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| <title>Extensible Markup Language (XML) 1.0 (Second Edition)</title> | |
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| <body> <div class="head"><p><a href="http://www.w3.org/"><img src="http://www.w3.org/Icons/w3c_home" | |
| alt="W3C" height="48" width="72"/></a></p><h1>Extensible Markup Language (XML) | |
| 1.0 (Second Edition)</h1> | |
| <h2>W3C Recommendation 6 October 2000</h2><dl> | |
| <dt>This version:</dt> | |
| <dd><a href="http://www.w3.org/TR/2000/REC-xml-20001006">http://www.w3.org/TR/2000/REC-xml-20001006</a> | |
| (<a href="http://www.w3.org/TR/2000/REC-xml-20001006.html">XHTML</a>, <a href="http://www.w3.org/TR/2000/REC-xml-20001006.xml">XML</a>, <a | |
| href="http://www.w3.org/TR/2000/REC-xml-20001006.pdf">PDF</a>, <a href="http://www.w3.org/TR/2000/REC-xml-20001006-review.html">XHTML | |
| review version</a> with color-coded revision indicators)</dd> | |
| <dt>Latest version:</dt> | |
| <dd><a href="http://www.w3.org/TR/REC-xml">http://www.w3.org/TR/REC-xml</a></dd> | |
| <dt>Previous versions:</dt> | |
| <dd><a href="http://www.w3.org/TR/2000/WD-xml-2e-20000814"> http://www.w3.org/TR/2000/WD-xml-2e-20000814</a> </dd> | |
| <dd><a href="http://www.w3.org/TR/1998/REC-xml-19980210"> http://www.w3.org/TR/1998/REC-xml-19980210</a> </dd> | |
| <dt>Editors:</dt> | |
| <dd>Tim Bray, Textuality and Netscape <a href="mailto:tbray@textuality.com"><tbray@textuality.com></a></dd> | |
| <dd>Jean Paoli, Microsoft <a href="mailto:jeanpa@microsoft.com"><jeanpa@microsoft.com></a></dd> | |
| <dd>C. M. Sperberg-McQueen, University of Illinois at Chicago and Text Encoding | |
| Initiative <a href="mailto:cmsmcq@uic.edu"><cmsmcq@uic.edu></a> </dd> | |
| <dd>Eve Maler, Sun Microsystems, Inc. <a href="mailto:elm@east.sun.com"><eve.maler@east.sun.com></a> | |
| - Second Edition</dd> | |
| </dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2000 <a | |
| href="http://www.w3.org/"><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> | |
| (<a href="http://www.lcs.mit.edu/"><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>, <a | |
| href="http://www.inria.fr/"><abbr title="Institut National de Recherche en Informatique et Automatique" | |
| lang="fr">INRIA</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All | |
| Rights Reserved. W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a | |
| href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>, <a | |
| href="http://www.w3.org/Consortium/Legal/copyright-documents-19990405">document | |
| use</a>, and <a href="http://www.w3.org/Consortium/Legal/copyright-software-19980720">software | |
| licensing</a> rules apply.</p></div><hr class="html_compat"/><div><h2><a | |
| name="abstract">Abstract</a></h2> <p>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.</p> </div><div> | |
| <h2><a name="status">Status of this Document</a></h2> <p>This | |
| document has been reviewed by W3C Members and other interested parties and | |
| has been endorsed by the Director as a W3C Recommendation. It is a stable | |
| document and may be used as reference material or cited as a normative reference | |
| from another document. W3C's role in making the Recommendation is to draw | |
| attention to the specification and to promote its widespread deployment. This | |
| enhances the functionality and interoperability of the Web.</p> <p>This document | |
| 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 W3C XML Activity, details of which can be found at <a href="http://www.w3.org/XML/">http://www.w3.org/XML</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/XML/#trans">http://www.w3.org/XML/#trans</a>. | |
| A list of current W3C Recommendations and other technical documents can be | |
| found at <a href="http://www.w3.org/TR/">http://www.w3.org/TR</a>.</p> <p>This | |
| second edition is <em>not</em> a new version of XML (first published 10 February 1998); it merely incorporates | |
| the changes dictated by the first-edition errata (available at <a href="http://www.w3.org/XML/xml-19980210-errata">http://www.w3.org/XML/xml-19980210-errata</a | |
| >) as a convenience to readers. The errata list for this second edition is | |
| available at <a href="http://www.w3.org/XML/xml-V10-2e-errata">http://www.w3.org/XML/xml-V10-2e-errata</a>.</p> <p>Please | |
| report errors in this document to <a href="mailto:xml-editor@w3.org">xml-editor@w3.org</a>; <a | |
| href="http://lists.w3.org/Archives/Public/xml-editor">archives</a> are available.</p> <div | |
| class="note"><p class="prefix"><b>Note:</b></p> <p>C. M. Sperberg-McQueen's | |
| affiliation has changed since the publication of the first edition. He is | |
| now at the World Wide Web Consortium, and can be contacted at <a href="mailto:cmsmcq@w3.org">cmsmcq@w3.org</a>.</p> </div> </div> <div | |
| class="toc"><h2><a name="contents">Table of Contents</a></h2><p class="toc">1 <a | |
| href="#sec-intro">Introduction</a><br class="html_compat"/> 1.1 <a | |
| href="#sec-origin-goals">Origin and Goals</a><br class="html_compat"/> 1.2 <a | |
| href="#sec-terminology">Terminology</a><br class="html_compat"/>2 <a href="#sec-documents">Documents</a><br | |
| class="html_compat"/> 2.1 <a href="#sec-well-formed">Well-Formed | |
| XML Documents</a><br class="html_compat"/> 2.2 <a href="#charsets">Characters</a><br | |
| class="html_compat"/> 2.3 <a href="#sec-common-syn">Common | |
| Syntactic Constructs</a><br class="html_compat"/> 2.4 <a | |
| href="#syntax">Character Data and Markup</a><br class="html_compat"/> 2.5 <a | |
| href="#sec-comments">Comments</a><br class="html_compat"/> 2.6 <a | |
| href="#sec-pi">Processing Instructions</a><br class="html_compat"/> 2.7 <a | |
| href="#sec-cdata-sect">CDATA Sections</a><br class="html_compat"/> 2.8 <a | |
| href="#sec-prolog-dtd">Prolog and Document Type Declaration</a><br class="html_compat"/> 2.9 <a | |
| href="#sec-rmd">Standalone Document Declaration</a><br class="html_compat"/> 2.10 <a | |
| href="#sec-white-space">White Space Handling</a><br class="html_compat"/> 2.11 <a | |
| href="#sec-line-ends">End-of-Line Handling</a><br class="html_compat"/> 2.12 <a | |
| href="#sec-lang-tag">Language Identification</a><br class="html_compat"/>3 <a | |
| href="#sec-logical-struct">Logical Structures</a><br class="html_compat"/> 3.1 <a | |
| href="#sec-starttags">Start-Tags, End-Tags, and Empty-Element Tags</a><br | |
| class="html_compat"/> 3.2 <a href="#elemdecls">Element | |
| Type Declarations</a><br class="html_compat"/> 3.2.1 <a | |
| href="#sec-element-content">Element Content</a><br class="html_compat"/> 3.2.2 <a | |
| href="#sec-mixed-content">Mixed Content</a><br class="html_compat"/> 3.3 <a | |
| href="#attdecls">Attribute-List Declarations</a><br class="html_compat"/> 3.3.1 <a | |
| href="#sec-attribute-types">Attribute Types</a><br class="html_compat"/> 3.3.2 <a | |
| href="#sec-attr-defaults">Attribute Defaults</a><br class="html_compat"/> 3.3.3 <a | |
| href="#AVNormalize">Attribute-Value Normalization</a><br class="html_compat"/> 3.4 <a | |
| href="#sec-condition-sect">Conditional Sections</a><br class="html_compat"/>4 <a | |
| href="#sec-physical-struct">Physical Structures</a><br class="html_compat"/> 4.1 <a | |
| href="#sec-references">Character and Entity References</a><br class="html_compat"/> 4.2 <a | |
| href="#sec-entity-decl">Entity Declarations</a><br class="html_compat"/> 4.2.1 <a | |
| href="#sec-internal-ent">Internal Entities</a><br class="html_compat"/> 4.2.2 <a | |
| href="#sec-external-ent">External Entities</a><br class="html_compat"/> 4.3 <a | |
| href="#TextEntities">Parsed Entities</a><br class="html_compat"/> 4.3.1 <a | |
| href="#sec-TextDecl">The Text Declaration</a><br class="html_compat"/> 4.3.2 <a | |
| href="#wf-entities">Well-Formed Parsed Entities</a><br class="html_compat"/> 4.3.3 <a | |
| href="#charencoding">Character Encoding in Entities</a><br class="html_compat"/> 4.4 <a | |
| href="#entproc">XML Processor Treatment of Entities and References</a><br | |
| class="html_compat"/> 4.4.1 <a | |
| href="#not-recognized">Not Recognized</a><br class="html_compat"/> 4.4.2 <a | |
| href="#included">Included</a><br class="html_compat"/> 4.4.3 <a | |
| href="#include-if-valid">Included If Validating</a><br class="html_compat"/> 4.4.4 <a | |
| href="#forbidden">Forbidden</a><br class="html_compat"/> 4.4.5 <a | |
| href="#inliteral">Included in Literal</a><br class="html_compat"/> 4.4.6 <a | |
| href="#notify">Notify</a><br class="html_compat"/> 4.4.7 <a | |
| href="#bypass">Bypassed</a><br class="html_compat"/> 4.4.8 <a | |
| href="#as-PE">Included as PE</a><br class="html_compat"/> 4.5 <a | |
| href="#intern-replacement">Construction of Internal Entity Replacement Text</a><br | |
| class="html_compat"/> 4.6 <a href="#sec-predefined-ent">Predefined | |
| Entities</a><br class="html_compat"/> 4.7 <a href="#Notations">Notation | |
| Declarations</a><br class="html_compat"/> 4.8 <a href="#sec-doc-entity">Document | |
| Entity</a><br class="html_compat"/>5 <a href="#sec-conformance">Conformance</a><br | |
| class="html_compat"/> 5.1 <a href="#proc-types">Validating | |
| and Non-Validating Processors</a><br class="html_compat"/> 5.2 <a | |
| href="#safe-behavior">Using XML Processors</a><br class="html_compat"/>6 <a | |
| href="#sec-notation">Notation</a><br class="html_compat"/></p><h3>Appendices</h3><p | |
| class="toc">A <a href="#sec-bibliography">References</a><br class="html_compat"/> A.1 <a | |
| href="#sec-existing-stds">Normative References</a><br class="html_compat"/> A.2 <a | |
| href="#null">Other References</a><br class="html_compat"/>B <a href="#CharClasses">Character | |
| Classes</a><br class="html_compat"/>C <a href="#sec-xml-and-sgml">XML and | |
| SGML</a> (Non-Normative)<br class="html_compat"/>D <a href="#sec-entexpand">Expansion | |
| of Entity and Character References</a> (Non-Normative)<br class="html_compat"/>E <a | |
| href="#determinism">Deterministic Content Models</a> (Non-Normative)<br class="html_compat"/>F <a | |
| href="#sec-guessing">Autodetection of Character Encodings</a> (Non-Normative)<br | |
| class="html_compat"/> F.1 <a href="#sec-guessing-no-ext-info">Detection | |
| Without External Encoding Information</a><br class="html_compat"/> F.2 <a | |
| href="#sec-guessing-with-ext-info">Priorities in the Presence of External | |
| Encoding Information</a><br class="html_compat"/>G <a href="#sec-xml-wg">W3C | |
| XML Working Group</a> (Non-Normative)<br class="html_compat"/>H <a href="#sec-core-wg">W3C | |
| XML Core Group</a> (Non-Normative)<br class="html_compat"/>I <a href="#b4d250b6c21">Production | |
| Notes</a> (Non-Normative)<br class="html_compat"/></p></div><hr class="html_compat"/><div | |
| class="body"> <div class="div1"> <h2><a name="sec-intro"></a>1 Introduction</h2> <p>Extensible | |
| Markup Language, abbreviated XML, describes a class of data objects called <a | |
| title="XML Document" href="#dt-xml-doc">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">[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">entities</a>, which contain either parsed | |
| or unparsed data. Parsed data is made up of <a title="Character" href="#dt-character">characters</a>, | |
| some of which form <a title="Character Data" href="#dt-chardata">character | |
| data</a>, and some of which form <a title="Markup" href="#dt-markup">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 title="XML Processor" name="dt-xml-proc">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 title="Application" | |
| name="dt-app">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"></a>1.1 Origin and Goals</h3> <p>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 WG's contact with the W3C.</p> <p>The | |
| design goals for XML are:</p> <ol> | |
| <li><p>XML shall be straightforwardly usable over the Internet.</p></li> | |
| <li><p>XML shall support a wide variety of applications.</p></li> | |
| <li><p>XML shall be compatible with SGML.</p></li> | |
| <li><p>It shall be easy to write programs which process XML documents.</p> </li> | |
| <li><p>The number of optional features in XML is to be kept to the absolute | |
| minimum, ideally zero.</p></li> | |
| <li><p>XML documents should be human-legible and reasonably clear.</p></li> | |
| <li><p>The XML design should be prepared quickly.</p></li> | |
| <li><p>The design of XML shall be formal and concise.</p></li> | |
| <li><p>XML documents shall be easy to create.</p></li> | |
| <li><p>Terseness in XML markup is of minimal importance.</p></li> | |
| </ol> <p>This specification, together with associated standards (Unicode and | |
| ISO/IEC 10646 for characters, Internet RFC 1766 for language identification | |
| tags, ISO 639 for language name codes, and ISO 3166 for country name codes), | |
| 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"></a>1.2 Terminology</h3> <p>The | |
| terminology used to describe XML documents is defined in the body of this | |
| specification. 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">may</dt> | |
| <dd> <p>[<a title="May" name="dt-may">Definition</a>: Conforming documents | |
| and XML processors are permitted to but need not behave as described.]</p> </dd> | |
| <dt class="label">must</dt> | |
| <dd> <p>[<a title="Must" name="dt-must">Definition</a>: Conforming documents | |
| and XML processors are required to behave as described; otherwise they are | |
| in error. ]</p> </dd> | |
| <dt class="label">error</dt> | |
| <dd> <p>[<a title="Error" name="dt-error">Definition</a>: A violation of the | |
| rules of this specification; results are undefined. Conforming software may | |
| detect and report an error and may recover from it.]</p> </dd> | |
| <dt class="label">fatal error</dt> | |
| <dd> <p>[<a title="Fatal Error" name="dt-fatal">Definition</a>: An error which | |
| a conforming <a title="XML Processor" href="#dt-xml-proc">XML processor</a> | |
| must detect and report to the application. After encountering a fatal error, | |
| the processor may continue processing the data to search for further errors | |
| and may report such errors to the application. In order to support correction | |
| of errors, the processor may 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 must not continue normal | |
| processing (i.e., it must not 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 title="At user option" name="dt-atuseroption">Definition</a>: | |
| Conforming software may or must (depending on the modal verb in the sentence) | |
| behave as described; if it does, it must provide users a means to enable or | |
| disable the behavior described.]</p> </dd> | |
| <dt class="label">validity constraint</dt> | |
| <dd> <p>[<a title="Validity constraint" name="dt-vc">Definition</a>: A rule | |
| which applies to all <a title="Validity" href="#dt-valid">valid</a> XML documents. | |
| Violations of validity constraints are errors; they must, at user option, | |
| be reported by <a title="Validating Processor" href="#dt-validating">validating | |
| XML processors</a>.]</p> </dd> | |
| <dt class="label">well-formedness constraint</dt> | |
| <dd> <p>[<a title="Well-formedness constraint" name="dt-wfc">Definition</a>: | |
| A rule which applies to all <a title="Well-Formed" href="#dt-wellformed">well-formed</a> | |
| XML documents. Violations of well-formedness constraints are <a title="Fatal Error" | |
| href="#dt-fatal">fatal errors</a>.]</p> </dd> | |
| <dt class="label">match</dt> | |
| <dd> <p>[<a title="match" name="dt-match">Definition</a>: (Of strings or names:) | |
| Two strings or names being compared must be 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 <a | |
| href="#elementvalid"><b>[VC: Element Valid]</b></a>.]</p> </dd> | |
| <dt class="label">for compatibility</dt> | |
| <dd> <p>[<a title="For Compatibility" name="dt-compat">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 title="For interoperability" name="dt-interop">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"></a>2 | |
| Documents</h2> <p>[<a title="XML Document" name="dt-xml-doc">Definition</a>: | |
| A data object is an <b>XML document</b> if it is <a title="Well-Formed" href="#dt-wellformed">well-formed</a>, | |
| as defined in this specification. A well-formed XML document may in addition | |
| be <a title="Validity" href="#dt-valid">valid</a> if it meets certain further | |
| constraints.]</p> <p>Each XML document has both a logical and a physical structure. | |
| Physically, the document is composed of units called <a title="Entity" href="#dt-entity">entities</a>. | |
| An entity may <a title="Entity Reference" href="#dt-entref">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">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 must nest | |
| properly, as described in <a href="#wf-entities"><b>4.3.2 Well-Formed Parsed | |
| Entities</b></a>.</p> <div class="div2"> <h3><a name="sec-well-formed"></a>2.1 | |
| Well-Formed XML Documents</h3> <p>[<a title="Well-Formed" name="dt-wellformed">Definition</a>: | |
| A textual object is a <b>well-formed</b> XML document if:]</p> <ol> | |
| <li><p>Taken as a whole, it matches the production labeled <a href="#NT-document">document</a>.</p> </li> | |
| <li><p>It meets all the well-formedness constraints given in this specification.</p> </li> | |
| <li><p>Each of the <a title="Text Entity" href="#dt-parsedent">parsed entities</a> | |
| which is referenced directly or indirectly within the document is <a title="Well-Formed" | |
| href="#dt-wellformed">well-formed</a>.</p></li> | |
| </ol> <h5>Document</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-document"></a>[1] </td> | |
| <td><code>document</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-prolog">prolog</a> <a href="#NT-element">element</a> <a | |
| href="#NT-Misc">Misc</a>*</code></td> | |
| </tr> | |
| </tbody></table> <p>Matching the <a href="#NT-document">document</a> production | |
| implies that:</p> <ol> | |
| <li><p>It contains one or more <a title="Element" href="#dt-element">elements</a>.</p> </li> | |
| <li><p>[<a title="Root Element" name="dt-root">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">content</a> of any other | |
| element.] For all other elements, if the <a title="Start-Tag" href="#dt-stag">start-tag</a> | |
| is in the content of another element, the <a title="End Tag" href="#dt-etag">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 title="Parent/Child" name="dt-parentchild">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"></a>2.2 | |
| Characters</h3> <p>[<a title="Text" name="dt-text">Definition</a>: A parsed | |
| entity contains <b>text</b>, a sequence of <a title="Character" href="#dt-character">characters</a>, | |
| which may represent markup or character data.] [<a title="Character" name="dt-character">Definition</a>: | |
| A <b>character</b> is an atomic unit of text as specified by ISO/IEC 10646 <a | |
| href="#ISO10646">[ISO/IEC 10646]</a> (see also <a href="#ISO10646-2000">[ISO/IEC | |
| 10646-2000]</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"><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 must accept any character in the range specified for <a href="#NT-Char">Char</a>. | |
| The use of "compatibility characters", as defined in section 6.8 of <a href="#Unicode">[Unicode]</a> | |
| (see also D21 in section 3.6 of <a href="#Unicode3">[Unicode3]</a>), is discouraged.]</p> <h5>Character | |
| Range</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Char"></a>[2] </td> | |
| <td><code>Char</code></td> | |
| <td> ::= </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>The mechanism for encoding character code points into | |
| bit patterns may vary from entity to entity. All XML processors must accept | |
| the UTF-8 and UTF-16 encodings of 10646; 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"><b>4.3.3 Character Encoding in Entities</b></a>.</p> | |
| </div> <div class="div2"> <h3><a name="sec-common-syn"></a>2.3 Common Syntactic | |
| Constructs</h3> <p>This section defines some symbols used widely in the grammar.</p> <p><a | |
| href="#NT-S">S</a> (white space) consists of one or more space (#x20) characters, | |
| carriage returns, line feeds, or tabs.</p> <h5>White Space</h5><table class="scrap"> | |
| <tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-S"></a>[3] </td> | |
| <td><code>S</code></td> | |
| <td> ::= </td> | |
| <td><code>(#x20 | #x9 | #xD | #xA)+</code></td> | |
| </tr> | |
| </tbody></table> <p>Characters are classified for convenience as letters, | |
| digits, or other characters. A letter consists of an alphabetic or syllabic | |
| base character or an ideographic character. Full definitions of the specific | |
| characters in each class are given in <a href="#CharClasses"><b>B Character | |
| Classes</b></a>.</p> <p>[<a title="Name" name="dt-name">Definition</a>: A <b>Name</b> | |
| is a token beginning with a letter or one of a few punctuation characters, | |
| and continuing with letters, digits, hyphens, underscores, colons, or full | |
| stops, together known as name characters.] Names beginning with the string | |
