><a href="#EDUnique" data-ss1529144233="1">[VC: Unique Element Type Declaration]</a></td></tr><tr valign="baseline"><td><a name="NT-contentspec" id="NT-contentspec" data-ss1529144233="1">[46]&nbsp;&nbsp;&nbsp;</a></td><td><code>contentspec</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'EMPTY' | 'ANY' | <a href="#NT-Mixed" data-ss1529144233="1">Mixed</a>
| <a href="#NT-children" data-ss1529144233="1">children</a>
							</code></td></tr></tbody></table><p><a name="d0e2553" id="d0e2553" data-ss1529144233="1">where the </a><a href="#NT-Name" data-ss1529144233="1">Name</a> gives the element type being declared.</p><div class="constraint"><p class="prefix"><a name="EDUnique" id="EDUnique" data-ss1529144233="1"><b>Validity constraint: Unique Element Type Declaration</b></a></p><p><a name="EDUnique" id="EDUnique" data-ss1529144233="1">An element type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be declared more than once.</a></p></div><p><a name="EDUnique" id="EDUnique" data-ss1529144233="1">Examples of element type declarations:</a></p><div class="exampleInner"><pre><a name="EDUnique" id="EDUnique" data-ss1529144233="1">&lt;!ELEMENT br EMPTY&gt;
&lt;!ELEMENT p (#PCDATA|emph)* &gt;
&lt;!ELEMENT %name.para; %content.para; &gt;
&lt;!ELEMENT container ANY&gt;</a></pre></div><div class="div3"><a name="EDUnique" id="EDUnique" data-ss1529144233="1">
</a><h4><a name="EDUnique" id="EDUnique" data-ss1529144233="1"></a><a name="sec-element-content" id="sec-element-content" data-ss1529144233="1">3.2.1 Element Content</a></h4><p><a name="sec-element-content" id="sec-element-content" data-ss1529144233="1">
						[</a><a name="dt-elemcontent" id="dt-elemcontent" title="Element content" data-ss1529144233="1">Definition</a>: An element <a title="Start-Tag" href="#dt-stag" data-ss1529144233="1">type</a> has <b>element content</b> when elements
of that type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> contain only <a title="Parent/Child" href="#dt-parentchild" data-ss1529144233="1">child</a>
elements (no character data), optionally separated by white space (characters
matching the nonterminal <a href="#NT-S" data-ss1529144233="1">S</a>).]
						[<a name="dt-content-model" id="dt-content-model" title="Content model" data-ss1529144233="1">Definition</a>: In this case, the constraint includes a <b>content
model</b>, a simple grammar governing the allowed types of the
child elements and the order in which they are allowed to appear.]
The grammar is built on content particles (<a href="#NT-cp" data-ss1529144233="1">cp</a>s), which
consist of names, choice lists of content particles, or sequence lists of
content particles:</p>
<h5><a name="d0e2638" id="d0e2638" data-ss1529144233="1">Element-content Models</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-children" id="NT-children" data-ss1529144233="1">[47]&nbsp;&nbsp;&nbsp;</a></td><td><code>children</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>(<a href="#NT-choice" data-ss1529144233="1">choice</a> | <a href="#NT-seq" data-ss1529144233="1">seq</a>)
('?' | '*' | '+')?</code></td></tr><tr valign="baseline"><td><a name="NT-cp" id="NT-cp" data-ss1529144233="1">[48]&nbsp;&nbsp;&nbsp;</a></td><td><code>cp</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>(<a href="#NT-Name" data-ss1529144233="1">Name</a> | <a href="#NT-choice" data-ss1529144233="1">choice</a>
| <a href="#NT-seq" data-ss1529144233="1">seq</a>) ('?' | '*' | '+')?</code></td></tr><tr valign="baseline"><td><a name="NT-choice" id="NT-choice" data-ss1529144233="1">[49]&nbsp;&nbsp;&nbsp;</a></td><td><code>choice</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'(' <a href="#NT-S" data-ss1529144233="1">S</a>? <a href="#NT-cp" data-ss1529144233="1">cp</a> ( <a href="#NT-S" data-ss1529144233="1">S</a>? '|' <a href="#NT-S" data-ss1529144233="1">S</a>? <a href="#NT-cp" data-ss1529144233="1">cp</a> )+ <a href="#NT-S" data-ss1529144233="1">S</a>? ')'</code></td><td><a href="#vc-PEinGroup" data-ss1529144233="1">[VC: Proper Group/PE Nesting]</a></td></tr><tr valign="baseline"><td><a name="NT-seq" id="NT-seq" data-ss1529144233="1">[50]&nbsp;&nbsp;&nbsp;</a></td><td><code>seq</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'(' <a href="#NT-S" data-ss1529144233="1">S</a>? <a href="#NT-cp" data-ss1529144233="1">cp</a> ( <a href="#NT-S" data-ss1529144233="1">S</a>? ',' <a href="#NT-S" data-ss1529144233="1">S</a>? <a href="#NT-cp" data-ss1529144233="1">cp</a> )* <a href="#NT-S" data-ss1529144233="1">S</a>? ')'</code></td><td><a href="#vc-PEinGroup" data-ss1529144233="1">[VC: Proper Group/PE Nesting]</a></td></tr></tbody></table><p><a name="d0e2638" id="d0e2638" data-ss1529144233="1">where each </a><a href="#NT-Name" data-ss1529144233="1">Name</a> is the type of an element which
may appear as a <a title="Parent/Child" href="#dt-parentchild" data-ss1529144233="1">child</a>. Any content
particle in a choice list may appear in the <a title="Element content" href="#dt-elemcontent" data-ss1529144233="1">element
content</a> at the location where the choice list appears in the grammar;
content 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" data-ss1529144233="1">element content</a> in the order given in the list.
The optional character following a name or list governs whether the element
or the content particles in the list may occur one or more (<code>+</code>),
zero or more (<code>*</code>), or zero or one times (<code>?</code>). The
absence of such an operator means that the element or content particle <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
appear exactly once. This syntax and meaning are identical to those used in
the productions in this specification.</p><p>The content of an element matches a content model if and only if it is
possible to trace out a path through the content model, obeying the sequence,
choice, and repetition operators and matching each element in the content
against an element type in the content model. <a title="For Compatibility" href="#dt-compat" data-ss1529144233="1">For
compatibility</a>, it is an error if the content model
allows an element to match more than one occurrence of an element type in the
content model. For more information, see <a href="#determinism" data-ss1529144233="1"><b>E Deterministic Content Models</b></a>.</p><div class="constraint"><p class="prefix"><a name="vc-PEinGroup" id="vc-PEinGroup" data-ss1529144233="1"><b>Validity constraint: Proper Group/PE Nesting</b></a></p><p><a name="vc-PEinGroup" id="vc-PEinGroup" data-ss1529144233="1">Parameter-entity </a><a title="Replacement Text" href="#dt-repltext" data-ss1529144233="1">replacement text</a>
							<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be properly nested with parenthesized
groups. That is to say, if either of the opening or closing parentheses in
a <a href="#NT-choice" data-ss1529144233="1">choice</a>, <a href="#NT-seq" data-ss1529144233="1">seq</a>, or <a href="#NT-Mixed" data-ss1529144233="1">Mixed</a>
construct is contained in the replacement text for a <a title="Parameter-entity reference" href="#dt-PERef" data-ss1529144233="1">parameter
entity</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" data-ss1529144233="1">For interoperability</a>, if a parameter-entity reference
appears in a <a href="#NT-choice" data-ss1529144233="1">choice</a>, <a href="#NT-seq" data-ss1529144233="1">seq</a>, or <a href="#NT-Mixed" data-ss1529144233="1">Mixed</a> construct, its replacement text <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> contain at
least one non-blank character, and neither the first nor last non-blank character
of 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;
&lt;!ELEMENT div1 (head, (p | list | note)*, div2*)&gt;
&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" data-ss1529144233="1">3.2.2 Mixed Content</a></h4><p><a name="sec-mixed-content" id="sec-mixed-content" data-ss1529144233="1">
						[</a><a name="dt-mixed" id="dt-mixed" title="Mixed Content" data-ss1529144233="1">Definition</a>: An element <a title="Start-Tag" href="#dt-stag" data-ss1529144233="1">type</a>
has <b>mixed content</b> when elements of that type may contain character
data, optionally interspersed with <a title="Parent/Child" href="#dt-parentchild" data-ss1529144233="1">child</a>
elements.] In this case, the types of the child elements may be constrained,
but not their order or their number of occurrences:</p>
<h5><a name="d0e2826" id="d0e2826" data-ss1529144233="1">Mixed-content Declaration</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-Mixed" id="NT-Mixed" data-ss1529144233="1">[51]&nbsp;&nbsp;&nbsp;</a></td><td><code>Mixed</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'(' <a href="#NT-S" data-ss1529144233="1">S</a>? '#PCDATA' (<a href="#NT-S" data-ss1529144233="1">S</a>?
'|' <a href="#NT-S" data-ss1529144233="1">S</a>? <a href="#NT-Name" data-ss1529144233="1">Name</a>)* <a href="#NT-S" data-ss1529144233="1">S</a>?
')*' </code></td></tr><tr valign="baseline"><td></td><td></td><td></td><td><code>| '(' <a href="#NT-S" data-ss1529144233="1">S</a>? '#PCDATA' <a href="#NT-S" data-ss1529144233="1">S</a>? ')' </code></td><td><a href="#vc-PEinGroup" data-ss1529144233="1">[VC: Proper Group/PE Nesting]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#vc-MixedChildrenUnique" data-ss1529144233="1">[VC: No Duplicate Types]</a></td></tr></tbody></table><p><a name="d0e2826" id="d0e2826" data-ss1529144233="1">where the </a><a href="#NT-Name" data-ss1529144233="1">Name</a>s give the types of elements that
may appear as children. The
keyword <b>#PCDATA</b> derives historically from the term "parsed
character data."
