Annotation of embedaddon/libxml2/result/valid/xhtml1.xhtml, revision 1.1
1.1 ! misho 1: <?xml version="1.0"?>
! 2: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "dtds/xhtml1-strict.dtd">
! 3: <?xml-stylesheet href="W3C-PR.css" type="text/css"?>
! 4: <html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
! 5: <head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
! 6: <title>XHTML 1.0: The Extensible HyperText Markup
! 7: Language</title>
! 8: <link rel="stylesheet" href="W3C-PR.css" type="text/css" />
! 9: <style type="text/css">
! 10: span.term { font-style: italic; color: rgb(0, 0, 192) }
! 11: code {
! 12: color: green;
! 13: font-family: monospace;
! 14: font-weight: bold;
! 15: }
! 16:
! 17: code.greenmono {
! 18: color: green;
! 19: font-family: monospace;
! 20: font-weight: bold;
! 21: }
! 22: .good {
! 23: border: solid green;
! 24: border-width: 2px;
! 25: color: green;
! 26: font-weight: bold;
! 27: margin-right: 5%;
! 28: margin-left: 0;
! 29: }
! 30: .bad {
! 31: border: solid red;
! 32: border-width: 2px;
! 33: margin-left: 0;
! 34: margin-right: 5%;
! 35: color: rgb(192, 101, 101);
! 36: }
! 37:
! 38: img {
! 39: color: white;
! 40: border: none;
! 41: }
! 42:
! 43: div.navbar { text-align: center; }
! 44: div.contents {
! 45: background-color: rgb(204,204,255);
! 46: padding: 0.5em;
! 47: border: none;
! 48: margin-right: 5%;
! 49: }
! 50: .tocline { list-style: none; }
! 51: table.exceptions { background-color: rgb(255,255,153); }
! 52: </style>
! 53: </head>
! 54: <body>
! 55: <div class="navbar">
! 56: <a href="#toc">table of contents</a>
! 57: <hr />
! 58: </div>
! 59: <div class="head"><p><a href="http://www.w3.org/"><img class="head" src="w3c_home.gif" alt="W3C" /></a></p>
! 60:
! 61: <h1 class="head"><a name="title" id="title">XHTML</a><sup>™</sup> 1.0:
! 62: The Extensible HyperText Markup Language</h1>
! 63:
! 64: <h2>A Reformulation of HTML 4.0 in XML 1.0</h2>
! 65:
! 66: <h3>W3C Proposed Recommendation 10 December 1999</h3>
! 67:
! 68: <dl>
! 69: <dt>This version:</dt>
! 70:
! 71: <dd><a href="http://www.w3.org/TR/1999/PR-xhtml1-19991210">
! 72: http://www.w3.org/TR/1999/PR-xhtml1-19991210</a> <br />
! 73: (<a href="xhtml1.ps">Postscript version</a>,
! 74: <a href="xhtml1.pdf">PDF version</a>,
! 75: <a href="xhtml1.zip">ZIP archive</a>, or
! 76: <a href="xhtml1.tgz">Gzip'd TAR archive</a>)
! 77: </dd>
! 78:
! 79: <dt>Latest version:</dt>
! 80:
! 81: <dd><a href="http://www.w3.org/TR/xhtml1">
! 82: http://www.w3.org/TR/xhtml1</a></dd>
! 83:
! 84: <dt>Previous versions:</dt>
! 85:
! 86: <dd><a href="http://www.w3.org/TR/1999/WD-xhtml1-19991124">
! 87: http://www.w3.org/TR/1999/WD-xhtml1-19991124</a></dd>
! 88: <dd><a href="http://www.w3.org/TR/1999/PR-xhtml1-19990824">
! 89: http://www.w3.org/TR/1999/PR-xhtml1-19990824</a></dd>
! 90:
! 91: <dt>Authors:</dt>
! 92:
! 93: <dd>See <a href="#acks">acknowledgements</a>.</dd>
! 94: </dl>
! 95:
! 96: <p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">
! 97: Copyright</a> © 1999 <a href="http://www.w3.org/">W3C</a><sup>®</sup>
! 98: (<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">
! 99: liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">
! 100: trademark</a>, <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document
! 101: use</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-software">software
! 102: licensing</a> rules apply.</p>
! 103: <hr />
! 104: </div>
! 105:
! 106: <h2 class="notoc">Abstract</h2>
! 107:
! 108: <p>This specification defines <abbr title="Extensible Hypertext Markup Language">XHTML</abbr> 1.0, a reformulation of HTML
! 109: 4.0 as an XML 1.0 application, and three <abbr title="Document Type Definition">DTDs</abbr> corresponding to
! 110: the ones defined by HTML 4.0. The semantics of the elements and
! 111: their attributes are defined in the W3C Recommendation for HTML
! 112: 4.0. These semantics provide the foundation for future
! 113: extensibility of XHTML. Compatibility with existing HTML user
! 114: agents is possible by following a small set of guidelines.</p>
! 115:
! 116: <h2>Status of this document</h2>
! 117:
! 118: <p><em>This section describes the status of this document at the time
! 119: of its publication. Other documents may supersede this document. The
! 120: latest status of this document series is maintained at the W3C.</em></p>
! 121:
! 122: <p>This specification is a Proposed Recommendation of the HTML Working Group. It is
! 123: a revision of the Proposed Recommendation dated <a href="http://www.w3.org/TR/1999/PR-xhtml1-19990824/">24 August
! 124: 1999</a> incorporating changes as a result of comments from the Proposed
! 125: Recommendation review, and
! 126: comments and further deliberations of the W3C HTML Working Group. A
! 127: <a href="xhtml1-diff-19991210.html">diff-marked version</a> from the previous
! 128: proposed recommendation is available for comparison purposes.</p>
! 129:
! 130: <p>On 10 December 1999, this document enters a
! 131: <a href="http://www.w3.org/Consortium/Process/#RecsPR">
! 132: Proposed Recommendation</a> review period. From that date until 8 January
! 133: 2000,
! 134: W3C Advisory Committee representatives are encouraged
! 135: to review this specification and return comments in their completed
! 136: ballots to w3c-html-review@w3.org. Please send any comments of a
! 137: confidential nature in separate email to w3t-html@w3.org, which is
! 138: visible to the Team only.</p>
! 139:
! 140: <p>No sooner than 14 days after the end of the review period, the
! 141: Director will announce the document's disposition: it may become a W3C
! 142: Recommendation (possibly with minor changes), it may revert to Working
! 143: Draft status, or it may be dropped as a W3C work item.</p>
! 144:
! 145: <p>Publication as a Proposed Recommendation does not imply endorsement
! 146: by the W3C membership. This is still a draft document and may be
! 147: updated, replaced or obsoleted by other documents at any time. It is
! 148: inappropriate to cite W3C Proposed Recommendation as other than "work
! 149: in progress."</p>
! 150:
! 151: <p>This document has been produced as part of the <a href="http://www.w3.org/MarkUp/">W3C HTML Activity</a>. The goals of
! 152: the <a href="http://www.w3.org/MarkUp/Group/">HTML Working
! 153: Group</a> <i>(<a href="http://cgi.w3.org/MemberAccess/">members
! 154: only</a>)</i> are discussed in the <a href="http://www.w3.org/MarkUp/Group/HTMLcharter">HTML Working Group
! 155: charter</a> <i>(<a href="http://cgi.w3.org/MemberAccess/">members
! 156: only</a>)</i>.</p>
! 157:
! 158: <p>A list of current W3C Recommendations and other technical documents
! 159: can be found at <a href="http://www.w3.org/TR">http://www.w3.org/TR</a>.</p>
! 160:
! 161: <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
! 162: staff contact for work on HTML is <a href="mailto:dsr@w3.org">Dave
! 163: Raggett</a>.</p>
! 164:
! 165: <p>Please report errors in this document to <a href="mailto:www-html-editor@w3.org">www-html-editor@w3.org</a>.</p>
! 166:
! 167: <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>
! 168:
! 169: <h2 class="notoc"><a id="toc" name="toc">Contents</a></h2>
! 170:
! 171: <div class="contents">
! 172: <ul class="toc">
! 173: <li class="tocline">1. <a href="#xhtml">What is XHTML?</a>
! 174:
! 175: <ul class="toc">
! 176: <li class="tocline">1.1 <a href="#html4">What is HTML 4.0?</a></li>
! 177:
! 178: <li class="tocline">1.2 <a href="#xml">What is XML?</a></li>
! 179:
! 180: <li class="tocline">1.3 <a href="#why">Why the need for XHTML?</a></li>
! 181: </ul>
! 182: </li>
! 183:
! 184: <li class="tocline">2. <a href="#defs">Definitions</a>
! 185:
! 186: <ul class="toc">
! 187: <li class="tocline">2.1 <a href="#terms">Terminology</a></li>
! 188:
! 189: <li class="tocline">2.2 <a href="#general">General Terms</a></li>
! 190: </ul>
! 191: </li>
! 192:
! 193: <li class="tocline">3. <a href="#normative">Normative Definition of XHTML 1.0</a>
! 194:
! 195:
! 196: <ul class="toc">
! 197: <li class="tocline">3.1 <a href="#docconf">Document Conformance</a></li>
! 198:
! 199: <li class="tocline">3.2 <a href="#uaconf">User Agent Conformance</a></li>
! 200: </ul>
! 201: </li>
! 202:
! 203: <li class="tocline">4. <a href="#diffs">Differences with HTML 4.0</a>
! 204:
! 205: </li>
! 206:
! 207: <li class="tocline">5. <a href="#issues">Compatibility Issues</a>
! 208:
! 209: <ul class="toc">
! 210: <li class="tocline">5.1 <a href="#media">Internet Media Types</a></li>
! 211: </ul>
! 212: </li>
! 213:
! 214: <li class="tocline">6. <a href="#future">Future Directions</a>
! 215:
! 216: <ul class="toc">
! 217: <li class="tocline">6.1 <a href="#mods">Modularizing HTML</a></li>
! 218:
! 219: <li class="tocline">6.2 <a href="#extensions">Subsets and Extensibility</a></li>
! 220:
! 221: <li class="tocline">6.3 <a href="#profiles">Document Profiles</a></li>
! 222: </ul>
! 223: </li>
! 224:
! 225: <li class="tocline"><a href="#dtds">Appendix A. DTDs</a></li>
! 226:
! 227: <li class="tocline"><a href="#prohibitions">Appendix B. Element
! 228: Prohibitions</a></li>
! 229:
! 230: <li class="tocline"><a href="#guidelines">Appendix C. HTML Compatibility Guidelines</a></li>
! 231:
! 232: <li class="tocline"><a href="#acks">Appendix D. Acknowledgements</a></li>
! 233:
! 234: <li class="tocline"><a href="#refs">Appendix E. References</a></li>
! 235: </ul>
! 236: </div>
! 237:
! 238: <!--OddPage-->
! 239: <h1><a name="xhtml" id="xhtml">1. What is XHTML?</a></h1>
! 240:
! 241: <p>XHTML is a family of current and future document types and modules that
! 242: 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,
! 243: and ultimately are designed to work in conjunction with XML-based user agents.
