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| <title>XHTML 1.0: The Extensible HyperText Markup |
| Language</title> |
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| <div class="navbar"> |
| <a href="#toc">table of contents</a> |
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| <div class="head"><p><a href="http://www.w3.org/"><img class="head" src="w3c_home.gif" alt="W3C"/></a></p> |
| |
| <h1 class="head"><a name="title" id="title">XHTML</a><sup>™</sup> 1.0: |
| The Extensible HyperText Markup Language</h1> |
| |
| <h2>A Reformulation of HTML 4.0 in XML 1.0</h2> |
| |
| <h3>W3C Proposed Recommendation 10 December 1999</h3> |
| |
| <dl><dt>This version:</dt><dd><a href="http://www.w3.org/TR/1999/PR-xhtml1-19991210"> |
| http://www.w3.org/TR/1999/PR-xhtml1-19991210</a> <br/> |
| (<a href="xhtml1.ps">Postscript version</a>, |
| <a href="xhtml1.pdf">PDF version</a>, |
| <a href="xhtml1.zip">ZIP archive</a>, or |
| <a href="xhtml1.tgz">Gzip'd TAR archive</a>) |
| </dd><dt>Latest version:</dt><dd><a href="http://www.w3.org/TR/xhtml1"> |
| http://www.w3.org/TR/xhtml1</a></dd><dt>Previous versions:</dt><dd><a href="http://www.w3.org/TR/1999/WD-xhtml1-19991124"> |
| http://www.w3.org/TR/1999/WD-xhtml1-19991124</a></dd><dd><a href="http://www.w3.org/TR/1999/PR-xhtml1-19990824"> |
| http://www.w3.org/TR/1999/PR-xhtml1-19990824</a></dd><dt>Authors:</dt><dd>See <a href="#acks">acknowledgements</a>.</dd></dl> |
| |
| <p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"> |
| Copyright</a> © 1999 <a href="http://www.w3.org/">W3C</a><sup>®</sup> |
| (<a href="http://www.lcs.mit.edu/">MIT</a>, <a href="http://www.inria.fr/">INRIA</a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. <abbr title="World Wide Web Consortium">W3C</abbr> <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer"> |
| liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks"> |
| trademark</a>, <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document |
| use</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-software">software |
| licensing</a> rules apply.</p> |
| <hr/> |
| </div> |
| <h2 class="notoc">Abstract</h2> |
| <p>This specification defines <abbr title="Extensible Hypertext Markup Language">XHTML</abbr> 1.0, a reformulation of HTML |
| 4.0 as an XML 1.0 application, and three <abbr title="Document Type Definition">DTDs</abbr> corresponding to |
| the ones defined by HTML 4.0. The semantics of the elements and |
| their attributes are defined in the W3C Recommendation for HTML |
| 4.0. These semantics provide the foundation for future |
| extensibility of XHTML. Compatibility with existing HTML user |
| agents is possible by following a small set of guidelines.</p> |
| <h2>Status of this document</h2> |
| <p> |
| <em>This section describes the status of this document at the time |
| of its publication. Other documents may supersede this document. The |
| latest status of this document series is maintained at the W3C.</em> |
| </p> |
| <p>This specification is a Proposed Recommendation of the HTML Working Group. It is |
| a revision of the Proposed Recommendation dated <a href="http://www.w3.org/TR/1999/PR-xhtml1-19990824/">24 August |
| 1999</a> incorporating changes as a result of comments from the Proposed |
| Recommendation review, and |
| comments and further deliberations of the W3C HTML Working Group. A |
| <a href="xhtml1-diff-19991210.html">diff-marked version</a> from the previous |
| proposed recommendation is available for comparison purposes.</p> |
| <p>On 10 December 1999, this document enters a |
| <a href="http://www.w3.org/Consortium/Process/#RecsPR"> |
| Proposed Recommendation</a> review period. From that date until 8 January |
| 2000, |
| W3C Advisory Committee representatives are encouraged |
| to review this specification and return comments in their completed |
| ballots to w3c-html-review@w3.org. Please send any comments of a |
| confidential nature in separate email to w3t-html@w3.org, which is |
| visible to the Team only.</p> |
| <p>No sooner than 14 days after the end of the review period, the |
| Director will announce the document's disposition: it may become a W3C |
| Recommendation (possibly with minor changes), it may revert to Working |
| Draft status, or it may be dropped as a W3C work item.</p> |
| <p>Publication as a Proposed Recommendation does not imply endorsement |
| by the W3C membership. This is still a draft document and may be |
| updated, replaced or obsoleted by other documents at any time. It is |
| inappropriate to cite W3C Proposed Recommendation as other than "work |
| in progress."</p> |
| <p>This document has been produced as part of the <a href="http://www.w3.org/MarkUp/">W3C HTML Activity</a>. The goals of |
| the <a href="http://www.w3.org/MarkUp/Group/">HTML Working |
| Group</a> <i>(<a href="http://cgi.w3.org/MemberAccess/">members |
| only</a>)</i> are discussed in the <a href="http://www.w3.org/MarkUp/Group/HTMLcharter">HTML Working Group |
| charter</a> <i>(<a href="http://cgi.w3.org/MemberAccess/">members |
| only</a>)</i>.</p> |
| <p>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>Public discussion on <abbr title="HyperText Markup Language">HTML</abbr> features takes place on the mailing list <a href="mailto:www-html@w3.org"> www-html@w3.org</a> (<a href="http://lists.w3.org/Archives/Public/www-html/">archive</a>). The W3C |
| staff contact for work on HTML is <a href="mailto:dsr@w3.org">Dave |
| Raggett</a>.</p> |
| <p>Please report errors in this document to <a href="mailto:www-html-editor@w3.org">www-html-editor@w3.org</a>.</p> |
| <p>The list of known errors in this specification is available at <a href="http://www.w3.org/1999/12/PR-xhtml1-19991210-errata">http://www.w3.org/1999/12/PR-xhtml1-19991210-errata</a>.</p> |
| <h2 class="notoc"> |
| <a id="toc" name="toc">Contents</a> |
| </h2> |
| <div class="contents"> |
| <ul class="toc"><li class="tocline">1. <a href="#xhtml">What is XHTML?</a> |
| |
| <ul class="toc"><li class="tocline">1.1 <a href="#html4">What is HTML 4.0?</a></li><li class="tocline">1.2 <a href="#xml">What is XML?</a></li><li class="tocline">1.3 <a href="#why">Why the need for XHTML?</a></li></ul> |
| </li><li class="tocline">2. <a href="#defs">Definitions</a> |
| |
| <ul class="toc"><li class="tocline">2.1 <a href="#terms">Terminology</a></li><li class="tocline">2.2 <a href="#general">General Terms</a></li></ul> |
| </li><li class="tocline">3. <a href="#normative">Normative Definition of XHTML 1.0</a> |
| |
| |
| <ul class="toc"><li class="tocline">3.1 <a href="#docconf">Document Conformance</a></li><li class="tocline">3.2 <a href="#uaconf">User Agent Conformance</a></li></ul> |
| </li><li class="tocline">4. <a href="#diffs">Differences with HTML 4.0</a> |
| |
| </li><li class="tocline">5. <a href="#issues">Compatibility Issues</a> |
| |
| <ul class="toc"><li class="tocline">5.1 <a href="#media">Internet Media Types</a></li></ul> |
| </li><li class="tocline">6. <a href="#future">Future Directions</a> |
| |
| <ul class="toc"><li class="tocline">6.1 <a href="#mods">Modularizing HTML</a></li><li class="tocline">6.2 <a href="#extensions">Subsets and Extensibility</a></li><li class="tocline">6.3 <a href="#profiles">Document Profiles</a></li></ul> |
| </li><li class="tocline"><a href="#dtds">Appendix A. DTDs</a></li><li class="tocline"><a href="#prohibitions">Appendix B. Element |