					</p><div class="constraint"><p class="prefix"><a name="vc-MixedChildrenUnique" id="vc-MixedChildrenUnique" data-ss1529144233="1"><b>Validity constraint: No Duplicate Types</b></a></p><p><a name="vc-MixedChildrenUnique" id="vc-MixedChildrenUnique" data-ss1529144233="1">The
same name <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear more than once in a single mixed-content declaration.</a></p></div><p><a name="vc-MixedChildrenUnique" id="vc-MixedChildrenUnique" data-ss1529144233="1">Examples of mixed content declarations:</a></p><div class="exampleInner"><pre><a name="vc-MixedChildrenUnique" id="vc-MixedChildrenUnique" data-ss1529144233="1">&lt;!ELEMENT p (#PCDATA|a|ul|b|i|em)*&gt;
&lt;!ELEMENT p (#PCDATA | %font; | %phrase; | %special; | %form;)* &gt;
&lt;!ELEMENT b (#PCDATA)&gt;</a></pre></div></div></div><div class="div2"><a name="vc-MixedChildrenUnique" id="vc-MixedChildrenUnique" data-ss1529144233="1">
</a><h3><a name="vc-MixedChildrenUnique" id="vc-MixedChildrenUnique" data-ss1529144233="1"></a><a name="attdecls" id="attdecls" data-ss1529144233="1">3.3 Attribute-List Declarations</a></h3><p><a name="attdecls" id="attdecls" data-ss1529144233="1">
					</a><a title="Attribute" href="#dt-attr" data-ss1529144233="1">Attributes</a> are used to associate name-value
pairs with <a title="Element" href="#dt-element" data-ss1529144233="1">elements</a>. Attribute specifications
<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear outside of <a title="Start-Tag" href="#dt-stag" data-ss1529144233="1">start-tags</a> and <a title="empty-element tag" href="#dt-eetag" data-ss1529144233="1">empty-element tags</a>; thus, the productions used to
recognize them appear in <a href="#sec-starttags" data-ss1529144233="1"><b>3.1 Start-Tags, End-Tags, and Empty-Element Tags</b></a>. Attribute-list declarations
may 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" data-ss1529144233="1">default values</a> for
attributes.</p></li></ul><p>
					[<a name="dt-attdecl" id="dt-attdecl" title="Attribute-List Declaration" data-ss1529144233="1">Definition</a>: 
						<b>Attribute-list
declarations</b> specify the name, data type, and default value (if any)
of each attribute associated with a given element type:]
				</p>
<h5><a name="d0e2926" id="d0e2926" data-ss1529144233="1">Attribute-list Declaration</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-AttlistDecl" id="NT-AttlistDecl" data-ss1529144233="1">[52]&nbsp;&nbsp;&nbsp;</a></td><td><code>AttlistDecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;!ATTLIST' <a href="#NT-S" data-ss1529144233="1">S</a>
							<a href="#NT-Name" data-ss1529144233="1">Name</a>
							<a href="#NT-AttDef" data-ss1529144233="1">AttDef</a>* <a href="#NT-S" data-ss1529144233="1">S</a>? '&gt;'</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-AttDef" id="NT-AttDef" data-ss1529144233="1">[53]&nbsp;&nbsp;&nbsp;</a></td><td><code>AttDef</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
							<a href="#NT-S" data-ss1529144233="1">S</a>
							<a href="#NT-Name" data-ss1529144233="1">Name</a>
							<a href="#NT-S" data-ss1529144233="1">S</a>
							<a href="#NT-AttType" data-ss1529144233="1">AttType</a>
							<a href="#NT-S" data-ss1529144233="1">S</a>
							<a href="#NT-DefaultDecl" data-ss1529144233="1">DefaultDecl</a>
						</code></td></tr></tbody></table><p><a name="d0e2926" id="d0e2926" data-ss1529144233="1">The </a><a href="#NT-Name" data-ss1529144233="1">Name</a> in the <a href="#NT-AttlistDecl" data-ss1529144233="1">AttlistDecl</a>
rule is the type of an element. At user option, an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> issue
a warning if attributes are declared for an element type not itself declared,
but this is not an error. The <a href="#NT-Name" data-ss1529144233="1">Name</a> in the <a href="#NT-AttDef" data-ss1529144233="1">AttDef</a>
rule is the name of the attribute.</p><p>When more than one <a href="#NT-AttlistDecl" data-ss1529144233="1">AttlistDecl</a> is provided
for a given element type, the contents of all those provided are merged. When
more than one definition is provided for the same attribute of a given element
type, the first declaration is binding and later declarations are ignored. <a title="For interoperability" href="#dt-interop" data-ss1529144233="1">For interoperability,</a> writers of DTDs may choose
to provide at most one attribute-list declaration for a given element type,
at most one attribute definition for a given attribute name in an attribute-list
declaration, and at least one attribute definition in each attribute-list
declaration. For interoperability, an XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> at user option
issue a warning when more than one attribute-list declaration is provided
for a given element type, or more than one attribute definition is provided
for a given attribute, but this is not an error.</p><div class="div3">
<h4><a name="sec-attribute-types" id="sec-attribute-types" data-ss1529144233="1">3.3.1 Attribute Types</a></h4><p><a name="sec-attribute-types" id="sec-attribute-types" data-ss1529144233="1">XML attribute types are of three kinds: a string type, a set of tokenized
types, and enumerated types. The string type may take any literal string as
a value; the tokenized types are more constrained.
The validity constraints noted in the grammar are applied after the attribute
value has been normalized as described in </a><a href="#AVNormalize" data-ss1529144233="1"><b>3.3.3 Attribute-Value Normalization</b></a>.</p>
<h5><a name="d0e3004" id="d0e3004" data-ss1529144233="1">Attribute Types</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-AttType" id="NT-AttType" data-ss1529144233="1">[54]&nbsp;&nbsp;&nbsp;</a></td><td><code>AttType</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
									<a href="#NT-StringType" data-ss1529144233="1">StringType</a> | <a href="#NT-TokenizedType" data-ss1529144233="1">TokenizedType</a>
| <a href="#NT-EnumeratedType" data-ss1529144233="1">EnumeratedType</a>
								</code></td></tr><tr valign="baseline"><td><a name="NT-StringType" id="NT-StringType" data-ss1529144233="1">[55]&nbsp;&nbsp;&nbsp;</a></td><td><code>StringType</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'CDATA'</code></td></tr><tr valign="baseline"><td><a name="NT-TokenizedType" id="NT-TokenizedType" data-ss1529144233="1">[56]&nbsp;&nbsp;&nbsp;</a></td><td><code>TokenizedType</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'ID'</code></td><td><a href="#id" data-ss1529144233="1">[VC: ID]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#one-id-per-el" data-ss1529144233="1">[VC: One ID per Element Type]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#id-default" data-ss1529144233="1">[VC: ID Attribute Default]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td><code>| 'IDREF'</code></td><td><a href="#idref" data-ss1529144233="1">[VC: IDREF]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td><code>| 'IDREFS'</code></td><td><a href="#idref" data-ss1529144233="1">[VC: IDREF]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td><code>| 'ENTITY'</code></td><td><a href="#entname" data-ss1529144233="1">[VC: Entity Name]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td><code>| 'ENTITIES'</code></td><td><a href="#entname" data-ss1529144233="1">[VC: Entity Name]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td><code>| 'NMTOKEN'</code></td><td><a href="#nmtok" data-ss1529144233="1">[VC: Name Token]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td><code>| 'NMTOKENS'</code></td><td><a href="#nmtok" data-ss1529144233="1">[VC: Name Token]</a></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="id" id="id" data-ss1529144233="1"><b>Validity constraint: ID</b></a></p><p><a name="id" id="id" data-ss1529144233="1">Values of type <b>ID</b>
							<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the </a><a href="#NT-Name" data-ss1529144233="1">Name</a> production. A name <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear more than once
in 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
identify the elements which bear them.</p></div><div class="constraint"><p class="prefix"><a name="one-id-per-el" id="one-id-per-el" data-ss1529144233="1"><b>Validity constraint: One ID per Element Type</b></a></p><p><a name="one-id-per-el" id="one-id-per-el" data-ss1529144233="1">An element type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> have more than one ID attribute specified.</a></p></div><div class="constraint"><p class="prefix"><a name="id-default" id="id-default" data-ss1529144233="1"><b>Validity constraint: ID Attribute Default</b></a></p><p><a name="id-default" id="id-default" data-ss1529144233="1">An ID attribute
<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> have a declared default of <b>#IMPLIED</b> or <b>#REQUIRED</b>.</a></p></div><div class="constraint"><p class="prefix"><a name="idref" id="idref" data-ss1529144233="1"><b>Validity constraint: IDREF</b></a></p><p><a name="idref" id="idref" data-ss1529144233="1">Values of type <b>IDREF</b>
							<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
match the </a><a href="#NT-Name" data-ss1529144233="1">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" data-ss1529144233="1">Names</a>; each <a href="#NT-Name" data-ss1529144233="1">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;