! 244: The details of this family and its evolution are
! 245: discussed in more detail in the section on <a href="#future">Future
! 246: Directions</a>. </p>
! 247:
! 248: <p>XHTML 1.0 (this specification) is the first document type in the XHTML
! 249: family. It is a reformulation of the three HTML 4.0 document types as
! 250: applications of XML 1.0 <a href="#ref-xml"> [XML]</a>. It is intended
! 251: to be used as a language for content that is both XML-conforming and, if some
! 252: simple <a href="#guidelines">guidelines</a> are followed,
! 253: operates in HTML 4.0 conforming user agents. Developers who migrate
! 254: their content to XHTML 1.0 will realize the following benefits:</p>
! 255:
! 256: <ul>
! 257: <li>XHTML documents are XML conforming. As such, they are readily viewed,
! 258: edited, and validated with standard XML tools.</li>
! 259: <li>XHTML documents can be written to
! 260: to operate as well or better than they did before in existing
! 261: HTML 4.0-conforming user agents as well as in new, XHTML 1.0 conforming user
! 262: agents.</li>
! 263: <li>XHTML documents can utilize applications (e.g. scripts and applets) that rely
! 264: upon either the HTML Document Object Model or the XML Document Object Model <a href="#ref-dom">[DOM]</a>.</li>
! 265: <li>As the XHTML family evolves, documents conforming to XHTML 1.0 will be more
! 266: likely to interoperate within and among various XHTML environments.</li>
! 267: </ul>
! 268:
! 269: <p>The XHTML family is the next step in the evolution of the Internet. By
! 270: migrating to XHTML today, content developers can enter the XML world with all
! 271: of its attendant benefits, while still remaining confident in their
! 272: content's backward and future compatibility.</p>
! 273:
! 274: <h2><a name="html4" id="html4">1.1 What is HTML 4.0?</a></h2>
! 275:
! 276: <p>HTML 4.0 <a href="#ref-html4">[HTML]</a> is an <abbr title="Standard Generalized Markup Language">SGML</abbr> (Standard
! 277: Generalized Markup Language) application conforming to
! 278: International Standard <abbr title="Organization for International Standardization">ISO</abbr> 8879, and is widely regarded as the
! 279: standard publishing language of the World Wide Web.</p>
! 280:
! 281: <p>SGML is a language for describing markup languages,
! 282: particularly those used in electronic document exchange, document
! 283: management, and document publishing. HTML is an example of a
! 284: language defined in SGML.</p>
! 285:
! 286: <p>SGML has been around since the middle 1980's and has remained
! 287: quite stable. Much of this stability stems from the fact that the
! 288: language is both feature-rich and flexible. This flexibility,
! 289: however, comes at a price, and that price is a level of
! 290: complexity that has inhibited its adoption in a diversity of
! 291: environments, including the World Wide Web.</p>
! 292:
! 293: <p>HTML, as originally conceived, was to be a language for the
! 294: exchange of scientific and other technical documents, suitable
! 295: for use by non-document specialists. HTML addressed the problem
! 296: of SGML complexity by specifying a small set of structural and
! 297: semantic tags suitable for authoring relatively simple documents.
! 298: In addition to simplifying the document structure, HTML added
! 299: support for hypertext. Multimedia capabilities were added
! 300: later.</p>
! 301:
! 302: <p>In a remarkably short space of time, HTML became wildly
! 303: popular and rapidly outgrew its original purpose. Since HTML's
! 304: inception, there has been rapid invention of new elements for use
! 305: within HTML (as a standard) and for adapting HTML to vertical,
! 306: highly specialized, markets. This plethora of new elements has
! 307: led to compatibility problems for documents across different
! 308: platforms.</p>
! 309:
! 310: <p>As the heterogeneity of both software and platforms rapidly
! 311: proliferate, it is clear that the suitability of 'classic' HTML
! 312: 4.0 for use on these platforms is somewhat limited.</p>
! 313:
! 314: <h2><a name="xml" id="xml">1.2 What is XML?</a></h2>
! 315:
! 316: <p>XML<sup>™</sup> is the shorthand for Extensible Markup
! 317: Language, and is an acronym of Extensible Markup Language <a href="#ref-xml">[XML]</a>.</p>
! 318:
! 319: <p>XML was conceived as a means of regaining the power and
! 320: flexibility of SGML without most of its complexity. Although a
! 321: restricted form of SGML, XML nonetheless preserves most of SGML's
! 322: power and richness, and yet still retains all of SGML's commonly
! 323: used features.</p>
! 324:
! 325: <p>While retaining these beneficial features, XML removes many of
! 326: the more complex features of SGML that make the authoring and
! 327: design of suitable software both difficult and costly.</p>
! 328:
! 329: <h2><a name="why" id="why">1.3 Why the need for XHTML?</a></h2>
! 330:
! 331: <p>The benefits of migrating to XHTML 1.0 are described above. Some of the
! 332: benefits of migrating to XHTML in general are:</p>
! 333:
! 334: <ul>
! 335: <li>Document developers and user agent designers are constantly
! 336: discovering new ways to express their ideas through new markup. In XML, it is
! 337: relatively easy to introduce new elements or additional element
! 338: attributes. The XHTML family is designed to accommodate these extensions
! 339: through XHTML modules and techniques for developing new XHTML-conforming
! 340: modules (described in the forthcoming XHTML Modularization specification).