| Prohibitions</a></li><li class="tocline"><a href="#guidelines">Appendix C. HTML Compatibility Guidelines</a></li><li class="tocline"><a href="#acks">Appendix D. Acknowledgements</a></li><li class="tocline"><a href="#refs">Appendix E. References</a></li></ul> |
| </div> |
| <!--OddPage--> |
| <h1> |
| <a name="xhtml" id="xhtml">1. What is XHTML?</a> |
| </h1> |
| <p>XHTML is a family of current and future document types and modules that |
| reproduce, subset, and extend HTML 4.0 <a href="#ref-html4">[HTML]</a>. XHTML family document types are <abbr title="Extensible Markup Language">XML</abbr> based, |
| and ultimately are designed to work in conjunction with XML-based user agents. |
| The details of this family and its evolution are |
| discussed in more detail in the section on <a href="#future">Future |
| Directions</a>. </p> |
| <p>XHTML 1.0 (this specification) is the first document type in the XHTML |
| family. It is a reformulation of the three HTML 4.0 document types as |
| applications of XML 1.0 <a href="#ref-xml"> [XML]</a>. It is intended |
| to be used as a language for content that is both XML-conforming and, if some |
| simple <a href="#guidelines">guidelines</a> are followed, |
| operates in HTML 4.0 conforming user agents. Developers who migrate |
| their content to XHTML 1.0 will realize the following benefits:</p> |
| <ul> |
| <li>XHTML documents are XML conforming. As such, they are readily viewed, |
| edited, and validated with standard XML tools.</li> |
| <li>XHTML documents can be written to |
| to operate as well or better than they did before in existing |
| HTML 4.0-conforming user agents as well as in new, XHTML 1.0 conforming user |
| agents.</li> |
| <li>XHTML documents can utilize applications (e.g. scripts and applets) that rely |
| upon either the HTML Document Object Model or the XML Document Object Model <a href="#ref-dom">[DOM]</a>.</li> |
| <li>As the XHTML family evolves, documents conforming to XHTML 1.0 will be more |
| likely to interoperate within and among various XHTML environments.</li> |
| </ul> |
| <p>The XHTML family is the next step in the evolution of the Internet. By |
| migrating to XHTML today, content developers can enter the XML world with all |
| of its attendant benefits, while still remaining confident in their |
| content's backward and future compatibility.</p> |
| <h2> |
| <a name="html4" id="html4">1.1 What is HTML 4.0?</a> |
| </h2> |
| <p>HTML 4.0 <a href="#ref-html4">[HTML]</a> is an <abbr title="Standard Generalized Markup Language">SGML</abbr> (Standard |
| Generalized Markup Language) application conforming to |
| International Standard <abbr title="Organization for International Standardization">ISO</abbr> 8879, and is widely regarded as the |
| standard publishing language of the World Wide Web.</p> |
| <p>SGML is a language for describing markup languages, |
| particularly those used in electronic document exchange, document |
| management, and document publishing. HTML is an example of a |
| language defined in SGML.</p> |
| <p>SGML has been around since the middle 1980's and has remained |
| quite stable. Much of this stability stems from the fact that the |
| language is both feature-rich and flexible. This flexibility, |
| however, comes at a price, and that price is a level of |
| complexity that has inhibited its adoption in a diversity of |
| environments, including the World Wide Web.</p> |
| <p>HTML, as originally conceived, was to be a language for the |
| exchange of scientific and other technical documents, suitable |
| for use by non-document specialists. HTML addressed the problem |
| of SGML complexity by specifying a small set of structural and |
| semantic tags suitable for authoring relatively simple documents. |
| In addition to simplifying the document structure, HTML added |
| support for hypertext. Multimedia capabilities were added |
| later.</p> |
| <p>In a remarkably short space of time, HTML became wildly |
| popular and rapidly outgrew its original purpose. Since HTML's |
| inception, there has been rapid invention of new elements for use |
| within HTML (as a standard) and for adapting HTML to vertical, |
| highly specialized, markets. This plethora of new elements has |
| led to compatibility problems for documents across different |
| platforms.</p> |
| <p>As the heterogeneity of both software and platforms rapidly |
| proliferate, it is clear that the suitability of 'classic' HTML |
| 4.0 for use on these platforms is somewhat limited.</p> |
| <h2> |
| <a name="xml" id="xml">1.2 What is XML?</a> |
| </h2> |
| <p>XML<sup>™</sup> is the shorthand for Extensible Markup |
| Language, and is an acronym of Extensible Markup Language <a href="#ref-xml">[XML]</a>.</p> |
| <p>XML was conceived as a means of regaining the power and |
| flexibility of SGML without most of its complexity. Although a |
| restricted form of SGML, XML nonetheless preserves most of SGML's |
| power and richness, and yet still retains all of SGML's commonly |
| used features.</p> |
| <p>While retaining these beneficial features, XML removes many of |
| the more complex features of SGML that make the authoring and |
| design of suitable software both difficult and costly.</p> |
| <h2> |
| <a name="why" id="why">1.3 Why the need for XHTML?</a> |
| </h2> |
| <p>The benefits of migrating to XHTML 1.0 are described above. Some of the |
| benefits of migrating to XHTML in general are:</p> |
| <ul> |
| <li>Document developers and user agent designers are constantly |
| discovering new ways to express their ideas through new markup. In XML, it is |
| relatively easy to introduce new elements or additional element |
| attributes. The XHTML family is designed to accommodate these extensions |
| through XHTML modules and techniques for developing new XHTML-conforming |
| modules (described in the forthcoming XHTML Modularization specification). |
| These modules will permit the combination of existing and |
| new feature sets when developing content and when designing new user |
| agents.</li> |
| <li>Alternate ways of accessing the Internet are constantly being |
| introduced. Some estimates indicate that by the year 2002, 75% of |
| Internet document viewing will be carried out on these alternate |
| platforms. The XHTML family is designed with general user agent |
| interoperability in mind. Through a new user agent and document profiling |
| mechanism, servers, proxies, and user agents will be able to perform |
| best effort content transformation. Ultimately, it will be possible to |
| develop XHTML-conforming content that is usable by any XHTML-conforming |
| user agent.</li> |
| </ul> |
| <!--OddPage--> |
| <h1> |
| <a name="defs" id="defs">2. Definitions</a> |
| </h1> |
| <h2> |
| <a name="terms" id="terms">2.1 Terminology</a> |
| </h2> |
| <p>The following terms are used in this specification. These |
| terms extend the definitions in <a href="#ref-rfc2119"> |
| [RFC2119]</a> in ways based upon similar definitions in ISO/<abbr title="International Electro-technical Commission">IEC</abbr> |
| 9945-1:1990 <a href="#ref-posix">[POSIX.1]</a>:</p> |
| <dl> |
| <dt>Implementation-defined</dt> |
| <dd>A value or behavior is implementation-defined when it is left |
| to the implementation to define [and document] the corresponding |
| requirements for correct document construction.</dd> |
| <dt>May</dt> |
| <dd>With respect to implementations, the word "may" is to be |