i.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" data-ss1529144233="1"><b>Validity constraint: Entity Name</b></a></p><p><a name="entname" id="entname" data-ss1529144233="1">Values of type <b>ENTITY</b>
							<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the </a><a href="#NT-Name" data-ss1529144233="1">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" data-ss1529144233="1">Names</a>; each <a href="#NT-Name" data-ss1529144233="1">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" data-ss1529144233="1">unparsed entity</a>
declared in the <a title="Document Type Declaration" href="#dt-doctype" data-ss1529144233="1">DTD</a>.</p></div><div class="constraint"><p class="prefix"><a name="nmtok" id="nmtok" data-ss1529144233="1"><b>Validity constraint: Name Token</b></a></p><p><a name="nmtok" id="nmtok" data-ss1529144233="1">Values of type <b>NMTOKEN</b>
							<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the </a><a href="#NT-Nmtoken" data-ss1529144233="1">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" data-ss1529144233="1">Nmtokens</a>.</p></div><p>
						[<a name="dt-enumerated" id="dt-enumerated" title="Enumerated Attribute Values" data-ss1529144233="1">Definition</a>: 
							<b>Enumerated attributes</b>
							have a list of allowed values in their declaration
						]. They <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> take one of those values.  There are two kinds of enumerated attribute types:</p>
<h5><a name="d0e3200" id="d0e3200" data-ss1529144233="1">Enumerated Attribute Types</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EnumeratedType" id="NT-EnumeratedType" data-ss1529144233="1">[57]&nbsp;&nbsp;&nbsp;</a></td><td><code>EnumeratedType</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-NotationType" data-ss1529144233="1">NotationType</a>
| <a href="#NT-Enumeration" data-ss1529144233="1">Enumeration</a>
							</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-NotationType" id="NT-NotationType" data-ss1529144233="1">[58]&nbsp;&nbsp;&nbsp;</a></td><td><code>NotationType</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'NOTATION' <a href="#NT-S" data-ss1529144233="1">S</a> '(' <a href="#NT-S" data-ss1529144233="1">S</a>? <a href="#NT-Name" data-ss1529144233="1">Name</a> (<a href="#NT-S" data-ss1529144233="1">S</a>? '|' <a href="#NT-S" data-ss1529144233="1">S</a>? <a href="#NT-Name" data-ss1529144233="1">Name</a>)* <a href="#NT-S" data-ss1529144233="1">S</a>? ')' </code></td><td><a href="#notatn" data-ss1529144233="1">[VC: Notation Attributes]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#OneNotationPer" data-ss1529144233="1">[VC: One Notation Per Element Type]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#NoNotationEmpty" data-ss1529144233="1">[VC: No Notation on Empty Element]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#NoDuplicateTokens" data-ss1529144233="1">[VC: No Duplicate Tokens]</a></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-Enumeration" id="NT-Enumeration" data-ss1529144233="1">[59]&nbsp;&nbsp;&nbsp;</a></td><td><code>Enumeration</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'(' <a href="#NT-S" data-ss1529144233="1">S</a>? <a href="#NT-Nmtoken" data-ss1529144233="1">Nmtoken</a>
(<a href="#NT-S" data-ss1529144233="1">S</a>? '|' <a href="#NT-S" data-ss1529144233="1">S</a>? <a href="#NT-Nmtoken" data-ss1529144233="1">Nmtoken</a>)* <a href="#NT-S" data-ss1529144233="1">S</a>? ')'</code></td><td><a href="#enum" data-ss1529144233="1">[VC: Enumeration]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#NoDuplicateTokens" data-ss1529144233="1">[VC: No Duplicate Tokens]</a></td></tr></tbody></table><p><a name="d0e3200" id="d0e3200" data-ss1529144233="1">A <b>NOTATION</b> attribute identifies a </a><a title="Notation" href="#dt-notation" data-ss1529144233="1">notation</a>,
declared in the DTD with associated system and/or public identifiers, to be
used in interpreting the element to which the attribute is attached.</p><div class="constraint"><p class="prefix"><a name="notatn" id="notatn" data-ss1529144233="1"><b>Validity constraint: Notation Attributes</b></a></p><p><a name="notatn" id="notatn" data-ss1529144233="1">Values of this type
<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match one of the </a><a href="#Notations" data-ss1529144233="1"><cite>notation</cite></a> names
included in the declaration; all notation names in the declaration <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be
declared.</p></div><div class="constraint"><p class="prefix"><a name="OneNotationPer" id="OneNotationPer" data-ss1529144233="1"><b>Validity constraint: One Notation Per Element Type</b></a></p><p><a name="OneNotationPer" id="OneNotationPer" data-ss1529144233="1">An element type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> have more than one <b>NOTATION</b>
attribute specified.</a></p></div><div class="constraint"><p class="prefix"><a name="NoNotationEmpty" id="NoNotationEmpty" data-ss1529144233="1"><b>Validity constraint: No Notation on Empty Element</b></a></p><p><a name="NoNotationEmpty" id="NoNotationEmpty" data-ss1529144233="1">
							</a><a title="For Compatibility" href="#dt-compat" data-ss1529144233="1">For compatibility</a>,
an attribute of type <b>NOTATION</b>
							<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be declared on an element
declared <b>EMPTY</b>.</p></div><div class="constraint"><p class="prefix"><a name="NoDuplicateTokens" id="NoDuplicateTokens" data-ss1529144233="1"><b>Validity constraint: No Duplicate Tokens</b></a></p><p><a name="NoDuplicateTokens" id="NoDuplicateTokens" data-ss1529144233="1">The notation names in a single </a><a href="#NT-NotationType" data-ss1529144233="1">NotationType</a>
attribute declaration, as well as the <a href="#NT-Nmtoken" data-ss1529144233="1">NmToken</a>s in a single
<a href="#NT-Enumeration" data-ss1529144233="1">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" data-ss1529144233="1"><b>Validity constraint: Enumeration</b></a></p><p><a name="enum" id="enum" data-ss1529144233="1">Values of this type <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match
one of the </a><a href="#NT-Nmtoken" data-ss1529144233="1">Nmtoken</a> tokens in the declaration.</p></div><p>
						<a title="For interoperability" href="#dt-interop" data-ss1529144233="1">For interoperability,</a> the same <a href="#NT-Nmtoken" data-ss1529144233="1">Nmtoken</a>
						<em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD NOT</em> occur more than once in the enumerated
attribute types of a single element type.</p></div><div class="div3">
<h4><a name="sec-attr-defaults" id="sec-attr-defaults" data-ss1529144233="1">3.3.2 Attribute Defaults</a></h4><p><a name="sec-attr-defaults" id="sec-attr-defaults" data-ss1529144233="1">An </a><a title="Attribute-List Declaration" href="#dt-attdecl" data-ss1529144233="1">attribute declaration</a> provides information
on whether the attribute's presence is <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>, and if not, how an XML processor
is to react if a declared attribute is absent in a document.</p>
<h5><a name="d0e3369" id="d0e3369" data-ss1529144233="1">Attribute Defaults</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-DefaultDecl" id="NT-DefaultDecl" data-ss1529144233="1">[60]&nbsp;&nbsp;&nbsp;</a></td><td><code>DefaultDecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'#REQUIRED' |&nbsp;'#IMPLIED' </code></td></tr><tr valign="baseline"><td></td><td></td><td></td><td><code>| (('#FIXED' <a href="#NT-S" data-ss1529144233="1">S</a>)? <a href="#NT-AttValue" data-ss1529144233="1">AttValue</a>)</code></td><td><a href="#RequiredAttr" data-ss1529144233="1">[VC: Required Attribute]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#defattrvalid" data-ss1529144233="1">[VC: Attribute Default Value Syntactically Correct]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#CleanAttrVals" data-ss1529144233="1">[WFC: No &lt; in Attribute Values]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#FixedAttr" data-ss1529144233="1">[VC: Fixed Attribute Default]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#NoExternalRefs" data-ss1529144233="1">[WFC: No External Entity References]</a></td></tr></tbody></table><p><a name="d0e3369" id="d0e3369" data-ss1529144233="1">In an attribute declaration, <b>#REQUIRED</b> means that the attribute
<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> always be provided, <b>#IMPLIED</b> that no default value is provided.

						[</a><a name="dt-default" id="dt-default" title="Attribute Default" data-ss1529144233="1">Definition</a>: If
the declaration is neither <b>#REQUIRED</b> nor <b>#IMPLIED</b>, then
the <a href="#NT-AttValue" data-ss1529144233="1">AttValue</a> value contains the declared <b>default</b>
value; the <b>#FIXED</b> keyword states that the attribute <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> always have
the default value.
When an XML processor encounters
an element
without a specification for an attribute for which it has read a default
value declaration, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> report the attribute with the declared default
value to the application.]