! 341: These modules will permit the combination of existing and
! 342: new feature sets when developing content and when designing new user
! 343: agents.</li>
! 344:
! 345: <li>Alternate ways of accessing the Internet are constantly being
! 346: introduced. Some estimates indicate that by the year 2002, 75% of
! 347: Internet document viewing will be carried out on these alternate
! 348: platforms. The XHTML family is designed with general user agent
! 349: interoperability in mind. Through a new user agent and document profiling
! 350: mechanism, servers, proxies, and user agents will be able to perform
! 351: best effort content transformation. Ultimately, it will be possible to
! 352: develop XHTML-conforming content that is usable by any XHTML-conforming
! 353: user agent.</li>
! 354:
! 355: </ul>
! 356: <!--OddPage-->
! 357: <h1><a name="defs" id="defs">2. Definitions</a></h1>
! 358:
! 359: <h2><a name="terms" id="terms">2.1 Terminology</a></h2>
! 360:
! 361: <p>The following terms are used in this specification. These
! 362: terms extend the definitions in <a href="#ref-rfc2119">
! 363: [RFC2119]</a> in ways based upon similar definitions in ISO/<abbr title="International Electro-technical Commission">IEC</abbr>
! 364: 9945-1:1990 <a href="#ref-posix">[POSIX.1]</a>:</p>
! 365:
! 366: <dl>
! 367: <dt>Implementation-defined</dt>
! 368:
! 369: <dd>A value or behavior is implementation-defined when it is left
! 370: to the implementation to define [and document] the corresponding
! 371: requirements for correct document construction.</dd>
! 372:
! 373: <dt>May</dt>
! 374:
! 375: <dd>With respect to implementations, the word "may" is to be
! 376: interpreted as an optional feature that is not required in this
! 377: specification but can be provided. With respect to <a href="#docconf">Document Conformance</a>, the word "may" means that
! 378: the optional feature must not be used. The term "optional" has
! 379: the same definition as "may".</dd>
! 380:
! 381: <dt>Must</dt>
! 382:
! 383: <dd>In this specification, the word "must" is to be interpreted
! 384: as a mandatory requirement on the implementation or on Strictly
! 385: Conforming XHTML Documents, depending upon the context. The term
! 386: "shall" has the same definition as "must".</dd>
! 387:
! 388: <dt>Reserved</dt>
! 389:
! 390: <dd>A value or behavior is unspecified, but it is not allowed to
! 391: be used by Conforming Documents nor to be supported by a
! 392: Conforming User Agents.</dd>
! 393:
! 394: <dt>Should</dt>
! 395:
! 396: <dd>With respect to implementations, the word "should" is to be
! 397: interpreted as an implementation recommendation, but not a
! 398: requirement. With respect to documents, the word "should" is to
! 399: be interpreted as recommended programming practice for documents
! 400: and a requirement for Strictly Conforming XHTML Documents.</dd>
! 401:
! 402: <dt>Supported</dt>
! 403:
! 404: <dd>Certain facilities in this specification are optional. If a
! 405: facility is supported, it behaves as specified by this
! 406: specification.</dd>
! 407:
! 408: <dt>Unspecified</dt>
! 409:
! 410: <dd>When a value or behavior is unspecified, the specification
! 411: defines no portability requirements for a facility on an
! 412: implementation even when faced with a document that uses the
! 413: facility. A document that requires specific behavior in such an
! 414: instance, rather than tolerating any behavior when using that
! 415: facility, is not a Strictly Conforming XHTML Document.</dd>
! 416: </dl>
! 417:
! 418: <h2><a name="general" id="general">2.2 General Terms</a></h2>
! 419:
! 420: <dl>
! 421: <dt>Attribute</dt>
! 422:
! 423: <dd>An attribute is a parameter to an element declared in the
! 424: DTD. An attribute's type and value range, including a possible
! 425: default value, are defined in the DTD.</dd>
! 426:
! 427: <dt>DTD</dt>
! 428:
! 429: <dd>A DTD, or document type definition, is a collection of XML
! 430: declarations that, as a collection, defines the legal structure,
! 431: <span class="term">elements</span>, and <span class="term">
! 432: attributes</span> that are available for use in a document that
! 433: complies to the DTD.</dd>
! 434:
! 435: <dt>Document</dt>
! 436:
! 437: <dd>A document is a stream of data that, after being combined
! 438: with any other streams it references, is structured such that it
! 439: holds information contained within <span class="term">
! 440: elements</span> that are organized as defined in the associated
! 441: <span class="term">DTD</span>. See <a href="#docconf">Document
! 442: Conformance</a> for more information.</dd>
! 443:
! 444: <dt>Element</dt>
! 445:
! 446: <dd>An element is a document structuring unit declared in the
! 447: <span class="term">DTD</span>. The element's content model is
! 448: defined in the <span class="term">DTD</span>, and additional
! 449: semantics may be defined in the prose description of the
! 450: element.</dd>
! 451:
! 452: <dt><a name="facilities" id="facilities">Facilities</a></dt>
! 453:
! 454: <dd>Functionality includes <span class="term">elements</span>,
! 455: <span class="term">attributes</span>, and the semantics
! 456: associated with those <span class="term">elements</span> and
! 457: <span class="term">attributes</span>. An implementation
! 458: supporting that functionality is said to provide the necessary
! 459: facilities.</dd>
! 460:
! 461: <dt>Implementation</dt>
! 462:
! 463: <dd>An implementation is a system that provides collection of
! 464: <span class="term">facilities</span> and services that supports
! 465: this specification. See <a href="#uaconf">User Agent
! 466: Conformance</a> for more information.</dd>
! 467:
! 468: <dt>Parsing</dt>
! 469:
! 470: <dd>Parsing is the act whereby a <span class="term">
! 471: document</span> is scanned, and the information contained within
! 472: the <span class="term">document</span> is filtered into the
! 473: context of the <span class="term">elements</span> in which the
! 474: information is structured.</dd>
! 475:
! 476: <dt>Rendering</dt>
! 477:
! 478: <dd>Rendering is the act whereby the information in a <span class="term">document</span> is presented. This presentation is
! 479: done in the form most appropriate to the environment (e.g.
! 480: aurally, visually, in print).</dd>
! 481:
! 482: <dt>User Agent</dt>
! 483:
! 484: <dd>A user agent is an <span class="term">implementation</span>
! 485: that retrieves and processes XHTML documents. See <a href="#uaconf">User Agent Conformance</a> for more information.</dd>
! 486:
! 487: <dt>Validation</dt>
! 488:
! 489: <dd>Validation is a process whereby <span class="term">
! 490: 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">
! 491: attributes</span> are consistent with the definitions in the
! 492: <span class="term">DTD</span>.</dd>
! 493:
! 494: <dt><a name="wellformed" id="wellformed">Well-formed</a></dt>
! 495:
! 496: <dd>A <span class="term">document</span> is well-formed when it
! 497: 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
! 498: the XML 1.0 Recommendation <a href="#ref-xml">[XML]</a>.
! 499: Basically, this definition states that elements, delimited by
! 500: their start and end tags, are nested properly within one
! 501: another.</dd>
! 502: </dl>
! 503:
! 504: <!--OddPage-->
! 505: <h1><a name="normative" id="normative">3. Normative Definition of
! 506: XHTML 1.0</a></h1>
! 507:
! 508: <h2><a name="docconf" id="docconf">3.1 Document
! 509: Conformance</a></h2>
! 510:
! 511: <p>This version of XHTML provides a definition of strictly
! 512: conforming XHTML documents, which are restricted to tags and
! 513: attributes from the XHTML namespace. See <a href="#well-formed">Section 3.1.2</a> for information on using XHTML
! 514: with other namespaces, for instance, to include metadata
! 515: expressed in <abbr title="Resource Description Format">RDF</abbr> within XHTML documents.</p>
! 516:
! 517: <h3><a name="strict" id="strict">3.1.1 Strictly Conforming
! 518: Documents</a></h3>
! 519:
! 520: <p>A Strictly Conforming XHTML Document is a document that
! 521: requires only the facilities described as mandatory in this
! 522: specification. Such a document must meet all of the following
! 523: criteria:</p>
! 524:
! 525: <ol>
! 526: <li>
! 527: <p>It must validate against one of the three DTDs found in <a href="#dtds">Appendix A</a>.</p>
! 528: </li>
! 529:
! 530: <li>
! 531: <p>The root element of the document must be <code>
! 532: <html></code>.</p>
! 533: </li>
! 534:
! 535: <li>
! 536: <p>The root element of the document must designate the XHTML
! 537: namespace using the <code>xmlns</code> attribute <a href="#ref-xmlns">[XMLNAMES]</a>. The namespace for XHTML is
! 538: defined to be
! 539: <code>http://www.w3.org/1999/xhtml</code>.</p>
! 540: </li>
! 541:
! 542: <li>
! 543: <p>There must be a DOCTYPE declaration in the document prior to
! 544: the root element. The public identifier included in
! 545: the DOCTYPE declaration must reference one of the three DTDs
! 546: found in <a href="#dtds">Appendix A</a> using the respective
! 547: Formal Public Identifier. The system identifier may be changed to reflect
! 548: local system conventions.</p>
! 549:
! 550: <pre>
! 551: <!DOCTYPE html
! 552: PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
! 553: "http://www.w3.org/TR/1999/PR-xhtml1-19991210/DTD/xhtml1-strict.dtd>
! 554:
! 555: <!DOCTYPE html
! 556: PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
! 557: "http://www.w3.org/TR/1999/PR-xhtml1-19991210/DTD/xhtml1-transitional.dtd>
! 558:
! 559: <!DOCTYPE html
! 560: PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN"
! 561: "http://www.w3.org/TR/1999/PR-xhtml1-19991210/DTD/xhtml1-frameset.dtd>