| "<code>xml</code>", or 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">[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>An <a href="#NT-Nmtoken">Nmtoken</a> | |
| (name token) is any mixture of name characters.</p> <h5>Names and Tokens</h5><table | |
| class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-NameChar"></a>[4] </td> | |
| <td><code>NameChar</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-Letter">Letter</a> | <a href="#NT-Digit">Digit</a> | |
| | '.' | '-' | '_' | ':' | <a href="#NT-CombiningChar">CombiningChar</a> | <a | |
| href="#NT-Extender">Extender</a></code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Name"></a>[5] </td> | |
| <td><code>Name</code></td> | |
| <td> ::= </td> | |
| <td><code>(<a href="#NT-Letter">Letter</a> | '_' | ':') (<a href="#NT-NameChar">NameChar</a>)*</code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Names"></a>[6] </td> | |
| <td><code>Names</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-Name">Name</a> (<a href="#NT-S">S</a> <a href="#NT-Name">Name</a>)*</code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Nmtoken"></a>[7] </td> | |
| <td><code>Nmtoken</code></td> | |
| <td> ::= </td> | |
| <td><code>(<a href="#NT-NameChar">NameChar</a>)+</code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Nmtokens"></a>[8] </td> | |
| <td><code>Nmtokens</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-Nmtoken">Nmtoken</a> (<a href="#NT-S">S</a> <a href="#NT-Nmtoken">Nmtoken</a>)*</code></td> | |
| </tr> | |
| </tbody></table> <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">EntityValue</a>), | |
| the values of attributes (<a href="#NT-AttValue">AttValue</a>), and external | |
| identifiers (<a href="#NT-SystemLiteral">SystemLiteral</a>). Note that a <a | |
| href="#NT-SystemLiteral">SystemLiteral</a> can be parsed without scanning | |
| for markup.</p> <h5>Literals</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-EntityValue"></a>[9] </td> | |
| <td><code>EntityValue</code></td> | |
| <td> ::= </td> | |
| <td><code>'"' ([^%&"] | <a href="#NT-PEReference">PEReference</a> | <a | |
| href="#NT-Reference">Reference</a>)* '"' </code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><code>| "'" ([^%&'] | <a href="#NT-PEReference">PEReference</a> | |
| | <a href="#NT-Reference">Reference</a>)* "'"</code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-AttValue"></a>[10] </td> | |
| <td><code>AttValue</code></td> | |
| <td> ::= </td> | |
| <td><code>'"' ([^<&"] | <a href="#NT-Reference">Reference</a>)* '"' </code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><code>| "'" ([^<&'] | <a href="#NT-Reference">Reference</a>)* | |
| "'"</code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-SystemLiteral"></a>[11] </td> | |
| <td><code>SystemLiteral</code></td> | |
| <td> ::= </td> | |
| <td><code>('"' [^"]* '"') | ("'" [^']* "'") </code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-PubidLiteral"></a>[12] </td> | |
| <td><code>PubidLiteral</code></td> | |
| <td> ::= </td> | |
| <td><code>'"' <a href="#NT-PubidChar">PubidChar</a>* '"' | "'" (<a href="#NT-PubidChar">PubidChar</a> | |
| - "'")* "'"</code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-PubidChar"></a>[13] </td> | |
| <td><code>PubidChar</code></td> | |
| <td> ::= </td> | |
| <td><code>#x20 | #xD | #xA | [a-zA-Z0-9] | [-'()+,./:=?;!*#@$_%]</code></td> | |
| </tr> | |
| </tbody></table> <div class="note"><p class="prefix"><b>Note:</b></p> <p>Although | |
| the <a href="#NT-EntityValue">EntityValue</a> production allows the definition | |
| of an entity consisting of a single explicit <code><</code> in the literal | |
| (e.g., <code><!ENTITY mylt "<"></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"></a>2.4 Character | |
| Data and Markup</h3> <p><a title="Text" href="#dt-text">Text</a> consists | |
| of intermingled <a title="Character Data" href="#dt-chardata">character data</a> | |
| and markup. [<a title="Markup" name="dt-markup">Definition</a>: <b>Markup</b> | |
| takes the form of <a title="Start-Tag" href="#dt-stag">start-tags</a>, <a | |
| title="End Tag" href="#dt-etag">end-tags</a>, <a title="Empty" href="#dt-empty">empty-element | |
| tags</a>, <a title="Entity Reference" href="#dt-entref">entity references</a>, <a | |
| title="Character Reference" href="#dt-charref">character references</a>, <a | |
| title="Comment" href="#dt-comment">comments</a>, <a title="CDATA Section" | |
| href="#dt-cdsection">CDATA section</a> delimiters, <a title="Document Type Declaration" | |
| href="#dt-doctype">document type declarations</a>, <a title="Processing instruction" | |
| href="#dt-pi">processing instructions</a>, <a href="#NT-XMLDecl">XML declarations</a>, <a | |
| href="#NT-TextDecl">text declarations</a>, 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 title="Character Data" name="dt-chardata">Definition</a>: | |
| All text that is not markup constitutes the <b>character data</b> of the document.]</p> <p>The | |
| ampersand character (&) and the left angle bracket (<) may appear in | |
| their literal form <em>only</em> when used as markup delimiters, or within | |
| a <a title="Comment" href="#dt-comment">comment</a>, a <a title="Processing instruction" | |
| href="#dt-pi">processing instruction</a>, or a <a title="CDATA Section" href="#dt-cdsection">CDATA | |
| section</a>. If they are needed elsewhere, they must be <a title="escape" | |
| href="#dt-escape">escaped</a> using either <a title="Character Reference" | |
| href="#dt-charref">numeric character references</a> or the strings "<code>&amp;</code>" | |
| and "<code>&lt;</code>" respectively. The right angle bracket (>) may | |
| be represented using the string "<code>&gt;</code>", and must, <a title="For Compatibility" | |
| href="#dt-compat">for compatibility</a>, be escaped using "<code>&gt;</code>" | |
| or a character reference when it appears in the string "<code>]]></code>" | |
| in content, when that string is not marking the end of a <a title="CDATA Section" | |
| href="#dt-cdsection">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. In a CDATA section, character data is any string of characters | |
| not including the CDATA-section-close delimiter, "<code>]]></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>&apos;</code>", | |
| and the double-quote character (") as "<code>&quot;</code>".</p> <h5>Character | |
| Data</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-CharData"></a>[14] </td> | |
| <td><code>CharData</code></td> | |
| <td> ::= </td> | |
| <td><code>[^<&]* - ([^<&]* ']]>' [^<&]*)</code></td> | |
| </tr> | |
| </tbody></table> </div> <div class="div2"> <h3><a name="sec-comments"></a>2.5 | |
| Comments</h3> <p>[<a title="Comment" name="dt-comment">Definition</a>: <b>Comments</b> | |
| may appear anywhere in a document outside other <a title="Markup" href="#dt-markup">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">character data</a>; an XML processor may, but need not, | |
| make it possible for an application to retrieve the text of comments. <a title="For Compatibility" | |
| href="#dt-compat">For compatibility</a>, the string "<code>--</code>" (double-hyphen) | |
| must not occur within comments.] Parameter entity references are not recognized | |
| within comments.</p> <h5>Comments</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Comment"></a>[15] </td> | |
| <td><code>Comment</code></td> | |
| <td> ::= </td> | |
| <td><code>'<!--' ((<a href="#NT-Char">Char</a> - '-') | ('-' (<a href="#NT-Char">Char</a> | |
| - '-')))* '-->'</code></td> | |
| </tr> | |
| </tbody></table> <p>An example of a comment:</p> <table class="eg" width="100%" | |
| border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!-- declarations for <head> & <body> --></pre></td> | |
| </tr> | |
| </table> <p>Note that the grammar does not allow a comment ending in <code>---></code>. | |
| The following example is <em>not</em> well-formed.</p> <table class="eg" width="100%" | |
| border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!-- B+, B, or B---></pre></td> | |
| </tr> | |
| </table> </div> <div class="div2"> <h3><a name="sec-pi"></a>2.6 Processing | |
| Instructions</h3> <p>[<a title="Processing instruction" name="dt-pi">Definition</a>: <b>Processing | |
| instructions</b> (PIs) allow documents to contain instructions for applications.]</p> <h5>Processing | |
| Instructions</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-PI"></a>[16] </td> | |
| <td><code>PI</code></td> | |
| <td> ::= </td> | |
| <td><code>'<?' <a href="#NT-PITarget">PITarget</a> (<a href="#NT-S">S</a> | |
| (<a href="#NT-Char">Char</a>* - (<a href="#NT-Char">Char</a>* '?>' <a href="#NT-Char">Char</a>*)))? | |
| '?>'</code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-PITarget"></a>[17] </td> | |
| <td><code>PITarget</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-Name">Name</a> - (('X' | 'x') ('M' | 'm') ('L' | 'l'))</code></td> | |
| </tr> | |
| </tbody></table> <p>PIs are not part of the document's <a title="Character Data" | |
| href="#dt-chardata">character data</a>, but must be passed through to the | |
| application. The PI begins with a target (<a href="#NT-PITarget">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">Notation</a> mechanism may be | |
| used for formal declaration of PI targets. Parameter entity references are | |
| not recognized within processing instructions.</p> </div> <div class="div2"> <h3><a | |
| name="sec-cdata-sect"></a>2.7 CDATA Sections</h3> <p>[<a title="CDATA Section" | |
| name="dt-cdsection">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><![CDATA[</code>" and end with the string "<code>]]></code>":]</p> <h5>CDATA | |
| Sections</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-CDSect"></a>[18] </td> | |
| <td><code>CDSect</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-CDStart">CDStart</a> <a href="#NT-CData">CData</a> <a | |
| href="#NT-CDEnd">CDEnd</a></code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-CDStart"></a>[19] </td> | |
| <td><code>CDStart</code></td> | |
| <td> ::= </td> | |
| <td><code>'<![CDATA['</code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-CData"></a>[20] </td> | |
| <td><code>CData</code></td> | |
| <td> ::= </td> | |
| <td><code>(<a href="#NT-Char">Char</a>* - (<a href="#NT-Char">Char</a>* ']]>' <a | |
| href="#NT-Char">Char</a>*)) </code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-CDEnd"></a>[21] </td> | |
| <td><code>CDEnd</code></td> | |
| <td> ::= </td> | |
| <td><code>']]>'</code></td> | |
| </tr> | |
| </tbody></table> <p>Within a CDATA section, only the <a href="#NT-CDEnd">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>&lt;</code>" and "<code>&amp;</code>". CDATA sections cannot | |
| nest.</p> <p>An example of a CDATA section, in which "<code><greeting></code>" | |
| and "<code></greeting></code>" are recognized as <a title="Character Data" | |
| href="#dt-chardata">character data</a>, not <a title="Markup" href="#dt-markup">markup</a>:</p> <table | |
| class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><![CDATA[<greeting>Hello, world!</greeting>]]> </pre></td> | |
| </tr> | |
| </table> </div> <div class="div2"> <h3><a name="sec-prolog-dtd"></a>2.8 Prolog | |
| and Document Type Declaration</h3> <p>[<a title="XML Declaration" name="dt-xmldecl">Definition</a>: | |
| XML documents should 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">well-formed</a> but | |
| not <a title="Validity" href="#dt-valid">valid</a>:</p> <table class="eg" | |
| width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><?xml version="1.0"?> <greeting>Hello, world!</greeting> </pre></td> | |
| </tr> | |
| </table> <p>and so is this:</p> <table class="eg" width="100%" border="1" | |
| cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><greeting>Hello, world!</greeting></pre></td> | |
| </tr> | |
| </table> <p>The version number "<code>1.0</code>" should be used to indicate | |
| conformance to this version of this specification; it is an error for a document | |
| to use the value "<code>1.0</code>" if it does not conform to this version | |
| of this specification. It is the intent of the XML working group to give later | |
| versions of this specification numbers other than "<code>1.0</code>", but | |
| this intent does not indicate a commitment to produce any future versions | |
| of XML, nor if any are produced, to use any particular numbering scheme. Since | |
| future versions are not ruled out, this construct is provided as a means to | |
| allow the possibility of automatic version recognition, should it become necessary. | |
| Processors may signal an error if they receive documents labeled with versions | |
| they do not support.</p> <p>The function of the markup in an XML document | |
| is to describe its storage and logical structure and to associate attribute-value | |
| pairs with its logical structures. XML provides a mechanism, the <a title="Document Type Declaration" | |
| href="#dt-doctype">document type declaration</a>, to define constraints on | |
| the logical structure and to support the use of predefined storage units. | |
| [<a title="Validity" name="dt-valid">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 | |
| must appear before the first <a title="Element" href="#dt-element">element</a> | |
| in the document.</p> <h5>Prolog</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-prolog"></a>[22] </td> | |
| <td><code>prolog</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-XMLDecl">XMLDecl</a>? <a href="#NT-Misc">Misc</a>* | |
| (<a href="#NT-doctypedecl">doctypedecl</a> <a href="#NT-Misc">Misc</a>*)?</code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-XMLDecl"></a>[23] </td> | |
| <td><code>XMLDecl</code></td> | |
| <td> ::= </td> | |
| <td><code>'<?xml' <a href="#NT-VersionInfo">VersionInfo</a> <a href="#NT-EncodingDecl">EncodingDecl</a>? <a | |
| href="#NT-SDDecl">SDDecl</a>? <a href="#NT-S">S</a>? '?>'</code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-VersionInfo"></a>[24] </td> | |
| <td><code>VersionInfo</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-S">S</a> 'version' <a href="#NT-Eq">Eq</a> ("'" <a | |
| href="#NT-VersionNum">VersionNum</a> "'" | '"' <a href="#NT-VersionNum">VersionNum</a> | |
| '"')<i>/* */</i></code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Eq"></a>[25] </td> | |
| <td><code>Eq</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-S">S</a>? '=' <a href="#NT-S">S</a>?</code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-VersionNum"></a>[26] </td> | |
| <td><code>VersionNum</code></td> | |
| <td> ::= </td> | |
| <td><code>([a-zA-Z0-9_.:] | '-')+</code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Misc"></a>[27] </td> | |
| <td><code>Misc</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-Comment">Comment</a> | <a href="#NT-PI">PI</a> | <a | |
| href="#NT-S">S</a></code></td> | |
| </tr> | |
| </tbody></table> <p>[<a title="Document Type Declaration" name="dt-doctype">Definition</a>: | |
| The XML <b>document type declaration</b> contains or points to <a title="markup declaration" | |
| href="#dt-markupdecl">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">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 title="markup declaration" name="dt-markupdecl">Definition</a>: | |
| A <b>markup declaration</b> is an <a title="Element Type declaration" href="#dt-eldecl">element | |
| type declaration</a>, an <a title="Attribute-List Declaration" href="#dt-attdecl">attribute-list | |
| declaration</a>, an <a title="entity declaration" href="#dt-entdecl">entity | |
| declaration</a>, or a <a title="Notation Declaration" href="#dt-notdecl">notation | |
| declaration</a>.] These declarations may be contained in whole or in part | |
| within <a title="Parameter entity" href="#dt-PE">parameter entities</a>, as | |
| described in the well-formedness and validity constraints below. For further | |
| information, see <a href="#sec-physical-struct"><b>4 Physical Structures</b></a>.</p> <h5>Document | |
| Type Definition</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-doctypedecl"></a>[28] </td> | |
| <td><code>doctypedecl</code></td> | |
| <td> ::= </td> | |
| <td><code>'<!DOCTYPE' <a href="#NT-S">S</a> <a href="#NT-Name">Name</a> | |
| (<a href="#NT-S">S</a> <a href="#NT-ExternalID">ExternalID</a>)? <a href="#NT-S">S</a>? | |
| ('[' (<a href="#NT-markupdecl">markupdecl</a> | <a href="#NT-DeclSep">DeclSep</a>)* | |
| ']' <a href="#NT-S">S</a>?)? '>'</code></td> | |
| <td><a href="#vc-roottype">[VC: Root Element Type]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#ExtSubset">[WFC: External Subset]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><i>/* */</i></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-DeclSep"></a>[28a] </td> | |
| <td><code>DeclSep</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-PEReference">PEReference</a> | <a href="#NT-S">S</a></code></td> | |
| <td><a href="#PE-between-Decls">[WFC: PE Between Declarations]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><i>/* */</i></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-markupdecl"></a>[29] </td> | |
| <td><code>markupdecl</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-elementdecl">elementdecl</a> | <a href="#NT-AttlistDecl">AttlistDecl</a> | |
| | <a href="#NT-EntityDecl">EntityDecl</a> | <a href="#NT-NotationDecl">NotationDecl</a> | |
| | <a href="#NT-PI">PI</a> | <a href="#NT-Comment">Comment</a> </code></td> | |
| <td><a href="#vc-PEinMarkupDecl">[VC: Proper Declaration/PE Nesting]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#wfc-PEinInternalSubset">[WFC: PEs in Internal Subset]</a></td> | |
| </tr> | |
| </tbody></table> <p>Note that it is possible to construct a well-formed document | |
| containing a <a href="#NT-doctypedecl">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">replacement | |
| text</a> of <a title="Parameter entity" href="#dt-PE">parameter entities</a>. | |
| The productions later in this specification for individual nonterminals (<a | |
| href="#NT-elementdecl">elementdecl</a>, <a href="#NT-AttlistDecl">AttlistDecl</a>, | |
| and so on) describe the declarations <em>after</em> all the parameter entities | |
| have been <a title="Include" href="#dt-include">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"><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"></a><b>Validity | |
| constraint: Root Element Type</b></p><p>The <a href="#NT-Name">Name</a> in | |
| the document type declaration must match the element type of the <a title="Root Element" | |
| href="#dt-root">root element</a>.</p> </div> <div class="constraint"><p class="prefix"><a | |
| name="vc-PEinMarkupDecl"></a><b>Validity constraint: Proper Declaration/PE | |
| Nesting</b></p> <p>Parameter-entity <a title="Replacement Text" href="#dt-repltext">replacement | |
| text</a> must 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">markupdecl</a> above) is contained in the replacement | |
| text for a <a title="Parameter-entity reference" href="#dt-PERef">parameter-entity | |
| reference</a>, both must be contained in the same replacement text.</p> </div> <div | |
| class="constraint"><p class="prefix"><a name="wfc-PEinInternalSubset"></a><b>Well-formedness | |
| constraint: PEs in Internal Subset</b></p><p>In the internal DTD subset, <a | |
| title="Parameter-entity reference" href="#dt-PERef">parameter-entity references</a> | |
| can occur only where markup declarations can occur, not within markup declarations. | |
| (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"></a><b>Well-formedness constraint: External Subset</b></p><p>The | |
| external subset, if any, must match the production for <a href="#NT-extSubset">extSubset</a>.</p> </div> <div | |
| class="constraint"><p class="prefix"><a name="PE-between-Decls"></a><b>Well-formedness | |
| constraint: PE Between Declarations</b></p><p>The replacement text of a parameter | |
| entity reference in a <a href="#NT-DeclSep">DeclSep</a> must match the production <a | |
| href="#NT-extSubsetDecl">extSubsetDecl</a>.</p> </div> <p>Like the internal | |
| subset, the external subset and any external parameter entities referenced | |
| in a <a href="#NT-DeclSep">DeclSep</a> must consist of a series of complete | |
| markup declarations of the types allowed by the non-terminal symbol <a href="#NT-markupdecl">markupdecl</a>, | |
| interspersed with white space or <a title="Parameter-entity reference" href="#dt-PERef">parameter-entity | |
| references</a>. However, portions of 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">conditional section</a> | |
| construct; this is not allowed in the internal subset.</p> <h5>External Subset</h5><table | |
| class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-extSubset"></a>[30] </td> | |
| <td><code>extSubset</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-TextDecl">TextDecl</a>? <a href="#NT-extSubsetDecl">extSubsetDecl</a></code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-extSubsetDecl"></a>[31] </td> | |
| <td><code>extSubsetDecl</code></td> | |
| <td> ::= </td> | |