					</p><div class="constraint"><p class="prefix"><a name="RequiredAttr" id="RequiredAttr" data-ss1529144233="1"><b>Validity constraint: Required Attribute</b></a></p><p><a name="RequiredAttr" id="RequiredAttr" data-ss1529144233="1">If the default
declaration is the keyword <b>#REQUIRED</b>, then the attribute <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be
specified for all elements of the type in the attribute-list declaration.</a></p></div><div class="constraint"><p class="prefix"><a name="defattrvalid" id="defattrvalid" data-ss1529144233="1"><b>Validity constraint: Attribute Default Value Syntactically Correct</b></a></p><p><a name="defattrvalid" id="defattrvalid" data-ss1529144233="1">The declared default value <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> meet the syntactic
constraints of the declared attribute type. That is, the default value of an attribute:
						</a></p><ul><li><p><a name="defattrvalid" id="defattrvalid" data-ss1529144233="1">
									of type IDREF or ENTITY must match the </a><a href="#NT-Name" data-ss1529144233="1">Name</a> production;</p></li><li><p>
									of type IDREFS or ENTITIES must match the <a href="#NT-Names" data-ss1529144233="1">Names</a> production;</p></li><li><p>
									of type NMTOKEN must match the <a href="#NT-Nmtoken" data-ss1529144233="1">Nmtoken</a> production;</p></li><li><p>
									of type NMTOKENS must match the <a href="#NT-Nmtokens" data-ss1529144233="1">Nmtokens</a> production;</p></li><li><p>
									of an <a href="#NT-EnumeratedType" data-ss1529144233="1">enumerated type</a> (either a <a href="#NT-NotationType" data-ss1529144233="1">NOTATION</a> type or an <a href="#NT-Enumeration" data-ss1529144233="1">enumeration</a>) must match one of the enumerated values.</p></li></ul><p>Note that only the
syntactic constraints of the type are required here; other constraints (e.g.
that the value be the name of a declared unparsed entity, for an attribute of
type ENTITY) will be reported by a validating
parser only if an element without a specification for this attribute
actually occurs.</p></div><div class="constraint"><p class="prefix"><a name="FixedAttr" id="FixedAttr" data-ss1529144233="1"><b>Validity constraint: Fixed Attribute Default</b></a></p><p><a name="FixedAttr" id="FixedAttr" data-ss1529144233="1">If an attribute
has a default value declared with the <b>#FIXED</b> keyword, instances of
that attribute <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the default value.</a></p></div><p><a name="FixedAttr" id="FixedAttr" data-ss1529144233="1">Examples of attribute-list declarations:</a></p><div class="exampleInner"><pre><a name="FixedAttr" id="FixedAttr" data-ss1529144233="1">&lt;!ATTLIST termdef
          id      ID      #REQUIRED
          name    CDATA   #IMPLIED&gt;
&lt;!ATTLIST list
          type    (bullets|ordered|glossary)  "ordered"&gt;
&lt;!ATTLIST form
          method  CDATA   #FIXED "POST"&gt;</a></pre></div></div><div class="div3"><a name="FixedAttr" id="FixedAttr" data-ss1529144233="1">
</a><h4><a name="FixedAttr" id="FixedAttr" data-ss1529144233="1"></a><a name="AVNormalize" id="AVNormalize" data-ss1529144233="1">3.3.3 Attribute-Value Normalization</a></h4><p><a name="AVNormalize" id="AVNormalize" data-ss1529144233="1">Before the value of an attribute is passed to the application or checked
for validity, the XML processor <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> normalize the attribute value by applying
the algorithm below, or by using some other method such that the value passed
to the application is the same as that produced by the algorithm.</a></p><ol class="enumar"><li><p><a name="AVNormalize" id="AVNormalize" data-ss1529144233="1">All line breaks <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> have been normalized on input to #xA as described
in </a><a href="#sec-line-ends" data-ss1529144233="1"><b>2.11 End-of-Line Handling</b></a>, so the rest of this algorithm operates
on 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
unnormalized attribute value, beginning with the first and continuing to the
last, do the following:</p><ul><li><p>For a character reference, append the referenced character to the
normalized value.</p></li><li><p>For an entity reference, recursively apply step 3 of this algorithm
to the replacement text of the entity.</p></li><li><p>For a white space character (#x20, #xD, #xA, #x9), append a space
character (#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
process the normalized attribute value by discarding any leading and trailing
space (#x20) characters, and by replacing sequences of space (#x20) characters
by a single space (#x20) character.</p><p>Note that if the unnormalized attribute value contains a character reference
to a white space character other than space (#x20), the normalized value contains
the referenced character itself (#xD, #xA or #x9). This contrasts with the
case where the unnormalized value contains a white space character (not a
reference), which is replaced with a space character (#x20) in the normalized
value and also contrasts with the case where the unnormalized value contains
an entity reference whose replacement text contains a white space character;
being recursively processed, the white space character is replaced with a
space 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
by a non-validating processor as if declared <b>CDATA</b>.</p><p>It is an error if an <a title="Attribute Value" href="#dt-attrval" data-ss1529144233="1">attribute
value</a> contains a <a title="Entity Reference" href="#dt-entref" data-ss1529144233="1">reference</a> to an
entity for which no declaration has been read.</p><p>Following are examples of attribute normalization. Given the following
declarations:</p><div class="exampleInner"><pre>&lt;!ENTITY d "&amp;#xD;"&gt;
&lt;!ENTITY a "&amp;#xA;"&gt;
&lt;!ENTITY da "&amp;#xD;&amp;#xA;"&gt;</pre></div><p>the attribute specifications in the left column below would be normalized
to the character sequences of the middle column if the attribute <code>a</code>
is declared <b>NMTOKENS</b> and to those of the right columns if <code>a</code>
is declared <b>CDATA</b>.</p><table frame="border" border="1"><thead><tr><th>Attribute specification</th><th>a is NMTOKENS</th><th>a is CDATA</th></tr></thead><tbody><tr><td>
									<div class="exampleInner"><pre>a="

xyz"</pre></div>
								</td><td>
									<div class="exampleInner"><pre>x y z</pre></div>
								</td><td>
									<div class="exampleInner"><pre>#x20 #x20 x y z</pre></div>
								</td></tr><tr><td>
									<div class="exampleInner"><pre>a="&amp;d;&amp;d;A&amp;a;&amp;#x20;&amp;a;B&amp;da;"</pre></div>
								</td><td>
									<div class="exampleInner"><pre>A #x20 B</pre></div>
								</td><td>
									<div class="exampleInner"><pre>#x20 #x20 A #x20 #x20 #x20 B #x20 #x20</pre></div>
								</td></tr><tr><td>
									<div class="exampleInner"><pre>a=
"&amp;#xd;&amp;#xd;A&amp;#xa;&amp;#xa;B&amp;#xd;&amp;#xa;"</pre></div>
								</td><td>
									<div class="exampleInner"><pre>#xD #xD A #xA #xA B #xD #xA</pre></div>
								</td><td>
									<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>
is declared to be of type <b>NMTOKENS</b>.</p></div></div><div class="div2">
<h3><a name="sec-condition-sect" id="sec-condition-sect" data-ss1529144233="1">3.4 Conditional Sections</a></h3><p><a name="sec-condition-sect" id="sec-condition-sect" data-ss1529144233="1">
					[</a><a name="dt-cond-section" id="dt-cond-section" title="conditional section" data-ss1529144233="1">Definition</a>: 
						<b>Conditional
sections</b> are portions of the <a title="Document Type Declaration" href="#dt-doctype" data-ss1529144233="1">document type
declaration external subset</a> or
of external parameter entities which are included in, or excluded from,
the logical structure of the DTD based on the keyword which governs them.]
				</p>
<h5><a name="d0e3658" id="d0e3658" data-ss1529144233="1">Conditional Section</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-conditionalSect" id="NT-conditionalSect" data-ss1529144233="1">[61]&nbsp;&nbsp;&nbsp;</a></td><td><code>conditionalSect</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-includeSect" data-ss1529144233="1">includeSect</a> | <a href="#NT-ignoreSect" data-ss1529144233="1">ignoreSect</a>
							</code></td></tr><tr valign="baseline"><td><a name="NT-includeSect" id="NT-includeSect" data-ss1529144233="1">[62]&nbsp;&nbsp;&nbsp;</a></td><td><code>includeSect</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;![' <a href="#NT-S" data-ss1529144233="1">S</a>? 'INCLUDE' <a href="#NT-S" data-ss1529144233="1">S</a>? '[' <a href="#NT-extSubsetDecl" data-ss1529144233="1">extSubsetDecl</a>
']]&gt;' </code></td><td><a href="#condsec-nesting" data-ss1529144233="1">[VC: Proper Conditional Section/PE Nesting]</a></td></tr><tr valign="baseline"><td><a name="NT-ignoreSect" id="NT-ignoreSect" data-ss1529144233="1">[63]&nbsp;&nbsp;&nbsp;</a></td><td><code>ignoreSect</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;![' <a href="#NT-S" data-ss1529144233="1">S</a>? 'IGNORE' <a href="#NT-S" data-ss1529144233="1">S</a>? '[' <a href="#NT-ignoreSectContents" data-ss1529144233="1">ignoreSectContents</a>*
']]&gt;'</code></td><td><a href="#condsec-nesting" data-ss1529144233="1">[VC: Proper Conditional Section/PE Nesting]</a></td></tr><tr valign="baseline"><td><a name="NT-ignoreSectContents" id="NT-ignoreSectContents" data-ss1529144233="1">[64]&nbsp;&nbsp;&nbsp;</a></td><td><code>ignoreSectContents</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-Ignore" data-ss1529144233="1">Ignore</a> ('&lt;![' <a href="#NT-ignoreSectContents" data-ss1529144233="1">ignoreSectContents</a> ']]&gt;' <a href="#NT-Ignore" data-ss1529144233="1">Ignore</a>)*</code></td></tr><tr valign="baseline"><td><a name="NT-Ignore" id="NT-Ignore" data-ss1529144233="1">[65]&nbsp;&nbsp;&nbsp;</a></td><td><code>Ignore</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-Char" data-ss1529144233="1">Char</a>* - (<a href="#NT-Char" data-ss1529144233="1">Char</a>*
('&lt;![' | ']]&gt;') <a href="#NT-Char" data-ss1529144233="1">Char</a>*) </code></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="condsec-nesting" id="condsec-nesting" data-ss1529144233="1"><b>Validity constraint: Proper Conditional Section/PE Nesting</b></a></p><p><a name="condsec-nesting" id="condsec-nesting" data-ss1529144233="1">If any of the "<code>&lt;![</code>",
"<code>[</code>", or "<code>]]&gt;</code>" of a conditional section is contained
in the replacement text for a parameter-entity reference, all of them <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
be contained in the same replacement text.</a></p></div><p><a name="condsec-nesting" id="condsec-nesting" data-ss1529144233="1">Like the internal and external DTD subsets, a conditional section may contain
one or more complete declarations, comments, processing instructions, or nested
conditional sections, intermingled with white space.</a></p><p><a name="condsec-nesting" id="condsec-nesting" data-ss1529144233="1">If the keyword of the conditional section is <b>INCLUDE</b>, then the
contents of the conditional section <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be processed as part of the DTD. If the keyword of
the conditional section is <b>IGNORE</b>, then the contents of the conditional
section <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> <em class="rfc2119" title="Keyword in RFC 2119 context">NOT</em> be processed as part of the DTD.