! 562: </pre>
! 563: </li>
! 564: </ol>
! 565:
! 566: <p>Here is an example of a minimal XHTML document.</p>
! 567:
! 568: <div class="good">
! 569: <pre>
! 570: <?xml version="1.0" encoding="UTF-8"?>
! 571: <!DOCTYPE html
! 572: PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
! 573: "http://www.w3.org/TR/1999/PR-xhtml1-19991210/DTD/xhtml1-strict.dtd">
! 574: <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
! 575: <head>
! 576: <title>Virtual Library</title>
! 577: </head>
! 578: <body>
! 579: <p>Moved to <a href="http://vlib.org/">vlib.org</a>.</p>
! 580: </body>
! 581: </html></pre>
! 582: </div>
! 583:
! 584: <p>Note that in this example, the XML declaration is included. An XML
! 585: declaration like the one above is
! 586: 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
! 587: when the character encoding of the document is other than the default UTF-8 or
! 588: UTF-16.</p>
! 589:
! 590: <h3><a name="well-formed" id="well-formed">3.1.2 Using XHTML with
! 591: other namespaces</a></h3>
! 592:
! 593: <p>The XHTML namespace may be used with other XML namespaces
! 594: as per <a href="#ref-xmlns">[XMLNAMES]</a>, although such
! 595: documents are not strictly conforming XHTML 1.0 documents as
! 596: defined above. Future work by W3C will address ways to specify
! 597: conformance for documents involving multiple namespaces.</p>
! 598:
! 599: <p>The following example shows the way in which XHTML 1.0 could
! 600: be used in conjunction with the MathML Recommendation:</p>
! 601:
! 602: <div class="good">
! 603: <pre>
! 604: <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
! 605: <head>
! 606: <title>A Math Example</title>
! 607: </head>
! 608: <body>
! 609: <p>The following is MathML markup:</p>
! 610: <math xmlns="http://www.w3.org/1998/Math/MathML">
! 611: <apply> <log/>
! 612: <logbase>
! 613: <cn> 3 </cn>
! 614: </logbase>
! 615: <ci> x </ci>
! 616: </apply>
! 617: </math>
! 618: </body>
! 619: </html>
! 620: </pre>
! 621: </div>
! 622:
! 623: <p>The following example shows the way in which XHTML 1.0 markup
! 624: could be incorporated into another XML namespace:</p>
! 625:
! 626: <div class="good">
! 627: <pre>
! 628: <?xml version="1.0" encoding="UTF-8"?>
! 629: <!-- initially, the default namespace is "books" -->
! 630: <book xmlns='urn:loc.gov:books'
! 631: xmlns:isbn='urn:ISBN:0-395-36341-6' xml:lang="en" lang="en">
! 632: <title>Cheaper by the Dozen</title>
! 633: <isbn:number>1568491379</isbn:number>
! 634: <notes>
! 635: <!-- make HTML the default namespace for a hypertext commentary -->
! 636: <p xmlns='http://www.w3.org/1999/xhtml'>
! 637: This is also available <a href="http://www.w3.org/">online</a>.
! 638: </p>
! 639: </notes>
! 640: </book>
! 641: </pre>
! 642: </div>
! 643:
! 644: <h2><a name="uaconf" id="uaconf">3.2 User Agent
! 645: Conformance</a></h2>
! 646:
! 647: <p>A conforming user agent must meet all of the following
! 648: criteria:</p>
! 649:
! 650: <ol>
! 651: <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
! 652: an XHTML document for well-formedness. If the user agent claims
! 653: to be a validating user agent, it must also validate documents
! 654: against their referenced DTDs according to <a href="#ref-xml">
! 655: [XML]</a>.</li>
! 656:
! 657: <li>When the user agent claims to support <a href="#facilities">
! 658: facilities</a> defined within this specification or required by
! 659: this specification through normative reference, it must do so in
! 660: ways consistent with the facilities' definition.</li>
! 661:
! 662: <li>When a user agent processes an XHTML document as generic XML,
! 663: it shall only recognize attributes of type
! 664: <code>ID</code> (e.g. the <code>id</code> attribute on most XHTML elements)
! 665: as fragment identifiers.</li>
! 666:
! 667: <li>If a user agent encounters an element it does not recognize,
! 668: it must render the element's content.</li>
! 669:
! 670: <li>If a user agent encounters an attribute it does not
! 671: recognize, it must ignore the entire attribute specification
! 672: (i.e., the attribute and its value).</li>
! 673:
! 674: <li>If a user agent encounters an attribute value it doesn't
! 675: recognize, it must use the default attribute value.</li>
! 676:
! 677: <li>If it encounters an entity reference (other than one
! 678: of the predefined entities) for which the User Agent has
! 679: processed no declaration (which could happen if the declaration
! 680: is in the external subset which the User Agent hasn't read), the entity
! 681: reference should be rendered as the characters (starting
! 682: with the ampersand and ending with the semi-colon) that
! 683: make up the entity reference.</li>
! 684:
! 685: <li>When rendering content, User Agents that encounter
! 686: 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>
! 687:
! 688: <li>
! 689: The following characters are defined in [XML] as whitespace characters:
! 690:
! 691: <ul>
! 692: <li>Space (&#x0020;)</li>
! 693: <li>Tab (&#x0009;)</li>
! 694: <li>Carriage return (&#x000D;)</li>
! 695: <li>Line feed (&#x000A;)</li>
! 696: </ul>
! 697:
! 698: <p>
! 699: The XML processor normalizes different system's line end codes into one
! 700: single line-feed character, that is passed up to the application. The XHTML
! 701: user agent in addition, must treat the following characters as whitespace:
! 702: </p>
! 703:
! 704: <ul>
! 705: <li>Form feed (&#x000C;)</li>
! 706: <li>Zero-width space (&#x200B;)</li>
! 707: </ul>
! 708:
! 709: <p>
! 710: In elements where the 'xml:space' attribute is set to 'preserve', the user
! 711: agent must leave all whitespace characters intact (with the exception of
! 712: leading and trailing whitespace characters, which should be removed).
! 713: Otherwise, whitespace
! 714: is handled according to the following rules:
! 715: </p>
! 716:
! 717: <ul>
! 718: <li>
! 719: All whitespace surrounding block elements should be removed.
! 720: </li>
! 721: <li>
! 722: Comments are removed entirely and do not affect whitespace handling. One
! 723: whitespace character on either side of a comment is treated as two white
! 724: space characters.
! 725: </li>
! 726: <li>
! 727: Leading and trailing whitespace inside a block element must be removed.
! 728: </li>
! 729: <li>Line feed characters within a block element must be converted into a
! 730: space (except when the 'xml:space' attribute is set to 'preserve').
! 731: </li>
! 732: <li>
! 733: A sequence of white space characters must be reduced to a single space
! 734: character (except when the 'xml:space' attribute is set to 'preserve').
! 735: </li>
! 736: <li>
! 737: With regard to rendition,
! 738: the User Agent should render the content in a
! 739: manner appropriate to the language in which the content is written.
! 740: In languages whose primary script is Latinate, the ASCII space
! 741: character is typically used to encode both grammatical word boundaries and
! 742: typographic whitespace; in languages whose script is related to Nagari
! 743: (e.g., Sanskrit, Thai, etc.), grammatical boundaries may be encoded using
! 744: the ZW 'space' character, but will not typically be represented by
! 745: typographic whitespace in rendered output; languages using Arabiform scripts
! 746: may encode typographic whitespace using a space character, but may also use
! 747: the ZW space character to delimit 'internal' grammatical boundaries (what
! 748: look like words in Arabic to an English eye frequently encode several words,
! 749: e.g. 'kitAbuhum' = 'kitAbu-hum' = 'book them' == their book); and languages
! 750: in the Chinese script tradition typically neither encode such delimiters nor
! 751: use typographic whitespace in this way.
! 752: </li>
! 753: </ul>
! 754:
! 755: <p>Whitespace in attribute values is processed according to <a href="#ref-xml">[XML]</a>.</p>
! 756: </li>
! 757: </ol>
! 758:
! 759: <!--OddPage-->
! 760: <h1><a name="diffs" id="diffs">4. Differences with HTML
! 761: 4.0</a></h1>
! 762:
! 763: <p>Due to the fact that XHTML is an XML application, certain
! 764: practices that were perfectly legal in SGML-based HTML 4.0 <a href="#ref-html4">[HTML]</a> must be changed.</p>
! 765:
! 766: <h2><a name="h-4.1" id="h-4.1">4.1 Documents must be
! 767: well-formed</a></h2>
! 768:
! 769: <p><a href="#wellformed">Well-formedness</a> is a new concept
! 770: introduced by <a href="#ref-xml">[XML]</a>. Essentially this
! 771: means that all elements must either have closing tags or be
! 772: written in a special form (as described below), and that all the
! 773: elements must nest.</p>
! 774:
! 775: <p>Although overlapping is illegal in SGML, it was widely
! 776: tolerated in existing browsers.</p>
! 777:
! 778: <div class="good">
! 779: <p><strong><em>CORRECT: nested elements.</em></strong></p>
! 780:
! 781: <p><p>here is an emphasized
! 782: <em>paragraph</em>.</p></p>
! 783: </div>
! 784:
! 785: <div class="bad">
! 786: <p><strong><em>INCORRECT: overlapping elements</em></strong></p>
! 787:
! 788: <p><p>here is an emphasized
! 789: <em>paragraph.</p></em></p>
! 790: </div>
! 791:
! 792: <h2><a name="h-4.2" id="h-4.2">4.2 Element and attribute
! 793: names must be in lower case</a></h2>
! 794:
! 795: <p>XHTML documents must use lower case for all HTML element and
! 796: attribute names. This difference is necessary because XML is
! 797: case-sensitive e.g. <li> and <LI> are different
! 798: tags.</p>
! 799:
! 800: <h2><a name="h-4.3" id="h-4.3">4.3 For non-empty elements,
! 801: end tags are required</a></h2>
! 802:
! 803: <p>In SGML-based HTML 4.0 certain elements were permitted to omit
! 804: the end tag; with the elements that followed implying closure.