| interpreted as an optional feature that is not required in this |
| specification but can be provided. With respect to <a href="#docconf">Document Conformance</a>, the word "may" means that |
| the optional feature must not be used. The term "optional" has |
| the same definition as "may".</dd> |
| <dt>Must</dt> |
| <dd>In this specification, the word "must" is to be interpreted |
| as a mandatory requirement on the implementation or on Strictly |
| Conforming XHTML Documents, depending upon the context. The term |
| "shall" has the same definition as "must".</dd> |
| <dt>Reserved</dt> |
| <dd>A value or behavior is unspecified, but it is not allowed to |
| be used by Conforming Documents nor to be supported by a |
| Conforming User Agents.</dd> |
| <dt>Should</dt> |
| <dd>With respect to implementations, the word "should" is to be |
| interpreted as an implementation recommendation, but not a |
| requirement. With respect to documents, the word "should" is to |
| be interpreted as recommended programming practice for documents |
| and a requirement for Strictly Conforming XHTML Documents.</dd> |
| <dt>Supported</dt> |
| <dd>Certain facilities in this specification are optional. If a |
| facility is supported, it behaves as specified by this |
| specification.</dd> |
| <dt>Unspecified</dt> |
| <dd>When a value or behavior is unspecified, the specification |
| defines no portability requirements for a facility on an |
| implementation even when faced with a document that uses the |
| facility. A document that requires specific behavior in such an |
| instance, rather than tolerating any behavior when using that |
| facility, is not a Strictly Conforming XHTML Document.</dd> |
| </dl> |
| <h2> |
| <a name="general" id="general">2.2 General Terms</a> |
| </h2> |
| <dl> |
| <dt>Attribute</dt> |
| <dd>An attribute is a parameter to an element declared in the |
| DTD. An attribute's type and value range, including a possible |
| default value, are defined in the DTD.</dd> |
| <dt>DTD</dt> |
| <dd>A DTD, or document type definition, is a collection of XML |
| declarations that, as a collection, defines the legal structure, |
| <span class="term">elements</span>, and <span class="term"> |
| attributes</span> that are available for use in a document that |
| complies to the DTD.</dd> |
| <dt>Document</dt> |
| <dd>A document is a stream of data that, after being combined |
| with any other streams it references, is structured such that it |
| holds information contained within <span class="term"> |
| elements</span> that are organized as defined in the associated |
| <span class="term">DTD</span>. See <a href="#docconf">Document |
| Conformance</a> for more information.</dd> |
| <dt>Element</dt> |
| <dd>An element is a document structuring unit declared in the |
| <span class="term">DTD</span>. The element's content model is |
| defined in the <span class="term">DTD</span>, and additional |
| semantics may be defined in the prose description of the |
| element.</dd> |
| <dt> |
| <a name="facilities" id="facilities">Facilities</a> |
| </dt> |
| <dd>Functionality includes <span class="term">elements</span>, |
| <span class="term">attributes</span>, and the semantics |
| associated with those <span class="term">elements</span> and |
| <span class="term">attributes</span>. An implementation |
| supporting that functionality is said to provide the necessary |
| facilities.</dd> |
| <dt>Implementation</dt> |
| <dd>An implementation is a system that provides collection of |
| <span class="term">facilities</span> and services that supports |
| this specification. See <a href="#uaconf">User Agent |
| Conformance</a> for more information.</dd> |
| <dt>Parsing</dt> |
| <dd>Parsing is the act whereby a <span class="term"> |
| document</span> is scanned, and the information contained within |
| the <span class="term">document</span> is filtered into the |
| context of the <span class="term">elements</span> in which the |
| information is structured.</dd> |
| <dt>Rendering</dt> |
| <dd>Rendering is the act whereby the information in a <span class="term">document</span> is presented. This presentation is |
| done in the form most appropriate to the environment (e.g. |
| aurally, visually, in print).</dd> |
| <dt>User Agent</dt> |
| <dd>A user agent is an <span class="term">implementation</span> |
| that retrieves and processes XHTML documents. See <a href="#uaconf">User Agent Conformance</a> for more information.</dd> |
| <dt>Validation</dt> |
| <dd>Validation is a process whereby <span class="term"> |
| documents</span> are verified against the associated <span class="term">DTD</span>, ensuring that the structure, use of <span class="term">elements</span>, and use of <span class="term"> |
| attributes</span> are consistent with the definitions in the |
| <span class="term">DTD</span>.</dd> |
| <dt> |
| <a name="wellformed" id="wellformed">Well-formed</a> |
| </dt> |
| <dd>A <span class="term">document</span> is well-formed when it |
| is structured according to the rules defined in <a href="http://www.w3.org/TR/REC-xml#sec-well-formed">Section 2.1</a> of |
| the XML 1.0 Recommendation <a href="#ref-xml">[XML]</a>. |
| Basically, this definition states that elements, delimited by |
| their start and end tags, are nested properly within one |
| another.</dd> |
| </dl> |
| <!--OddPage--> |
| <h1> |
| <a name="normative" id="normative">3. Normative Definition of |
| XHTML 1.0</a> |
| </h1> |
| <h2> |
| <a name="docconf" id="docconf">3.1 Document |
| Conformance</a> |
| </h2> |
| <p>This version of XHTML provides a definition of strictly |
| conforming XHTML documents, which are restricted to tags and |
| attributes from the XHTML namespace. See <a href="#well-formed">Section 3.1.2</a> for information on using XHTML |
| with other namespaces, for instance, to include metadata |
| expressed in <abbr title="Resource Description Format">RDF</abbr> within XHTML documents.</p> |
| <h3> |
| <a name="strict" id="strict">3.1.1 Strictly Conforming |
| Documents</a> |
| </h3> |
| <p>A Strictly Conforming XHTML Document is a document that |
| requires only the facilities described as mandatory in this |
| specification. Such a document must meet all of the following |
| criteria:</p> |
| <ol> |
| <li> |
| <p>It must validate against one of the three DTDs found in <a href="#dtds">Appendix A</a>.</p> |
| </li> |
| <li> |
| <p>The root element of the document must be <code> |
| <html></code>.</p> |
| </li> |
| <li> |
| <p>The root element of the document must designate the XHTML |
| namespace using the <code>xmlns</code> attribute <a href="#ref-xmlns">[XMLNAMES]</a>. The namespace for XHTML is |
| defined to be |
| <code>http://www.w3.org/1999/xhtml</code>.</p> |
| </li> |
| <li> |
| <p>There must be a DOCTYPE declaration in the document prior to |
| the root element. The public identifier included in |
| the DOCTYPE declaration must reference one of the three DTDs |
| found in <a href="#dtds">Appendix A</a> using the respective |
| Formal Public Identifier. The system identifier may be changed to reflect |
| local system conventions.</p> |
| |
| <pre> |
| <!DOCTYPE html |
| PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" |
| "http://www.w3.org/TR/1999/PR-xhtml1-19991210/DTD/xhtml1-strict.dtd> |
| |
| <!DOCTYPE html |
| PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" |