If a conditional section with a keyword of <b>INCLUDE</b> occurs within
a larger conditional section with a keyword of <b>IGNORE</b>, both the outer
and the inner conditional sections <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be ignored. The contents
of an ignored conditional section <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be parsed by ignoring all characters after
the "<code>[</code>" following the keyword, except conditional section starts
"<code>&lt;![</code>" and ends "<code>]]&gt;</code>", until the matching conditional
section end is found. Parameter entity references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> be recognized in this
process.</a></p><p><a name="condsec-nesting" id="condsec-nesting" data-ss1529144233="1">If the keyword of the conditional section is a parameter-entity reference,
the parameter entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be replaced by its content before the processor
decides whether to include or ignore the conditional section.</a></p><p><a name="condsec-nesting" id="condsec-nesting" data-ss1529144233="1">An example:</a></p><div class="exampleInner"><pre><a name="condsec-nesting" id="condsec-nesting" data-ss1529144233="1">&lt;!ENTITY % draft 'INCLUDE' &gt;
&lt;!ENTITY % final 'IGNORE' &gt;

&lt;![%draft;[
&lt;!ELEMENT book (comments*, title, body, supplements?)&gt;
]]&gt;
&lt;![%final;[
&lt;!ELEMENT book (title, body, supplements?)&gt;
]]&gt;</a></pre></div></div></div><div class="div1"><a name="condsec-nesting" id="condsec-nesting" data-ss1529144233="1">
</a><h2><a name="condsec-nesting" id="condsec-nesting" data-ss1529144233="1"></a><a name="sec-physical-struct" id="sec-physical-struct" data-ss1529144233="1">4 Physical Structures</a></h2><p><a name="sec-physical-struct" id="sec-physical-struct" data-ss1529144233="1">
				[</a><a name="dt-entity" id="dt-entity" title="Entity" data-ss1529144233="1">Definition</a>: An XML document may consist of one
or many storage units. These
are called <b>entities</b>; they all have <b>content</b> and are
all (except for the <a title="Document Entity" href="#dt-docent" data-ss1529144233="1">document entity</a> and
the <a title="Document Type Declaration" href="#dt-doctype" data-ss1529144233="1">external DTD subset</a>) identified by
entity <b>name</b>.] Each XML document has one entity
called the <a title="Document Entity" href="#dt-docent" data-ss1529144233="1">document entity</a>, which serves
as the starting point for the <a title="XML Processor" href="#dt-xml-proc" data-ss1529144233="1">XML processor</a>
and may contain the whole document.</p><p>Entities may be either parsed or unparsed. [<a name="dt-parsedent" id="dt-parsedent" title="Text Entity" data-ss1529144233="1">Definition</a>: The contents of a <b>parsed
entity</b> are referred to as its <a title="Replacement Text" href="#dt-repltext" data-ss1529144233="1">replacement
text</a>; this <a title="Text" href="#dt-text" data-ss1529144233="1">text</a> is considered an
integral part of the document.]
			</p><p>
				[<a name="dt-unparsed" id="dt-unparsed" title="Unparsed Entity" data-ss1529144233="1">Definition</a>: An <b>unparsed entity</b>
is a resource whose contents may or may not be <a title="Text" href="#dt-text" data-ss1529144233="1">text</a>,
and if text, may
be other than XML. Each unparsed entity has an associated <a title="Notation" href="#dt-notation" data-ss1529144233="1">notation</a>, identified by name. Beyond a requirement
that an XML processor make the identifiers for the entity and notation available
to the application, XML places no constraints on the contents of unparsed
entities.]
			</p><p>Parsed entities are invoked by name using entity references; unparsed entities
by 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" data-ss1529144233="1">Definition</a>: 
					<b>General entities</b>
are entities for use within the document content. In this specification, general
entities are sometimes referred to with the unqualified term <em>entity</em>
when this leads to no ambiguity.]
				[<a name="dt-PE" id="dt-PE" title="Parameter entity" data-ss1529144233="1">Definition</a>: 
					<b>Parameter
entities</b> are parsed entities for use within the DTD.]
These two types of entities use different forms of reference and are recognized
in different contexts. Furthermore, they occupy different namespaces; a parameter
entity and a general entity with the same name are two distinct entities.</p><div class="div2">
<h3><a name="sec-references" id="sec-references" data-ss1529144233="1">4.1 Character and Entity References</a></h3><p><a name="sec-references" id="sec-references" data-ss1529144233="1">
					[</a><a name="dt-charref" id="dt-charref" title="Character Reference" data-ss1529144233="1">Definition</a>:  A <b>character
reference</b> refers to a specific character in the ISO/IEC 10646 character
set, for example one not directly accessible from available input devices.]
				</p>
<h5><a name="d0e3895" id="d0e3895" data-ss1529144233="1">Character Reference</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-CharRef" id="NT-CharRef" data-ss1529144233="1">[66]&nbsp;&nbsp;&nbsp;</a></td><td><code>CharRef</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&amp;#' [0-9]+ ';' </code></td></tr><tr valign="baseline"><td></td><td></td><td></td><td><code>| '&amp;#x' [0-9a-fA-F]+ ';'</code></td><td><a href="#wf-Legalchar" data-ss1529144233="1">[WFC: Legal Character]</a></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="wf-Legalchar" id="wf-Legalchar" data-ss1529144233="1"><b>Well-formedness constraint: Legal Character</b></a></p><p><a name="wf-Legalchar" id="wf-Legalchar" data-ss1529144233="1">Characters referred
to using character references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> match the production for </a><a href="#NT-Char" data-ss1529144233="1">Char</a>.</p></div><p>If the character reference begins with "
						<code>&amp;#x</code>
					",
the digits and letters up to the terminating <code>;</code> provide a hexadecimal
representation of the character's code point in ISO/IEC 10646. If it begins
just with "
						<code>&amp;#</code>
					", the digits up to the terminating <code>;</code>
provide a decimal representation of the character's code point.</p><p>
					[<a name="dt-entref" id="dt-entref" title="Entity Reference" data-ss1529144233="1">Definition</a>: An <b>entity reference</b>
refers to the content of a named entity.]
					[<a name="dt-GERef" id="dt-GERef" title="General Entity Reference" data-ss1529144233="1">Definition</a>: References to parsed general entities use
ampersand (<code>&amp;</code>) and semicolon (<code>;</code>) as delimiters.]
					[<a name="dt-PERef" id="dt-PERef" title="Parameter-entity reference" data-ss1529144233="1">Definition</a>: 
						<b>Parameter-entity references</b>
use percent-sign (<code>%</code>) and semicolon (<code>;</code>) as delimiters.]
				</p>
<h5><a name="d0e3966" id="d0e3966" data-ss1529144233="1">Entity Reference</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-Reference" id="NT-Reference" data-ss1529144233="1">[67]&nbsp;&nbsp;&nbsp;</a></td><td><code>Reference</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
							<a href="#NT-EntityRef" data-ss1529144233="1">EntityRef</a> | <a href="#NT-CharRef" data-ss1529144233="1">CharRef</a>
						</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-EntityRef" id="NT-EntityRef" data-ss1529144233="1">[68]&nbsp;&nbsp;&nbsp;</a></td><td><code>EntityRef</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&amp;' <a href="#NT-Name" data-ss1529144233="1">Name</a> ';'</code></td><td><a href="#wf-entdeclared" data-ss1529144233="1">[WFC: Entity Declared]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#vc-entdeclared" data-ss1529144233="1">[VC: Entity Declared]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#textent" data-ss1529144233="1">[WFC: Parsed Entity]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#norecursion" data-ss1529144233="1">[WFC: No Recursion]</a></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-PEReference" id="NT-PEReference" data-ss1529144233="1">[69]&nbsp;&nbsp;&nbsp;</a></td><td><code>PEReference</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'%' <a href="#NT-Name" data-ss1529144233="1">Name</a> ';'</code></td><td><a href="#vc-entdeclared" data-ss1529144233="1">[VC: Entity Declared]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#norecursion" data-ss1529144233="1">[WFC: No Recursion]</a></td></tr><tr valign="baseline"><td></td><td></td><td></td><td></td><td><a href="#indtd" data-ss1529144233="1">[WFC: In DTD]</a></td></tr></tbody></table><div class="constraint"><p class="prefix"><a name="wf-entdeclared" id="wf-entdeclared" data-ss1529144233="1"><b>Well-formedness constraint: Entity Declared</b></a></p><p><a name="wf-entdeclared" id="wf-entdeclared" data-ss1529144233="1">In a document
without any DTD, a document with only an internal DTD subset which contains
no parameter entity references, or a document with "
							<code>standalone='yes'</code>
						", for
an entity reference that does not occur within the external subset or a parameter
entity, the </a><a href="#NT-Name" data-ss1529144233="1">Name</a> given in the entity reference <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
						<a title="match" href="#dt-match" data-ss1529144233="1">match</a> that in an <a href="#sec-entity-decl" data-ss1529144233="1"><cite>entity
declaration</cite></a> that does not occur within the external subset or a
parameter entity, except that well-formed documents need not declare
any of the following entities: <code>amp</code>,
<code>lt</code>,
<code>gt</code>,
<code>apos</code>,
<code>quot</code>. The
declaration of a general entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> precede any reference to it which appears
in a default value in an attribute-list declaration.</p><p>Note that non-validating processors are <a href="#include-if-valid" data-ss1529144233="1"><cite>not
obligated to</cite></a> read and process entity declarations occurring in parameter entities or in
the external subset; for such documents,
the rule that an entity must be declared is a well-formedness constraint only
if <a href="#sec-rmd" data-ss1529144233="1"><cite>standalone='yes'</cite></a>.</p></div><div class="constraint"><p class="prefix"><a name="vc-entdeclared" id="vc-entdeclared" data-ss1529144233="1"><b>Validity constraint: Entity Declared</b></a></p><p><a name="vc-entdeclared" id="vc-entdeclared" data-ss1529144233="1">In a document with an external subset or parameter  entity references<span>,
						if the document is not standalone (either "<code>standalone='no'</code>"
						is specified or there is no standalone declaration), then</span>
the </a><a href="#NT-Name" data-ss1529144233="1">Name</a> given in the entity reference <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
						<a title="match" href="#dt-match" data-ss1529144233="1">match</a> that in an <a href="#sec-entity-decl" data-ss1529144233="1"><cite>entity
declaration</cite></a>. For interoperability, valid documents <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> declare
the entities <code>amp</code>,
<code>lt</code>,
<code>gt</code>,
<code>apos</code>,
<code>quot</code>, in the form specified in <a href="#sec-predefined-ent" data-ss1529144233="1"><b>4.6 Predefined Entities</b></a>.