! 805: This omission is not permitted in XML-based XHTML. All elements
! 806: other than those declared in the DTD as <code>EMPTY</code> must
! 807: have an end tag.</p>
! 808:
! 809: <div class="good">
! 810: <p><strong><em>CORRECT: terminated elements</em></strong></p>
! 811:
! 812: <p><p>here is a paragraph.</p><p>here is
! 813: another paragraph.</p></p>
! 814: </div>
! 815:
! 816: <div class="bad">
! 817: <p><strong><em>INCORRECT: unterminated elements</em></strong></p>
! 818:
! 819: <p><p>here is a paragraph.<p>here is another
! 820: paragraph.</p>
! 821: </div>
! 822:
! 823: <h2><a name="h-4.4" id="h-4.4">4.4 Attribute values must
! 824: always be quoted</a></h2>
! 825:
! 826: <p>All attribute values must be quoted, even those which appear
! 827: to be numeric.</p>
! 828:
! 829: <div class="good">
! 830: <p><strong><em>CORRECT: quoted attribute values</em></strong></p>
! 831:
! 832: <p><table rows="3"></p>
! 833: </div>
! 834:
! 835: <div class="bad">
! 836: <p><strong><em>INCORRECT: unquoted attribute values</em></strong></p>
! 837:
! 838: <p><table rows=3></p>
! 839: </div>
! 840:
! 841: <h2><a name="h-4.5" id="h-4.5">4.5 Attribute
! 842: Minimization</a></h2>
! 843:
! 844: <p>XML does not support attribute minimization. Attribute-value
! 845: pairs must be written in full. Attribute names such as <code>
! 846: compact</code> and <code>checked</code> cannot occur in elements
! 847: without their value being specified.</p>
! 848:
! 849: <div class="good">
! 850: <p><strong><em>CORRECT: unminimized attributes</em></strong></p>
! 851:
! 852: <p><dl compact="compact"></p>
! 853: </div>
! 854:
! 855: <div class="bad">
! 856: <p><strong><em>INCORRECT: minimized attributes</em></strong></p>
! 857:
! 858: <p><dl compact></p>
! 859: </div>
! 860:
! 861: <h2><a name="h-4.6" id="h-4.6">4.6 Empty Elements</a></h2>
! 862:
! 863: <p>Empty elements must either have an end tag or the start tag must end with <code>/></code>. For instance,
! 864: <code><br/></code> or <code><hr></hr></code>. See <a href="#guidelines">HTML Compatibility Guidelines</a> for information on ways to
! 865: ensure this is backward compatible with HTML 4.0 user agents.</p>
! 866:
! 867: <div class="good">
! 868: <p><strong><em>CORRECT: terminated empty tags</em></strong></p>
! 869:
! 870: <p><br/><hr/></p>
! 871: </div>
! 872:
! 873: <div class="bad">
! 874: <p><strong><em>INCORRECT: unterminated empty tags</em></strong></p>
! 875:
! 876: <p><br><hr></p>
! 877: </div>
! 878:
! 879: <h2><a name="h-4.7" id="h-4.7">4.7 Whitespace handling in
! 880: attribute values</a></h2>
! 881:
! 882: <p>In attribute values, user agents will strip leading and
! 883: trailing whitespace from attribute values and map sequences
! 884: of one or more whitespace characters (including line breaks) to
! 885: a single inter-word space (an ASCII space character for western
! 886: scripts). See <a href="http://www.w3.org/TR/REC-xml#AVNormalize">
! 887: Section 3.3.3</a> of <a href="#ref-xml">[XML]</a>.</p>
! 888:
! 889: <h2><a name="h-4.8" id="h-4.8">4.8 Script and Style
! 890: elements</a></h2>
! 891:
! 892: <p>In XHTML, the script and style elements are declared as having
! 893: <code>#PCDATA</code> content. As a result, <code><</code> and
! 894: <code>&</code> will be treated as the start of markup, and
! 895: entities such as <code>&lt;</code> and <code>&amp;</code>
! 896: will be recognized as entity references by the XML processor to
! 897: <code><</code> and <code>&</code> respectively. Wrapping
! 898: the content of the script or style element within a <code>
! 899: CDATA</code> marked section avoids the expansion of these
! 900: entities.</p>
! 901:
! 902: <div class="good">
! 903: <pre>
! 904: <script>
! 905: <![CDATA[
! 906: ... unescaped script content ...
! 907: ]]>
! 908: </script>
! 909: </pre>
! 910: </div>
! 911:
! 912: <p><code>CDATA</code> sections are recognized by the XML
! 913: processor and appear as nodes in the Document Object Model, see
! 914: <a href="http://www.w3.org/TR/REC-DOM-Level-1/level-one-core.html#ID-E067D597">
! 915: Section 1.3</a> of the DOM Level 1 Recommendation <a href="#ref-dom">[DOM]</a>.</p>
! 916:
! 917: <p>An alternative is to use external script and style
! 918: documents.</p>
! 919:
! 920: <h2><a name="h-4.9" id="h-4.9">4.9 SGML exclusions</a></h2>
! 921:
! 922: <p>SGML gives the writer of a DTD the ability to exclude specific
! 923: elements from being contained within an element. Such
! 924: prohibitions (called "exclusions") are not possible in XML.</p>
! 925:
! 926: <p>For example, the HTML 4.0 Strict DTD forbids the nesting of an
! 927: '<code>a</code>' element within another '<code>a</code>' element
! 928: to any descendant depth. It is not possible to spell out such
! 929: prohibitions in XML. Even though these prohibitions cannot be
! 930: defined in the DTD, certain elements should not be nested. A
! 931: summary of such elements and the elements that should not be
! 932: nested in them is found in the normative <a href="#prohibitions">
! 933: Appendix B</a>.</p>
! 934:
! 935: <h2><a name="h-4.10" id="h-4.10">4.10 The elements with 'id' and 'name'
! 936: attributes</a></h2>
! 937:
! 938: <p>HTML 4.0 defined the <code>name</code> attribute for the elements
! 939: <code>a</code>,
! 940: <code>applet</code>, <code>frame</code>,
! 941: <code>iframe</code>, <code>img</code>, and <code>map</code>.
! 942: HTML 4.0 also introduced
! 943: the <code>id</code> attribute. Both of these attributes are designed to be
! 944: used as fragment identifiers.</p>
! 945: <p>In XML, fragment identifiers are of type <code>ID</code>, and
! 946: there can only be a single attribute of type <code>ID</code> per element.
! 947: Therefore, in XHTML 1.0 the <code>id</code>
! 948: attribute is defined to be of type <code>ID</code>. In order to
! 949: ensure that XHTML 1.0 documents are well-structured XML documents, XHTML 1.0
! 950: documents MUST use the <code>id</code> attribute when defining fragment
! 951: identifiers, even on elements that historically have also had a
! 952: <code>name</code> attribute.
! 953: See the <a href="#guidelines">HTML Compatibility
! 954: Guidelines</a> for information on ensuring such anchors are backwards
! 955: compatible when serving XHTML documents as media type <code>text/html</code>.
