Annotation of embedaddon/libxml2/result/valid/REC-xml-19980210.xml, revision 1.1.1.1
1.1 misho 1: <?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
2: <!DOCTYPE spec SYSTEM "dtds/spec.dtd" [
3: <!-- LAST TOUCHED BY: Tim Bray, 8 February 1997 --><!-- The words 'FINAL EDIT' in comments mark places where changes
4: need to be made after approval of the document by the ERB, before
5: publication. --><!ENTITY XML.version "1.0">
6: <!ENTITY doc.date "10 February 1998">
7: <!ENTITY iso6.doc.date "19980210">
8: <!ENTITY w3c.doc.date "02-Feb-1998">
9: <!ENTITY draft.day "10">
10: <!ENTITY draft.month "February">
11: <!ENTITY draft.year "1998">
12: <!ENTITY WebSGML "WebSGML Adaptations Annex to ISO 8879">
13: <!ENTITY lt "<">
14: <!ENTITY gt ">">
15: <!ENTITY xmlpio "'<?xml'">
16: <!ENTITY pic "'?>'">
17: <!ENTITY br "\n">
18: <!ENTITY cellback "#c0d9c0">
19: <!ENTITY mdash "--">
20: <!-- —, but nsgmls doesn't grok hex --><!ENTITY com "--">
21: <!ENTITY como "--">
22: <!ENTITY comc "--">
23: <!ENTITY hcro "&#x">
24: <!-- <!ENTITY nbsp " "> --><!ENTITY nbsp " ">
25: <!ENTITY magicents "<code>amp</code>,
26: <code>lt</code>,
27: <code>gt</code>,
28: <code>apos</code>,
29: <code>quot</code>">
30: <!-- audience and distribution status: for use at publication time --><!ENTITY doc.audience "public review and discussion">
31: <!ENTITY doc.distribution "may be distributed freely, as long as
32: all text and legal notices remain intact">
33: ]>
34: <!-- for Panorama *-->
35: <?VERBATIM "eg" ?>
36: <spec>
37: <header>
38: <title>Extensible Markup Language (XML) 1.0</title>
39: <version/>
40: <w3c-designation>REC-xml-&iso6.doc.date;</w3c-designation>
41: <w3c-doctype>W3C Recommendation</w3c-doctype>
42: <pubdate><day>&draft.day;</day><month>&draft.month;</month><year>&draft.year;</year></pubdate>
43:
44: <publoc>
45: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;">
46: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;</loc>
47: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.xml">
48: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.xml</loc>
49: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.html">
50: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.html</loc>
51: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.pdf">
52: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.pdf</loc>
53: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.ps">
54: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.ps</loc>
55: </publoc>
56: <latestloc>
57: <loc href="http://www.w3.org/TR/REC-xml">
58: http://www.w3.org/TR/REC-xml</loc>
59: </latestloc>
60: <prevlocs>
61: <loc href="http://www.w3.org/TR/PR-xml-971208">
62: http://www.w3.org/TR/PR-xml-971208</loc>
63: <!--
64: <loc href='http://www.w3.org/TR/WD-xml-961114'>
65: http://www.w3.org/TR/WD-xml-961114</loc>
66: <loc href='http://www.w3.org/TR/WD-xml-lang-970331'>
67: http://www.w3.org/TR/WD-xml-lang-970331</loc>
68: <loc href='http://www.w3.org/TR/WD-xml-lang-970630'>
69: http://www.w3.org/TR/WD-xml-lang-970630</loc>
70: <loc href='http://www.w3.org/TR/WD-xml-970807'>
71: http://www.w3.org/TR/WD-xml-970807</loc>
72: <loc href='http://www.w3.org/TR/WD-xml-971117'>
73: http://www.w3.org/TR/WD-xml-971117</loc>-->
74: </prevlocs>
75: <authlist>
76: <author><name>Tim Bray</name>
77: <affiliation>Textuality and Netscape</affiliation>
78: <email href="mailto:tbray@textuality.com">tbray@textuality.com</email></author>
79: <author><name>Jean Paoli</name>
80: <affiliation>Microsoft</affiliation>
81: <email href="mailto:jeanpa@microsoft.com">jeanpa@microsoft.com</email></author>
82: <author><name>C. M. Sperberg-McQueen</name>
83: <affiliation>University of Illinois at Chicago</affiliation>
84: <email href="mailto:cmsmcq@uic.edu">cmsmcq@uic.edu</email></author>
85: </authlist>
86: <abstract>
87: <p>The Extensible Markup Language (XML) is a subset of