The declaration of a parameter entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> precede any reference to it. Similarly,
the declaration of a general entity <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> precede any attribute-list
declaration containing a default value with a direct or indirect reference
to that general entity.</p></div><div class="constraint"><p class="prefix"><a name="textent" id="textent" data-ss1529144233="1"><b>Well-formedness constraint: Parsed Entity</b></a></p><p><a name="textent" id="textent" data-ss1529144233="1">An entity reference <em class="rfc2119" title="Keyword in RFC 2119 context">MUST
NOT</em> contain the name of an </a><a title="Unparsed Entity" href="#dt-unparsed" data-ss1529144233="1">unparsed entity</a>.
Unparsed entities may be referred to only in <a title="Attribute Value" href="#dt-attrval" data-ss1529144233="1">attribute
values</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" data-ss1529144233="1"><b>Well-formedness constraint: No Recursion</b></a></p><p><a name="norecursion" id="norecursion" data-ss1529144233="1">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.</a></p></div><div class="constraint"><p class="prefix"><a name="indtd" id="indtd" data-ss1529144233="1"><b>Well-formedness constraint: In DTD</b></a></p><p><a name="indtd" id="indtd" data-ss1529144233="1">Parameter-entity references <em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear outside
 the </a><a title="Document Type Declaration" href="#dt-doctype" data-ss1529144233="1">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.
This document was prepared on &amp;docdate; and
is 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;
&lt;!ENTITY % ISOLat2
         SYSTEM "http://www.xml.com/iso/isolat2-xml.entities" &gt;
&lt;!-- ... now reference it. --&gt;
%ISOLat2;</pre></div></div><div class="div2">
<h3><a name="sec-entity-decl" id="sec-entity-decl" data-ss1529144233="1">4.2 Entity Declarations</a></h3><p><a name="sec-entity-decl" id="sec-entity-decl" data-ss1529144233="1">
					[</a><a name="dt-entdecl" id="dt-entdecl" title="entity declaration" data-ss1529144233="1">Definition</a>:  Entities are declared
thus:]
				</p>
<h5><a name="d0e4163" id="d0e4163" data-ss1529144233="1">Entity Declaration</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EntityDecl" id="NT-EntityDecl" data-ss1529144233="1">[70]&nbsp;&nbsp;&nbsp;</a></td><td><code>EntityDecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-GEDecl" data-ss1529144233="1">GEDecl</a>
								 | <a href="#NT-PEDecl" data-ss1529144233="1">PEDecl</a>
							</code></td></tr><tr valign="baseline"><td><a name="NT-GEDecl" id="NT-GEDecl" data-ss1529144233="1">[71]&nbsp;&nbsp;&nbsp;</a></td><td><code>GEDecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;!ENTITY' <a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-Name" data-ss1529144233="1">Name</a>
								<a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-EntityDef" data-ss1529144233="1">EntityDef</a>
								<a href="#NT-S" data-ss1529144233="1">S</a>?
'&gt;'</code></td></tr><tr valign="baseline"><td><a name="NT-PEDecl" id="NT-PEDecl" data-ss1529144233="1">[72]&nbsp;&nbsp;&nbsp;</a></td><td><code>PEDecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;!ENTITY' <a href="#NT-S" data-ss1529144233="1">S</a> '%' <a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-Name" data-ss1529144233="1">Name</a>
								<a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-PEDef" data-ss1529144233="1">PEDef</a>
								<a href="#NT-S" data-ss1529144233="1">S</a>? '&gt;'</code></td></tr><tr valign="baseline"><td><a name="NT-EntityDef" id="NT-EntityDef" data-ss1529144233="1">[73]&nbsp;&nbsp;&nbsp;</a></td><td><code>EntityDef</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-EntityValue" data-ss1529144233="1">EntityValue</a>
								| (<a href="#NT-ExternalID" data-ss1529144233="1">ExternalID</a>
								<a href="#NT-NDataDecl" data-ss1529144233="1">NDataDecl</a>?)</code></td></tr><tr valign="baseline"><td><a name="NT-PEDef" id="NT-PEDef" data-ss1529144233="1">[74]&nbsp;&nbsp;&nbsp;</a></td><td><code>PEDef</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-EntityValue" data-ss1529144233="1">EntityValue</a> | <a href="#NT-ExternalID" data-ss1529144233="1">ExternalID</a>
							</code></td></tr></tbody></table><p><a name="d0e4163" id="d0e4163" data-ss1529144233="1">The </a><a href="#NT-Name" data-ss1529144233="1">Name</a> identifies the entity in an <a title="Entity Reference" href="#dt-entref" data-ss1529144233="1">entity
reference</a> or, in the case of an unparsed entity, in the value of
an <b>ENTITY</b> or <b>ENTITIES</b> attribute. If the same entity is declared
more than once, the first declaration encountered is binding; at user option,
an 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" data-ss1529144233="1">4.2.1 Internal Entities</a></h4><p><a name="sec-internal-ent" id="sec-internal-ent" data-ss1529144233="1">
						[</a><a name="dt-internent" id="dt-internent" title="Internal Entity Replacement Text" data-ss1529144233="1">Definition</a>: If the
entity definition is an <a href="#NT-EntityValue" data-ss1529144233="1">EntityValue</a>, the defined
entity is called an <b>internal entity</b>. There is no separate physical
storage object, and the content of the entity is given in the declaration.]
Note that some processing of entity and character references in the <a title="Literal Entity Value" href="#dt-litentval" data-ss1529144233="1">literal entity value</a> may be required to produce
the correct <a title="Replacement Text" href="#dt-repltext" data-ss1529144233="1">replacement text</a>: see <a href="#intern-replacement" data-ss1529144233="1"><b>4.5 Construction of Entity Replacement Text</b></a>.</p><p>An internal entity is a <a title="Text Entity" href="#dt-parsedent" data-ss1529144233="1">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
 specification."&gt;</pre></div></div><div class="div3">
<h4><a name="sec-external-ent" id="sec-external-ent" data-ss1529144233="1">4.2.2 External Entities</a></h4><p><a name="sec-external-ent" id="sec-external-ent" data-ss1529144233="1">
						[</a><a name="dt-extent" id="dt-extent" title="External Entity" data-ss1529144233="1">Definition</a>: If the entity is not internal,
it is an <b>external entity</b>, declared as follows:]
					</p>
<h5><a name="d0e4313" id="d0e4313" data-ss1529144233="1">External Entity Declaration</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-ExternalID" id="NT-ExternalID" data-ss1529144233="1">[75]&nbsp;&nbsp;&nbsp;</a></td><td><code>ExternalID</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'SYSTEM' <a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-SystemLiteral" data-ss1529144233="1">SystemLiteral</a>
							</code></td></tr><tr valign="baseline"><td></td><td></td><td></td><td><code>| 'PUBLIC' <a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-PubidLiteral" data-ss1529144233="1">PubidLiteral</a>
								<a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-SystemLiteral" data-ss1529144233="1">SystemLiteral</a>
							</code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-NDataDecl" id="NT-NDataDecl" data-ss1529144233="1">[76]&nbsp;&nbsp;&nbsp;</a></td><td><code>NDataDecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-S" data-ss1529144233="1">S</a> 'NDATA' <a href="#NT-S" data-ss1529144233="1">S</a>
								<a href="#NT-Name" data-ss1529144233="1">Name</a>
							</code></td><td><a href="#not-declared" data-ss1529144233="1">[VC: Notation Declared]</a></td></tr></tbody></table><p><a name="d0e4313" id="d0e4313" data-ss1529144233="1">If the </a><a href="#NT-NDataDecl" data-ss1529144233="1">NDataDecl</a> is present, this is a general <a title="Unparsed Entity" href="#dt-unparsed" data-ss1529144233="1">unparsed entity</a>; otherwise it is a parsed entity.</p><div class="constraint"><p class="prefix"><a name="not-declared" id="not-declared" data-ss1529144233="1"><b>Validity constraint: Notation Declared</b></a></p><p><a name="not-declared" id="not-declared" data-ss1529144233="1">The </a><a href="#NT-Name" data-ss1529144233="1">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" data-ss1529144233="1">notation</a>.</p></div><p>
						[<a name="dt-sysid" id="dt-sysid" title="System Identifier" data-ss1529144233="1">Definition</a>: The <a href="#NT-SystemLiteral" data-ss1529144233="1">SystemLiteral</a> is called the entity's <b>system
identifier</b>. It is meant to be converted to a URI reference
(as defined in <a href="#rfc3986" data-ss1529144233="1">[IETF RFC 3986]</a>),
as part of the
process of dereferencing it to obtain input for the XML processor to construct the
entity's replacement text.] It is an error for a fragment identifier
(beginning with a <code>#</code> character) to be part of a system identifier.