! 956: </p>
! 957: <p>Note that in XHTML 1.0, the <code>name</code> attribute of these
! 958: elements is formally deprecated, and will be removed in a
! 959: subsequent version of XHTML.</p>
! 960:
! 961: <!--OddPage-->
! 962: <h1><a name="issues" id="issues">5. Compatibility Issues</a></h1>
! 963:
! 964: <p>Although there is no requirement for XHTML 1.0 documents to be
! 965: compatible with existing user agents, in practice this is easy to
! 966: accomplish. Guidelines for creating compatible documents can be
! 967: found in <a href="#guidelines">Appendix C</a>.</p>
! 968:
! 969: <h2><a name="media" id="media">5.1 Internet Media Type</a></h2>
! 970: <p>As of the publication of this recommendation, the general
! 971: recommended MIME labeling for XML-based applications
! 972: has yet to be resolved.</p>
! 973:
! 974: <p>However, XHTML Documents which follow the guidelines set forth
! 975: in <a href="#guidelines">Appendix C</a>, "HTML Compatibility Guidelines" may be
! 976: labeled with the Internet Media Type "text/html", as they
! 977: are compatible with most HTML browsers. This document
! 978: makes no recommendation about MIME labeling of other
! 979: XHTML documents.</p>
! 980:
! 981: <!--OddPage-->
! 982: <h1><a name="future" id="future">6. Future Directions</a></h1>
! 983:
! 984: <p>XHTML 1.0 provides the basis for a family of document types
! 985: that will extend and subset XHTML, in order to support a wide
! 986: range of new devices and applications, by defining modules and
! 987: specifying a mechanism for combining these modules. This
! 988: mechanism will enable the extension and sub-setting of XHTML 1.0
! 989: in a uniform way through the definition of new modules.</p>
! 990:
! 991: <h2><a name="mods" id="mods">6.1 Modularizing HTML</a></h2>
! 992:
! 993: <p>As the use of XHTML moves from the traditional desktop user
! 994: agents to other platforms, it is clear that not all of the XHTML
! 995: elements will be required on all platforms. For example a hand
! 996: held device or a cell-phone may only support a subset of XHTML
! 997: elements.</p>
! 998:
! 999: <p>The process of modularization breaks XHTML up into a series of
! 1000: smaller element sets. These elements can then be recombined to
! 1001: meet the needs of different communities.</p>
! 1002:
! 1003: <p>These modules will be defined in a later W3C document.</p>
! 1004:
! 1005: <h2><a name="extensions" id="extensions">6.2 Subsets and
! 1006: Extensibility</a></h2>
! 1007:
! 1008: <p>Modularization brings with it several advantages:</p>
! 1009:
! 1010: <ul>
! 1011: <li>
! 1012: <p>It provides a formal mechanism for sub-setting XHTML.</p>
! 1013: </li>
! 1014:
! 1015: <li>
! 1016: <p>It provides a formal mechanism for extending XHTML.</p>
! 1017: </li>
! 1018:
! 1019: <li>
! 1020: <p>It simplifies the transformation between document types.</p>
! 1021: </li>
! 1022:
! 1023: <li>
! 1024: <p>It promotes the reuse of modules in new document types.</p>
! 1025: </li>
! 1026: </ul>
! 1027:
! 1028: <h2><a name="profiles" id="profiles">6.3 Document
! 1029: Profiles</a></h2>
! 1030:
! 1031: <p>A document profile specifies the syntax and semantics of a set
! 1032: of documents. Conformance to a document profile provides a basis
! 1033: for interoperability guarantees. The document profile specifies
! 1034: the facilities required to process documents of that type, e.g.
! 1035: which image formats can be used, levels of scripting, style sheet
! 1036: support, and so on.</p>
! 1037:
! 1038: <p>For product designers this enables various groups to define
! 1039: their own standard profile.</p>
! 1040:
! 1041: <p>For authors this will obviate the need to write several
! 1042: different versions of documents for different clients.</p>
! 1043:
! 1044: <p>For special groups such as chemists, medical doctors, or
! 1045: mathematicians this allows a special profile to be built using
! 1046: standard HTML elements plus a group of elements geared to the
! 1047: specialist's needs.</p>
! 1048:
! 1049: <!--OddPage-->
! 1050: <h1><a name="appendices" id="appendices"></a>
! 1051: <a name="dtds" id="dtds">Appendix A. DTDs</a></h1>
! 1052:
! 1053: <p><b>This appendix is normative.</b></p>
! 1054:
! 1055: <p>These DTDs and entity sets form a normative part of this
! 1056: specification. The complete set of DTD files together with an XML
! 1057: declaration and SGML Open Catalog is included in the <a href="xhtml1.zip">zip file</a> for this specification.</p>
! 1058:
! 1059: <h2><a name="h-A1" id="h-A1">A.1 Document Type
! 1060: Definitions</a></h2>
! 1061:
! 1062: <p>These DTDs approximate the HTML 4.0 DTDs. It is likely that
! 1063: when the DTDs are modularized, a method of DTD construction will
! 1064: be employed that corresponds more closely to HTML 4.0.</p>
! 1065:
! 1066: <ul>
! 1067: <li>
! 1068: <p><a href="DTD/xhtml1-strict.dtd" type="text/plain">
! 1069: XHTML-1.0-Strict</a></p>
! 1070: </li>
! 1071:
! 1072: <li>
! 1073: <p><a href="DTD/xhtml1-transitional.dtd" type="text/plain">
! 1074: XHTML-1.0-Transitional</a></p>
! 1075: </li>
! 1076:
! 1077: <li>
! 1078: <p><a href="DTD/xhtml1-frameset.dtd" type="text/plain">
! 1079: XHTML-1.0-Frameset</a></p>
! 1080: </li>
! 1081: </ul>
! 1082:
! 1083: <h2><a name="h-A2" id="h-A2">A.2 Entity Sets</a></h2>
! 1084:
! 1085: <p>The XHTML entity sets are the same as for HTML 4.0, but have
! 1086: been modified to be valid XML 1.0 entity declarations. Note the
! 1087: entity for the Euro currency sign (<code>&euro;</code> or
! 1088: <code>&#8364;</code> or <code>&#x20AC;</code>) is defined
! 1089: as part of the special characters.</p>
! 1090:
! 1091: <ul>
! 1092: <li>
! 1093: <p><a href="DTD/xhtml-lat1.ent">Latin-1 characters</a></p>
! 1094: </li>
! 1095:
! 1096: <li>
! 1097: <p><a href="DTD/xhtml-special.ent">Special characters</a></p>
! 1098: </li>
! 1099:
! 1100: <li>
! 1101: <p><a href="DTD/xhtml-symbol.ent">Symbols</a></p>
! 1102: </li>
! 1103: </ul>
! 1104:
! 1105: <!--OddPage-->
! 1106: <h1><a name="prohibitions" id="prohibitions">Appendix B. Element
! 1107: Prohibitions</a></h1>
! 1108:
! 1109: <p><b>This appendix is normative.</b></p>
! 1110:
! 1111: <p>The following elements have prohibitions on which elements
! 1112: they can contain (see <a href="#h-4.9">Section 4.9</a>). This
! 1113: prohibition applies to all depths of nesting, i.e. it contains
! 1114: all the descendant elements.</p>
! 1115:
! 1116: <dl><dt><code class="tag">a</code></dt>
! 1117: <dd>
! 1118: cannot contain other <code>a</code> elements.</dd>
! 1119: <dt><code class="tag">pre</code></dt>
! 1120: <dd>cannot contain the <code>img</code>, <code>object</code>,
! 1121: <code>big</code>, <code>small</code>, <code>sub</code>, or <code>
! 1122: sup</code> elements.</dd>
! 1123:
! 1124: <dt><code class="tag">button</code></dt>
! 1125: <dd>cannot contain the <code>input</code>, <code>select</code>,
! 1126: <code>textarea</code>, <code>label</code>, <code>button</code>,
! 1127: <code>form</code>, <code>fieldset</code>, <code>iframe</code> or
! 1128: <code>isindex</code> elements.</dd>
! 1129: <dt><code class="tag">label</code></dt>
! 1130: <dd>cannot contain other <code class="tag">label</code> elements.</dd>
! 1131: <dt><code class="tag">form</code></dt>
! 1132: <dd>cannot contain other <code>form</code> elements.</dd>
! 1133: </dl>
! 1134:
! 1135: <!--OddPage-->
! 1136: <h1><a name="guidelines" id="guidelines">Appendix C.