88: SGML that is completely described in this document. Its goal is to
89: enable generic SGML to be served, received, and processed on the Web
90: in the way that is now possible with HTML. XML has been designed for
91: ease of implementation and for interoperability with both SGML and
92: HTML.</p>
93: </abstract>
94: <status>
95: <p>This document has been reviewed by W3C Members and
96: other interested parties and has been endorsed by the
97: Director as a W3C Recommendation. It is a stable
98: document and may be used as reference material or cited
99: as a normative reference from another document. W3C's
100: role in making the Recommendation is to draw attention
101: to the specification and to promote its widespread
102: deployment. This enhances the functionality and
103: interoperability of the Web.</p>
104: <p>
105: This document specifies a syntax created by subsetting an existing,
106: widely used international text processing standard (Standard
107: Generalized Markup Language, ISO 8879:1986(E) as amended and
108: corrected) for use on the World Wide Web. It is a product of the W3C
109: XML Activity, details of which can be found at <loc href="http://www.w3.org/XML">http://www.w3.org/XML</loc>. A list of
110: current W3C Recommendations and other technical documents can be found
111: at <loc href="http://www.w3.org/TR">http://www.w3.org/TR</loc>.
112: </p>
113: <p>This specification uses the term URI, which is defined by <bibref ref="Berners-Lee"/>, a work in progress expected to update <bibref ref="RFC1738"/> and <bibref ref="RFC1808"/>.
114: </p>
115: <p>The list of known errors in this specification is
116: available at
117: <loc href="http://www.w3.org/XML/xml-19980210-errata">http://www.w3.org/XML/xml-19980210-errata</loc>.</p>
118: <p>Please report errors in this document to
119: <loc href="mailto:xml-editor@w3.org">xml-editor@w3.org</loc>.
120: </p>
121: </status>
122:
123:
124: <pubstmt>
125: <p>Chicago, Vancouver, Mountain View, et al.:
126: World-Wide Web Consortium, XML Working Group, 1996, 1997.</p>
127: </pubstmt>
128: <sourcedesc>
129: <p>Created in electronic form.</p>
130: </sourcedesc>
131: <langusage>
132: <language id="EN">English</language>
133: <language id="ebnf">Extended Backus-Naur Form (formal grammar)</language>
134: </langusage>
135: <revisiondesc>
136: <slist>
137: <sitem>1997-12-03 : CMSMcQ : yet further changes</sitem>
138: <sitem>1997-12-02 : TB : further changes (see TB to XML WG,
139: 2 December 1997)</sitem>
140: <sitem>1997-12-02 : CMSMcQ : deal with as many corrections and
141: comments from the proofreaders as possible:
142: entify hard-coded document date in pubdate element,
143: change expansion of entity WebSGML,
144: update status description as per Dan Connolly (am not sure
145: about refernece to Berners-Lee et al.),
146: add 'The' to abstract as per WG decision,
147: move Relationship to Existing Standards to back matter and
148: combine with References,
149: re-order back matter so normative appendices come first,
150: re-tag back matter so informative appendices are tagged informdiv1,
151: remove XXX XXX from list of 'normative' specs in prose,
152: move some references from Other References to Normative References,
153: add RFC 1738, 1808, and 2141 to Other References (they are not
154: normative since we do not require the processor to enforce any
155: rules based on them),
156: add reference to 'Fielding draft' (Berners-Lee et al.),
157: move notation section to end of body,
158: drop URIchar non-terminal and use SkipLit instead,
159: lose stray reference to defunct nonterminal 'markupdecls',
160: move reference to Aho et al. into appendix (Tim's right),
161: add prose note saying that hash marks and fragment identifiers are
162: NOT part of the URI formally speaking, and are NOT legal in
163: system identifiers (processor 'may' signal an error).