| "http://www.w3.org/TR/1999/PR-xhtml1-19991210/DTD/xhtml1-transitional.dtd> |
| |
| <!DOCTYPE html |
| PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" |
| "http://www.w3.org/TR/1999/PR-xhtml1-19991210/DTD/xhtml1-frameset.dtd> |
| </pre> |
| </li> |
| </ol> |
| <p>Here is an example of a minimal XHTML document.</p> |
| <div class="good"> |
| <pre> |
| <?xml version="1.0" encoding="UTF-8"?> |
| <!DOCTYPE html |
| PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" |
| "http://www.w3.org/TR/1999/PR-xhtml1-19991210/DTD/xhtml1-strict.dtd"> |
| <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> |
| <head> |
| <title>Virtual Library</title> |
| </head> |
| <body> |
| <p>Moved to <a href="http://vlib.org/">vlib.org</a>.</p> |
| </body> |
| </html></pre> |
| </div> |
| <p>Note that in this example, the XML declaration is included. An XML |
| declaration like the one above is |
| not required in all XML documents. XHTML document authors are strongly encouraged to use XML declarations in all their documents. Such a declaration is required |
| when the character encoding of the document is other than the default UTF-8 or |
| UTF-16.</p> |
| <h3> |
| <a name="well-formed" id="well-formed">3.1.2 Using XHTML with |
| other namespaces</a> |
| </h3> |
| <p>The XHTML namespace may be used with other XML namespaces |
| as per <a href="#ref-xmlns">[XMLNAMES]</a>, although such |
| documents are not strictly conforming XHTML 1.0 documents as |
| defined above. Future work by W3C will address ways to specify |
| conformance for documents involving multiple namespaces.</p> |
| <p>The following example shows the way in which XHTML 1.0 could |
| be used in conjunction with the MathML Recommendation:</p> |
| <div class="good"> |
| <pre> |
| <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> |
| <head> |
| <title>A Math Example</title> |
| </head> |
| <body> |
| <p>The following is MathML markup:</p> |
| <math xmlns="http://www.w3.org/1998/Math/MathML"> |
| <apply> <log/> |
| <logbase> |
| <cn> 3 </cn> |
| </logbase> |
| <ci> x </ci> |
| </apply> |
| </math> |
| </body> |
| </html> |
| </pre> |
| </div> |
| <p>The following example shows the way in which XHTML 1.0 markup |
| could be incorporated into another XML namespace:</p> |
| <div class="good"> |
| <pre> |
| <?xml version="1.0" encoding="UTF-8"?> |
| <!-- initially, the default namespace is "books" --> |
| <book xmlns='urn:loc.gov:books' |
| xmlns:isbn='urn:ISBN:0-395-36341-6' xml:lang="en" lang="en"> |
| <title>Cheaper by the Dozen</title> |
| <isbn:number>1568491379</isbn:number> |
| <notes> |
| <!-- make HTML the default namespace for a hypertext commentary --> |
| <p xmlns='http://www.w3.org/1999/xhtml'> |
| This is also available <a href="http://www.w3.org/">online</a>. |
| </p> |
| </notes> |
| </book> |
| </pre> |
| </div> |
| <h2> |
| <a name="uaconf" id="uaconf">3.2 User Agent |
| Conformance</a> |
| </h2> |
| <p>A conforming user agent must meet all of the following |
| criteria:</p> |
| <ol> |
| <li>In order to be consistent with the XML 1.0 Recommendation <a href="#ref-xml">[XML]</a>, the user agent must parse and evaluate |
| an XHTML document for well-formedness. If the user agent claims |
| to be a validating user agent, it must also validate documents |
| against their referenced DTDs according to <a href="#ref-xml"> |
| [XML]</a>.</li> |
| <li>When the user agent claims to support <a href="#facilities"> |
| facilities</a> defined within this specification or required by |
| this specification through normative reference, it must do so in |
| ways consistent with the facilities' definition.</li> |
| <li>When a user agent processes an XHTML document as generic XML, |
| it shall only recognize attributes of type |
| <code>ID</code> (e.g. the <code>id</code> attribute on most XHTML elements) |
| as fragment identifiers.</li> |
| <li>If a user agent encounters an element it does not recognize, |
| it must render the element's content.</li> |
| <li>If a user agent encounters an attribute it does not |
| recognize, it must ignore the entire attribute specification |
| (i.e., the attribute and its value).</li> |
| <li>If a user agent encounters an attribute value it doesn't |
| recognize, it must use the default attribute value.</li> |
| <li>If it encounters an entity reference (other than one |
| of the predefined entities) for which the User Agent has |
| processed no declaration (which could happen if the declaration |
| is in the external subset which the User Agent hasn't read), the entity |
| reference should be rendered as the characters (starting |
| with the ampersand and ending with the semi-colon) that |
| make up the entity reference.</li> |
| <li>When rendering content, User Agents that encounter |
| characters or character entity references that are recognized but not renderable should display the document in such a way that it is obvious to the user that normal rendering has not taken place.</li> |
| <li> |
| The following characters are defined in [XML] as whitespace characters: |
| |
| <ul><li>Space (&#x0020;)</li><li>Tab (&#x0009;)</li><li>Carriage return (&#x000D;)</li><li>Line feed (&#x000A;)</li></ul> |
| |
| <p> |
| The XML processor normalizes different system's line end codes into one |
| single line-feed character, that is passed up to the application. The XHTML |
| user agent in addition, must treat the following characters as whitespace: |
| </p> |
| |
| <ul><li>Form feed (&#x000C;)</li><li>Zero-width space (&#x200B;)</li></ul> |
| |
| <p> |
| In elements where the 'xml:space' attribute is set to 'preserve', the user |
| agent must leave all whitespace characters intact (with the exception of |
| leading and trailing whitespace characters, which should be removed). |
| Otherwise, whitespace |
| is handled according to the following rules: |
| </p> |
| |
| <ul><li> |
| All whitespace surrounding block elements should be removed. |
| </li><li> |
| Comments are removed entirely and do not affect whitespace handling. One |
| whitespace character on either side of a comment is treated as two white |
| space characters. |
| </li><li> |
| Leading and trailing whitespace inside a block element must be removed. |
| </li><li>Line feed characters within a block element must be converted into a |
| space (except when the 'xml:space' attribute is set to 'preserve'). |
| </li><li> |
| A sequence of white space characters must be reduced to a single space |
| character (except when the 'xml:space' attribute is set to 'preserve'). |
| </li><li> |
| With regard to rendition, |
| the User Agent should render the content in a |
| manner appropriate to the language in which the content is written. |
| In languages whose primary script is Latinate, the ASCII space |
| character is typically used to encode both grammatical word boundaries and |
| typographic whitespace; in languages whose script is related to Nagari |
| (e.g., Sanskrit, Thai, etc.), grammatical boundaries may be encoded using |
| the ZW 'space' character, but will not typically be represented by |
| typographic whitespace in rendered output; languages using Arabiform scripts |
| may encode typographic whitespace using a space character, but may also use |
| the ZW space character to delimit 'internal' grammatical boundaries (what |
| look like words in Arabic to an English eye frequently encode several words, |
| e.g. 'kitAbuhum' = 'kitAbu-hum' = 'book them' == their book); and languages |