! 1137: HTML Compatibility Guidelines</a></h1>
! 1138:
! 1139: <p><b>This appendix is informative.</b></p>
! 1140:
! 1141: <p>This appendix summarizes design guidelines for authors who
! 1142: wish their XHTML documents to render on existing HTML user
! 1143: agents.</p>
! 1144:
! 1145: <h2>C.1 Processing Instructions</h2>
! 1146: <p>Be aware that processing instructions are rendered on some
! 1147: user agents. However, also note that when the XML declaration is not included
! 1148: in a document, the document can only use the default character encodings UTF-8
! 1149: or UTF-16.</p>
! 1150:
! 1151: <h2>C.2 Empty Elements</h2>
! 1152: <p>Include a space before the trailing <code>/</code> and <code>
! 1153: ></code> of empty elements, e.g. <code class="greenmono">
! 1154: <br /></code>, <code class="greenmono">
! 1155: <hr /></code> and <code class="greenmono"><img
! 1156: src="karen.jpg" alt="Karen" /></code>. Also, use the
! 1157: 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
! 1158: gives uncertain results in many existing user agents.</p>
! 1159:
! 1160: <h2>C.3 Element Minimization and Empty Element Content</h2>
! 1161: <p>Given an empty instance of an element whose content model is
! 1162: not <code>EMPTY</code> (for example, an empty title or paragraph)
! 1163: do not use the minimized form (e.g. use <code class="greenmono">
! 1164: <p> </p></code> and not <code class="greenmono">
! 1165: <p /></code>).</p>
! 1166:
! 1167: <h2>C.4 Embedded Style Sheets and Scripts</h2>
! 1168: <p>Use external style sheets if your style sheet uses <code>
! 1169: <</code> or <code>&</code> or <code>]]></code> or <code>--</code>. Use
! 1170: external scripts if your script uses <code><</code> or <code>
! 1171: &</code> or <code>]]></code> or <code>--</code>. Note that XML parsers
! 1172: are permitted to silently remove the contents of comments. Therefore, the historical
! 1173: practice of "hiding" scripts and style sheets within comments to make the
! 1174: documents backward compatible is likely to not work as expected in XML-based
! 1175: implementations.</p>
! 1176:
! 1177: <h2>C.5 Line Breaks within Attribute Values</h2>
! 1178: <p>Avoid line breaks and multiple whitespace characters within
! 1179: attribute values. These are handled inconsistently by user
! 1180: agents.</p>
! 1181:
! 1182: <h2>C.6 Isindex</h2>
! 1183: <p>Don't include more than one <code>isindex</code> element in
! 1184: the document <code>head</code>. The <code>isindex</code> element
! 1185: is deprecated in favor of the <code>input</code> element.</p>
! 1186:
! 1187: <h2>C.7 The <code>lang</code> and <code>xml:lang</code> Attributes</h2>
! 1188: <p>Use both the <code>lang</code> and <code>xml:lang</code>
! 1189: attributes when specifying the language of an element. The value
! 1190: of the <code>xml:lang</code> attribute takes precedence.</p>
! 1191:
! 1192: <h2>C.8 Fragment Identifiers</h2>
! 1193: <p>In XML, <abbr title="Uniform Resource Identifiers">URIs</abbr> [<a href="#ref-rfc2396">RFC2396</a>] that end with fragment identifiers of the form
! 1194: <code>"#foo"</code> do not refer to elements with an attribute
! 1195: <code>name="foo"</code>; rather, they refer to elements with an
! 1196: attribute defined to be of type <code>ID</code>, e.g., the <code>
! 1197: id</code> attribute in HTML 4.0. Many existing HTML clients don't
! 1198: support the use of <code>ID</code>-type attributes in this way,
! 1199: so identical values may be supplied for both of these attributes to ensure
! 1200: maximum forward and backward compatibility (e.g., <code class="greenmono"><a id="foo" name="foo">...</a></code>).</p>
! 1201:
! 1202: <p>Further, since the set of
! 1203: legal values for attributes of type <code>ID</code> is much smaller than
! 1204: for those of type <code>CDATA</code>, the type of the <code>name</code>
! 1205: attribute has been changed to <code>NMTOKEN</code>. This attribute is
! 1206: constrained such that it can only have the same values as type
! 1207: <code>ID</code>, or as the <code>Name</code> production in XML 1.0 Section
! 1208: 2.5, production 5. Unfortunately, this constraint cannot be expressed in the
! 1209: XHTML 1.0 DTDs. Because of this change, care must be taken when
! 1210: converting existing HTML documents. The values of these attributes
! 1211: must be unique within the document, valid, and any references to these
! 1212: fragment identifiers (both
! 1213: internal and external) must be updated should the values be changed during
! 1214: conversion.</p>
! 1215: <p>Finally, note that XHTML 1.0 has deprecated the
! 1216: <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>
! 1217: elements, and it will be
! 1218: removed from XHTML in subsequent versions.</p>
! 1219:
! 1220: <h2>C.9 Character Encoding</h2>
! 1221: <p>To specify a character encoding in the document, use both the
! 1222: encoding attribute specification on the xml declaration (e.g.
! 1223: <code class="greenmono"><?xml version="1.0"
! 1224: encoding="EUC-JP"?></code>) and a meta http-equiv statement
! 1225: (e.g. <code class="greenmono"><meta http-equiv="Content-type"
! 1226: content='text/html; charset="EUC-JP"' /></code>). The
! 1227: value of the encoding attribute of the xml processing instruction
! 1228: takes precedence.</p>
! 1229:
! 1230: <h2>C.10 Boolean Attributes</h2>
! 1231: <p>Some HTML user agents are unable to interpret boolean
! 1232: attributes when these appear in their full (non-minimized) form,
! 1233: as required by XML 1.0. Note this problem doesn't effect user
! 1234: agents compliant with HTML 4.0. The following attributes are
! 1235: involved: <code>compact</code>, <code>nowrap</code>, <code>
! 1236: ismap</code>, <code>declare</code>, <code>noshade</code>, <code>
! 1237: checked</code>, <code>disabled</code>, <code>readonly</code>,
! 1238: <code>multiple</code>, <code>selected</code>, <code>
! 1239: noresize</code>, <code>defer</code>.</p>
! 1240:
! 1241: <h2>C.11 Document Object Model and XHTML</h2>
! 1242: <p>
! 1243: The Document Object Model level 1 Recommendation [<a href="#ref-dom">DOM</a>]
! 1244: defines document object model interfaces for XML and HTML 4.0. The HTML 4.0
! 1245: document object model specifies that HTML element and attribute names are
! 1246: returned in upper-case. The XML document object model specifies that
! 1247: element and attribute names are returned in the case they are specified. In
! 1248: XHTML 1.0, elements and attributes are specified in lower-case. This apparent difference can be
! 1249: addressed in two ways:
! 1250: </p>
! 1251: <ol>
! 1252: <li>Applications that access XHTML documents served as Internet media type
! 1253: <code>text/html</code>
! 1254: via the <abbr title="Document Object Model">DOM</abbr> can use the HTML DOM,
! 1255: and can rely upon element and attribute names being returned in
! 1256: upper-case from those interfaces.</li>
! 1257: <li>Applications that access XHTML documents served as Internet media types
! 1258: <code>text/xml</code> or <code>application/xml</code>
! 1259: can also use the XML DOM. Elements and attributes will be returned in lower-case.
! 1260: Also, some XHTML elements may or may
! 1261: not appear
! 1262: in the object tree because they are optional in the content model
! 1263: (e.g. the <code>tbody</code> element within
! 1264: <code>table</code>). This occurs because in HTML 4.0 some elements were
! 1265: permitted to be minimized such that their start and end tags are both omitted
! 1266: (an SGML feature).
! 1267: This is not possible in XML. Rather than require document authors to insert
! 1268: extraneous elements, XHTML has made the elements optional.
! 1269: Applications need to adapt to this
! 1270: accordingly.</li>
! 1271: </ol>
! 1272:
! 1273: <h2>C.12 Using Ampersands in Attribute Values</h2>
! 1274: <p>
! 1275: When an attribute value contains an ampersand, it must be expressed as a character
! 1276: entity reference
! 1277: (e.g. "<code>&amp;</code>"). For example, when the
! 1278: <code>href</code> attribute
! 1279: of the <code>a</code> element refers to a
! 1280: CGI script that takes parameters, it must be expressed as
! 1281: <code>http://my.site.dom/cgi-bin/myscript.pl?class=guest&amp;name=user</code>
! 1282: rather than as
! 1283: <code>http://my.site.dom/cgi-bin/myscript.pl?class=guest&name=user</code>.
! 1284: </p>
! 1285:
! 1286: <h2>C.13 Cascading Style Sheets (CSS) and XHTML</h2>
! 1287:
! 1288: <p>The Cascading Style Sheets level 2 Recommendation [<a href="#ref-css2">CSS2</a>] defines style
! 1289: properties which are applied to the parse tree of the HTML or XML
! 1290: document. Differences in parsing will produce different visual or
! 1291: aural results, depending on the selectors used. The following hints
! 1292: will reduce this effect for documents which are served without
! 1293: modification as both media types:</p>
! 1294:
! 1295: <ol>
! 1296: <li>
! 1297: CSS style sheets for XHTML should use lower case element and
! 1298: attribute names.</li>
! 1299:
! 1300:
! 1301: <li>In tables, the tbody element will be inferred by the parser of an
! 1302: HTML user agent, but not by the parser of an XML user agent. Therefore
! 1303: you should always explicitely add a tbody element if it is referred to
! 1304: in a CSS selector.</li>
! 1305:
! 1306: <li>Within the XHTML name space, user agents are expected to
! 1307: recognize the "id" attribute as an attribute of type ID.