| <td><code>( <a href="#NT-markupdecl">markupdecl</a> | <a href="#NT-conditionalSect">conditionalSect</a> | |
| | <a href="#NT-DeclSep">DeclSep</a>)*</code></td> | |
| <td><i>/* */</i></td> | |
| </tr> | |
| </tbody></table> <p>The external subset and external parameter entities also | |
| differ from the internal subset in that in them, <a title="Parameter-entity reference" | |
| href="#dt-PERef">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> <table class="eg" | |
| width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><?xml version="1.0"?> <!DOCTYPE greeting SYSTEM "hello.dtd"> <greeting>Hello, world!</greeting> </pre></td> | |
| </tr> | |
| </table> <p>The <a title="System Identifier" href="#dt-sysid">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> <table class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><?xml version="1.0" encoding="UTF-8" ?> | |
| <!DOCTYPE greeting [ | |
| <!ELEMENT greeting (#PCDATA)> | |
| ]> | |
| <greeting>Hello, world!</greeting></pre></td> | |
| </tr> | |
| </table> <p>If both the external and internal subsets are used, the internal | |
| subset is 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"></a>2.9 | |
| Standalone Document Declaration</h3> <p>Markup declarations can affect the | |
| content of the document, as passed from an <a title="XML Processor" href="#dt-xml-proc">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">document | |
| entity</a> or in parameter entities. [<a title="External Markup Declaration" | |
| name="dt-extmkpdecl">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>Standalone | |
| Document Declaration</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-SDDecl"></a>[32] </td> | |
| <td><code>SDDecl</code></td> | |
| <td> ::= </td> | |
| <td><code> <a href="#NT-S">S</a> 'standalone' <a href="#NT-Eq">Eq</a> (("'" | |
| ('yes' | 'no') "'") | ('"' ('yes' | 'no') '"')) </code></td> | |
| <td><a href="#vc-check-rmd">[VC: Standalone Document Declaration]</a></td> | |
| </tr> | |
| </tbody></table> <p>In a standalone document declaration, the value "yes" | |
| indicates that there are no <a title="External Markup Declaration" href="#dt-extmkpdecl">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"></a><b>Validity | |
| constraint: Standalone Document Declaration</b></p><p>The standalone document | |
| declaration must have the value "no" if any external markup declarations contain | |
| declarations of:</p> <ul> | |
| <li><p>attributes with <a title="Attribute Default" href="#dt-default">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">references</a> to those entities | |
| appear in the document, or</p></li> | |
| <li><p>attributes with values subject to <a href="#AVNormalize"><cite>normalization</cite></a>, | |
| where the attribute appears in the document with a value which will change | |
| as a result of normalization, or</p></li> | |
| <li><p>element types with <a title="Element content" href="#dt-elemcontent">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> <table | |
| class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><?xml version="1.0" standalone='yes'?></pre></td> | |
| </tr> | |
| </table> </div> <div class="div2"> <h3><a name="sec-white-space"></a>2.10 | |
| White Space Handling</h3> <p>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.</p> <p>An <a title="XML Processor" href="#dt-xml-proc">XML | |
| processor</a> must always pass all characters in a document that are not markup | |
| through to the application. A <a title="Validating Processor" href="#dt-validating"> | |
| validating XML processor</a> must also inform the application which of these | |
| characters constitute white space appearing in <a title="Element content" | |
| href="#dt-elemcontent">element content</a>.</p> <p>A special <a title="Attribute" | |
| href="#dt-attr">attribute</a> named <code>xml:space</code> 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, must be <a title="Attribute-List Declaration" href="#dt-attdecl">declared</a> | |
| if it is used. When declared, it must be given as an <a title="Enumerated Attribute Values" | |
| href="#dt-enumerated">enumerated type</a> whose values are one or both of | |
| "default" and "preserve". For example:</p> <table class="eg" width="100%" | |
| border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ATTLIST poem xml:space (default|preserve) 'preserve'> | |
| <!-- --> | |
| <!ATTLIST pre xml:space (preserve) #FIXED 'preserve'></pre></td> | |
| </tr> | |
| </table> <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 overriden with another instance of the <code>xml:space</code> | |
| attribute.</p> <p>The <a title="Root Element" href="#dt-root">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"></a>2.11 | |
| End-of-Line Handling</h3> <p>XML <a title="Text Entity" href="#dt-parsedent">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">applications</a>, the characters | |
| passed to an application by the <a title="XML Processor" href="#dt-xml-proc">XML | |
| processor</a> must be as if the XML processor 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"></a>2.12 Language Identification</h3> <p>In document processing, | |
| it is often useful to identify the natural or formal language in which the | |
| content is written. A special <a title="Attribute" href="#dt-attr">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, must be <a title="Attribute-List Declaration" | |
| href="#dt-attdecl">declared</a> if it is used. The values of the attribute | |
| are language identifiers as defined by <a href="#RFC1766">[IETF RFC 1766]</a>, <cite>Tags | |
| for the Identification of Languages</cite>, or its successor on the IETF Standards | |
| Track.</p> <div class="note"><p class="prefix"><b>Note:</b></p> <p><a href="#RFC1766">[IETF | |
| RFC 1766]</a> tags are constructed from two-letter language codes as defined | |
| by <a href="#ISO639">[ISO 639]</a>, from two-letter country codes as defined | |
| by <a href="#ISO3166">[ISO 3166]</a>, or from language identifiers registered | |
| with the Internet Assigned Numbers Authority <a href="#IANA-LANGCODES">[IANA-LANGCODES]</a>. | |
| It is expected that the successor to <a href="#RFC1766">[IETF RFC 1766]</a> | |
| will introduce three-letter language codes for languages not presently covered | |
| by <a href="#ISO639">[ISO 639]</a>.</p> </div> <p>(Productions 33 through | |
| 38 have been removed.)</p> <p>For example:</p> <table class="eg" width="100%" | |
| border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><p xml:lang="en">The quick brown fox jumps over the lazy dog.</p> | |
| <p xml:lang="en-GB">What colour is it?</p> | |
| <p xml:lang="en-US">What color is it?</p> | |
| <sp who="Faust" desc='leise' xml:lang="de"> | |
| <l>Habe nun, ach! Philosophie,</l> | |
| <l>Juristerei, und Medizin</l> | |
| <l>und leider auch Theologie</l> | |
| <l>durchaus studiert mit heißem Bemüh'n.</l> | |
| </sp></pre></td> | |
| </tr> | |
| </table> <p>The intent declared with <code>xml:lang</code> is considered | |
| to apply to all attributes and content of the element where it is specified, | |
| unless overridden with an instance of <code>xml:lang</code> on another element | |
| within that content.</p> <p>A simple declaration for <code>xml:lang</code> | |
| might take the form</p> <table class="eg" width="100%" border="1" cellpadding="5" | |
| bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre>xml:lang NMTOKEN #IMPLIED</pre></td> | |
| </tr> | |
| </table> <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> <table | |
| class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ATTLIST poem xml:lang NMTOKEN 'fr'> | |
| <!ATTLIST gloss xml:lang NMTOKEN 'en'> | |
| <!ATTLIST note xml:lang NMTOKEN 'en'></pre></td> | |
| </tr> | |
| </table> </div> </div> <div class="div1"> <h2><a name="sec-logical-struct"></a>3 | |
| Logical Structures</h2> <p>[<a title="Element" name="dt-element">Definition</a>: | |
| Each <a title="XML Document" href="#dt-xml-doc">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">start-tags</a> and <a title="End Tag" | |
| href="#dt-etag">end-tags</a>, or, for <a title="Empty" href="#dt-empty">empty</a> | |
| elements, by an <a title="empty-element tag" href="#dt-eetag">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">name</a> | |
| and a <a title="Attribute Value" href="#dt-attrval">value</a>.</p> <h5>Element</h5><table | |
| class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-element"></a>[39] </td> | |
| <td><code>element</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-EmptyElemTag">EmptyElemTag</a></code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><code>| <a href="#NT-STag">STag</a> <a href="#NT-content">content</a> <a | |
| href="#NT-ETag">ETag</a></code></td> | |
| <td><a href="#GIMatch">[WFC: Element Type Match]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#elementvalid">[VC: Element Valid]</a></td> | |
| </tr> | |
| </tbody></table> <p>This specification does not constrain the semantics, use, | |
| or (beyond syntax) 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.</p> <div | |
| class="constraint"><p class="prefix"><a name="GIMatch"></a><b>Well-formedness | |
| constraint: Element Type Match</b></p><p>The <a href="#NT-Name">Name</a> in | |
| an element's end-tag must match the element type in the start-tag.</p> </div> <div | |
| class="constraint"><p class="prefix"><a name="elementvalid"></a><b>Validity | |
| constraint: Element Valid</b></p><p>An element is valid if there is a declaration | |
| matching <a href="#NT-elementdecl">elementdecl</a> where the <a href="#NT-Name">Name</a> | |
| matches the element type, and one of the following holds:</p> <ol> | |
| <li><p>The declaration matches <b>EMPTY</b> and the element has no <a title="Content" | |
| href="#dt-content">content</a>.</p></li> | |
| <li><p>The declaration matches <a href="#NT-children">children</a> and the | |
| sequence of <a title="Parent/Child" href="#dt-parentchild">child elements</a> | |
| belongs to the language generated by the regular expression in the content | |
| model, with optional white space (characters matching the nonterminal <a href="#NT-S">S</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 does not match the nonterminal <a href="#NT-S">S</a>, | |
| and hence cannot appear in these positions.</p></li> | |
| <li><p>The declaration matches <a href="#NT-Mixed">Mixed</a> and the content | |
| consists of <a title="Character Data" href="#dt-chardata">character data</a> | |
| and <a title="Parent/Child" href="#dt-parentchild">child elements</a> whose | |
| types match names in the content model.</p></li> | |
| <li><p>The declaration matches <b>ANY</b>, and the types of any <a title="Parent/Child" | |
| href="#dt-parentchild">child elements</a> have been declared.</p></li> | |
| </ol> </div> <div class="div2"> <h3><a name="sec-starttags"></a>3.1 Start-Tags, | |
| End-Tags, and Empty-Element Tags</h3> <p>[<a title="Start-Tag" name="dt-stag">Definition</a>: | |
| The beginning of every non-empty XML element is marked by a <b>start-tag</b>.]</p> <h5>Start-tag</h5><table | |
| class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-STag"></a>[40] </td> | |
| <td><code>STag</code></td> | |
| <td> ::= </td> | |
| <td><code>'<' <a href="#NT-Name">Name</a> (<a href="#NT-S">S</a> <a href="#NT-Attribute">Attribute</a>)* <a | |
| href="#NT-S">S</a>? '>'</code></td> | |
| <td><a href="#uniqattspec">[WFC: Unique Att Spec]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Attribute"></a>[41] </td> | |
| <td><code>Attribute</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-Name">Name</a> <a href="#NT-Eq">Eq</a> <a href="#NT-AttValue">AttValue</a></code></td> | |
| <td><a href="#ValueType">[VC: Attribute Value Type]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#NoExternalRefs">[WFC: No External Entity References]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#CleanAttrVals">[WFC: No < in Attribute Values]</a></td> | |
| </tr> | |
| </tbody></table> <p>The <a href="#NT-Name">Name</a> in the start- and end-tags | |
| gives the element's <b>type</b>. [<a title="Attribute" name="dt-attr">Definition</a>: | |
| The <a href="#NT-Name">Name</a>-<a href="#NT-AttValue">AttValue</a> pairs | |
| are referred to as the <b>attribute specifications</b> of the element], [<a | |
| title="Attribute Name" name="dt-attrname">Definition</a>: with the <a href="#NT-Name">Name</a> | |
| in each pair referred to as the <b>attribute name</b>] and [<a title="Attribute Value" | |
| name="dt-attrval">Definition</a>: the content of the <a href="#NT-AttValue">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"></a><b>Well-formedness constraint: Unique Att Spec</b></p><p>No | |
| attribute name may appear more than once in the same start-tag or empty-element | |
| tag.</p> </div> <div class="constraint"><p class="prefix"><a name="ValueType"></a><b>Validity | |
| constraint: Attribute Value Type</b></p><p>The attribute must have been declared; | |
| the value must be of the type declared for it. (For attribute types, see <a | |
| href="#attdecls"><b>3.3 Attribute-List Declarations</b></a>.)</p> </div> <div | |
| class="constraint"><p class="prefix"><a name="NoExternalRefs"></a><b>Well-formedness | |
| constraint: No External Entity References</b></p><p>Attribute values cannot | |
| contain direct or indirect entity references to external entities.</p> </div> <div | |
| class="constraint"><p class="prefix"><a name="CleanAttrVals"></a><b>Well-formedness | |
| constraint: No <code><</code> in Attribute Values</b></p> <p>The <a title="Replacement Text" | |
| href="#dt-repltext">replacement text</a> of any entity referred to directly | |
| or indirectly in an attribute value must not contain a <code><</code>.</p> </div> <p>An | |
| example of a start-tag:</p> <table class="eg" width="100%" border="1" cellpadding="5" | |
| bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><termdef id="dt-dog" term="dog"></pre></td> | |
| </tr> | |
| </table> <p>[<a title="End Tag" name="dt-etag">Definition</a>: The end of | |
| every element that begins with a start-tag must 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>End-tag</h5><table | |
| class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-ETag"></a>[42] </td> | |
| <td><code>ETag</code></td> | |
| <td> ::= </td> | |
| <td><code>'</' <a href="#NT-Name">Name</a> <a href="#NT-S">S</a>? '>'</code></td> | |
| </tr> | |
| </tbody></table> <p>An example of an end-tag:</p> <table class="eg" width="100%" | |
| border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre></termdef></pre></td> | |
| </tr> | |
| </table> <p>[<a title="Content" name="dt-content">Definition</a>: The <a title="Text" | |
| href="#dt-text">text</a> between the start-tag and end-tag is called the element's <b>content</b>:]</p> <h5>Content | |
| of Elements</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-content"></a>[43] </td> | |
| <td><code>content</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-CharData">CharData</a>? ((<a href="#NT-element">element</a> | |
| | <a href="#NT-Reference">Reference</a> | <a href="#NT-CDSect">CDSect</a> | |
| | <a href="#NT-PI">PI</a> | <a href="#NT-Comment">Comment</a>) <a href="#NT-CharData">CharData</a>?)*</code></td> | |
| <td><i>/* */</i></td> | |
| </tr> | |
| </tbody></table> <p>[<a title="Empty" name="dt-empty">Definition</a>: An element | |
| with no content 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 title="empty-element tag" name="dt-eetag">Definition</a>: An <b>empty-element | |
| tag</b> takes a special form:]</p> <h5>Tags for Empty Elements</h5><table | |
| class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-EmptyElemTag"></a>[44] </td> | |
| <td><code>EmptyElemTag</code></td> | |
| <td> ::= </td> | |
| <td><code>'<' <a href="#NT-Name">Name</a> (<a href="#NT-S">S</a> <a href="#NT-Attribute">Attribute</a>)* <a | |
| href="#NT-S">S</a>? '/>'</code></td> | |
| <td><a href="#uniqattspec">[WFC: Unique Att Spec]</a></td> | |
| </tr> | |
| </tbody></table> <p>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 | |
| title="For interoperability" href="#dt-interop">For interoperability</a>, | |
| the empty-element tag should be used, and should only be used, for elements | |
| which are declared EMPTY.</p> <p>Examples of empty elements:</p> <table class="eg" | |
| width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><IMG align="left" | |
| src="http://www.w3.org/Icons/WWW/w3c_home" /> | |
| <br></br> | |
| <br/></pre></td> | |
| </tr> | |
| </table> </div> <div class="div2"> <h3><a name="elemdecls"></a>3.2 Element | |
| Type Declarations</h3> <p>The <a title="Element" href="#dt-element">element</a> | |
| structure of an <a title="XML Document" href="#dt-xml-doc">XML document</a> | |
| may, for <a title="Validity" href="#dt-valid">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">content</a>.</p> <p>Element | |
| type declarations often constrain which element types can appear as <a title="Parent/Child" | |
| href="#dt-parentchild">children</a> of the element. At user option, an XML | |
| processor may 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 | |
| title="Element Type declaration" name="dt-eldecl">Definition</a>: An <b>element | |
| type declaration</b> takes the form:]</p> <h5>Element Type Declaration</h5><table | |
| class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-elementdecl"></a>[45] </td> | |
| <td><code>elementdecl</code></td> | |
| <td> ::= </td> | |
| <td><code>'<!ELEMENT' <a href="#NT-S">S</a> <a href="#NT-Name">Name</a> <a | |
| href="#NT-S">S</a> <a href="#NT-contentspec">contentspec</a> <a href="#NT-S">S</a>? | |
| '>'</code></td> | |
| <td><a href="#EDUnique">[VC: Unique Element Type Declaration]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-contentspec"></a>[46] </td> | |
| <td><code>contentspec</code></td> | |
| <td> ::= </td> | |
| <td><code>'EMPTY' | 'ANY' | <a href="#NT-Mixed">Mixed</a> | <a href="#NT-children">children</a> </code></td> | |
| </tr> | |
| </tbody></table> <p>where the <a href="#NT-Name">Name</a> gives the element | |
| type being declared.</p> <div class="constraint"><p class="prefix"><a name="EDUnique"></a><b>Validity | |
| constraint: Unique Element Type Declaration</b></p><p>No element type may | |
| be declared more than once.</p> </div> <p>Examples of element type declarations:</p> <table | |
| class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ELEMENT br EMPTY> | |
| <!ELEMENT p (#PCDATA|emph)* > | |
| <!ELEMENT %name.para; %content.para; > | |
| <!ELEMENT container ANY></pre></td> | |
| </tr> | |
| </table> <div class="div3"> <h4><a name="sec-element-content"></a>3.2.1 Element | |
| Content</h4> <p>[<a title="Element content" name="dt-elemcontent">Definition</a>: | |
| An element <a title="Start-Tag" href="#dt-stag">type</a> has <b>element content</b> | |
| when elements of that type must contain only <a title="Parent/Child" href="#dt-parentchild">child</a> | |
| elements (no character data), optionally separated by white space (characters | |
| matching the nonterminal <a href="#NT-S">S</a>).][<a title="Content model" | |
| name="dt-content-model">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">cp</a>s), which consist of | |
| names, choice lists of content particles, or sequence lists of content particles:</p> <h5>Element-content | |
| Models</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-children"></a>[47] </td> | |
| <td><code>children</code></td> | |
| <td> ::= </td> | |
| <td><code>(<a href="#NT-choice">choice</a> | <a href="#NT-seq">seq</a>) ('?' | |
| | '*' | '+')?</code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-cp"></a>[48] </td> | |
| <td><code>cp</code></td> | |
| <td> ::= </td> | |
| <td><code>(<a href="#NT-Name">Name</a> | <a href="#NT-choice">choice</a> | <a | |
| href="#NT-seq">seq</a>) ('?' | '*' | '+')?</code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-choice"></a>[49] </td> | |
| <td><code>choice</code></td> | |
| <td> ::= </td> | |
| <td><code>'(' <a href="#NT-S">S</a>? <a href="#NT-cp">cp</a> ( <a href="#NT-S">S</a>? | |
| '|' <a href="#NT-S">S</a>? <a href="#NT-cp">cp</a> )+ <a href="#NT-S">S</a>? | |
| ')'</code></td> | |
| <td><i>/* */</i></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><i>/* */</i></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#vc-PEinGroup">[VC: Proper Group/PE Nesting]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-seq"></a>[50] </td> | |
| <td><code>seq</code></td> | |
| <td> ::= </td> | |
| <td><code>'(' <a href="#NT-S">S</a>? <a href="#NT-cp">cp</a> ( <a href="#NT-S">S</a>? | |
| ',' <a href="#NT-S">S</a>? <a href="#NT-cp">cp</a> )* <a href="#NT-S">S</a>? | |
| ')'</code></td> | |
| <td><i>/* */</i></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#vc-PEinGroup">[VC: Proper Group/PE Nesting]</a></td> | |
| </tr> | |
| </tbody></table> <p>where each <a href="#NT-Name">Name</a> is the type of | |
| an element which may appear as a <a title="Parent/Child" href="#dt-parentchild">child</a>. | |
| Any content particle in a choice list may appear in the <a title="Element content" | |
| href="#dt-elemcontent">element content</a> at the location where the choice | |