| in the Chinese script tradition typically neither encode such delimiters nor |
| use typographic whitespace in this way. |
| </li></ul> |
| |
| <p>Whitespace in attribute values is processed according to <a href="#ref-xml">[XML]</a>.</p> |
| </li> |
| </ol> |
| <!--OddPage--> |
| <h1> |
| <a name="diffs" id="diffs">4. Differences with HTML |
| 4.0</a> |
| </h1> |
| <p>Due to the fact that XHTML is an XML application, certain |
| practices that were perfectly legal in SGML-based HTML 4.0 <a href="#ref-html4">[HTML]</a> must be changed.</p> |
| <h2> |
| <a name="h-4.1" id="h-4.1">4.1 Documents must be |
| well-formed</a> |
| </h2> |
| <p><a href="#wellformed">Well-formedness</a> is a new concept |
| introduced by <a href="#ref-xml">[XML]</a>. Essentially this |
| means that all elements must either have closing tags or be |
| written in a special form (as described below), and that all the |
| elements must nest.</p> |
| <p>Although overlapping is illegal in SGML, it was widely |
| tolerated in existing browsers.</p> |
| <div class="good"> |
| <p><strong><em>CORRECT: nested elements.</em></strong></p> |
| |
| <p><p>here is an emphasized |
| <em>paragraph</em>.</p></p> |
| </div> |
| <div class="bad"> |
| <p><strong><em>INCORRECT: overlapping elements</em></strong></p> |
| |
| <p><p>here is an emphasized |
| <em>paragraph.</p></em></p> |
| </div> |
| <h2> |
| <a name="h-4.2" id="h-4.2">4.2 Element and attribute |
| names must be in lower case</a> |
| </h2> |
| <p>XHTML documents must use lower case for all HTML element and |
| attribute names. This difference is necessary because XML is |
| case-sensitive e.g. <li> and <LI> are different |
| tags.</p> |
| <h2> |
| <a name="h-4.3" id="h-4.3">4.3 For non-empty elements, |
| end tags are required</a> |
| </h2> |
| <p>In SGML-based HTML 4.0 certain elements were permitted to omit |
| the end tag; with the elements that followed implying closure. |
| This omission is not permitted in XML-based XHTML. All elements |
| other than those declared in the DTD as <code>EMPTY</code> must |
| have an end tag.</p> |
| <div class="good"> |
| <p><strong><em>CORRECT: terminated elements</em></strong></p> |
| |
| <p><p>here is a paragraph.</p><p>here is |
| another paragraph.</p></p> |
| </div> |
| <div class="bad"> |
| <p><strong><em>INCORRECT: unterminated elements</em></strong></p> |
| |
| <p><p>here is a paragraph.<p>here is another |
| paragraph.</p> |
| </div> |
| <h2> |
| <a name="h-4.4" id="h-4.4">4.4 Attribute values must |
| always be quoted</a> |
| </h2> |
| <p>All attribute values must be quoted, even those which appear |
| to be numeric.</p> |
| <div class="good"> |
| <p><strong><em>CORRECT: quoted attribute values</em></strong></p> |
| |
| <p><table rows="3"></p> |
| </div> |
| <div class="bad"> |
| <p><strong><em>INCORRECT: unquoted attribute values</em></strong></p> |
| |
| <p><table rows=3></p> |
| </div> |
| <h2> |
| <a name="h-4.5" id="h-4.5">4.5 Attribute |
| Minimization</a> |
| </h2> |
| <p>XML does not support attribute minimization. Attribute-value |
| pairs must be written in full. Attribute names such as <code> |
| compact</code> and <code>checked</code> cannot occur in elements |
| without their value being specified.</p> |
| <div class="good"> |
| <p><strong><em>CORRECT: unminimized attributes</em></strong></p> |
| |
| <p><dl compact="compact"></p> |
| </div> |
| <div class="bad"> |
| <p><strong><em>INCORRECT: minimized attributes</em></strong></p> |
| |
| <p><dl compact></p> |
| </div> |
| <h2> |
| <a name="h-4.6" id="h-4.6">4.6 Empty Elements</a> |
| </h2> |
| <p>Empty elements must either have an end tag or the start tag must end with <code>/></code>. For instance, |
| <code><br/></code> or <code><hr></hr></code>. See <a href="#guidelines">HTML Compatibility Guidelines</a> for information on ways to |
| ensure this is backward compatible with HTML 4.0 user agents.</p> |
| <div class="good"> |
| <p><strong><em>CORRECT: terminated empty tags</em></strong></p> |
| |
| <p><br/><hr/></p> |
| </div> |
| <div class="bad"> |
| <p><strong><em>INCORRECT: unterminated empty tags</em></strong></p> |
| |
| <p><br><hr></p> |
| </div> |
| <h2> |
| <a name="h-4.7" id="h-4.7">4.7 Whitespace handling in |
| attribute values</a> |
| </h2> |
| <p>In attribute values, user agents will strip leading and |
| trailing whitespace from attribute values and map sequences |
| of one or more whitespace characters (including line breaks) to |
| a single inter-word space (an ASCII space character for western |
| scripts). See <a href="http://www.w3.org/TR/REC-xml#AVNormalize"> |
| Section 3.3.3</a> of <a href="#ref-xml">[XML]</a>.</p> |
| <h2> |
| <a name="h-4.8" id="h-4.8">4.8 Script and Style |
| elements</a> |
| </h2> |
| <p>In XHTML, the script and style elements are declared as having |
| <code>#PCDATA</code> content. As a result, <code><</code> and |
| <code>&</code> will be treated as the start of markup, and |
| entities such as <code>&lt;</code> and <code>&amp;</code> |
| will be recognized as entity references by the XML processor to |
| <code><</code> and <code>&</code> respectively. Wrapping |
| the content of the script or style element within a <code> |
| CDATA</code> marked section avoids the expansion of these |
| entities.</p> |
| <div class="good"> |
| <pre> |
| <script> |
| <![CDATA[ |
| ... unescaped script content ... |
| ]]> |
| </script> |
| </pre> |
| </div> |
| <p><code>CDATA</code> sections are recognized by the XML |
| processor and appear as nodes in the Document Object Model, see |
| <a href="http://www.w3.org/TR/REC-DOM-Level-1/level-one-core.html#ID-E067D597"> |
| Section 1.3</a> of the DOM Level 1 Recommendation <a href="#ref-dom">[DOM]</a>.</p> |
| <p>An alternative is to use external script and style |
| documents.</p> |
| <h2> |
| <a name="h-4.9" id="h-4.9">4.9 SGML exclusions</a> |
| </h2> |
| <p>SGML gives the writer of a DTD the ability to exclude specific |
| elements from being contained within an element. Such |
| prohibitions (called "exclusions") are not possible in XML.</p> |
| <p>For example, the HTML 4.0 Strict DTD forbids the nesting of an |
| '<code>a</code>' element within another '<code>a</code>' element |
| to any descendant depth. It is not possible to spell out such |
| prohibitions in XML. Even though these prohibitions cannot be |
| defined in the DTD, certain elements should not be nested. A |
| summary of such elements and the elements that should not be |
| nested in them is found in the normative <a href="#prohibitions"> |
| Appendix B</a>.</p> |
| <h2> |
| <a name="h-4.10" id="h-4.10">4.10 The elements with 'id' and 'name' |
| attributes</a> |
| </h2> |
| <p>HTML 4.0 defined the <code>name</code> attribute for the elements |
| <code>a</code>, |
| <code>applet</code>, <code>frame</code>, |
| <code>iframe</code>, <code>img</code>, and <code>map</code>. |
| HTML 4.0 also introduced |
| the <code>id</code> attribute. Both of these attributes are designed to be |
| used as fragment identifiers.</p> |
| <p>In XML, fragment identifiers are of type <code>ID</code>, and |
| there can only be a single attribute of type <code>ID</code> per element. |
| Therefore, in XHTML 1.0 the <code>id</code> |
| attribute is defined to be of type <code>ID</code>. In order to |
| ensure that XHTML 1.0 documents are well-structured XML documents, XHTML 1.0 |
| documents MUST use the <code>id</code> attribute when defining fragment |