! 1308: Therefore, style sheets should be able to continue using the
! 1309: shorthand "#" selector syntax even if the user agent does not read
! 1310: the DTD.</li>
! 1311:
! 1312: <li>Within the XHTML name space, user agents are expected to
! 1313: recognize the "class" attribute. Therefore, style sheets should be
! 1314: able to continue using the shorthand "." selector syntax.</li>
! 1315:
! 1316: <li>
! 1317: CSS defines different conformance rules for HTML and XML documents;
! 1318: be aware that the HTML rules apply to XHTML documents delivered as
! 1319: HTML and the XML rules apply to XHTML documents delivered as XML.</li>
! 1320: </ol>
! 1321: <!--OddPage-->
! 1322: <h1><a name="acks" id="acks">Appendix D.
! 1323: Acknowledgements</a></h1>
! 1324:
! 1325: <p><b>This appendix is informative.</b></p>
! 1326:
! 1327: <p>This specification was written with the participation of the
! 1328: members of the W3C HTML working group:</p>
! 1329:
! 1330: <dl>
! 1331: <dd>Steven Pemberton, CWI (HTML Working Group Chair)<br />
! 1332: Murray Altheim, Sun Microsystems<br />
! 1333: Daniel Austin, CNET: The Computer Network<br />
! 1334: Frank Boumphrey, HTML Writers Guild<br />
! 1335: John Burger, Mitre<br />
! 1336: Andrew W. Donoho, IBM<br />
! 1337: Sam Dooley, IBM<br />
! 1338: Klaus Hofrichter, GMD<br />
! 1339: Philipp Hoschka, W3C<br />
! 1340: Masayasu Ishikawa, W3C<br />
! 1341: Warner ten Kate, Philips Electronics<br />
! 1342: Peter King, Phone.com<br />
! 1343: Paula Klante, JetForm<br />
! 1344: Shin'ichi Matsui, W3C/Panasonic<br />
! 1345: Shane McCarron, Applied Testing and Technology (The Open Group through August
! 1346: 1999)<br />
! 1347: Ann Navarro, HTML Writers Guild<br />
! 1348: Zach Nies, Quark<br />
! 1349: Dave Raggett, W3C/HP (W3C lead for HTML)<br />
! 1350: Patrick Schmitz, Microsoft<br />
! 1351: Sebastian Schnitzenbaumer, Stack Overflow<br />
! 1352: Chris Wilson, Microsoft<br />
! 1353: Ted Wugofski, Gateway 2000<br />
! 1354: Dan Zigmond, WebTV Networks</dd>
! 1355: </dl>
! 1356:
! 1357: <!--OddPage-->
! 1358: <h1><a name="refs" id="refs">Appendix E. References</a></h1>
! 1359:
! 1360: <p><b>This appendix is informative.</b></p>
! 1361:
! 1362: <dl>
! 1363:
! 1364: <dt><a name="ref-css2" id="ref-css2"><b>[CSS2]</b></a></dt>
! 1365:
! 1366: <dd><a href="http://www.w3.org/TR/REC-CSS2">"Cascading Style Sheets, level 2 (CSS2) Specification"</a>, B.
! 1367: Bos, H. W. Lie, C. Lilley, I. Jacobs, 12 May 1998.<br />
! 1368: Available at: <a href="http://www.w3.org/TR/REC-CSS2">
! 1369: http://www.w3.org/TR/REC-CSS2</a></dd>
! 1370:
! 1371: <dt><a name="ref-dom" id="ref-dom"><b>[DOM]</b></a></dt>
! 1372:
! 1373: <dd><a href="http://www.w3.org/TR/REC-DOM-Level-1">"Document Object Model (DOM) Level 1 Specification"</a>, Lauren
! 1374: Wood <i>et al.</i>, 1 October 1998.<br />
! 1375: Available at: <a href="http://www.w3.org/TR/REC-DOM-Level-1">
! 1376: http://www.w3.org/TR/REC-DOM-Level-1</a></dd>
! 1377:
! 1378: <dt><a name="ref-html4" id="ref-html4"><b>[HTML]</b></a></dt>
! 1379:
! 1380: <dd><a href="http://www.w3.org/TR/1999/PR-html40-19990824">"HTML 4.01 Specification"</a>, D. Raggett, A. Le Hors, I.
! 1381: Jacobs, 24 August 1999.<br />
! 1382: Available at: <a href="http://www.w3.org/TR/1999/PR-html40-19990824">
! 1383: http://www.w3.org/TR/1999/PR-html40-19990824</a></dd>
! 1384:
! 1385: <dt><a name="ref-posix" id="ref-posix"><b>[POSIX.1]</b></a></dt>
! 1386:
! 1387: <dd>"ISO/IEC 9945-1:1990 Information Technology - Portable
! 1388: Operating System Interface (POSIX) - Part 1: System Application
! 1389: Program Interface (API) [C Language]", Institute of Electrical
! 1390: and Electronics Engineers, Inc, 1990.</dd>
! 1391:
! 1392: <dt><a name="ref-rfc2046" id="ref-rfc2046"><b>
! 1393: [RFC2046]</b></a></dt>
! 1394:
! 1395: <dd><a href="http://www.ietf.org/rfc/rfc2046.txt">"RFC2046: Multipurpose Internet Mail Extensions (MIME) Part
! 1396: Two: Media Types"</a>, N. Freed and N. Borenstein, November
! 1397: 1996.<br />
! 1398: Available at <a href="http://www.ietf.org/rfc/rfc2046.txt">
! 1399: http://www.ietf.org/rfc/rfc2046.txt</a>. Note that this RFC
! 1400: obsoletes RFC1521, RFC1522, and RFC1590.</dd>
! 1401:
! 1402: <dt><a name="ref-rfc2119" id="ref-rfc2119"><b>
! 1403: [RFC2119]</b></a></dt>
! 1404:
! 1405: <dd><a href="http://www.ietf.org/rfc/rfc2119.txt">"RFC2119: Key words for use in RFCs to Indicate Requirement
! 1406: Levels"</a>, S. Bradner, March 1997.<br />
! 1407: Available at: <a href="http://www.ietf.org/rfc/rfc2119.txt">
! 1408: http://www.ietf.org/rfc/rfc2119.txt</a></dd>
! 1409:
! 1410: <dt><a name="ref-rfc2376" id="ref-rfc2376"><b>
! 1411: [RFC2376]</b></a></dt>
! 1412:
! 1413: <dd><a href="http://www.ietf.org/rfc/rfc2376.txt">"RFC2376: XML Media Types"</a>, E. Whitehead, M. Murata, July
! 1414: 1998.<br />
! 1415: Available at: <a href="http://www.ietf.org/rfc/rfc2376.txt">
! 1416: http://www.ietf.org/rfc/rfc2376.txt</a></dd>
! 1417:
! 1418: <dt><a name="ref-rfc2396" id="ref-rfc2396"><b>
! 1419: [RFC2396]</b></a></dt>
! 1420:
! 1421: <dd><a href="http://www.ietf.org/rfc/rfc2396.txt">"RFC2396: Uniform Resource Identifiers (URI): Generic
! 1422: Syntax"</a>, T. Berners-Lee, R. Fielding, L. Masinter, August
! 1423: 1998.<br />
! 1424: This document updates RFC1738 and RFC1808.<br />
! 1425: Available at: <a href="http://www.ietf.org/rfc/rfc2396.txt">
! 1426: http://www.ietf.org/rfc/rfc2396.txt</a></dd>
! 1427:
! 1428: <dt><a name="ref-xml" id="ref-xml"><b>[XML]</b></a></dt>
! 1429:
! 1430: <dd><a href="http://www.w3.org/TR/REC-xml">"Extensible Markup Language (XML) 1.0 Specification"</a>, T.
! 1431: Bray, J. Paoli, C. M. Sperberg-McQueen, 10 February 1998.<br />
! 1432: Available at: <a href="http://www.w3.org/TR/REC-xml">
! 1433: http://www.w3.org/TR/REC-xml</a></dd>
! 1434:
! 1435: <dt><a name="ref-xmlns" id="ref-xmlns"><b>[XMLNAMES]</b></a></dt>
! 1436:
! 1437: <dd><a href="http://www.w3.org/TR/REC-xml-names">"Namespaces in XML"</a>, T. Bray, D. Hollander, A. Layman, 14
! 1438: January 1999.<br />
! 1439: XML namespaces provide a simple method for qualifying names used
! 1440: in XML documents by associating them with namespaces identified
! 1441: by URI.<br />
! 1442: Available at: <a href="http://www.w3.org/TR/REC-xml-names">
! 1443: http://www.w3.org/TR/REC-xml-names</a></dd>
! 1444:
! 1445: </dl>
! 1446: <p><a href="http://www.w3.org/WAI/WCAG1AAA-Conformance" title="Explanation of Level Triple-A Conformance">
! 1447: <img height="32" width="88" src="wcag1AAA.gif" alt="Level Triple-A conformance icon, W3C-WAI Web Content Accessibility Guidelines 1.0" /></a></p>
! 1448: <div class="navbar">
! 1449: <hr />
! 1450: <a href="#toc">table of contents</a>
! 1451: </div>
! 1452: </body>
! 1453: </html>
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