| list appears in the grammar; content particles occurring in a sequence list | |
| must each appear in the <a title="Element content" href="#dt-elemcontent">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 must 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">For | |
| compatibility</a>, it is an error if an element in the document can match | |
| more than one occurrence of an element type in the content model. For more | |
| information, see <a href="#determinism"><b>E Deterministic Content Models</b></a>.</p> | |
| <div class="constraint"><p class="prefix"><a name="vc-PEinGroup"></a><b>Validity | |
| constraint: Proper Group/PE Nesting</b></p><p>Parameter-entity <a title="Replacement Text" | |
| href="#dt-repltext">replacement text</a> must be properly nested with parenthesized | |
| groups. That is to say, if either of the opening or closing parentheses in | |
| a <a href="#NT-choice">choice</a>, <a href="#NT-seq">seq</a>, or <a href="#NT-Mixed">Mixed</a> | |
| construct is contained in the replacement text for a <a title="Parameter-entity reference" | |
| href="#dt-PERef">parameter entity</a>, both must be contained in the same | |
| replacement text.</p> <p><a title="For interoperability" href="#dt-interop">For | |
| interoperability</a>, if a parameter-entity reference appears in a <a href="#NT-choice">choice</a>, <a | |
| href="#NT-seq">seq</a>, or <a href="#NT-Mixed">Mixed</a> construct, its replacement | |
| text should contain at least one non-blank character, and neither the first | |
| nor last non-blank character of the replacement text should be a connector | |
| (<code>|</code> or <code>,</code>).</p> </div> <p>Examples of element-content | |
| models:</p> <table class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ELEMENT spec (front, body, back?)> | |
| <!ELEMENT div1 (head, (p | list | note)*, div2*)> | |
| <!ELEMENT dictionary-body (%div.mix; | %dict.mix;)*></pre></td> | |
| </tr> | |
| </table> </div> <div class="div3"> <h4><a name="sec-mixed-content"></a>3.2.2 | |
| Mixed Content</h4> <p>[<a title="Mixed Content" name="dt-mixed">Definition</a>: | |
| An element <a title="Start-Tag" href="#dt-stag">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">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>Mixed-content Declaration</h5><table | |
| class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Mixed"></a>[51] </td> | |
| <td><code>Mixed</code></td> | |
| <td> ::= </td> | |
| <td><code>'(' <a href="#NT-S">S</a>? '#PCDATA' (<a href="#NT-S">S</a>? '|' <a | |
| href="#NT-S">S</a>? <a href="#NT-Name">Name</a>)* <a href="#NT-S">S</a>? ')*' </code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><code>| '(' <a href="#NT-S">S</a>? '#PCDATA' <a href="#NT-S">S</a>? ')' </code></td> | |
| <td><a href="#vc-PEinGroup">[VC: Proper Group/PE Nesting]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#vc-MixedChildrenUnique">[VC: No Duplicate Types]</a></td> | |
| </tr> | |
| </tbody></table> <p>where the <a href="#NT-Name">Name</a>s give the types | |
| of elements that 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"></a><b>Validity constraint: | |
| No Duplicate Types</b></p><p>The same name must not appear more than once | |
| in a single mixed-content declaration.</p> </div> <p>Examples of mixed content | |
| declarations:</p> <table class="eg" width="100%" border="1" cellpadding="5" | |
| bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ELEMENT p (#PCDATA|a|ul|b|i|em)*> | |
| <!ELEMENT p (#PCDATA | %font; | %phrase; | %special; | %form;)* > | |
| <!ELEMENT b (#PCDATA)></pre></td> | |
| </tr> | |
| </table> </div> </div> <div class="div2"> <h3><a name="attdecls"></a>3.3 Attribute-List | |
| Declarations</h3> <p><a title="Attribute" href="#dt-attr">Attributes</a> are | |
| used to associate name-value pairs with <a title="Element" href="#dt-element">elements</a>. | |
| Attribute specifications may appear only within <a title="Start-Tag" href="#dt-stag">start-tags</a> | |
| and <a title="empty-element tag" href="#dt-eetag">empty-element tags</a>; | |
| thus, the productions used to recognize them appear in <a href="#sec-starttags"><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">default | |
| values</a> for attributes.</p></li> | |
| </ul> <p>[<a title="Attribute-List Declaration" name="dt-attdecl">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>Attribute-list | |
| Declaration</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-AttlistDecl"></a>[52] </td> | |
| <td><code>AttlistDecl</code></td> | |
| <td> ::= </td> | |
| <td><code>'<!ATTLIST' <a href="#NT-S">S</a> <a href="#NT-Name">Name</a> <a | |
| href="#NT-AttDef">AttDef</a>* <a href="#NT-S">S</a>? '>'</code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-AttDef"></a>[53] </td> | |
| <td><code>AttDef</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-S">S</a> <a href="#NT-Name">Name</a> <a href="#NT-S">S</a> <a | |
| href="#NT-AttType">AttType</a> <a href="#NT-S">S</a> <a href="#NT-DefaultDecl">DefaultDecl</a></code></td> | |
| </tr> | |
| </tbody></table> <p>The <a href="#NT-Name">Name</a> in the <a href="#NT-AttlistDecl">AttlistDecl</a> | |
| rule is the type of an element. At user option, an XML processor may 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">Name</a> in the <a href="#NT-AttDef">AttDef</a> | |
| rule is the name of the attribute.</p> <p>When more than one <a href="#NT-AttlistDecl">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">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 | |
| may 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"></a>3.3.1 Attribute Types</h4> <p>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 have varying lexical and semantic constraints. The validity constraints | |
| noted in the grammar are applied after the attribute value has been normalized | |
| as described in <a href="#attdecls"><b>3.3 Attribute-List Declarations</b></a>.</p> <h5>Attribute | |
| Types</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-AttType"></a>[54] </td> | |
| <td><code>AttType</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-StringType">StringType</a> | <a href="#NT-TokenizedType">TokenizedType</a> | |
| | <a href="#NT-EnumeratedType">EnumeratedType</a> </code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-StringType"></a>[55] </td> | |
| <td><code>StringType</code></td> | |
| <td> ::= </td> | |
| <td><code>'CDATA'</code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-TokenizedType"></a>[56] </td> | |
| <td><code>TokenizedType</code></td> | |
| <td> ::= </td> | |
| <td><code>'ID'</code></td> | |
| <td><a href="#id">[VC: ID]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#one-id-per-el">[VC: One ID per Element Type]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#id-default">[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">[VC: IDREF]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><code>| 'IDREFS'</code></td> | |
| <td><a href="#idref">[VC: IDREF]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><code>| 'ENTITY'</code></td> | |
| <td><a href="#entname">[VC: Entity Name]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><code>| 'ENTITIES'</code></td> | |
| <td><a href="#entname">[VC: Entity Name]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><code>| 'NMTOKEN'</code></td> | |
| <td><a href="#nmtok">[VC: Name Token]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><code>| 'NMTOKENS'</code></td> | |
| <td><a href="#nmtok">[VC: Name Token]</a></td> | |
| </tr> | |
| </tbody></table> <div class="constraint"><p class="prefix"><a name="id"></a><b>Validity | |
| constraint: ID</b></p><p>Values of type <b>ID</b> must match the <a href="#NT-Name">Name</a> | |
| production. A name must not appear more than once in an XML document as a | |
| value of this type; i.e., ID values must uniquely identify the elements which | |
| bear them.</p> </div> <div class="constraint"><p class="prefix"><a name="one-id-per-el"></a><b>Validity | |
| constraint: One ID per Element Type</b></p><p>No element type may have more | |
| than one ID attribute specified.</p> </div> <div class="constraint"><p class="prefix"><a | |
| name="id-default"></a><b>Validity constraint: ID Attribute Default</b></p><p>An | |
| ID attribute must have a declared default of <b>#IMPLIED</b> or <b>#REQUIRED</b>.</p> </div> <div | |
| class="constraint"><p class="prefix"><a name="idref"></a><b>Validity constraint: | |
| IDREF</b></p><p>Values of type <b>IDREF</b> must match the <a href="#NT-Name">Name</a> | |
| production, and values of type <b>IDREFS</b> must match <a href="#NT-Names">Names</a>; | |
| each <a href="#NT-Name">Name</a> must match the value of an ID attribute on | |
| some element in the XML document; i.e. <b>IDREF</b> values must match the | |
| value of some ID attribute.</p> </div> <div class="constraint"><p class="prefix"><a | |
| name="entname"></a><b>Validity constraint: Entity Name</b></p><p>Values of | |
| type <b>ENTITY</b> must match the <a href="#NT-Name">Name</a> production, | |
| values of type <b>ENTITIES</b> must match <a href="#NT-Names">Names</a>; each <a | |
| href="#NT-Name">Name</a> must match the name of an <a title="Unparsed Entity" | |
| href="#dt-unparsed">unparsed entity</a> declared in the <a title="Document Type Declaration" | |
| href="#dt-doctype">DTD</a>.</p> </div> <div class="constraint"><p class="prefix"><a | |
| name="nmtok"></a><b>Validity constraint: Name Token</b></p><p>Values of type <b>NMTOKEN</b> | |
| must match the <a href="#NT-Nmtoken">Nmtoken</a> production; values of type <b>NMTOKENS</b> | |
| must match <a title="" href="#NT-Nmtokens">Nmtokens</a>.</p> </div> <p>[<a | |
| title="Enumerated Attribute Values" name="dt-enumerated">Definition</a>: <b>Enumerated | |
| attributes</b> can take one of a list of values provided in the declaration]. | |
| There are two kinds of enumerated types:</p> <h5>Enumerated Attribute Types</h5><table | |
| class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-EnumeratedType"></a>[57] </td> | |
| <td><code>EnumeratedType</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-NotationType">NotationType</a> | <a href="#NT-Enumeration">Enumeration</a> </code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-NotationType"></a>[58] </td> | |
| <td><code>NotationType</code></td> | |
| <td> ::= </td> | |
| <td><code>'NOTATION' <a href="#NT-S">S</a> '(' <a href="#NT-S">S</a>? <a href="#NT-Name">Name</a> | |
| (<a href="#NT-S">S</a>? '|' <a href="#NT-S">S</a>? <a href="#NT-Name">Name</a>)* <a | |
| href="#NT-S">S</a>? ')' </code></td> | |
| <td><a href="#notatn">[VC: Notation Attributes]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#OneNotationPer">[VC: One Notation Per Element Type]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#NoNotationEmpty">[VC: No Notation on Empty Element]</a></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Enumeration"></a>[59] </td> | |
| <td><code>Enumeration</code></td> | |
| <td> ::= </td> | |
| <td><code>'(' <a href="#NT-S">S</a>? <a href="#NT-Nmtoken">Nmtoken</a> (<a | |
| href="#NT-S">S</a>? '|' <a href="#NT-S">S</a>? <a href="#NT-Nmtoken">Nmtoken</a>)* <a | |
| href="#NT-S">S</a>? ')'</code></td> | |
| <td><a href="#enum">[VC: Enumeration]</a></td> | |
| </tr> | |
| </tbody></table> <p>A <b>NOTATION</b> attribute identifies a <a title="Notation" | |
| href="#dt-notation">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"></a><b>Validity constraint: Notation Attributes</b></p><p>Values | |
| of this type must match one of the <a href="#Notations"><cite>notation</cite></a> | |
| names included in the declaration; all notation names in the declaration must | |
| be declared.</p> </div> <div class="constraint"><p class="prefix"><a name="OneNotationPer"></a><b>Validity | |
| constraint: One Notation Per Element Type</b></p><p>No element type may have | |
| more than one <b>NOTATION</b> attribute specified.</p> </div> <div class="constraint"><p | |
| class="prefix"><a name="NoNotationEmpty"></a><b>Validity constraint: No Notation | |
| on Empty Element</b></p><p><a title="For Compatibility" href="#dt-compat">For | |
| compatibility</a>, an attribute of type <b>NOTATION</b> must not be declared | |
| on an element declared <b>EMPTY</b>.</p> </div> <div class="constraint"><p | |
| class="prefix"><a name="enum"></a><b>Validity constraint: Enumeration</b></p><p>Values | |
| of this type must match one of the <a href="#NT-Nmtoken">Nmtoken</a> tokens | |
| in the declaration.</p> </div> <p><a title="For interoperability" href="#dt-interop">For | |
| interoperability,</a> the same <a href="#NT-Nmtoken">Nmtoken</a> should not | |
| 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"></a>3.3.2 | |
| Attribute Defaults</h4> <p>An <a title="Attribute-List Declaration" href="#dt-attdecl">attribute | |
| declaration</a> provides information on whether the attribute's presence is | |
| required, and if not, how an XML processor should react if a declared attribute | |
| is absent in a document.</p> <h5>Attribute Defaults</h5><table class="scrap"> | |
| <tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-DefaultDecl"></a>[60] </td> | |
| <td><code>DefaultDecl</code></td> | |
| <td> ::= </td> | |
| <td><code>'#REQUIRED' | '#IMPLIED' </code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><code>| (('#FIXED' S)? <a href="#NT-AttValue">AttValue</a>)</code></td> | |
| <td><a href="#RequiredAttr">[VC: Required Attribute]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#defattrvalid">[VC: Attribute Default Legal]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#CleanAttrVals">[WFC: No < in Attribute Values]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#FixedAttr">[VC: Fixed Attribute Default]</a></td> | |
| </tr> | |
| </tbody></table> <p>In an attribute declaration, <b>#REQUIRED</b> means that | |
| the attribute must always be provided, <b>#IMPLIED</b> that no default value | |
| is provided. [<a title="Attribute Default" name="dt-default">Definition</a>: | |
| If the declaration is neither <b>#REQUIRED</b> nor <b>#IMPLIED</b>, then the <a | |
| href="#NT-AttValue">AttValue</a> value contains the declared <b>default</b> | |
| value; the <b>#FIXED</b> keyword states that the attribute must always have | |
| the default value. If a default value is declared, when an XML processor encounters | |
| an omitted attribute, it is to behave as though the attribute were present | |
| with the declared default value.]</p> <div class="constraint"><p class="prefix"><a | |
| name="RequiredAttr"></a><b>Validity constraint: Required Attribute</b></p><p>If | |
| the default declaration is the keyword <b>#REQUIRED</b>, then the attribute | |
| must be specified for all elements of the type in the attribute-list declaration.</p> </div> <div | |
| class="constraint"><p class="prefix"><a name="defattrvalid"></a><b>Validity | |
| constraint: Attribute Default Legal</b></p><p>The declared default value must | |
| meet the lexical constraints of the declared attribute type.</p> </div> <div | |
| class="constraint"><p class="prefix"><a name="FixedAttr"></a><b>Validity constraint: | |
| Fixed Attribute Default</b></p><p>If an attribute has a default value declared | |
| with the <b>#FIXED</b> keyword, instances of that attribute must match the | |
| default value.</p> </div> <p>Examples of attribute-list declarations:</p> <table | |
| class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ATTLIST termdef | |
| id ID #REQUIRED | |
| name CDATA #IMPLIED> | |
| <!ATTLIST list | |
| type (bullets|ordered|glossary) "ordered"> | |
| <!ATTLIST form | |
| method CDATA #FIXED "POST"></pre></td> | |
| </tr> | |
| </table> </div> <div class="div3"> <h4><a name="AVNormalize"></a>3.3.3 Attribute-Value | |
| Normalization</h4> <p>Before the value of an attribute is passed to the application | |
| or checked for validity, the XML processor must 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.</p> <ol> | |
| <li><p>All line breaks must have been normalized on input to #xA as described | |
| in <a href="#sec-line-ends"><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 must 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 should | |
| be treated by a non-validating processor as if declared <b>CDATA</b>.</p> <p>Following | |
| are examples of attribute normalization. Given the following declarations:</p> <table | |
| class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ENTITY d "&#xD;"> | |
| <!ENTITY a "&#xA;"> | |
| <!ENTITY da "&#xD;&#xA;"></pre></td> | |
| </tr> | |
| </table> <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 border="1" frame="border"><thead> | |
| <tr> | |
| <th rowspan="1" colspan="1">Attribute specification</th> | |
| <th rowspan="1" colspan="1">a is NMTOKENS</th> | |
| <th rowspan="1" colspan="1">a is CDATA</th> | |
| </tr> | |
| </thead><tbody> | |
| <tr> | |
| <td rowspan="1" colspan="1"><table class="eg" width="100%" border="1" cellpadding="5" | |
| bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre>a=" | |
| xyz"</pre></td> | |
| </tr> | |
| </table></td> | |
| <td rowspan="1" colspan="1"><code>x y z</code></td> | |
| <td rowspan="1" colspan="1"><code>#x20 #x20 x y z</code></td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><table class="eg" width="100%" border="1" cellpadding="5" | |
| bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre>a="&d;&d;A&a;&a;B&da;"</pre></td> | |
| </tr> | |
| </table></td> | |
| <td rowspan="1" colspan="1"><code>A #x20 B</code></td> | |
| <td rowspan="1" colspan="1"><code>#x20 #x20 A #x20 #x20 B #x20 #x20</code></td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><table class="eg" width="100%" border="1" cellpadding="5" | |
| bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre>a= | |
| "&#xd;&#xd;A&#xa;&#xa;B&#xd;&#xa;"</pre></td> | |
| </tr> | |
| </table></td> | |
| <td rowspan="1" colspan="1"><code>#xD #xD A #xA #xA B #xD #xA</code></td> | |
| <td rowspan="1" colspan="1"><code>#xD #xD A #xA #xA B #xD #xD</code></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"></a>3.4 Conditional Sections</h3> <p>[<a | |
| title="conditional section" name="dt-cond-section">Definition</a>: <b>Conditional | |
| sections</b> are portions of the <a title="Document Type Declaration" href="#dt-doctype">document | |
| type declaration external subset</a> which are included in, or excluded from, | |
| the logical structure of the DTD based on the keyword which governs them.]</p> <h5>Conditional | |
| Section</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-conditionalSect"></a>[61] </td> | |
| <td><code>conditionalSect</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-includeSect">includeSect</a> | <a href="#NT-ignoreSect">ignoreSect</a> </code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-includeSect"></a>[62] </td> | |
| <td><code>includeSect</code></td> | |
| <td> ::= </td> | |
| <td><code>'<![' S? 'INCLUDE' S? '[' <a href="#NT-extSubsetDecl">extSubsetDecl</a> | |
| ']]>' </code></td> | |
| <td><i>/* */</i></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#condsec-nesting">[VC: Proper Conditional Section/PE Nesting]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-ignoreSect"></a>[63] </td> | |
| <td><code>ignoreSect</code></td> | |
| <td> ::= </td> | |
| <td><code>'<![' S? 'IGNORE' S? '[' <a href="#NT-ignoreSectContents">ignoreSectContents</a>* | |
| ']]>'</code></td> | |
| <td><i>/* */</i></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#condsec-nesting">[VC: Proper Conditional Section/PE Nesting]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-ignoreSectContents"></a>[64] </td> | |
| <td><code>ignoreSectContents</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-Ignore">Ignore</a> ('<![' <a href="#NT-ignoreSectContents">ignoreSectContents</a> | |
| ']]>' <a href="#NT-Ignore">Ignore</a>)*</code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Ignore"></a>[65] </td> | |
| <td><code>Ignore</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-Char">Char</a>* - (<a href="#NT-Char">Char</a>* ('<![' | |
| | ']]>') <a href="#NT-Char">Char</a>*) </code></td> | |
| </tr> | |
| </tbody></table> <div class="constraint"><p class="prefix"><a name="condsec-nesting"></a><b>Validity | |
| constraint: Proper Conditional Section/PE Nesting</b></p><p>If any of the | |
| "<code><![</code>", "<code>[</code>", or "<code>]]></code>" of a conditional | |
| section is contained in the replacement text for a parameter-entity reference, | |
| all of them must be contained in the same replacement text.</p> </div> <p>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.</p> <p>If the keyword | |
| of the conditional section is <b>INCLUDE</b>, then the contents of the conditional | |
| section are part of the DTD. If the keyword of the conditional section is <b>IGNORE</b>, | |
| then the contents of the conditional section are not logically 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 are ignored. The contents of an ignored | |
| conditional section are parsed by ignoring all characters after the "<code>[</code>" | |
| following the keyword, except conditional section starts "<code><![</code>" | |