Unless otherwise provided by information outside the scope of this specification
(e.g. a special XML element type defined by a particular DTD, or a processing
instruction defined by a particular application specification), relative URIs
are relative to the location of the resource within which the entity declaration
occurs. This is defined to
be the external entity containing the '&lt;' which starts the declaration, at the
point when it is parsed as a declaration.
A URI might thus be relative to the <a title="Document Entity" href="#dt-docent" data-ss1529144233="1">document
entity</a>, to the entity containing the <a title="Document Type Declaration" href="#dt-doctype" data-ss1529144233="1">external
DTD subset</a>, or to some other <a title="External Entity" href="#dt-extent" data-ss1529144233="1">external parameter
entity</a>. Attempts to
retrieve the resource identified by a URI may be redirected at the parser
level (for example, in an entity resolver) or below (at the protocol level,
for example, via an HTTP <code>Location:</code> header). In the absence of additional
information outside the scope of this specification within the resource,
the base URI of a resource is always the URI of the actual resource returned.
In other words, it is the URI of the resource retrieved after all redirection
has occurred.</p><p>System
identifiers (and other XML strings meant to be used as URI references) may contain
characters that, according to <a href="#rfc3986" data-ss1529144233="1">[IETF RFC 3986]</a>,
must be escaped before a URI can be used to retrieve the referenced resource. The
characters to be escaped are the control characters #x0 to #x1F and #x7F (most of
which cannot appear in XML), space #x20, the delimiters '&lt;' #x3C, '&gt;' #x3E and
'"' #x22, the <em>unwise</em> characters '{' #x7B, '}' #x7D, '|' #x7C, '\' #x5C, '^' #x5E and
'`' #x60, as well as all characters above #x7F. Since escaping is not always a fully
reversible process, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be performed only when absolutely necessary and as late
as possible in a processing chain. In particular, neither the process of converting
a relative URI to an absolute one nor the process of passing a URI reference to a
process or software component responsible for dereferencing it <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> trigger escaping.
When 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 UTF-8 <span><a href="#Unicode" data-ss1529144233="1">[Unicode]</a></span>
as one or more bytes.</p></li><li><p>The resulting bytes are escaped with
the URI escaping mechanism (that is, converted to <code>%</code>
								<var>HH</var>,
where 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><div class="note"><p class="prefix"><b>Note:</b></p><p>In
 a future edition of this specification, the XML Core Working Group 
intends to replace the preceding paragraph
							and list of steps with a normative reference to an upcoming 
revision of IETF RFC 3987, which will define
							"Legacy Extended IRIs (LEIRIs)".  When this revision is 
available, it is the intent of the XML Core WG to use it to replace
							language similar to the above in any future revisions of 
XML-related specifications under its purview.</p></div><p>
						[<a name="dt-pubid" id="dt-pubid" title="Public identifier" data-ss1529144233="1">Definition</a>:  In addition to a system
identifier, an external identifier may include a <b>public identifier</b>.]
An XML processor attempting to retrieve the entity's content may use
any combination of
the public and system identifiers as well as additional information outside the
scope of this specification to try to generate an alternative URI reference.
If the processor is unable to do so, it <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> use the URI
reference specified in the system literal. Before a match is attempted,
all strings of white space in the public identifier <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be normalized to
single space characters (#x20), and leading and trailing white space <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em>
be removed.</p><p>Examples of external entity declarations:</p><div class="exampleInner"><pre>&lt;!ENTITY open-hatch
         SYSTEM "http://www.textuality.com/boilerplate/OpenHatch.xml"&gt;
&lt;!ENTITY open-hatch
         PUBLIC "-//Textuality//TEXT Standard open-hatch boilerplate//EN"
         "http://www.textuality.com/boilerplate/OpenHatch.xml"&gt;
&lt;!ENTITY hatch-pic
         SYSTEM "../grafix/OpenHatch.gif"
         NDATA gif &gt;</pre></div></div></div><div class="div2">
<h3><a name="TextEntities" id="TextEntities" data-ss1529144233="1">4.3 Parsed Entities</a></h3><div class="div3"><a name="TextEntities" id="TextEntities" data-ss1529144233="1">
</a><h4><a name="TextEntities" id="TextEntities" data-ss1529144233="1"></a><a name="sec-TextDecl" id="sec-TextDecl" data-ss1529144233="1">4.3.1 The Text Declaration</a></h4><p><a name="sec-TextDecl" id="sec-TextDecl" data-ss1529144233="1">External parsed entities <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> each begin with a <b>text declaration</b>.</a></p><a name="sec-TextDecl" id="sec-TextDecl" data-ss1529144233="1">
</a><h5><a name="sec-TextDecl" id="sec-TextDecl" data-ss1529144233="1"></a><a name="d0e4481" id="d0e4481" data-ss1529144233="1">Text Declaration</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-TextDecl" id="NT-TextDecl" data-ss1529144233="1">[77]&nbsp;&nbsp;&nbsp;</a></td><td><code>TextDecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>'&lt;?xml' <a href="#NT-VersionInfo" data-ss1529144233="1">VersionInfo</a>? <a href="#NT-EncodingDecl" data-ss1529144233="1">EncodingDecl</a>
									<a href="#NT-S" data-ss1529144233="1">S</a>? '?&gt;'</code></td></tr></tbody></table><p><a name="d0e4481" id="d0e4481" data-ss1529144233="1">The text declaration <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be provided literally, not by reference
					to a parsed entity. The text declaration
					<em class="rfc2119" title="Keyword in RFC 2119 context">MUST NOT</em> appear at any
					position other than the beginning of an external parsed entity. The text declaration
          in an external parsed entity is not considered part of its </a><a title="Replacement Text" href="#dt-repltext" data-ss1529144233="1">replacement text</a>.</p></div><div class="div3">
<h4><a name="wf-entities" id="wf-entities" data-ss1529144233="1">4.3.2 Well-Formed Parsed Entities</a></h4><p><a name="wf-entities" id="wf-entities" data-ss1529144233="1">The document entity is well-formed if it matches the production labeled </a><a href="#NT-document" data-ss1529144233="1">document</a>. An external general parsed entity is well-formed
if it matches the production labeled <a href="#NT-extParsedEnt" data-ss1529144233="1">extParsedEnt</a>. All
external parameter entities are well-formed by definition.</p><div class="note"><p class="prefix"><b>Note:</b></p><p>Only parsed entities that are referenced directly or indirectly within the document are required to be well-formed.</p></div>
<h5><a name="d0e4524" id="d0e4524" data-ss1529144233="1">Well-Formed External Parsed Entity</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-extParsedEnt" id="NT-extParsedEnt" data-ss1529144233="1">[78]&nbsp;&nbsp;&nbsp;</a></td><td><code>extParsedEnt</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-TextDecl" data-ss1529144233="1">TextDecl</a>? <a href="#NT-content" data-ss1529144233="1">content</a>
							</code></td></tr></tbody></table><p><a name="d0e4524" id="d0e4524" data-ss1529144233="1">An internal general parsed entity is well-formed if its replacement text
matches the production labeled </a><a href="#NT-content" data-ss1529144233="1">content</a>. All internal
parameter entities are well-formed by definition.</p><p>A consequence of well-formedness in general
entities is that the logical and physical
structures in an XML document are properly nested; no <a title="Start-Tag" href="#dt-stag" data-ss1529144233="1">start-tag</a>, <a title="End Tag" href="#dt-etag" data-ss1529144233="1">end-tag</a>, <a title="Empty" href="#dt-empty" data-ss1529144233="1">empty-element tag</a>, <a title="Element" href="#dt-element" data-ss1529144233="1">element</a>, <a title="Comment" href="#dt-comment" data-ss1529144233="1">comment</a>, <a title="Processing instruction" href="#dt-pi" data-ss1529144233="1">processing instruction</a>, <a title="Character Reference" href="#dt-charref" data-ss1529144233="1">character
reference</a>, or <a title="Entity Reference" href="#dt-entref" data-ss1529144233="1">entity reference</a>
can begin in one entity and end in another.</p></div><div class="div3">
<h4><a name="charencoding" id="charencoding" data-ss1529144233="1">4.3.3 Character Encoding in Entities</a></h4><p><a name="charencoding" id="charencoding" data-ss1529144233="1">Each external parsed entity in an XML document may use a different encoding
for its characters. All XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be able to read entities in both
the UTF-8 and UTF-16 encodings. The terms "UTF-8"
and "UTF-16" in this specification do not apply to 

<span>related character encodings, including but not limited to UTF-16BE, UTF-16LE, or CESU-8.</span></a></p><p><a name="charencoding" id="charencoding" data-ss1529144233="1">Entities encoded in UTF-16 <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> and entities