| identifiers, even on elements that historically have also had a |
| <code>name</code> attribute. |
| See the <a href="#guidelines">HTML Compatibility |
| Guidelines</a> for information on ensuring such anchors are backwards |
| compatible when serving XHTML documents as media type <code>text/html</code>. |
| </p> |
| <p>Note that in XHTML 1.0, the <code>name</code> attribute of these |
| elements is formally deprecated, and will be removed in a |
| subsequent version of XHTML.</p> |
| <!--OddPage--> |
| <h1> |
| <a name="issues" id="issues">5. Compatibility Issues</a> |
| </h1> |
| <p>Although there is no requirement for XHTML 1.0 documents to be |
| compatible with existing user agents, in practice this is easy to |
| accomplish. Guidelines for creating compatible documents can be |
| found in <a href="#guidelines">Appendix C</a>.</p> |
| <h2> |
| <a name="media" id="media">5.1 Internet Media Type</a> |
| </h2> |
| <p>As of the publication of this recommendation, the general |
| recommended MIME labeling for XML-based applications |
| has yet to be resolved.</p> |
| <p>However, XHTML Documents which follow the guidelines set forth |
| in <a href="#guidelines">Appendix C</a>, "HTML Compatibility Guidelines" may be |
| labeled with the Internet Media Type "text/html", as they |
| are compatible with most HTML browsers. This document |
| makes no recommendation about MIME labeling of other |
| XHTML documents.</p> |
| <!--OddPage--> |
| <h1> |
| <a name="future" id="future">6. Future Directions</a> |
| </h1> |
| <p>XHTML 1.0 provides the basis for a family of document types |
| that will extend and subset XHTML, in order to support a wide |
| range of new devices and applications, by defining modules and |
| specifying a mechanism for combining these modules. This |
| mechanism will enable the extension and sub-setting of XHTML 1.0 |
| in a uniform way through the definition of new modules.</p> |
| <h2> |
| <a name="mods" id="mods">6.1 Modularizing HTML</a> |
| </h2> |
| <p>As the use of XHTML moves from the traditional desktop user |
| agents to other platforms, it is clear that not all of the XHTML |
| elements will be required on all platforms. For example a hand |
| held device or a cell-phone may only support a subset of XHTML |
| elements.</p> |
| <p>The process of modularization breaks XHTML up into a series of |
| smaller element sets. These elements can then be recombined to |
| meet the needs of different communities.</p> |
| <p>These modules will be defined in a later W3C document.</p> |
| <h2> |
| <a name="extensions" id="extensions">6.2 Subsets and |
| Extensibility</a> |
| </h2> |
| <p>Modularization brings with it several advantages:</p> |
| <ul> |
| <li> |
| <p>It provides a formal mechanism for sub-setting XHTML.</p> |
| </li> |
| <li> |
| <p>It provides a formal mechanism for extending XHTML.</p> |
| </li> |
| <li> |
| <p>It simplifies the transformation between document types.</p> |
| </li> |
| <li> |
| <p>It promotes the reuse of modules in new document types.</p> |
| </li> |
| </ul> |
| <h2> |
| <a name="profiles" id="profiles">6.3 Document |
| Profiles</a> |
| </h2> |
| <p>A document profile specifies the syntax and semantics of a set |
| of documents. Conformance to a document profile provides a basis |
| for interoperability guarantees. The document profile specifies |
| the facilities required to process documents of that type, e.g. |
| which image formats can be used, levels of scripting, style sheet |
| support, and so on.</p> |
| <p>For product designers this enables various groups to define |
| their own standard profile.</p> |
| <p>For authors this will obviate the need to write several |
| different versions of documents for different clients.</p> |
| <p>For special groups such as chemists, medical doctors, or |
| mathematicians this allows a special profile to be built using |
| standard HTML elements plus a group of elements geared to the |
| specialist's needs.</p> |
| <!--OddPage--> |
| <h1><a name="appendices" id="appendices"/> |
| <a name="dtds" id="dtds">Appendix A. DTDs</a></h1> |
| <p> |
| <b>This appendix is normative.</b> |
| </p> |
| <p>These DTDs and entity sets form a normative part of this |
| specification. The complete set of DTD files together with an XML |
| declaration and SGML Open Catalog is included in the <a href="xhtml1.zip">zip file</a> for this specification.</p> |
| <h2> |
| <a name="h-A1" id="h-A1">A.1 Document Type |
| Definitions</a> |
| </h2> |
| <p>These DTDs approximate the HTML 4.0 DTDs. It is likely that |
| when the DTDs are modularized, a method of DTD construction will |
| be employed that corresponds more closely to HTML 4.0.</p> |
| <ul> |
| <li> |
| <p><a href="DTD/xhtml1-strict.dtd" type="text/plain"> |
| XHTML-1.0-Strict</a></p> |
| </li> |
| <li> |
| <p><a href="DTD/xhtml1-transitional.dtd" type="text/plain"> |
| XHTML-1.0-Transitional</a></p> |
| </li> |
| <li> |
| <p><a href="DTD/xhtml1-frameset.dtd" type="text/plain"> |
| XHTML-1.0-Frameset</a></p> |
| </li> |
| </ul> |
| <h2> |
| <a name="h-A2" id="h-A2">A.2 Entity Sets</a> |
| </h2> |
| <p>The XHTML entity sets are the same as for HTML 4.0, but have |
| been modified to be valid XML 1.0 entity declarations. Note the |
| entity for the Euro currency sign (<code>&euro;</code> or |
| <code>&#8364;</code> or <code>&#x20AC;</code>) is defined |
| as part of the special characters.</p> |
| <ul> |
| <li> |
| <p><a href="DTD/xhtml-lat1.ent">Latin-1 characters</a></p> |
| </li> |
| <li> |
| <p><a href="DTD/xhtml-special.ent">Special characters</a></p> |
| </li> |
| <li> |
| <p><a href="DTD/xhtml-symbol.ent">Symbols</a></p> |
| </li> |
| </ul> |
| <!--OddPage--> |
| <h1> |
| <a name="prohibitions" id="prohibitions">Appendix B. Element |
| Prohibitions</a> |
| </h1> |
| <p> |
| <b>This appendix is normative.</b> |
| </p> |
| <p>The following elements have prohibitions on which elements |
| they can contain (see <a href="#h-4.9">Section 4.9</a>). This |
| prohibition applies to all depths of nesting, i.e. it contains |
| all the descendant elements.</p> |
| <dl> |
| <dt> |
| <code class="tag">a</code> |
| </dt> |
| <dd> |
| cannot contain other <code>a</code> elements.</dd> |
| <dt> |
| <code class="tag">pre</code> |
| </dt> |
| <dd>cannot contain the <code>img</code>, <code>object</code>, |
| <code>big</code>, <code>small</code>, <code>sub</code>, or <code> |
| sup</code> elements.</dd> |
| <dt> |
| <code class="tag">button</code> |
| </dt> |
| <dd>cannot contain the <code>input</code>, <code>select</code>, |
| <code>textarea</code>, <code>label</code>, <code>button</code>, |
| <code>form</code>, <code>fieldset</code>, <code>iframe</code> or |
| <code>isindex</code> elements.</dd> |
| <dt> |
| <code class="tag">label</code> |
| </dt> |
| <dd>cannot contain other <code class="tag">label</code> elements.</dd> |
| <dt> |
| <code class="tag">form</code> |
| </dt> |
| <dd>cannot contain other <code>form</code> elements.</dd> |
| </dl> |
| <!--OddPage--> |
| <h1> |
| <a name="guidelines" id="guidelines">Appendix C. |
| HTML Compatibility Guidelines</a> |
| </h1> |
| <p> |
| <b>This appendix is informative.</b> |
| </p> |
| <p>This appendix summarizes design guidelines for authors who |
| wish their XHTML documents to render on existing HTML user |
| agents.</p> |
| <h2>C.1 Processing Instructions</h2> |
| <p>Be aware that processing instructions are rendered on some |