| and ends "<code>]]></code>", until the matching conditional section end | |
| is found. Parameter entity references are not recognized in this process.</p> <p>If | |
| the keyword of the conditional section is a parameter-entity reference, the | |
| parameter entity must be replaced by its content before the processor decides | |
| whether to include or ignore the conditional section.</p> <p>An example:</p> <table | |
| class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ENTITY % draft 'INCLUDE' > | |
| <!ENTITY % final 'IGNORE' > | |
| <![%draft;[ | |
| <!ELEMENT book (comments*, title, body, supplements?)> | |
| ]]> | |
| <![%final;[ | |
| <!ELEMENT book (title, body, supplements?)> | |
| ]]></pre></td> | |
| </tr> | |
| </table> </div> </div> <div class="div1"> <h2><a name="sec-physical-struct"></a>4 | |
| Physical Structures</h2> <p>[<a title="Entity" name="dt-entity">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">document entity</a> and the <a title="Document Type Declaration" | |
| href="#dt-doctype">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">document | |
| entity</a>, which serves as the starting point for the <a title="XML Processor" | |
| href="#dt-xml-proc">XML processor</a> and may contain the whole document.</p> <p>Entities | |
| may be either parsed or unparsed. [<a title="Text Entity" name="dt-parsedent">Definition</a>: | |
| A <b>parsed entity's</b> contents are referred to as its <a title="Replacement Text" | |
| href="#dt-repltext">replacement text</a>; this <a title="Text" href="#dt-text">text</a> | |
| is considered an integral part of the document.]</p> <p>[<a title="Unparsed Entity" | |
| name="dt-unparsed">Definition</a>: An <b>unparsed entity</b> is a resource | |
| whose contents may or may not be <a title="Text" href="#dt-text">text</a>, | |
| and if text, may be other than XML. Each unparsed entity has an associated <a | |
| title="Notation" href="#dt-notation">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 title="general entity" name="gen-entity">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 title="Parameter entity" name="dt-PE">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"></a>4.1 Character and Entity References</h3> <p>[<a | |
| title="Character Reference" name="dt-charref">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>Character | |
| Reference</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-CharRef"></a>[66] </td> | |
| <td><code>CharRef</code></td> | |
| <td> ::= </td> | |
| <td><code>'&#' [0-9]+ ';' </code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><code>| '&#x' [0-9a-fA-F]+ ';'</code></td> | |
| <td><a href="#wf-Legalchar">[WFC: Legal Character]</a></td> | |
| </tr> | |
| </tbody></table> <div class="constraint"><p class="prefix"><a name="wf-Legalchar"></a><b>Well-formedness | |
| constraint: Legal Character</b></p><p>Characters referred to using character | |
| references must match the production for <a title="" href="#NT-Char">Char</a>.</p> </div> <p>If | |
| the character reference begins with "<code>&#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>&#</code>", | |
| the digits up to the terminating <code>;</code> provide a decimal representation | |
| of the character's code point.</p> <p>[<a title="Entity Reference" name="dt-entref">Definition</a>: | |
| An <b>entity reference</b> refers to the content of a named entity.] [<a title="General Entity Reference" | |
| name="dt-GERef">Definition</a>: References to parsed general entities use | |
| ampersand (<code>&</code>) and semicolon (<code>;</code>) as delimiters.] | |
| [<a title="Parameter-entity reference" name="dt-PERef">Definition</a>: <b>Parameter-entity | |
| references</b> use percent-sign (<code>%</code>) and semicolon (<code>;</code>) | |
| as delimiters.]</p> <h5>Entity Reference</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Reference"></a>[67] </td> | |
| <td><code>Reference</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-EntityRef">EntityRef</a> | <a href="#NT-CharRef">CharRef</a></code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-EntityRef"></a>[68] </td> | |
| <td><code>EntityRef</code></td> | |
| <td> ::= </td> | |
| <td><code>'&' <a href="#NT-Name">Name</a> ';'</code></td> | |
| <td><a href="#wf-entdeclared">[WFC: Entity Declared]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#vc-entdeclared">[VC: Entity Declared]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#textent">[WFC: Parsed Entity]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#norecursion">[WFC: No Recursion]</a></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-PEReference"></a>[69] </td> | |
| <td><code>PEReference</code></td> | |
| <td> ::= </td> | |
| <td><code>'%' <a href="#NT-Name">Name</a> ';'</code></td> | |
| <td><a href="#vc-entdeclared">[VC: Entity Declared]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#norecursion">[WFC: No Recursion]</a></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><a href="#indtd">[WFC: In DTD]</a></td> | |
| </tr> | |
| </tbody></table> <div class="constraint"><p class="prefix"><a name="wf-entdeclared"></a><b>Well-formedness | |
| constraint: Entity Declared</b></p><p>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 | |
| href="#NT-Name">Name</a> given in the entity reference must <a title="match" | |
| href="#dt-match">match</a> that in an <a href="#sec-entity-decl"><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 must precede any reference to it which | |
| appears in a default value in an attribute-list declaration.</p> <p>Note that | |
| if entities are declared in the external subset or in external parameter entities, | |
| a non-validating processor is <a href="#include-if-valid"><cite>not obligated | |
| to</cite></a> read and process their declarations; for such documents, the | |
| rule that an entity must be declared is a well-formedness constraint only | |
| if <a href="#sec-rmd"><cite>standalone='yes'</cite></a>.</p> </div> <div class="constraint"><p | |
| class="prefix"><a name="vc-entdeclared"></a><b>Validity constraint: Entity | |
| Declared</b></p><p>In a document with an external subset or external parameter | |
| entities with "<code>standalone='no'</code>", the <a href="#NT-Name">Name</a> | |
| given in the entity reference must <a title="match" href="#dt-match">match</a> | |
| that in an <a href="#sec-entity-decl"><cite>entity declaration</cite></a>. | |
| For interoperability, valid documents should 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"><b>4.6 Predefined | |
| Entities</b></a>. The declaration of a parameter entity must precede any reference | |
| to it. Similarly, the declaration of a general entity must 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"></a><b>Well-formedness constraint: Parsed Entity</b></p><p>An | |
| entity reference must not contain the name of an <a title="Unparsed Entity" | |
| href="#dt-unparsed">unparsed entity</a>. Unparsed entities may be referred | |
| to only in <a title="Attribute Value" href="#dt-attrval">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"></a><b>Well-formedness constraint: No | |
| Recursion</b></p><p>A parsed entity must not contain a recursive reference | |
| to itself, either directly or indirectly.</p> </div> <div class="constraint"><p | |
| class="prefix"><a name="indtd"></a><b>Well-formedness constraint: In DTD</b></p><p>Parameter-entity | |
| references may only appear in the <a title="Document Type Declaration" href="#dt-doctype">DTD</a>.</p> </div> <p>Examples | |
| of character and entity references:</p> <table class="eg" width="100%" border="1" | |
| cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre>Type <key>less-than</key> (&#x3C;) to save options. | |
| This document was prepared on &docdate; and | |
| is classified &security-level;.</pre></td> | |
| </tr> | |
| </table> <p>Example of a parameter-entity reference:</p> <table class="eg" | |
| width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!-- declare the parameter entity "ISOLat2"... --> | |
| <!ENTITY % ISOLat2 | |
| SYSTEM "http://www.xml.com/iso/isolat2-xml.entities" > | |
| <!-- ... now reference it. --> | |
| %ISOLat2;</pre></td> | |
| </tr> | |
| </table> </div> <div class="div2"> <h3><a name="sec-entity-decl"></a>4.2 Entity | |
| Declarations</h3> <p>[<a title="entity declaration" name="dt-entdecl">Definition</a>: | |
| Entities are declared thus:]</p> <h5>Entity Declaration</h5><table class="scrap"> | |
| <tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-EntityDecl"></a>[70] </td> | |
| <td><code>EntityDecl</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-GEDecl">GEDecl</a> | <a href="#NT-PEDecl">PEDecl</a></code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-GEDecl"></a>[71] </td> | |
| <td><code>GEDecl</code></td> | |
| <td> ::= </td> | |
| <td><code>'<!ENTITY' <a href="#NT-S">S</a> <a href="#NT-Name">Name</a> <a | |
| href="#NT-S">S</a> <a href="#NT-EntityDef">EntityDef</a> <a href="#NT-S">S</a>? | |
| '>'</code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-PEDecl"></a>[72] </td> | |
| <td><code>PEDecl</code></td> | |
| <td> ::= </td> | |
| <td><code>'<!ENTITY' <a href="#NT-S">S</a> '%' <a href="#NT-S">S</a> <a | |
| href="#NT-Name">Name</a> <a href="#NT-S">S</a> <a href="#NT-PEDef">PEDef</a> <a | |
| href="#NT-S">S</a>? '>'</code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-EntityDef"></a>[73] </td> | |
| <td><code>EntityDef</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-EntityValue">EntityValue</a> | (<a href="#NT-ExternalID">ExternalID</a> <a | |
| href="#NT-NDataDecl">NDataDecl</a>?)</code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-PEDef"></a>[74] </td> | |
| <td><code>PEDef</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-EntityValue">EntityValue</a> | <a href="#NT-ExternalID">ExternalID</a></code></td> | |
| </tr> | |
| </tbody></table> <p>The <a href="#NT-Name">Name</a> identifies the entity | |
| in an <a title="Entity Reference" href="#dt-entref">entity 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 may issue a warning | |
| if entities are declared multiple times.</p> <div class="div3"> <h4><a name="sec-internal-ent"></a>4.2.1 | |
| Internal Entities</h4> <p>[<a title="Internal Entity Replacement Text" name="dt-internent">Definition</a>: | |
| If the entity definition is an <a href="#NT-EntityValue">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">literal entity value</a> may be required to produce the | |
| correct <a title="Replacement Text" href="#dt-repltext">replacement text</a>: | |
| see <a href="#intern-replacement"><b>4.5 Construction of Internal Entity Replacement | |
| Text</b></a>.</p> <p>An internal entity is a <a title="Text Entity" href="#dt-parsedent">parsed | |
| entity</a>.</p> <p>Example of an internal entity declaration:</p> <table class="eg" | |
| width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ENTITY Pub-Status "This is a pre-release of the | |
| specification."></pre></td> | |
| </tr> | |
| </table> </div> <div class="div3"> <h4><a name="sec-external-ent"></a>4.2.2 | |
| External Entities</h4> <p>[<a title="External Entity" name="dt-extent">Definition</a>: | |
| If the entity is not internal, it is an <b>external entity</b>, declared as | |
| follows:]</p> <h5>External Entity Declaration</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-ExternalID"></a>[75] </td> | |
| <td><code>ExternalID</code></td> | |
| <td> ::= </td> | |
| <td><code>'SYSTEM' <a href="#NT-S">S</a> <a href="#NT-SystemLiteral">SystemLiteral</a></code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td></td> | |
| <td></td> | |
| <td></td> | |
| <td><code>| 'PUBLIC' <a href="#NT-S">S</a> <a href="#NT-PubidLiteral">PubidLiteral</a> <a | |
| href="#NT-S">S</a> <a href="#NT-SystemLiteral">SystemLiteral</a> </code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-NDataDecl"></a>[76] </td> | |
| <td><code>NDataDecl</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-S">S</a> 'NDATA' <a href="#NT-S">S</a> <a href="#NT-Name">Name</a></code></td> | |
| <td><a href="#not-declared">[VC: Notation Declared]</a></td> | |
| </tr> | |
| </tbody></table> <p>If the <a href="#NT-NDataDecl">NDataDecl</a> is present, | |
| this is a general <a title="Unparsed Entity" href="#dt-unparsed">unparsed | |
| entity</a>; otherwise it is a parsed entity.</p> <div class="constraint"><p | |
| class="prefix"><a name="not-declared"></a><b>Validity constraint: Notation | |
| Declared</b></p><p>The <a href="#NT-Name">Name</a> must match the declared | |
| name of a <a title="Notation" href="#dt-notation">notation</a>.</p> </div> <p>[<a | |
| title="System Identifier" name="dt-sysid">Definition</a>: The <a href="#NT-SystemLiteral">SystemLiteral</a> | |
| is called the entity's <b>system identifier</b>. It is a URI reference (as | |
| defined in <a href="#rfc2396">[IETF RFC 2396]</a>, updated by <a href="#rfc2732">[IETF | |
| RFC 2732]</a>), meant to be dereferenced 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. A URI might thus be relative to the <a title="Document Entity" | |
| href="#dt-docent">document entity</a>, to the entity containing the <a title="Document Type Declaration" | |
| href="#dt-doctype">external DTD subset</a>, or to some other <a title="External Entity" | |
| href="#dt-extent">external parameter entity</a>.</p> <p>URI references require | |
| encoding and escaping of certain characters. The disallowed characters include | |
| all non-ASCII characters, plus the excluded characters listed in Section 2.4 | |
| of <a href="#rfc2396">[IETF RFC 2396]</a>, except for the number sign (<code>#</code>) | |
| and percent sign (<code>%</code>) characters and the square bracket characters | |
| re-allowed in <a href="#rfc2732">[IETF RFC 2732]</a>. Disallowed characters | |
| must be escaped as follows:</p> <ol> | |
| <li><p>Each disallowed character is converted to UTF-8 <a href="#rfc2279">[IETF | |
| RFC 2279]</a> as one or more bytes.</p></li> | |
| <li><p>Any octets corresponding to a disallowed character 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> <p>[<a title="Public identifier" name="dt-pubid">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 the public identifier to try to generate an alternative URI reference. | |
| If the processor is unable to do so, it must use the URI reference specified | |
| in the system literal. Before a match is attempted, all strings of white space | |
| in the public identifier must be normalized to single space characters (#x20), | |
| and leading and trailing white space must be removed.</p> <p>Examples of external | |
| entity declarations:</p> <table class="eg" width="100%" border="1" cellpadding="5" | |
| bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ENTITY open-hatch | |
| SYSTEM "http://www.textuality.com/boilerplate/OpenHatch.xml"> | |
| <!ENTITY open-hatch | |
| PUBLIC "-//Textuality//TEXT Standard open-hatch boilerplate//EN" | |
| "http://www.textuality.com/boilerplate/OpenHatch.xml"> | |
| <!ENTITY hatch-pic | |
| SYSTEM "../grafix/OpenHatch.gif" | |
| NDATA gif ></pre></td> | |
| </tr> | |
| </table> </div> </div> <div class="div2"> <h3><a name="TextEntities"></a>4.3 | |
| Parsed Entities</h3> <div class="div3"> <h4><a name="sec-TextDecl"></a>4.3.1 | |
| The Text Declaration</h4> <p>External parsed entities should each begin with | |
| a <b>text declaration</b>.</p> <h5>Text Declaration</h5><table class="scrap"> | |
| <tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-TextDecl"></a>[77] </td> | |
| <td><code>TextDecl</code></td> | |
| <td> ::= </td> | |
| <td><code>'<?xml' <a href="#NT-VersionInfo">VersionInfo</a>? <a href="#NT-EncodingDecl">EncodingDecl</a> <a | |
| href="#NT-S">S</a>? '?>'</code></td> | |
| </tr> | |
| </tbody></table> <p>The text declaration must be provided literally, not by | |
| reference to a parsed entity. No text declaration may 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 title="Replacement Text" | |
| href="#dt-repltext">replacement text</a>.</p> </div> <div class="div3"> <h4><a | |
| name="wf-entities"></a>4.3.2 Well-Formed Parsed Entities</h4> <p>The document | |
| entity is well-formed if it matches the production labeled <a href="#NT-document">document</a>. | |
| An external general parsed entity is well-formed if it matches the production | |
| labeled <a href="#NT-extParsedEnt">extParsedEnt</a>. All external parameter | |
| entities are well-formed by definition.</p> <h5>Well-Formed External Parsed | |
| Entity</h5><table class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-extParsedEnt"></a>[78] </td> | |
| <td><code>extParsedEnt</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-TextDecl">TextDecl</a>? <a href="#NT-content">content</a></code></td> | |
| </tr> | |
| </tbody></table> <p>An internal general parsed entity is well-formed if its | |
| replacement text matches the production labeled <a href="#NT-content">content</a>. | |
| All internal parameter entities are well-formed by definition.</p> <p>A consequence | |
| of well-formedness in entities is that the logical and physical structures | |
| in an XML document are properly nested; no <a title="Start-Tag" href="#dt-stag">start-tag</a>, <a | |
| title="End Tag" href="#dt-etag">end-tag</a>, <a title="Empty" href="#dt-empty">empty-element | |
| tag</a>, <a title="Element" href="#dt-element">element</a>, <a title="Comment" | |
| href="#dt-comment">comment</a>, <a title="Processing instruction" href="#dt-pi">processing | |
| instruction</a>, <a title="Character Reference" href="#dt-charref">character | |
| reference</a>, or <a title="Entity Reference" href="#dt-entref">entity reference</a> | |
| can begin in one entity and end in another.</p> </div> <div class="div3"> <h4><a | |
| name="charencoding"></a>4.3.3 Character Encoding in Entities</h4> <p>Each | |
| external parsed entity in an XML document may use a different encoding for | |
| its characters. All XML processors must 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 character encodings with any other labels, even if the encodings | |
| or labels are very similar to UTF-8 or UTF-16.</p> <p>Entities encoded in | |
| UTF-16 must begin with the Byte Order Mark described by Annex F of <a href="#ISO10646">[ISO/IEC | |
| 10646]</a>, Annex H of <a href="#ISO10646-2000">[ISO/IEC 10646-2000]</a>, | |
| section 2.4 of <a href="#Unicode">[Unicode]</a>, and section 2.7 of <a href="#Unicode3">[Unicode3]</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 must be able to use this character to differentiate between UTF-8 | |
| and UTF-16 encoded documents.</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 must begin with a text | |
| declaration (see <a href="#sec-TextDecl"><b>4.3.1 The Text Declaration</b></a>) | |
| containing an encoding declaration:</p> <h5>Encoding Declaration</h5><table | |
| class="scrap"><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-EncodingDecl"></a>[80] </td> | |
| <td><code>EncodingDecl</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-S">S</a> 'encoding' <a href="#NT-Eq">Eq</a> ('"' <a | |
| href="#NT-EncName">EncName</a> '"' | "'" <a href="#NT-EncName">EncName</a> | |
| "'" ) </code></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-EncName"></a>[81] </td> | |
| <td><code>EncName</code></td> | |
| <td> ::= </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>In the <a title="Document Entity" href="#dt-docent">document | |
| entity</a>, the encoding declaration is part of the <a title="XML Declaration" | |
| href="#dt-xmldecl">XML declaration</a>. The <a href="#NT-EncName">EncName</a> | |
| is the name of the encoding used.</p> <p>In an encoding declaration, the | |
| values "<code>UTF-8</code>", "<code>UTF-16</code>", "<code>ISO-10646-UCS-2</code>", | |
| and "<code>ISO-10646-UCS-4</code>" should 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) should 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>" | |
| should be used for the various encoded forms of JIS X-0208-1997. It is recommended | |
| that character encodings registered (as <em>charset</em>s) with the Internet | |
| Assigned Numbers Authority <a href="#IANA">[IANA-CHARSETS]</a>, other than | |
| those just listed, be referred to using their registered names; other encodings | |
| should use names starting with an "x-" prefix. XML processors should match | |
| character encoding names in a case-insensitive way and should 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 an <a title="Error" | |
| href="#dt-error">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 fatal error for a <a href="#NT-TextDecl">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">fatal error</a> when an XML processor | |
| encounters an entity with an encoding that it is unable to process. It is | |
| a fatal error if an XML entity is determined (via default, encoding declaration, | |
| or higher-level protocol) to be in a certain encoding but contains octet sequences | |
| that are not legal in that encoding. It is also a fatal error 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> <table class="eg" | |