encoded in UTF-8 <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> begin with the Byte Order Mark described by
Annex H of </a><a href="#ISO10646-2000" data-ss1529144233="1">[ISO/IEC 10646:2000]</a>, section
<span>16.8</span> of <a href="#Unicode" data-ss1529144233="1">[Unicode]</a>
(the ZERO WIDTH NO-BREAK SPACE character, #xFEFF). This is an encoding signature,
not part of either the markup or the character data of the XML document. XML
processors <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be able to use this character to differentiate between UTF-8
and UTF-16 encoded documents.</p><p>If the replacement text of an external entity is to
						begin with the character U+FEFF, and no text declaration
						is present, then a Byte Order Mark MUST be present,
						whether the entity is encoded in UTF-8 or UTF-16.</p><p>Although an XML processor is required to read only entities in the UTF-8
and UTF-16 encodings, it is recognized that other encodings are used around
the world, and it may be desired for XML processors to read entities that
use them. In
the absence of external character encoding information (such as MIME headers),
parsed entities which are stored in an encoding other than UTF-8 or UTF-16
<em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> begin with a text declaration (see <a href="#sec-TextDecl" data-ss1529144233="1"><b>4.3.1 The Text Declaration</b></a>) containing
an encoding declaration:</p>
<h5><a name="d0e4623" id="d0e4623" data-ss1529144233="1">Encoding Declaration</a></h5><table class="scrap" summary="Scrap"><tbody><tr valign="baseline"><td><a name="NT-EncodingDecl" id="NT-EncodingDecl" data-ss1529144233="1">[80]&nbsp;&nbsp;&nbsp;</a></td><td><code>EncodingDecl</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>
								<a href="#NT-S" data-ss1529144233="1">S</a> 'encoding' <a href="#NT-Eq" data-ss1529144233="1">Eq</a>
('"' <a href="#NT-EncName" data-ss1529144233="1">EncName</a> '"' | "'" <a href="#NT-EncName" data-ss1529144233="1">EncName</a>
"'" ) </code></td></tr></tbody><tbody><tr valign="baseline"><td><a name="NT-EncName" id="NT-EncName" data-ss1529144233="1">[81]&nbsp;&nbsp;&nbsp;</a></td><td><code>EncName</code></td><td>&nbsp;&nbsp;&nbsp;::=&nbsp;&nbsp;&nbsp;</td><td><code>[A-Za-z] ([A-Za-z0-9._] | '-')*</code></td><td><i>/* Encoding
name contains only Latin characters */</i></td></tr></tbody></table><p><a name="d0e4623" id="d0e4623" data-ss1529144233="1">In the </a><a title="Document Entity" href="#dt-docent" data-ss1529144233="1">document entity</a>, the encoding
declaration is part of the <a title="XML Declaration" href="#dt-xmldecl" data-ss1529144233="1">XML declaration</a>.
The <a href="#NT-EncName" data-ss1529144233="1">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>
						",
"
							<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
for the various encodings and transformations of Unicode / ISO/IEC 10646,
the values "
							<code>ISO-8859-1</code>
						", "
							<code>ISO-8859-2</code>
						",
... "
							<code>ISO-8859-</code>
							<var>n</var>
						" (where <var>n</var>
is the part number) <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be used for the parts of ISO 8859, and
the values "
							<code>ISO-2022-JP</code>
						", "
							<code>Shift_JIS</code>
						",
and "
							<code>EUC-JP</code>
						"
						<em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> be used for the various encoded
forms of JIS X-0208-1997. It
is <em class="rfc2119" title="Keyword in RFC 2119 context">RECOMMENDED</em> that character encodings registered (as <em>charset</em>s)
with the Internet Assigned Numbers Authority <a href="#IANA" data-ss1529144233="1">[IANA-CHARSETS]</a>,
other than those just listed, be referred to using their registered names;
other encodings <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> use names starting with an "x-" prefix.
XML processors <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> match character encoding names in a case-insensitive
way and <em class="rfc2119" title="Keyword in RFC 2119 context">SHOULD</em> either interpret an IANA-registered name as the encoding registered
at IANA for that name or treat it as unknown (processors are, of course, not
required to support all IANA-registered encodings).</p><p>In the absence of information provided by an external transport protocol
(e.g. HTTP or MIME), it is a <a title="Fatal Error" href="#dt-fatal" data-ss1529144233="1">fatal error</a> for
an entity including an encoding declaration to be presented to the XML processor
in an encoding other than that named in the declaration, or for an entity which
begins with neither a Byte Order Mark
nor an encoding declaration to use an encoding other than UTF-8. Note that
since ASCII is a subset of UTF-8, ordinary ASCII entities do not strictly
need an encoding declaration.</p><p>It is a <a title="Fatal Error" href="#dt-fatal" data-ss1529144233="1">fatal error</a> for a <a href="#NT-TextDecl" data-ss1529144233="1">TextDecl</a> to occur other
than at the beginning of an external entity.</p><p>It is a <a title="Fatal Error" href="#dt-fatal" data-ss1529144233="1">fatal error</a> when an XML processor
encounters an entity with an encoding that it is unable to process. It
is a <a title="Fatal Error" href="#dt-fatal" data-ss1529144233="1">fatal error</a> if an XML entity is determined (via default, encoding declaration,
or higher-level protocol) to be in a certain encoding but contains byte
sequences that are not legal in that encoding. Specifically, it is a
fatal error if an entity encoded in UTF-8 contains any <span>ill-formed</span> code unit sequences,
as defined in <span>section 3.9 of </span> Unicode <span><a href="#Unicode" data-ss1529144233="1">[Unicode]</a></span>. Unless an encoding
is determined by a higher-level protocol, it is also a <a title="Fatal Error" href="#dt-fatal" data-ss1529144233="1">fatal error</a> if an XML entity
contains 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;
&lt;?xml encoding='EUC-JP'?&gt;</pre></div></div></div><div class="div2">
<h3><a name="entproc" id="entproc" data-ss1529144233="1">4.4 XML Processor Treatment of Entities and References</a></h3><p><a name="entproc" id="entproc" data-ss1529144233="1">The table below summarizes the contexts in which character references,
entity references, and invocations of unparsed entities might appear and the
<em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> behavior of an </a><a title="XML Processor" href="#dt-xml-proc" data-ss1529144233="1">XML processor</a>
in 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" data-ss1529144233="1">start-tag</a>
and before the <a title="End Tag" href="#dt-etag" data-ss1529144233="1">end-tag</a> of an element; corresponds
to the nonterminal <a href="#NT-content" data-ss1529144233="1">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" data-ss1529144233="1">start-tag</a>,
or a default value in an <a title="Attribute-List Declaration" href="#dt-attdecl" data-ss1529144233="1">attribute declaration</a>;
corresponds to the nonterminal <a href="#NT-AttValue" data-ss1529144233="1">AttValue</a>.</p></dd><dt class="label">Occurs as Attribute Value</dt><dd><p>as a <a href="#NT-Name" data-ss1529144233="1">Name</a>, not a reference, appearing either as
the value of an attribute which has been declared as type <b>ENTITY</b>,
or as one of the space-separated tokens in the value of an attribute which
has 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" data-ss1529144233="1">literal
entity value</a> in the entity's declaration; corresponds to the nonterminal <a href="#NT-EntityValue" data-ss1529144233="1">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" data-ss1529144233="1">DTD</a>, but outside of an <a href="#NT-EntityValue" data-ss1529144233="1">EntityValue</a>, <a href="#NT-AttValue" data-ss1529144233="1">AttValue</a>, <a href="#NT-PI" data-ss1529144233="1">PI</a>, <a href="#NT-Comment" data-ss1529144233="1">Comment</a>, <a href="#NT-SystemLiteral" data-ss1529144233="1">SystemLiteral</a>, <a href="#NT-PubidLiteral" data-ss1529144233="1">PubidLiteral</a>,
or the contents of an ignored conditional section (see <a href="#sec-condition-sect" data-ss1529144233="1"><b>3.4 Conditional Sections</b></a>).</p><p>.</p></dd></dl><p>
				</p><table frame="border" cellpadding="7" border="1"><tbody align="center"><tr><td rowspan="2"></td><td colspan="4" align="center" valign="bottom">Entity
Type</td><td rowspan="2" align="center">Character</td></tr><tr align="center" valign="bottom"><td>Parameter</td><td>Internal General</td><td>External Parsed
General</td><td>Unparsed</td></tr><tr align="center" valign="middle"><td align="right">Reference
in Content</td><td>
								<a href="#not-recognized" data-ss1529144233="1"><cite>Not recognized</cite></a>
							</td><td>
								<a href="#included" data-ss1529144233="1"><cite>Included</cite></a>
							</td><td>
								<a href="#include-if-valid" data-ss1529144233="1"><cite>Included
if validating</cite></a>
							</td><td>
								<a href="#forbidden" data-ss1529144233="1"><cite>Forbidden</cite></a>
							</td><td>
								<a href="#included" data-ss1529144233="1"><cite>Included</cite></a>
							</td></tr><tr align="center" valign="middle"><td align="right">Reference in Attribute Value</td><td>
								<a href="#not-recognized" data-ss1529144233="1"><cite>Not recognized</cite></a>
							</td><td>
								<a href="#inliteral" data-ss1529144233="1"><cite>Included
in literal</cite></a>
							</td><td&