| user agents. However, also note that when the XML declaration is not included |
| in a document, the document can only use the default character encodings UTF-8 |
| or UTF-16.</p> |
| <h2>C.2 Empty Elements</h2> |
| <p>Include a space before the trailing <code>/</code> and <code> |
| ></code> of empty elements, e.g. <code class="greenmono"> |
| <br /></code>, <code class="greenmono"> |
| <hr /></code> and <code class="greenmono"><img |
| src="karen.jpg" alt="Karen" /></code>. Also, use the |
| minimized tag syntax for empty elements, e.g. <code class="greenmono"><br /></code>, as the alternative syntax <code class="greenmono"><br></br></code> allowed by XML |
| gives uncertain results in many existing user agents.</p> |
| <h2>C.3 Element Minimization and Empty Element Content</h2> |
| <p>Given an empty instance of an element whose content model is |
| not <code>EMPTY</code> (for example, an empty title or paragraph) |
| do not use the minimized form (e.g. use <code class="greenmono"> |
| <p> </p></code> and not <code class="greenmono"> |
| <p /></code>).</p> |
| <h2>C.4 Embedded Style Sheets and Scripts</h2> |
| <p>Use external style sheets if your style sheet uses <code> |
| <</code> or <code>&</code> or <code>]]></code> or <code>--</code>. Use |
| external scripts if your script uses <code><</code> or <code> |
| &</code> or <code>]]></code> or <code>--</code>. Note that XML parsers |
| are permitted to silently remove the contents of comments. Therefore, the historical |
| practice of "hiding" scripts and style sheets within comments to make the |
| documents backward compatible is likely to not work as expected in XML-based |
| implementations.</p> |
| <h2>C.5 Line Breaks within Attribute Values</h2> |
| <p>Avoid line breaks and multiple whitespace characters within |
| attribute values. These are handled inconsistently by user |
| agents.</p> |
| <h2>C.6 Isindex</h2> |
| <p>Don't include more than one <code>isindex</code> element in |
| the document <code>head</code>. The <code>isindex</code> element |
| is deprecated in favor of the <code>input</code> element.</p> |
| <h2>C.7 The <code>lang</code> and <code>xml:lang</code> Attributes</h2> |
| <p>Use both the <code>lang</code> and <code>xml:lang</code> |
| attributes when specifying the language of an element. The value |
| of the <code>xml:lang</code> attribute takes precedence.</p> |
| <h2>C.8 Fragment Identifiers</h2> |
| <p>In XML, <abbr title="Uniform Resource Identifiers">URIs</abbr> [<a href="#ref-rfc2396">RFC2396</a>] that end with fragment identifiers of the form |
| <code>"#foo"</code> do not refer to elements with an attribute |
| <code>name="foo"</code>; rather, they refer to elements with an |
| attribute defined to be of type <code>ID</code>, e.g., the <code> |
| id</code> attribute in HTML 4.0. Many existing HTML clients don't |
| support the use of <code>ID</code>-type attributes in this way, |
| so identical values may be supplied for both of these attributes to ensure |
| maximum forward and backward compatibility (e.g., <code class="greenmono"><a id="foo" name="foo">...</a></code>).</p> |
| <p>Further, since the set of |
| legal values for attributes of type <code>ID</code> is much smaller than |
| for those of type <code>CDATA</code>, the type of the <code>name</code> |
| attribute has been changed to <code>NMTOKEN</code>. This attribute is |
| constrained such that it can only have the same values as type |
| <code>ID</code>, or as the <code>Name</code> production in XML 1.0 Section |
| 2.5, production 5. Unfortunately, this constraint cannot be expressed in the |
| XHTML 1.0 DTDs. Because of this change, care must be taken when |
| converting existing HTML documents. The values of these attributes |
| must be unique within the document, valid, and any references to these |
| fragment identifiers (both |
| internal and external) must be updated should the values be changed during |
| conversion.</p> |
| <p>Finally, note that XHTML 1.0 has deprecated the |
| <code>name</code> attribute of the <code>a</code>, <code>applet</code>, <code>frame</code>, <code>iframe</code>, <code>img</code>, and <code>map</code> |
| elements, and it will be |
| removed from XHTML in subsequent versions.</p> |
| <h2>C.9 Character Encoding</h2> |
| <p>To specify a character encoding in the document, use both the |
| encoding attribute specification on the xml declaration (e.g. |
| <code class="greenmono"><?xml version="1.0" |
| encoding="EUC-JP"?></code>) and a meta http-equiv statement |
| (e.g. <code class="greenmono"><meta http-equiv="Content-type" |
| content='text/html; charset="EUC-JP"' /></code>). The |
| value of the encoding attribute of the xml processing instruction |
| takes precedence.</p> |
| <h2>C.10 Boolean Attributes</h2> |
| <p>Some HTML user agents are unable to interpret boolean |
| attributes when these appear in their full (non-minimized) form, |
| as required by XML 1.0. Note this problem doesn't effect user |
| agents compliant with HTML 4.0. The following attributes are |
| involved: <code>compact</code>, <code>nowrap</code>, <code> |
| ismap</code>, <code>declare</code>, <code>noshade</code>, <code> |
| checked</code>, <code>disabled</code>, <code>readonly</code>, |
| <code>multiple</code>, <code>selected</code>, <code> |
| noresize</code>, <code>defer</code>.</p> |
| <h2>C.11 Document Object Model and XHTML</h2> |
| <p> |
| The Document Object Model level 1 Recommendation [<a href="#ref-dom">DOM</a>] |
| defines document object model interfaces for XML and HTML 4.0. The HTML 4.0 |
| document object model specifies that HTML element and attribute names are |
| returned in upper-case. The XML document object model specifies that |
| element and attribute names are returned in the case they are specified. In |
| XHTML 1.0, elements and attributes are specified in lower-case. This apparent difference can be |
| addressed in two ways: |
| </p> |
| <ol> |
| <li>Applications that access XHTML documents served as Internet media type |
| <code>text/html</code> |
| via the <abbr title="Document Object Model">DOM</abbr> can use the HTML DOM, |
| and can rely upon element and attribute names being returned in |
| upper-case from those interfaces.</li> |
| <li>Applications that access XHTML documents served as Internet media types |
| <code>text/xml</code> or <code>application/xml</code> |
| can also use the XML DOM. Elements and attributes will be returned in lower-case. |
| Also, some XHTML elements may or may |
| not appear |
| in the object tree because they are optional in the content model |
| (e.g. the <code>tbody</code> element within |
| <code>table</code>). This occurs because in HTML 4.0 some elements were |
| permitted to be minimized such that their start and end tags are both omitted |
| (an SGML feature). |
| This is not possible in XML. Rather than require document authors to insert |
| extraneous elements, XHTML has made the elements optional. |
| Applications need to adapt to this |
| accordingly.</li> |
| </ol> |
| <h2>C.12 Using Ampersands in Attribute Values</h2> |
| <p> |
| When an attribute value contains an ampersand, it must be expressed as a character |
| entity reference |
| (e.g. "<code>&amp;</code>"). For example, when the |
| <code>href</code> attribute |
| of the <code>a</code> element refers to a |
| CGI script that takes parameters, it must be expressed as |