| width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><?xml encoding='UTF-8'?> | |
| <?xml encoding='EUC-JP'?></pre></td> | |
| </tr> | |
| </table> </div> </div> <div class="div2"> <h3><a name="entproc"></a>4.4 XML | |
| Processor Treatment of Entities and References</h3> <p>The table below summarizes | |
| the contexts in which character references, entity references, and invocations | |
| of unparsed entities might appear and the required behavior of an <a title="XML Processor" | |
| href="#dt-xml-proc">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">start-tag</a> | |
| and before the <a title="End Tag" href="#dt-etag">end-tag</a> of an element; | |
| corresponds to the nonterminal <a href="#NT-content">content</a>.</p> </dd> | |
| <dt class="label">Reference in Attribute Value</dt> | |
| <dd> <p>as a reference within either the value of an attribute in a <a title="Start-Tag" | |
| href="#dt-stag">start-tag</a>, or a default value in an <a title="Attribute-List Declaration" | |
| href="#dt-attdecl">attribute declaration</a>; corresponds to the nonterminal <a | |
| href="#NT-AttValue">AttValue</a>.</p> </dd> | |
| <dt class="label">Occurs as Attribute Value</dt> | |
| <dd> <p>as a <a href="#NT-Name">Name</a>, not a reference, appearing either | |
| as 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">literal entity value</a> in the entity's declaration; | |
| corresponds to the nonterminal <a href="#NT-EntityValue">EntityValue</a>.</p> </dd> | |
| <dt class="label">Reference in DTD</dt> | |
| <dd> <p>as a reference within either the internal or external subsets of the <a | |
| title="Document Type Declaration" href="#dt-doctype">DTD</a>, but outside | |
| of an <a href="#NT-EntityValue">EntityValue</a>, <a href="#NT-AttValue">AttValue</a>, <a | |
| href="#NT-PI">PI</a>, <a href="#NT-Comment">Comment</a>, <a href="#NT-SystemLiteral">SystemLiteral</a>, <a | |
| href="#NT-PubidLiteral">PubidLiteral</a>, or the contents of an ignored conditional | |
| section (see <a href="#sec-condition-sect"><b>3.4 Conditional Sections</b></a>).</p> <p>.</p> </dd> | |
| </dl><p></p> <table border="1" frame="border" cellpadding="7"><tbody align="center"> | |
| <tr> | |
| <td rowspan="2" colspan="1"></td> | |
| <td rowspan="1" colspan="4" align="center" valign="bottom">Entity Type</td> | |
| <td rowspan="2" colspan="1" align="center">Character</td> | |
| </tr> | |
| <tr align="center" valign="bottom"> | |
| <td rowspan="1" colspan="1">Parameter</td> | |
| <td rowspan="1" colspan="1">Internal General</td> | |
| <td rowspan="1" colspan="1">External Parsed General</td> | |
| <td rowspan="1" colspan="1">Unparsed</td> | |
| </tr> | |
| <tr align="center" valign="middle"> | |
| <td rowspan="1" colspan="1" align="right">Reference in Content</td> | |
| <td rowspan="1" colspan="1"><a href="#not-recognized"><cite>Not recognized</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#included"><cite>Included</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#include-if-valid"><cite>Included if | |
| validating</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#included"><cite>Included</cite></a></td> | |
| </tr> | |
| <tr align="center" valign="middle"> | |
| <td rowspan="1" colspan="1" align="right">Reference in Attribute Value</td> | |
| <td rowspan="1" colspan="1"><a href="#not-recognized"><cite>Not recognized</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#inliteral"><cite>Included in literal</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#included"><cite>Included</cite></a></td> | |
| </tr> | |
| <tr align="center" valign="middle"> | |
| <td rowspan="1" colspan="1" align="right">Occurs as Attribute Value</td> | |
| <td rowspan="1" colspan="1"><a href="#not-recognized"><cite>Not recognized</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#notify"><cite>Notify</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#not-recognized"><cite>Not recognized</cite></a></td> | |
| </tr> | |
| <tr align="center" valign="middle"> | |
| <td rowspan="1" colspan="1" align="right">Reference in EntityValue</td> | |
| <td rowspan="1" colspan="1"><a href="#inliteral"><cite>Included in literal</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#bypass"><cite>Bypassed</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#bypass"><cite>Bypassed</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#included"><cite>Included</cite></a></td> | |
| </tr> | |
| <tr align="center" valign="middle"> | |
| <td rowspan="1" colspan="1" align="right">Reference in DTD</td> | |
| <td rowspan="1" colspan="1"><a href="#as-PE"><cite>Included as PE</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td> | |
| <td rowspan="1" colspan="1"><a href="#forbidden"><cite>Forbidden</cite></a></td> | |
| </tr> | |
| </tbody></table> <div class="div3"> <h4><a name="not-recognized"></a>4.4.1 | |
| Not Recognized</h4> <p>Outside the DTD, the <code>%</code> character has no | |
| special significance; thus, what would be parameter entity references in the | |
| DTD are not recognized as markup in <a href="#NT-content">content</a>. Similarly, | |
| the names of unparsed entities are not recognized except when they appear | |
| in the value of an appropriately declared attribute.</p> </div> <div class="div3"> <h4><a | |
| name="included"></a>4.4.2 Included</h4> <p>[<a title="Include" name="dt-include">Definition</a>: | |
| An entity is <b>included</b> when its <a title="Replacement Text" href="#dt-repltext">replacement | |
| text</a> is retrieved and processed, in place of the reference itself, as | |
| though it were part of the document at the location the reference was recognized.] | |
| The replacement text may contain both <a title="Character Data" href="#dt-chardata">character | |
| data</a> and (except for parameter entities) <a title="Markup" href="#dt-markup">markup</a>, | |
| which must be recognized in the usual way. (The string "<code>AT&amp;T;</code>" | |
| expands to "<code>AT&T;</code>" and the remaining ampersand is not recognized | |
| as an entity-reference delimiter.) A character reference is <b>included</b> | |
| when the indicated character is processed in place of the reference itself. </p> </div> <div | |
| class="div3"> <h4><a name="include-if-valid"></a>4.4.3 Included If Validating</h4> <p>When | |
| an XML processor recognizes a reference to a parsed entity, in order to <a | |
| title="Validity" href="#dt-valid">validate</a> the document, the processor | |
| must <a title="Include" href="#dt-include">include</a> its replacement text. | |
| If the entity is external, and the processor is not attempting to validate | |
| the XML document, the processor <a title="May" href="#dt-may">may</a>, but | |
| need not, include the entity's replacement text. If a non-validating processor | |
| does not include the replacement text, it must inform the application that | |
| it recognized, but did not read, the entity.</p> <p>This rule is based on | |
| the recognition that the automatic inclusion provided by the SGML and XML | |
| entity mechanism, primarily designed to support modularity in authoring, is | |
| not necessarily appropriate for other applications, in particular document | |
| browsing. Browsers, for example, when encountering an external parsed entity | |
| reference, might choose to provide a visual indication of the entity's presence | |
| and retrieve it for display only on demand.</p> </div> <div class="div3"> <h4><a | |
| name="forbidden"></a>4.4.4 Forbidden</h4> <p>The following are forbidden, | |
| and constitute <a title="Fatal Error" href="#dt-fatal">fatal</a> errors:</p> <ul> | |
| <li><p>the appearance of a reference to an <a title="Unparsed Entity" href="#dt-unparsed">unparsed | |
| entity</a>.</p></li> | |
| <li><p>the appearance of any character or general-entity reference in the | |
| DTD except within an <a href="#NT-EntityValue">EntityValue</a> or <a href="#NT-AttValue">AttValue</a>.</p> </li> | |
| <li><p>a reference to an external entity in an attribute value.</p></li> | |
| </ul> </div> <div class="div3"> <h4><a name="inliteral"></a>4.4.5 Included | |
| in Literal</h4> <p>When an <a title="Entity Reference" href="#dt-entref">entity | |
| reference</a> appears in an attribute value, or a parameter entity reference | |
| appears in a literal entity value, its <a title="Replacement Text" href="#dt-repltext">replacement | |
| text</a> is processed in place of the reference itself as though it were part | |
| of the document at the location the reference was recognized, except that | |
| a single or double quote character in the replacement text is always treated | |
| as a normal data character and will not terminate the literal. For example, | |
| this is well-formed:</p> <table class="eg" width="100%" border="1" cellpadding="5" | |
| bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!-- --> | |
| <!ENTITY % YN '"Yes"' > | |
| <!ENTITY WhatHeSaid "He said %YN;" ></pre></td> | |
| </tr> | |
| </table> <p>while this is not:</p> <table class="eg" width="100%" border="1" | |
| cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ENTITY EndAttr "27'" > | |
| <element attribute='a-&EndAttr;></pre></td> | |
| </tr> | |
| </table> </div> <div class="div3"> <h4><a name="notify"></a>4.4.6 Notify</h4> <p>When | |
| the name of an <a title="Unparsed Entity" href="#dt-unparsed">unparsed entity</a> | |
| appears as a token in the value of an attribute of declared type <b>ENTITY</b> | |
| or <b>ENTITIES</b>, a validating processor must inform the application of | |
| the <a title="System Identifier" href="#dt-sysid">system</a> and <a title="Public identifier" | |
| href="#dt-pubid">public</a> (if any) identifiers for both the entity and its | |
| associated <a title="Notation" href="#dt-notation">notation</a>.</p> </div> <div | |
| class="div3"> <h4><a name="bypass"></a>4.4.7 Bypassed</h4> <p>When a general | |
| entity reference appears in the <a href="#NT-EntityValue">EntityValue</a> | |
| in an entity declaration, it is bypassed and left as is.</p> </div> <div class="div3"> <h4><a | |
| name="as-PE"></a>4.4.8 Included as PE</h4> <p>Just as with external parsed | |
| entities, parameter entities need only be <a href="#include-if-valid"><cite>included | |
| if validating</cite></a>. When a parameter-entity reference is recognized | |
| in the DTD and included, its <a title="Replacement Text" href="#dt-repltext">replacement | |
| text</a> is enlarged by the attachment of one leading and one following space | |
| (#x20) character; the intent is to constrain the replacement text of parameter | |
| entities to contain an integral number of grammatical tokens in the DTD. This | |
| behavior does not apply to parameter entity references within entity values; | |
| these are described in <a href="#inliteral"><b>4.4.5 Included in Literal</b></a>.</p> </div> </div> <div | |
| class="div2"> <h3><a name="intern-replacement"></a>4.5 Construction of Internal | |
| Entity Replacement Text</h3> <p>In discussing the treatment of internal entities, | |
| it is useful to distinguish two forms of the entity's value. [<a title="Literal Entity Value" | |
| name="dt-litentval">Definition</a>: The <b>literal entity value</b> is the | |
| quoted string actually present in the entity declaration, corresponding to | |
| the non-terminal <a href="#NT-EntityValue">EntityValue</a>.] [<a title="Replacement Text" | |
| name="dt-repltext">Definition</a>: The <b>replacement text</b> is the content | |
| of the entity, after replacement of character references and parameter-entity | |
| references.]</p> <p>The literal entity value as given in an internal entity | |
| declaration (<a href="#NT-EntityValue">EntityValue</a>) may contain character, | |
| parameter-entity, and general-entity references. Such references must be contained | |
| entirely within the literal entity value. The actual replacement text that | |
| is <a title="Include" href="#dt-include">included</a> as described above must | |
| contain the <em>replacement text</em> of any parameter entities referred to, | |
| and must contain the character referred to, in place of any character references | |
| in the literal entity value; however, general-entity references must be left | |
| as-is, unexpanded. For example, given the following declarations:</p> <table | |
| class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ENTITY % pub "&#xc9;ditions Gallimard" > | |
| <!ENTITY rights "All rights reserved" > | |
| <!ENTITY book "La Peste: Albert Camus, | |
| &#xA9; 1947 %pub;. &rights;" ></pre></td> | |
| </tr> | |
| </table> <p>then the replacement text for the entity "<code>book</code>" is:</p> <table | |
| class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre>La Peste: Albert Camus, | |
| © 1947 Éditions Gallimard. &rights;</pre></td> | |
| </tr> | |
| </table> <p>The general-entity reference "<code>&rights;</code>" would | |
| be expanded should the reference "<code>&book;</code>" appear in the document's | |
| content or an attribute value.</p> <p>These simple rules may have complex | |
| interactions; for a detailed discussion of a difficult example, see <a href="#sec-entexpand"><b>D | |
| Expansion of Entity and Character References</b></a>.</p> </div> <div class="div2"> <h3><a | |
| name="sec-predefined-ent"></a>4.6 Predefined Entities</h3> <p>[<a title="escape" | |
| name="dt-escape">Definition</a>: Entity and character references can both | |
| be used to <b>escape</b> the left angle bracket, ampersand, and other delimiters. | |
| A set of general entities (<code>amp</code>, <code>lt</code>, <code>gt</code>, <code>apos</code>, <code>quot</code>) | |
| is specified for this purpose. Numeric character references may also be used; | |
| they are expanded immediately when recognized and must be treated as character | |
| data, so the numeric character references "<code>&#60;</code>" and "<code>&#38;</code>" | |
| may be used to escape <code><</code> and <code>&</code> when they occur | |
| in character data.]</p> <p>All XML processors must recognize these entities | |
| whether they are declared or not. <a title="For interoperability" href="#dt-interop">For | |
| interoperability</a>, valid XML documents should declare these entities, like | |
| any others, before using them. If the entities <code>lt</code> or <code>amp</code> | |
| are declared, they must be declared as internal entities whose replacement | |
| text is a character reference to the respective character (less-than sign | |
| or ampersand) being escaped; the double escaping is required for these entities | |
| so that references to them produce a well-formed result. If the entities <code>gt</code>, <code>apos</code>, | |
| or <code>quot</code> are declared, they must be declared as internal entities | |
| whose replacement text is the single character being escaped (or a character | |
| reference to that character; the double escaping here is unnecessary but harmless). | |
| For example:</p> <table class="eg" width="100%" border="1" cellpadding="5" | |
| bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ENTITY lt "&#38;#60;"> | |
| <!ENTITY gt "&#62;"> | |
| <!ENTITY amp "&#38;#38;"> | |
| <!ENTITY apos "&#39;"> | |
| <!ENTITY quot "&#34;"></pre></td> | |
| </tr> | |
| </table> </div> <div class="div2"> <h3><a name="Notations"></a>4.7 Notation | |
| Declarations</h3> <p>[<a title="Notation" name="dt-notation">Definition</a>: <b>Notations</b> | |
| identify by name the format of <a title="External Entity" href="#dt-extent">unparsed | |
| entities</a>, the format of elements which bear a notation attribute, or the | |
| application to which a <a title="Processing instruction" href="#dt-pi">processing | |
| instruction</a> is addressed.]</p> <p>[<a title="Notation Declaration" name="dt-notdecl">Definition</a>: | |
| <b>Notation declarations</b> provide a name for the notation, for use in | |
| entity and attribute-list declarations and in attribute specifications, and | |
| an external identifier for the notation which may allow an XML processor or | |
| its client application to locate a helper application capable of processing | |
| data in the given notation.]</p> <h5>Notation Declarations</h5><table class="scrap"> | |
| <tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-NotationDecl"></a>[82] </td> | |
| <td><code>NotationDecl</code></td> | |
| <td> ::= </td> | |
| <td><code>'<!NOTATION' <a href="#NT-S">S</a> <a href="#NT-Name">Name</a> <a | |
| href="#NT-S">S</a> (<a href="#NT-ExternalID">ExternalID</a> | <a href="#NT-PublicID">PublicID</a>) <a | |
| href="#NT-S">S</a>? '>'</code></td> | |
| <td><a href="#UniqueNotationName">[VC: Unique Notation Name]</a></td> | |
| </tr> | |
| </tbody><tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-PublicID"></a>[83] </td> | |
| <td><code>PublicID</code></td> | |
| <td> ::= </td> | |
| <td><code>'PUBLIC' <a href="#NT-S">S</a> <a href="#NT-PubidLiteral">PubidLiteral</a> </code></td> | |
| </tr> | |
| </tbody></table> <div class="constraint"><p class="prefix"><a name="UniqueNotationName"></a><b>Validity | |
| constraint: Unique Notation Name</b></p><p>Only one notation declaration can | |
| declare a given <a href="#NT-Name">Name</a>.</p> </div> <p>XML processors | |
| must provide applications with the name and external identifier(s) of any | |
| notation declared and referred to in an attribute value, attribute definition, | |
| or entity declaration. They may additionally resolve the external identifier | |
| into the <a title="System Identifier" href="#dt-sysid">system identifier</a>, | |
| file name, or other information needed to allow the application to call a | |
| processor for data in the notation described. (It is not an error, however, | |
| for XML documents to declare and refer to notations for which notation-specific | |
| applications are not available on the system where the XML processor or application | |
| is running.)</p> </div> <div class="div2"> <h3><a name="sec-doc-entity"></a>4.8 | |
| Document Entity</h3> <p>[<a title="Document Entity" name="dt-docent">Definition</a>: | |
| The <b>document entity</b> serves as the root of the entity tree and a starting-point | |
| for an <a title="XML Processor" href="#dt-xml-proc">XML processor</a>.] This | |
| specification does not specify how the document entity is to be located by | |
| an XML processor; unlike other entities, the document entity has no name and | |
| might well appear on a processor input stream without any identification at | |
| all.</p> </div> </div> <div class="div1"> <h2><a name="sec-conformance"></a>5 | |
| Conformance</h2> <div class="div2"> <h3><a name="proc-types"></a>5.1 Validating | |
| and Non-Validating Processors</h3> <p>Conforming <a title="XML Processor" | |
| href="#dt-xml-proc">XML processors</a> fall into two classes: validating and | |
| non-validating.</p> <p>Validating and non-validating processors alike must | |
| report violations of this specification's well-formedness constraints in the | |
| content of the <a title="Document Entity" href="#dt-docent">document entity</a> | |
| and any other <a title="Text Entity" href="#dt-parsedent">parsed entities</a> | |
| that they read.</p> <p>[<a title="Validating Processor" name="dt-validating">Definition</a>: <b>Validating | |
| processors</b> must, at user option, report violations of the constraints | |
| expressed by the declarations in the <a title="Document Type Declaration" | |
| href="#dt-doctype">DTD</a>, and failures to fulfill the validity constraints | |
| given in this specification.] To accomplish this, validating XML processors | |
| must read and process the entire DTD and all external parsed entities referenced | |
| in the document.</p> <p>Non-validating processors are required to check only | |
| the <a title="Document Entity" href="#dt-docent">document entity</a>, including | |
| the entire internal DTD subset, for well-formedness. [<a title="Process Declarations" | |
| name="dt-use-mdecl">Definition</a>: While they are not required to check | |
| the document for validity, they are required to <b>process</b> all the declarations | |
| they read in the internal DTD subset and in any parameter entity that they | |
| read, up to the first reference to a parameter entity that they do <em>not</em> | |
| read; that is to say, they must use the information in those declarations | |
| to <a href="#AVNormalize"><cite>normalize</cite></a> attribute values, <a | |
| href="#included"><cite>include</cite></a> the replacement text of internal | |
| entities, and supply <a href="#sec-attr-defaults"><cite>default attribute | |
| values</cite></a>.] Except when <code>standalone="yes"</code>, they must not <a | |
| title="Process Declarations" href="#dt-use-mdecl">process</a> <a title="entity declaration" | |
| href="#dt-entdecl">entity declarations</a> or <a title="Attribute-List Declaration" | |
| href="#dt-attdecl">attribute-list declarations</a> encountered after a reference | |
| to a parameter entity that is not read, since the entity may have contained | |
| overriding declarations.</p> </div> <div class="div2"> <h3><a name="safe-behavior"></a>5.2 | |
| Using XML Processors</h3> <p>The behavior of a validating XML processor is | |
| highly predictable; it must read every piece of a document and report all | |
| well-formedness and validity violations. Less is required of a non-validating | |
| processor; it need not read any part of the document other than the document | |
| entity. This has two effects that may be important to users of XML processors:</p> <ul> | |
| <li><p>Certain well-formedness errors, specifically those that require reading | |
| external entities, may not be detected by a non-validating processor. Examples | |
| include the constraints entitled <a href="#wf-entdeclared"><cite>Entity Declared</cite></a>, <a | |
| href="#textent"><cite>Parsed Entity</cite></a>, and <a href="#norecursion"><cite>No | |
| Recursion</cite></a>, as well as some of the cases described as <a href="#forbidden"><cite>forbidden</cite></a> | |
| in <a href="#entproc"><b>4.4 XML Processor Treatment of Entities and References</b></a>.</p></li> | |
| <li><p>The information passed from the processor to the application may vary, | |
| depending on whether the processor reads parameter and external entities. | |
| For example, a non-validating processor may not <a href="#AVNormalize"><cite>normalize</cite></a> | |
| attribute values, <a href="#included"><cite>include</cite></a> the replacement | |
| text of internal entities, or supply <a href="#sec-attr-defaults"><cite>default | |
| attribute values</cite></a>, where doing so depends on having read declarations | |
| in external or parameter entities.</p></li> | |
| </ul> <p>For maximum reliability in interoperating between different XML processors, | |
| applications which use non-validating processors should not rely on any behaviors | |
| not required of such processors. Applications which require facilities such | |
| as the use of default attributes or internal entities which are declared in | |
| external entities should use validating XML processors.</p> </div> </div> <div | |
| class="div1"> <h2><a name="sec-notation"></a>6 Notation</h2> <p>The formal | |
| grammar of XML is given in this specification using a simple Extended Backus-Naur | |
| Form (EBNF) notation. Each rule in the grammar defines one symbol, in the | |
| form</p> <table class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre>symbol ::= expression</pre></td> | |
| </tr> | |
| </table> <p>Symbols are written with an initial capital letter if they are | |
| the start symbol of a regular language, otherwise with an initial lower case | |
| letter. Literal strings are quoted.</p> <p>Within the expression on the right-hand | |
| side of a rule, the following expressions are used to match strings of one | |
| or more characters: </p><dl> | |
| <dt class="label"><code>#xN</code></dt> | |
| <dd> <p>where <code>N</code> is a hexadecimal integer, the expression matches | |
| the character in ISO/IEC 10646 whose canonical (UCS-4) code value, when interpreted | |
| as an unsigned binary number, has the value indicated. The number of leading | |
| zeros in the <code>#xN</code> form is insignificant; the number of leading | |
| zeros in the corresponding code value is governed by the character encoding | |
| in use and is not significant for XML.</p> </dd> | |
| <dt class="label"><code>[a-zA-Z]</code>, <code>[#xN-#xN]</code></dt> | |
| <dd> <p>matches any <a href="#NT-Char">Char</a> with a value in the range(s) | |
| indicated (inclusive).</p> </dd> | |
| <dt class="label"><code>[abc]</code>, <code>[#xN#xN#xN]</code></dt> | |
| <dd> <p>matches any <a href="#NT-Char">Char</a> with a value among the characters | |
| enumerated. Enumerations and ranges can be mixed in one set of brackets.</p> </dd> | |
| <dt class="label"><code>[^a-z]</code>, <code>[^#xN-#xN]</code></dt> | |
| <dd> <p>matches any <a href="#NT-Char">Char</a> with a value <em>outside</em> | |
| the range indicated.</p> </dd> | |
| <dt class="label"><code>[^abc]</code>, <code>[^#xN#xN#xN]</code></dt> | |
| <dd> <p>matches any <a href="#NT-Char">Char</a> with a value not among the | |
| characters given. Enumerations and ranges of forbidden values can be mixed | |
| in one set of brackets.</p> </dd> | |
| <dt class="label"><code>"string"</code></dt> | |
| <dd> <p>matches a literal string <a title="match" href="#dt-match">matching</a> | |
| that given inside the double quotes.</p> </dd> | |
| <dt class="label"><code>'string'</code></dt> | |
| <dd> <p>matches a literal string <a title="match" href="#dt-match">matching</a> | |
| that given inside the single quotes.</p> </dd> | |
| </dl><p> These symbols may be combined to match more complex patterns as follows, | |
| where <code>A</code> and <code>B</code> represent simple expressions: </p><dl> | |
| <dt class="label">(<code>expression</code>)</dt> | |
| <dd> <p><code>expression</code> is treated as a unit and may be combined as | |
| described in this list.</p> </dd> | |
| <dt class="label"><code>A?</code></dt> | |
| <dd> <p>matches <code>A</code> or nothing; optional <code>A</code>.</p> </dd> | |
| <dt class="label"><code>A B</code></dt> | |
| <dd> <p>matches <code>A</code> followed by <code>B</code>. This operator has | |
| higher precedence than alternation; thus <code>A B | C D</code> is identical | |
| to <code>(A B) | (C D)</code>.</p> </dd> | |
| <dt class="label"><code>A | B</code></dt> | |
| <dd> <p>matches <code>A</code> or <code>B</code> but not both.</p> </dd> | |
| <dt class="label"><code>A - B</code></dt> | |
| <dd> <p>matches any string that matches <code>A</code> but does not match <code>B</code>.</p> </dd> | |
| <dt class="label"><code>A+</code></dt> | |
| <dd> <p>matches one or more occurrences of <code>A</code>.Concatenation has | |
| higher precedence than alternation; thus <code>A+ | B+</code> is identical | |
| to <code>(A+) | (B+)</code>.</p> </dd> | |
| <dt class="label"><code>A*</code></dt> | |
| <dd> <p>matches zero or more occurrences of <code>A</code>. Concatenation | |
| has higher precedence than alternation; thus <code>A* | B*</code> is identical | |
| to <code>(A*) | (B*)</code>.</p> </dd> | |
| </dl><p> Other notations used in the productions are: </p><dl> | |
| <dt class="label"><code>/* ... */</code></dt> | |
| <dd> <p>comment.</p> </dd> | |
| <dt class="label"><code>[ wfc: ... ]</code></dt> | |
| <dd> <p>well-formedness constraint; this identifies by name a constraint on <a | |
| title="Well-Formed" href="#dt-wellformed">well-formed</a> documents associated | |
| with a production.</p> </dd> | |
| <dt class="label"><code>[ vc: ... ]</code></dt> | |
| <dd> <p>validity constraint; this identifies by name a constraint on <a title="Validity" | |
| href="#dt-valid">valid</a> documents associated with a production.</p> </dd> | |
| </dl><p></p> </div> </div><div class="back"> <div class="div1"> <h2><a name="sec-bibliography"></a>A | |
| References</h2> <div class="div2"> <h3><a name="sec-existing-stds"></a>A.1 | |
| Normative References</h3> <dl> | |
| <dt class="label"><a name="IANA"></a>IANA-CHARSETS</dt> | |
| <dd>(Internet Assigned Numbers Authority) <cite>Official Names for Character | |
| Sets</cite>, ed. Keld Simonsen et al. See <a href="ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets">ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets</a | |
| >. </dd> | |
| <dt class="label"><a name="RFC1766"></a>IETF RFC 1766</dt> | |
| <dd>IETF (Internet Engineering Task Force). <cite>RFC 1766: Tags for the Identification | |
| of Languages</cite>, ed. H. Alvestrand. 1995. (See <a href="http://www.ietf.org/rfc/rfc1766.txt">http://www.ietf.org/rfc/rfc1766.txt</a>.)</dd> | |
| <dt class="label"><a name="ISO10646"></a>ISO/IEC 10646</dt> | |
| <dd>ISO (International Organization for Standardization). <cite>ISO/IEC 10646-1993 | |
| (E). Information technology -- Universal Multiple-Octet Coded Character Set | |
| (UCS) -- Part 1: Architecture and Basic Multilingual Plane.</cite> [Geneva]: | |
| International Organization for Standardization, 1993 (plus amendments AM 1 | |
| through AM 7).</dd> | |
| <dt class="label"><a name="ISO10646-2000"></a>ISO/IEC 10646-2000</dt> | |
| <dd> ISO (International Organization for Standardization). <cite>ISO/IEC 10646-1:2000. | |
| Information technology -- Universal Multiple-Octet Coded Character Set (UCS) | |
| -- Part 1: Architecture and Basic Multilingual Plane.</cite> [Geneva]: International | |
| Organization for Standardization, 2000.</dd> | |
| <dt class="label"><a name="Unicode"></a>Unicode</dt> | |
| <dd>The Unicode Consortium. <em>The Unicode Standard, Version 2.0.</em> Reading, | |
| Mass.: Addison-Wesley Developers Press, 1996.</dd> | |
| <dt class="label"><a name="Unicode3"></a>Unicode3</dt> | |
| <dd> The Unicode Consortium. <em>The Unicode Standard, Version 3.0.</em> Reading, | |
| Mass.: Addison-Wesley Developers Press, 2000. ISBN 0-201-61633-5.</dd> | |
| </dl></div> <div class="div2"> <h3><a name="null"></a>A.2 Other References</h3> <dl> | |
| <dt class="label"><a name="Aho"></a>Aho/Ullman</dt> | |
| <dd>Aho, Alfred V., Ravi Sethi, and Jeffrey D. Ullman. <cite>Compilers: Principles, | |
| Techniques, and Tools</cite>. Reading: Addison-Wesley, 1986, rpt. corr. 1988.</dd> | |
| <dt class="label"><a name="Berners-Lee"></a>Berners-Lee et al.</dt> | |
| <dd> Berners-Lee, T., R. Fielding, and L. Masinter. <cite>Uniform Resource | |
| Identifiers (URI): Generic Syntax and Semantics</cite>. 1997. (Work in progress; | |
| see updates to RFC1738.)</dd> | |
| <dt class="label"><a name="ABK"></a>Brüggemann-Klein</dt> | |
| <dd>Brüggemann-Klein, Anne. Formal Models in Document Processing. Habilitationsschrift. | |
| Faculty of Mathematics at the University of Freiburg, 1993. (See <a href="ftp://ftp.informatik.uni-freiburg.de/documents/papers/brueggem/habil.ps" | |
| >ftp://ftp.informatik.uni-freiburg.de/documents/papers/brueggem/habil.ps</a>.)</dd> | |
| <dt class="label"><a name="ABKDW"></a>Brüggemann-Klein and Wood</dt> | |
| <dd>Brüggemann-Klein, Anne, and Derick Wood. <cite>Deterministic Regular | |
| Languages</cite>. Universität Freiburg, Institut für Informatik, | |
| Bericht 38, Oktober 1991. Extended abstract in A. Finkel, M. Jantzen, Hrsg., | |
| STACS 1992, S. 173-184. Springer-Verlag, Berlin 1992. Lecture Notes in Computer | |
| Science 577. Full version titled <cite>One-Unambiguous Regular Languages</cite> | |
| in Information and Computation 140 (2): 229-253, February 1998.</dd> | |
| <dt class="label"><a name="Clark"></a>Clark</dt> | |
| <dd>James Clark. Comparison of SGML and XML. See <a href="http://www.w3.org/TR/NOTE-sgml-xml-971215">http://www.w3.org/TR/NOTE-sgml-xml-971215</a | |
| >. </dd> | |
| <dt class="label"><a name="IANA-LANGCODES"></a>IANA-LANGCODES</dt> | |
| <dd>(Internet Assigned Numbers Authority) <cite>Registry of Language Tags</cite>, | |
| ed. Keld Simonsen et al. (See <a href="http://www.isi.edu/in-notes/iana/assignments/languages/">http://www.isi.edu/in-notes/iana/assignments/languages/</a | |
| >.)</dd> | |
| <dt class="label"><a name="RFC2141"></a>IETF RFC2141</dt> | |
| <dd>IETF (Internet Engineering Task Force). <em>RFC 2141: URN Syntax</em>, | |
| ed. R. Moats. 1997. (See <a href="http://www.ietf.org/rfc/rfc2141.txt">http://www.ietf.org/rfc/rfc2141.txt</a>.)</dd> | |
| <dt class="label"><a name="rfc2279"></a>IETF RFC 2279</dt> | |
| <dd>IETF (Internet Engineering Task Force). <cite>RFC 2279: UTF-8, a transformation | |
| format of ISO 10646</cite>, ed. F. Yergeau, 1998. (See <a href="http://www.ietf.org/rfc/rfc2279.txt">http://www.ietf.org/rfc/rfc2279.txt</a>.)</dd> | |
| <dt class="label"><a name="rfc2376"></a>IETF RFC 2376</dt> | |
| <dd>IETF (Internet Engineering Task Force). <cite>RFC 2376: XML Media Types</cite>. | |
| ed. E. Whitehead, M. Murata. 1998. (See <a href="http://www.ietf.org/rfc/rfc2376.txt">http://www.ietf.org/rfc/rfc2376.txt</a>.)</dd> | |
| <dt class="label"><a name="rfc2396"></a>IETF RFC 2396</dt> | |
| <dd>IETF (Internet Engineering Task Force). <cite>RFC 2396: Uniform Resource | |
| Identifiers (URI): Generic Syntax</cite>. T. Berners-Lee, R. Fielding, L. | |
| Masinter. 1998. (See <a href="http://www.ietf.org/rfc/rfc2396.txt">http://www.ietf.org/rfc/rfc2396.txt</a>.)</dd> | |
| <dt class="label"><a name="rfc2732"></a>IETF RFC 2732</dt> | |
| <dd>IETF (Internet Engineering Task Force). <cite>RFC 2732: Format for Literal | |
| IPv6 Addresses in URL's</cite>. R. Hinden, B. Carpenter, L. Masinter. 1999. | |
| (See <a href="http://www.ietf.org/rfc/rfc2732.txt">http://www.ietf.org/rfc/rfc2732.txt</a>.)</dd> | |
| <dt class="label"><a name="rfc2781"></a>IETF RFC 2781</dt> | |
| <dd> IETF (Internet Engineering Task Force). <em>RFC 2781: UTF-16, an encoding | |
| of ISO 10646</em>, ed. P. Hoffman, F. Yergeau. 2000. (See <a href="http://www.ietf.org/rfc/rfc2781.txt">http://www.ietf.org/rfc/rfc2781.txt</a>.)</dd> | |
| <dt class="label"><a name="ISO639"></a>ISO 639</dt> | |
| <dd> (International Organization for Standardization). <cite>ISO 639:1988 | |
| (E). Code for the representation of names of languages.</cite> [Geneva]: International | |
| Organization for Standardization, 1988.</dd> | |
| <dt class="label"><a name="ISO3166"></a>ISO 3166</dt> | |
| <dd> (International Organization for Standardization). <cite>ISO 3166-1:1997 | |
| (E). Codes for the representation of names of countries and their subdivisions | |
| -- Part 1: Country codes</cite> [Geneva]: International Organization for Standardization, | |
| 1997.</dd> | |
| <dt class="label"><a name="ISO8879"></a>ISO 8879</dt> | |
| <dd>ISO (International Organization for Standardization). <cite>ISO 8879:1986(E). | |
| Information processing -- Text and Office Systems -- Standard Generalized | |
| Markup Language (SGML).</cite> First edition -- 1986-10-15. [Geneva]: International | |
| Organization for Standardization, 1986. </dd> | |
| <dt class="label"><a name="ISO10744"></a>ISO/IEC 10744</dt> | |
| <dd>ISO (International Organization for Standardization). <cite>ISO/IEC 10744-1992 | |
| (E). Information technology -- Hypermedia/Time-based Structuring Language | |
| (HyTime). </cite> [Geneva]: International Organization for Standardization, | |
| 1992. <em>Extended Facilities Annexe.</em> [Geneva]: International Organization | |
| for Standardization, 1996. </dd> | |
| <dt class="label"><a name="websgml"></a>WEBSGML</dt> | |
| <dd>ISO (International Organization for Standardization). <cite>ISO 8879:1986 | |
| TC2. Information technology -- Document Description and Processing Languages. </cite> | |
| [Geneva]: International Organization for Standardization, 1998. (See <a href="http://www.sgmlsource.com/8879rev/n0029.htm">http://www.sgmlsource.com/8879rev/n0029.htm</a | |
| >.)</dd> | |
| <dt class="label"><a name="xml-names"></a>XML Names</dt> | |
| <dd>Tim Bray, Dave Hollander, and Andrew Layman, editors. <cite>Namespaces | |
| in XML</cite>. Textuality, Hewlett-Packard, and Microsoft. World Wide Web | |
| Consortium, 1999. (See <a href="http://www.w3.org/TR/REC-xml-names/">http://www.w3.org/TR/REC-xml-names/</a>.)</dd> | |
| </dl></div> </div> <div class="div1"> <h2><a name="CharClasses"></a>B Character | |
| Classes</h2> <p>Following the characteristics defined in the Unicode standard, | |
| characters are classed as base characters (among others, these contain the | |
| alphabetic characters of the Latin alphabet), ideographic characters, and | |
| combining characters (among others, this class contains most diacritics) Digits | |
| and extenders are also distinguished.</p> <h5>Characters</h5><table class="scrap"> | |
| <tbody> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Letter"></a>[84] </td> | |
| <td><code>Letter</code></td> | |
| <td> ::= </td> | |
| <td><code><a href="#NT-BaseChar">BaseChar</a> | <a href="#NT-Ideographic">Ideographic</a></code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-BaseChar"></a>[85] </td> | |
| <td><code>BaseChar</code></td> | |
| <td> ::= </td> | |
| <td><code>[#x0041-#x005A] | [#x0061-#x007A] | [#x00C0-#x00D6] | [#x00D8-#x00F6] | |
| | [#x00F8-#x00FF] | [#x0100-#x0131] | [#x0134-#x013E] | [#x0141-#x0148] | |
| | [#x014A-#x017E] | [#x0180-#x01C3] | [#x01CD-#x01F0] | [#x01F4-#x01F5] | |
| | [#x01FA-#x0217] | [#x0250-#x02A8] | [#x02BB-#x02C1] | #x0386 | |
| | [#x0388-#x038A] | #x038C | [#x038E-#x03A1] | [#x03A3-#x03CE] | |
| | [#x03D0-#x03D6] | #x03DA | #x03DC | #x03DE | #x03E0 | |
| | [#x03E2-#x03F3] | [#x0401-#x040C] | [#x040E-#x044F] | [#x0451-#x045C] | |
| | [#x045E-#x0481] | [#x0490-#x04C4] | [#x04C7-#x04C8] | [#x04CB-#x04CC] | |
| | [#x04D0-#x04EB] | [#x04EE-#x04F5] | [#x04F8-#x04F9] | [#x0531-#x0556] | |
| | #x0559 | [#x0561-#x0586] | [#x05D0-#x05EA] | [#x05F0-#x05F2] | |
| | [#x0621-#x063A] | [#x0641-#x064A] | [#x0671-#x06B7] | [#x06BA-#x06BE] | |
| | [#x06C0-#x06CE] | [#x06D0-#x06D3] | #x06D5 | [#x06E5-#x06E6] | |
| | [#x0905-#x0939] | #x093D | [#x0958-#x0961] | [#x0985-#x098C] | |
| | [#x098F-#x0990] | [#x0993-#x09A8] | [#x09AA-#x09B0] | #x09B2 | |
| | [#x09B6-#x09B9] | [#x09DC-#x09DD] | [#x09DF-#x09E1] | [#x09F0-#x09F1] | |
| | [#x0A05-#x0A0A] | [#x0A0F-#x0A10] | [#x0A13-#x0A28] | [#x0A2A-#x0A30] | |
| | [#x0A32-#x0A33] | [#x0A35-#x0A36] | [#x0A38-#x0A39] | [#x0A59-#x0A5C] | |
| | #x0A5E | [#x0A72-#x0A74] | [#x0A85-#x0A8B] | #x0A8D | |
| | [#x0A8F-#x0A91] | [#x0A93-#x0AA8] | [#x0AAA-#x0AB0] | [#x0AB2-#x0AB3] | |
| | [#x0AB5-#x0AB9] | #x0ABD | #x0AE0 | [#x0B05-#x0B0C] | |
| | [#x0B0F-#x0B10] | [#x0B13-#x0B28] | [#x0B2A-#x0B30] | [#x0B32-#x0B33] | |
| | [#x0B36-#x0B39] | #x0B3D | [#x0B5C-#x0B5D] | [#x0B5F-#x0B61] | |
| | [#x0B85-#x0B8A] | [#x0B8E-#x0B90] | [#x0B92-#x0B95] | [#x0B99-#x0B9A] | |
| | #x0B9C | [#x0B9E-#x0B9F] | [#x0BA3-#x0BA4] | [#x0BA8-#x0BAA] | |
| | [#x0BAE-#x0BB5] | [#x0BB7-#x0BB9] | [#x0C05-#x0C0C] | [#x0C0E-#x0C10] | |
| | [#x0C12-#x0C28] | [#x0C2A-#x0C33] | [#x0C35-#x0C39] | [#x0C60-#x0C61] | |
| | [#x0C85-#x0C8C] | [#x0C8E-#x0C90] | [#x0C92-#x0CA8] | [#x0CAA-#x0CB3] | |
| | [#x0CB5-#x0CB9] | #x0CDE | [#x0CE0-#x0CE1] | [#x0D05-#x0D0C] | |
| | [#x0D0E-#x0D10] | [#x0D12-#x0D28] | [#x0D2A-#x0D39] | [#x0D60-#x0D61] | |
| | [#x0E01-#x0E2E] | #x0E30 | [#x0E32-#x0E33] | [#x0E40-#x0E45] | |
| | [#x0E81-#x0E82] | #x0E84 | [#x0E87-#x0E88] | #x0E8A | |
| | #x0E8D | [#x0E94-#x0E97] | [#x0E99-#x0E9F] | [#x0EA1-#x0EA3] | |
| | #x0EA5 | #x0EA7 | [#x0EAA-#x0EAB] | [#x0EAD-#x0EAE] | |
| | #x0EB0 | [#x0EB2-#x0EB3] | #x0EBD | [#x0EC0-#x0EC4] | |
| | [#x0F40-#x0F47] | [#x0F49-#x0F69] | [#x10A0-#x10C5] | [#x10D0-#x10F6] | |
| | #x1100 | [#x1102-#x1103] | [#x1105-#x1107] | #x1109 | |
| | [#x110B-#x110C] | [#x110E-#x1112] | #x113C | #x113E | |
| | #x1140 | #x114C | #x114E | #x1150 | [#x1154-#x1155] | |
| | #x1159 | [#x115F-#x1161] | #x1163 | #x1165 | #x1167 | |
| | #x1169 | [#x116D-#x116E] | [#x1172-#x1173] | #x1175 | |
| | #x119E | #x11A8 | #x11AB | [#x11AE-#x11AF] | [#x11B7-#x11B8] | |
| | #x11BA | [#x11BC-#x11C2] | #x11EB | #x11F0 | #x11F9 | |
| | [#x1E00-#x1E9B] | [#x1EA0-#x1EF9] | [#x1F00-#x1F15] | [#x1F18-#x1F1D] | |
| | [#x1F20-#x1F45] | [#x1F48-#x1F4D] | [#x1F50-#x1F57] | #x1F59 | |
| | #x1F5B | #x1F5D | [#x1F5F-#x1F7D] | [#x1F80-#x1FB4] | |
| | [#x1FB6-#x1FBC] | #x1FBE | [#x1FC2-#x1FC4] | [#x1FC6-#x1FCC] | |
| | [#x1FD0-#x1FD3] | [#x1FD6-#x1FDB] | [#x1FE0-#x1FEC] | [#x1FF2-#x1FF4] | |
| | [#x1FF6-#x1FFC] | #x2126 | [#x212A-#x212B] | #x212E | |
| | [#x2180-#x2182] | [#x3041-#x3094] | [#x30A1-#x30FA] | [#x3105-#x312C] | |
| | [#xAC00-#xD7A3] </code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Ideographic"></a>[86] </td> | |
| <td><code>Ideographic</code></td> | |
| <td> ::= </td> | |
| <td><code>[#x4E00-#x9FA5] | #x3007 | [#x3021-#x3029] </code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-CombiningChar"></a>[87] </td> | |
| <td><code>CombiningChar</code></td> | |
| <td> ::= </td> | |
| <td><code>[#x0300-#x0345] | [#x0360-#x0361] | [#x0483-#x0486] | [#x0591-#x05A1] | |
| | [#x05A3-#x05B9] | [#x05BB-#x05BD] | #x05BF | [#x05C1-#x05C2] | |
| | #x05C4 | [#x064B-#x0652] | #x0670 | [#x06D6-#x06DC] | |
| | [#x06DD-#x06DF] | [#x06E0-#x06E4] | [#x06E7-#x06E8] | [#x06EA-#x06ED] | |
| | [#x0901-#x0903] | #x093C | [#x093E-#x094C] | #x094D | |
| | [#x0951-#x0954] | [#x0962-#x0963] | [#x0981-#x0983] | #x09BC | |
| | #x09BE | #x09BF | [#x09C0-#x09C4] | [#x09C7-#x09C8] | |
| | [#x09CB-#x09CD] | #x09D7 | [#x09E2-#x09E3] | #x0A02 | |
| | #x0A3C | #x0A3E | #x0A3F | [#x0A40-#x0A42] | [#x0A47-#x0A48] | |
| | [#x0A4B-#x0A4D] | [#x0A70-#x0A71] | [#x0A81-#x0A83] | #x0ABC | |
| | [#x0ABE-#x0AC5] | [#x0AC7-#x0AC9] | [#x0ACB-#x0ACD] | [#x0B01-#x0B03] | |
| | #x0B3C | [#x0B3E-#x0B43] | [#x0B47-#x0B48] | [#x0B4B-#x0B4D] | |
| | [#x0B56-#x0B57] | [#x0B82-#x0B83] | [#x0BBE-#x0BC2] | [#x0BC6-#x0BC8] | |
| | [#x0BCA-#x0BCD] | #x0BD7 | [#x0C01-#x0C03] | [#x0C3E-#x0C44] | |
| | [#x0C46-#x0C48] | [#x0C4A-#x0C4D] | [#x0C55-#x0C56] | [#x0C82-#x0C83] | |
| | [#x0CBE-#x0CC4] | [#x0CC6-#x0CC8] | [#x0CCA-#x0CCD] | [#x0CD5-#x0CD6] | |
| | [#x0D02-#x0D03] | [#x0D3E-#x0D43] | [#x0D46-#x0D48] | [#x0D4A-#x0D4D] | |
| | #x0D57 | #x0E31 | [#x0E34-#x0E3A] | [#x0E47-#x0E4E] | |
| | #x0EB1 | [#x0EB4-#x0EB9] | [#x0EBB-#x0EBC] | [#x0EC8-#x0ECD] | |
| | [#x0F18-#x0F19] | #x0F35 | #x0F37 | #x0F39 | #x0F3E | |
| | #x0F3F | [#x0F71-#x0F84] | [#x0F86-#x0F8B] | [#x0F90-#x0F95] | |