| <code>http://my.site.dom/cgi-bin/myscript.pl?class=guest&amp;name=user</code> |
| rather than as |
| <code>http://my.site.dom/cgi-bin/myscript.pl?class=guest&name=user</code>. |
| </p> |
| <h2>C.13 Cascading Style Sheets (CSS) and XHTML</h2> |
| <p>The Cascading Style Sheets level 2 Recommendation [<a href="#ref-css2">CSS2</a>] defines style |
| properties which are applied to the parse tree of the HTML or XML |
| document. Differences in parsing will produce different visual or |
| aural results, depending on the selectors used. The following hints |
| will reduce this effect for documents which are served without |
| modification as both media types:</p> |
| <ol> |
| <li> |
| CSS style sheets for XHTML should use lower case element and |
| attribute names.</li> |
| <li>In tables, the tbody element will be inferred by the parser of an |
| HTML user agent, but not by the parser of an XML user agent. Therefore |
| you should always explicitely add a tbody element if it is referred to |
| in a CSS selector.</li> |
| <li>Within the XHTML name space, user agents are expected to |
| recognize the "id" attribute as an attribute of type ID. |
| Therefore, style sheets should be able to continue using the |
| shorthand "#" selector syntax even if the user agent does not read |
| the DTD.</li> |
| <li>Within the XHTML name space, user agents are expected to |
| recognize the "class" attribute. Therefore, style sheets should be |
| able to continue using the shorthand "." selector syntax.</li> |
| <li> |
| CSS defines different conformance rules for HTML and XML documents; |
| be aware that the HTML rules apply to XHTML documents delivered as |
| HTML and the XML rules apply to XHTML documents delivered as XML.</li> |
| </ol> |
| <!--OddPage--> |
| <h1> |
| <a name="acks" id="acks">Appendix D. |
| Acknowledgements</a> |
| </h1> |
| <p> |
| <b>This appendix is informative.</b> |
| </p> |
| <p>This specification was written with the participation of the |
| members of the W3C HTML working group:</p> |
| <dl> |
| <dd>Steven Pemberton, CWI (HTML Working Group Chair)<br/> |
| Murray Altheim, Sun Microsystems<br/> |
| Daniel Austin, CNET: The Computer Network<br/> |
| Frank Boumphrey, HTML Writers Guild<br/> |
| John Burger, Mitre<br/> |
| Andrew W. Donoho, IBM<br/> |
| Sam Dooley, IBM<br/> |
| Klaus Hofrichter, GMD<br/> |
| Philipp Hoschka, W3C<br/> |
| Masayasu Ishikawa, W3C<br/> |
| Warner ten Kate, Philips Electronics<br/> |
| Peter King, Phone.com<br/> |
| Paula Klante, JetForm<br/> |
| Shin'ichi Matsui, W3C/Panasonic<br/> |
| Shane McCarron, Applied Testing and Technology (The Open Group through August |
| 1999)<br/> |
| Ann Navarro, HTML Writers Guild<br/> |
| Zach Nies, Quark<br/> |
| Dave Raggett, W3C/HP (W3C lead for HTML)<br/> |
| Patrick Schmitz, Microsoft<br/> |
| Sebastian Schnitzenbaumer, Stack Overflow<br/> |
| Chris Wilson, Microsoft<br/> |
| Ted Wugofski, Gateway 2000<br/> |
| Dan Zigmond, WebTV Networks</dd> |
| </dl> |
| <!--OddPage--> |
| <h1> |
| <a name="refs" id="refs">Appendix E. References</a> |
| </h1> |
| <p> |
| <b>This appendix is informative.</b> |
| </p> |
| <dl> |
| <dt> |
| <a name="ref-css2" id="ref-css2"> |
| <b>[CSS2]</b> |
| </a> |
| </dt> |
| <dd><a href="http://www.w3.org/TR/REC-CSS2">"Cascading Style Sheets, level 2 (CSS2) Specification"</a>, B. |
| Bos, H. W. Lie, C. Lilley, I. Jacobs, 12 May 1998.<br/> |
| Available at: <a href="http://www.w3.org/TR/REC-CSS2"> |
| http://www.w3.org/TR/REC-CSS2</a></dd> |
| <dt> |
| <a name="ref-dom" id="ref-dom"> |
| <b>[DOM]</b> |
| </a> |
| </dt> |
| <dd><a href="http://www.w3.org/TR/REC-DOM-Level-1">"Document Object Model (DOM) Level 1 Specification"</a>, Lauren |
| Wood <i>et al.</i>, 1 October 1998.<br/> |
| Available at: <a href="http://www.w3.org/TR/REC-DOM-Level-1"> |
| http://www.w3.org/TR/REC-DOM-Level-1</a></dd> |
| <dt> |
| <a name="ref-html4" id="ref-html4"> |
| <b>[HTML]</b> |
| </a> |
| </dt> |
| <dd><a href="http://www.w3.org/TR/1999/PR-html40-19990824">"HTML 4.01 Specification"</a>, D. Raggett, A. Le Hors, I. |
| Jacobs, 24 August 1999.<br/> |
| Available at: <a href="http://www.w3.org/TR/1999/PR-html40-19990824"> |
| http://www.w3.org/TR/1999/PR-html40-19990824</a></dd> |
| <dt> |
| <a name="ref-posix" id="ref-posix"> |
| <b>[POSIX.1]</b> |
| </a> |
| </dt> |
| <dd>"ISO/IEC 9945-1:1990 Information Technology - Portable |
| Operating System Interface (POSIX) - Part 1: System Application |
| Program Interface (API) [C Language]", Institute of Electrical |
| and Electronics Engineers, Inc, 1990.</dd> |
| <dt> |
| <a name="ref-rfc2046" id="ref-rfc2046"> |
| <b> |
| [RFC2046]</b> |
| </a> |
| </dt> |
| <dd><a href="http://www.ietf.org/rfc/rfc2046.txt">"RFC2046: Multipurpose Internet Mail Extensions (MIME) Part |
| Two: Media Types"</a>, N. Freed and N. Borenstein, November |
| 1996.<br/> |
| Available at <a href="http://www.ietf.org/rfc/rfc2046.txt"> |
| http://www.ietf.org/rfc/rfc2046.txt</a>. Note that this RFC |
| obsoletes RFC1521, RFC1522, and RFC1590.</dd> |
| <dt> |
| <a name="ref-rfc2119" id="ref-rfc2119"> |
| <b> |
| [RFC2119]</b> |
| </a> |
| </dt> |
| <dd><a href="http://www.ietf.org/rfc/rfc2119.txt">"RFC2119: Key words for use in RFCs to Indicate Requirement |
| Levels"</a>, S. Bradner, March 1997.<br/> |
| Available at: <a href="http://www.ietf.org/rfc/rfc2119.txt"> |
| http://www.ietf.org/rfc/rfc2119.txt</a></dd> |
| <dt> |
| <a name="ref-rfc2376" id="ref-rfc2376"> |
| <b> |
| [RFC2376]</b> |
| </a> |
| </dt> |
| <dd><a href="http://www.ietf.org/rfc/rfc2376.txt">"RFC2376: XML Media Types"</a>, E. Whitehead, M. Murata, July |
| 1998.<br/> |
| Available at: <a href="http://www.ietf.org/rfc/rfc2376.txt"> |
| http://www.ietf.org/rfc/rfc2376.txt</a></dd> |
| <dt> |
| <a name="ref-rfc2396" id="ref-rfc2396"> |
| <b> |
| [RFC2396]</b> |
| </a> |
| </dt> |
| <dd><a href="http://www.ietf.org/rfc/rfc2396.txt">"RFC2396: Uniform Resource Identifiers (URI): Generic |
| Syntax"</a>, T. Berners-Lee, R. Fielding, L. Masinter, August |
| 1998.<br/> |
| This document updates RFC1738 and RFC1808.<br/> |
| Available at: <a href="http://www.ietf.org/rfc/rfc2396.txt"> |
| http://www.ietf.org/rfc/rfc2396.txt</a></dd> |
| <dt> |
| <a name="ref-xml" id="ref-xml"> |
| <b>[XML]</b> |
| </a> |
| </dt> |
| <dd><a href="http://www.w3.org/TR/REC-xml">"Extensible Markup Language (XML) 1.0 Specification"</a>, T. |
| Bray, J. Paoli, C. M. Sperberg-McQueen, 10 February 1998.<br/> |
| Available at: <a href="http://www.w3.org/TR/REC-xml"> |
| http://www.w3.org/TR/REC-xml</a></dd> |
| <dt> |
| <a name="ref-xmlns" id="ref-xmlns"> |
| <b>[XMLNAMES]</b> |
| </a> |
| </dt> |
| <dd><a href="http://www.w3.org/TR/REC-xml-names">"Namespaces in XML"</a>, T. Bray, D. Hollander, A. Layman, 14 |
| January 1999.<br/> |
| XML namespaces provide a simple method for qualifying names used |
| in XML documents by associating them with namespaces identified |
| by URI.<br/> |
| Available at: <a href="http://www.w3.org/TR/REC-xml-names"> |
| http://www.w3.org/TR/REC-xml-names</a></dd> |
| </dl> |
| <p> |
| <a href="http://www.w3.org/WAI/WCAG1AAA-Conformance" title="Explanation of Level Triple-A Conformance"> |
| <img height="32" width="88" src="wcag1AAA.gif" alt="Level Triple-A conformance icon, W3C-WAI Web Content Accessibility Guidelines 1.0"/></a> |
| </p> |
| <div class="navbar"> |
| <hr/> |
| <a href="#toc">table of contents</a> |
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