| | #x0F97 | [#x0F99-#x0FAD] | [#x0FB1-#x0FB7] | #x0FB9 | |
| | [#x20D0-#x20DC] | #x20E1 | [#x302A-#x302F] | #x3099 | |
| | #x309A </code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Digit"></a>[88] </td> | |
| <td><code>Digit</code></td> | |
| <td> ::= </td> | |
| <td><code>[#x0030-#x0039] | [#x0660-#x0669] | [#x06F0-#x06F9] | [#x0966-#x096F] | |
| | [#x09E6-#x09EF] | [#x0A66-#x0A6F] | [#x0AE6-#x0AEF] | [#x0B66-#x0B6F] | |
| | [#x0BE7-#x0BEF] | [#x0C66-#x0C6F] | [#x0CE6-#x0CEF] | [#x0D66-#x0D6F] | |
| | [#x0E50-#x0E59] | [#x0ED0-#x0ED9] | [#x0F20-#x0F29] </code></td> | |
| </tr> | |
| <tr valign="baseline"> | |
| <td><a name="NT-Extender"></a>[89] </td> | |
| <td><code>Extender</code></td> | |
| <td> ::= </td> | |
| <td><code>#x00B7 | #x02D0 | #x02D1 | #x0387 | #x0640 | #x0E46 | |
| | #x0EC6 | #x3005 | [#x3031-#x3035] | [#x309D-#x309E] | |
| | [#x30FC-#x30FE] </code></td> | |
| </tr> | |
| </tbody></table> <p>The character classes defined here can be derived from | |
| the Unicode 2.0 character database as follows:</p> <ul> | |
| <li><p>Name start characters must have one of the categories Ll, Lu, Lo, Lt, | |
| Nl.</p></li> | |
| <li><p>Name characters other than Name-start characters must have one of the | |
| categories Mc, Me, Mn, Lm, or Nd.</p></li> | |
| <li><p>Characters in the compatibility area (i.e. with character code greater | |
| than #xF900 and less than #xFFFE) are not allowed in XML names.</p></li> | |
| <li><p>Characters which have a font or compatibility decomposition (i.e. those | |
| with a "compatibility formatting tag" in field 5 of the database -- marked | |
| by field 5 beginning with a "<") are not allowed.</p></li> | |
| <li><p>The following characters are treated as name-start characters rather | |
| than name characters, because the property file classifies them as Alphabetic: | |
| [#x02BB-#x02C1], #x0559, #x06E5, #x06E6.</p></li> | |
| <li><p>Characters #x20DD-#x20E0 are excluded (in accordance with Unicode 2.0, | |
| section 5.14).</p></li> | |
| <li><p>Character #x00B7 is classified as an extender, because the property | |
| list so identifies it.</p></li> | |
| <li><p>Character #x0387 is added as a name character, because #x00B7 is its | |
| canonical equivalent.</p></li> | |
| <li><p>Characters ':' and '_' are allowed as name-start characters.</p> </li> | |
| <li><p>Characters '-' and '.' are allowed as name characters.</p></li> | |
| </ul> </div> <div class="div1"> <h2><a name="sec-xml-and-sgml"></a>C XML and | |
| SGML (Non-Normative)</h2> <p>XML is designed to be a subset of SGML, in that | |
| every XML document should also be a conforming SGML document. For a detailed | |
| comparison of the additional restrictions that XML places on documents beyond | |
| those of SGML, see <a href="#Clark">[Clark]</a>.</p> </div> <div class="div1"> <h2><a | |
| name="sec-entexpand"></a>D Expansion of Entity and Character References (Non-Normative)</h2> <p>This | |
| appendix contains some examples illustrating the sequence of entity- and character-reference | |
| recognition and expansion, as specified in <a href="#entproc"><b>4.4 XML Processor | |
| Treatment of Entities and References</b></a>.</p> <p>If the DTD contains the | |
| declaration</p> <table class="eg" width="100%" border="1" cellpadding="5" | |
| bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><!ENTITY example "<p>An ampersand (&#38;#38;) may be escaped | |
| numerically (&#38;#38;#38;) or with a general entity | |
| (&amp;amp;).</p>" ></pre></td> | |
| </tr> | |
| </table> <p>then the XML processor will recognize the character references | |
| when it parses the entity declaration, and resolve them before storing the | |
| following string as the value of the entity "<code>example</code>":</p> <table | |
| class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre><p>An ampersand (&#38;) may be escaped | |
| numerically (&#38;#38;) or with a general entity | |
| (&amp;amp;).</p></pre></td> | |
| </tr> | |
| </table> <p>A reference in the document to "<code>&example;</code>" will | |
| cause the text to be reparsed, at which time the start- and end-tags of the <code>p</code> | |
| element will be recognized and the three references will be recognized and | |
| expanded, resulting in a <code>p</code> element with the following content | |
| (all data, no delimiters or markup):</p> <table class="eg" width="100%" border="1" | |
| cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre>An ampersand (&) may be escaped | |
| numerically (&#38;) or with a general entity | |
| (&amp;).</pre></td> | |
| </tr> | |
| </table> <p>A more complex example will illustrate the rules and their effects | |
| fully. In the following example, the line numbers are solely for reference.</p> <table | |
| class="eg" width="100%" border="1" cellpadding="5" bgcolor="#99ffff"> | |
| <tr> | |
| <td><pre>1 <?xml version='1.0'?> | |
| 2 <!DOCTYPE test [ | |
| 3 <!ELEMENT test (#PCDATA) > | |
| 4 <!ENTITY % xx '&#37;zz;'> | |
| 5 <!ENTITY % zz '&#60;!ENTITY tricky "error-prone" >' > | |
| 6 %xx; | |
| 7 ]> | |
| 8 <test>This sample shows a &tricky; method.</test></pre></td> | |
| </tr> | |
| </table> <p>This produces the following:</p> <ul> | |
| <li><p>in line 4, the reference to character 37 is expanded immediately, and | |
| the parameter entity "<code>xx</code>" is stored in the symbol table with | |
| the value "<code>%zz;</code>". Since the replacement text is not rescanned, | |
| the reference to parameter entity "<code>zz</code>" is not recognized. (And | |
| it would be an error if it were, since "<code>zz</code>" is not yet declared.)</p></li> | |
| <li><p>in line 5, the character reference "<code>&#60;</code>" is expanded | |
| immediately and the parameter entity "<code>zz</code>" is stored with the | |
| replacement text "<code><!ENTITY tricky "error-prone" ></code>", which | |
| is a well-formed entity declaration.</p></li> | |
| <li><p>in line 6, the reference to "<code>xx</code>" is recognized, and the | |
| replacement text of "<code>xx</code>" (namely "<code>%zz;</code>") is parsed. | |
| The reference to "<code>zz</code>" is recognized in its turn, and its replacement | |
| text ("<code><!ENTITY tricky "error-prone" ></code>") is parsed. The general | |
| entity "<code>tricky</code>" has now been declared, with the replacement text | |
| "<code>error-prone</code>".</p> </li> | |
| <li><p>in line 8, the reference to the general entity "<code>tricky</code>" | |
| is recognized, and it is expanded, so the full content of the <code>test</code> | |
| element is the self-describing (and ungrammatical) string <em>This sample | |
| shows a error-prone method.</em></p></li> | |
| </ul> </div> <div class="div1"> <h2><a name="determinism"></a>E Deterministic | |
| Content Models (Non-Normative)</h2> <p>As noted in <a href="#sec-element-content"><b>3.2.1 | |
| Element Content</b></a>, it is required that content models in element type | |
| declarations be deterministic. This requirement is <a title="For Compatibility" | |
| href="#dt-compat">for compatibility</a> with SGML (which calls deterministic | |
| content models "unambiguous"); XML processors built using SGML systems may | |
| flag non-deterministic content models as errors.</p> <p>For example, the content | |
| model <code>((b, c) | (b, d))</code> is non-deterministic, because given an | |
| initial <code>b</code> the XML processor cannot know which <code>b</code> | |
| in the model is being matched without looking ahead to see which element follows | |
| the <code>b</code>. In this case, the two references to <code>b</code> can | |
| be collapsed into a single reference, making the model read <code>(b, (c | | |
| d))</code>. An initial <code>b</code> now clearly matches only a single name | |
| in the content model. The processor doesn't need to look ahead to see what | |
| follows; either <code>c</code> or <code>d</code> would be accepted.</p> <p>More | |
| formally: a finite state automaton may be constructed from the content model | |
| using the standard algorithms, e.g. algorithm 3.5 in section 3.9 of Aho, Sethi, | |
| and Ullman <a href="#Aho">[Aho/Ullman]</a>. In many such algorithms, a follow | |
| set is constructed for each position in the regular expression (i.e., each | |
| leaf node in the syntax tree for the regular expression); if any position | |
| has a follow set in which more than one following position is labeled with | |
| the same element type name, then the content model is in error and may be | |
| reported as an error.</p> <p>Algorithms exist which allow many but not all | |
| non-deterministic content models to be reduced automatically to equivalent | |
| deterministic models; see Brüggemann-Klein 1991 <a href="#ABK">[Brüggemann-Klein]</a>.</p> </div> <div | |
| class="div1"> <h2><a name="sec-guessing"></a>F Autodetection of Character | |
| Encodings (Non-Normative)</h2> <p>The XML encoding declaration functions as | |
| an internal label on each entity, indicating which character encoding is in | |
| use. Before an XML processor can read the internal label, however, it apparently | |
| has to know what character encoding is in use--which is what the internal | |
| label is trying to indicate. In the general case, this is a hopeless situation. | |
| It is not entirely hopeless in XML, however, because XML limits the general | |
| case in two ways: each implementation is assumed to support only a finite | |
| set of character encodings, and the XML encoding declaration is restricted | |
| in position and content in order to make it feasible to autodetect the character | |
| encoding in use in each entity in normal cases. Also, in many cases other | |
| sources of information are available in addition to the XML data stream itself. | |
| Two cases may be distinguished, depending on whether the XML entity is presented | |
| to the processor without, or with, any accompanying (external) information. | |
| We consider the first case first.</p> <div class="div2"> <h3><a name="sec-guessing-no-ext-info"></a>F.1 | |
| Detection Without External Encoding Information</h3> <p>Because each XML entity | |
| not accompanied by external encoding information and not in UTF-8 or UTF-16 | |
| encoding <em>must</em> begin with an XML encoding declaration, in which the | |
| first characters must be '<code><?xml</code>', any conforming processor | |
| can detect, after two to four octets of input, which of the following cases | |
| apply. In reading this list, it may help to know that in UCS-4, '<' is | |
| "<code>#x0000003C</code>" and '?' is "<code>#x0000003F</code>", and the Byte | |
| Order Mark required of UTF-16 data streams is "<code>#xFEFF</code>". The notation <var>##</var> | |
| is used to denote any byte value except that two consecutive <var>##</var>s | |
| cannot be both 00.</p> <p>With a Byte Order Mark:</p> <table border="1" frame="border"> | |
| <tbody> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>00 00 FE FF</code></td> | |
| <td rowspan="1" colspan="1">UCS-4, big-endian machine (1234 order)</td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>FF FE 00 00</code></td> | |
| <td rowspan="1" colspan="1">UCS-4, little-endian machine (4321 order)</td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>00 00 FF FE</code></td> | |
| <td rowspan="1" colspan="1">UCS-4, unusual octet order (2143)</td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>FE FF 00 00</code></td> | |
| <td rowspan="1" colspan="1">UCS-4, unusual octet order (3412)</td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>FE FF ## ##</code></td> | |
| <td rowspan="1" colspan="1">UTF-16, big-endian</td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>FF FE ## ##</code></td> | |
| <td rowspan="1" colspan="1">UTF-16, little-endian</td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>EF BB BF</code></td> | |
| <td rowspan="1" colspan="1">UTF-8</td> | |
| </tr> | |
| </tbody></table> <p>Without a Byte Order Mark:</p> <table border="1" frame="border"> | |
| <tbody> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>00 00 00 3C</code></td> | |
| <td rowspan="4" colspan="1">UCS-4 or other encoding with a 32-bit code unit | |
| and ASCII characters encoded as ASCII values, in respectively big-endian (1234), | |
| little-endian (4321) and two unusual byte orders (2143 and 3412). The encoding | |
| declaration must be read to determine which of UCS-4 or other supported 32-bit | |
| encodings applies.</td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>3C 00 00 00</code></td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>00 00 3C 00</code></td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>00 3C 00 00</code></td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>00 3C 00 3F</code></td> | |
| <td rowspan="1" colspan="1">UTF-16BE or big-endian ISO-10646-UCS-2 or other | |
| encoding with a 16-bit code unit in big-endian order and ASCII characters | |
| encoded as ASCII values (the encoding declaration must be read to determine | |
| which)</td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>3C 00 3F 00</code></td> | |
| <td rowspan="1" colspan="1">UTF-16LE or little-endian ISO-10646-UCS-2 or other | |
| encoding with a 16-bit code unit in little-endian order and ASCII characters | |
| encoded as ASCII values (the encoding declaration must be read to determine | |
| which)</td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>3C 3F 78 6D</code></td> | |
| <td rowspan="1" colspan="1">UTF-8, ISO 646, ASCII, some part of ISO 8859, | |
| Shift-JIS, EUC, or any other 7-bit, 8-bit, or mixed-width encoding which ensures | |
| that the characters of ASCII have their normal positions, width, and values; | |
| the actual encoding declaration must be read to detect which of these applies, | |
| but since all of these encodings use the same bit patterns for the relevant | |
| ASCII characters, the encoding declaration itself may be read reliably</td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1"><code>4C 6F A7 94</code></td> | |
| <td rowspan="1" colspan="1">EBCDIC (in some flavor; the full encoding declaration | |
| must be read to tell which code page is in use)</td> | |
| </tr> | |
| <tr> | |
| <td rowspan="1" colspan="1">Other</td> | |
| <td rowspan="1" colspan="1">UTF-8 without an encoding declaration, or else | |
| the data stream is mislabeled (lacking a required encoding declaration), corrupt, | |
| fragmentary, or enclosed in a wrapper of some kind</td> | |
| </tr> | |
| </tbody></table> <div class="note"><p class="prefix"><b>Note:</b></p> <p>In | |
| cases above which do not require reading the encoding declaration to determine | |
| the encoding, section 4.3.3 still requires that the encoding declaration, | |
| if present, be read and that the encoding name be checked to match the actual | |
| encoding of the entity. Also, it is possible that new character encodings | |
| will be invented that will make it necessary to use the encoding declaration | |
| to determine the encoding, in cases where this is not required at present.</p> </div> <p>This | |
| level of autodetection is enough to read the XML encoding declaration and | |
| parse the character-encoding identifier, which is still necessary to distinguish | |
| the individual members of each family of encodings (e.g. to tell UTF-8 from | |
| 8859, and the parts of 8859 from each other, or to distinguish the specific | |
| EBCDIC code page in use, and so on).</p> <p>Because the contents of the encoding | |
| declaration are restricted to characters from the ASCII repertoire (however | |
| encoded), a processor can reliably read the entire encoding declaration as | |
| soon as it has detected which family of encodings is in use. Since in practice, | |
| all widely used character encodings fall into one of the categories above, | |
| the XML encoding declaration allows reasonably reliable in-band labeling of | |
| character encodings, even when external sources of information at the operating-system | |
| or transport-protocol level are unreliable. Character encodings such as UTF-7 | |
| that make overloaded usage of ASCII-valued bytes may fail to be reliably detected.</p> <p>Once | |
| the processor has detected the character encoding in use, it can act appropriately, | |
| whether by invoking a separate input routine for each case, or by calling | |
| the proper conversion function on each character of input.</p> <p>Like any | |
| self-labeling system, the XML encoding declaration will not work if any software | |
| changes the entity's character set or encoding without updating the encoding | |
| declaration. Implementors of character-encoding routines should be careful | |
| to ensure the accuracy of the internal and external information used to label | |
| the entity.</p> </div> <div class="div2"> <h3><a name="sec-guessing-with-ext-info"></a>F.2 | |
| Priorities in the Presence of External Encoding Information</h3> <p>The second | |
| possible case occurs when the XML entity is accompanied by encoding information, | |
| as in some file systems and some network protocols. When multiple sources | |
| of information are available, their relative priority and the preferred method | |
| of handling conflict should be specified as part of the higher-level protocol | |
| used to deliver XML. In particular, please refer to <a href="#rfc2376">[IETF | |
| RFC 2376]</a> or its successor, which defines the <code>text/xml</code> and <code>application/xml</code> | |
| MIME types and provides some useful guidance. In the interests of interoperability, | |
| however, the following rule is recommended.</p> <ul> | |
| <li><p>If an XML entity is in a file, the Byte-Order Mark and encoding declaration | |
| are used (if present) to determine the character encoding.</p> </li> | |
| </ul> </div> </div> <div class="div1"> <h2><a name="sec-xml-wg"></a>G W3C | |
| XML Working Group (Non-Normative)</h2> <p>This specification was prepared | |
| and approved for publication by the W3C XML Working Group (WG). WG approval | |
| of this specification does not necessarily imply that all WG members voted | |
| for its approval. The current and former members of the XML WG are:</p> <ul> | |
| <li>Jon Bosak, Sun (<i>Chair</i>) </li> | |
| <li>James Clark (<i>Technical Lead</i>) </li> | |
| <li>Tim Bray, Textuality and Netscape (<i>XML Co-editor</i>) </li> | |
| <li>Jean Paoli, Microsoft (<i>XML Co-editor</i>) </li> | |
| <li>C. M. Sperberg-McQueen, U. of Ill. (<i>XML Co-editor</i>) </li> | |
| <li>Dan Connolly, W3C (<i>W3C Liaison</i>) </li> | |
| <li>Paula Angerstein, Texcel</li> | |
| <li>Steve DeRose, INSO</li> | |
| <li>Dave Hollander, HP</li> | |
| <li>Eliot Kimber, ISOGEN</li> | |
| <li>Eve Maler, ArborText</li> | |
| <li>Tom Magliery, NCSA</li> | |
| <li>Murray Maloney, SoftQuad, Grif SA, Muzmo and Veo Systems</li> | |
| <li>MURATA Makoto (FAMILY Given), Fuji Xerox Information Systems</li> | |
| <li>Joel Nava, Adobe</li> | |
| <li>Conleth O'Connell, Vignette </li> | |
| <li>Peter Sharpe, SoftQuad</li> | |
| <li>John Tigue, DataChannel</li> | |
| </ul> </div> <div class="div1"> <h2><a name="sec-core-wg"></a>H W3C XML Core | |
| Group (Non-Normative)</h2> <p>The second edition of this specification was | |
| prepared by the W3C XML Core Working Group (WG). The members of the WG at | |
| the time of publication of this edition were:</p> <ul> | |
| <li>Paula Angerstein, Vignette</li> | |
| <li>Daniel Austin, Ask Jeeves</li> | |
| <li>Tim Boland</li> | |
| <li>Allen Brown, Microsoft</li> | |
| <li>Dan Connolly, W3C (<i>Staff Contact</i>) </li> | |
| <li>John Cowan, Reuters Limited </li> | |
| <li>John Evdemon, XMLSolutions Corporation </li> | |
| <li>Paul Grosso, Arbortext (<i>Co-Chair</i>) </li> | |
| <li>Arnaud Le Hors, IBM (<i>Co-Chair</i>) </li> | |
| <li>Eve Maler, Sun Microsystems (<i>Second Edition Editor</i>) </li> | |
| <li>Jonathan Marsh, Microsoft</li> | |
| <li>MURATA Makoto (FAMILY Given), IBM </li> | |
| <li>Mark Needleman, Data Research Associates </li> | |
| <li>David Orchard, Jamcracker</li> | |
| <li>Lew Shannon, NCR</li> | |
| <li>Richard Tobin, University of Edinburgh </li> | |
| <li>Daniel Veillard, W3C</li> | |
| <li>Dan Vint, Lexica</li> | |
| <li>Norman Walsh, Sun Microsystems </li> | |
| <li>François Yergeau, Alis Technologies (<i>Errata List Editor</i>) </li> | |
| <li>Kongyi Zhou, Oracle</li> | |
| </ul> </div> <div class="div1"> <h2><a name="b4d250b6c21"></a>I Production | |
| Notes (Non-Normative)</h2> <p>This Second Edition was encoded in the <a href="http://www.w3.org/XML/1998/06/xmlspec-v21.dtd">XMLspec | |
| DTD</a> (which has <a href="http://www.w3.org/XML/1998/06/xmlspec-report-v21.htm">documentation</a> | |
| available). The HTML versions were produced with a combination of the <a href="http://www.w3.org/XML/1998/06/xmlspec.xsl">xmlspec.xsl</a>, <a | |
| href="http://www.w3.org/XML/1998/06/diffspec.xsl">diffspec.xsl</a>, and <a | |
| href="http://www.w3.org/XML/1998/06/REC-xml-2e.xsl">REC-xml-2e.xsl</a> XSLT | |
| stylesheets. The PDF version was produced with the <a href="http://www.tdb.uu.se/~jan/html2ps.html">html2ps</a> | |
| facility and a distiller program.</p> </div> </div></body> | |
| </html> |