164: Work through:
165: Tim Bray reacting to James Clark,
166: Tim Bray on his own,
167: Eve Maler,
168:
169: NOT DONE YET:
170: change binary / text to unparsed / parsed.
171: handle James's suggestion about < in attriubte values
172: uppercase hex characters,
173: namechar list,
174: </sitem>
175: <sitem>1997-12-01 : JB : add some column-width parameters</sitem>
176: <sitem>1997-12-01 : CMSMcQ : begin round of changes to incorporate
177: recent WG decisions and other corrections:
178: binding sources of character encoding info (27 Aug / 3 Sept),
179: correct wording of Faust quotation (restore dropped line),
180: drop SDD from EncodingDecl,
181: change text at version number 1.0,
182: drop misleading (wrong!) sentence about ignorables and extenders,
183: modify definition of PCData to make bar on msc grammatical,
184: change grammar's handling of internal subset (drop non-terminal markupdecls),
185: change definition of includeSect to allow conditional sections,
186: add integral-declaration constraint on internal subset,
187: drop misleading / dangerous sentence about relationship of
188: entities with system storage objects,
189: change table body tag to htbody as per EM change to DTD,
190: add rule about space normalization in public identifiers,
191: add description of how to generate our name-space rules from
192: Unicode character database (needs further work!).
193: </sitem>
194: <sitem>1997-10-08 : TB : Removed %-constructs again, new rules
195: for PE appearance.</sitem>
196: <sitem>1997-10-01 : TB : Case-sensitive markup; cleaned up
197: element-type defs, lotsa little edits for style</sitem>
198: <sitem>1997-09-25 : TB : Change to elm's new DTD, with
199: substantial detail cleanup as a side-effect</sitem>
200: <sitem>1997-07-24 : CMSMcQ : correct error (lost *) in definition
201: of ignoreSectContents (thanks to Makoto Murata)</sitem>
202: <sitem>Allow all empty elements to have end-tags, consistent with
203: SGML TC (as per JJC).</sitem>
204: <sitem>1997-07-23 : CMSMcQ : pre-emptive strike on pending corrections:
205: introduce the term 'empty-element tag', note that all empty elements
206: may use it, and elements declared EMPTY must use it.
207: Add WFC requiring encoding decl to come first in an entity.
208: Redefine notations to point to PIs as well as binary entities.
209: Change autodetection table by removing bytes 3 and 4 from
210: examples with Byte Order Mark.
211: Add content model as a term and clarify that it applies to both
212: mixed and element content.
213: </sitem>
214: <sitem>1997-06-30 : CMSMcQ : change date, some cosmetic changes,
215: changes to productions for choice, seq, Mixed, NotationType,
216: Enumeration. Follow James Clark's suggestion and prohibit
217: conditional sections in internal subset. TO DO: simplify
218: production for ignored sections as a result, since we don't
219: need to worry about parsers which don't expand PErefs finding
220: a conditional section.</sitem>
221: <sitem>1997-06-29 : TB : various edits</sitem>
222: <sitem>1997-06-29 : CMSMcQ : further changes:
223: Suppress old FINAL EDIT comments and some dead material.
224: Revise occurrences of % in grammar to exploit Henry Thompson's pun,
225: especially markupdecl and attdef.
226: Remove RMD requirement relating to element content (?).
227: </sitem>
228: <sitem>1997-06-28 : CMSMcQ : Various changes for 1 July draft:
229: Add text for draconian error handling (introduce
230: the term Fatal Error).
231: RE deleta est (changing wording from
232: original announcement to restrict the requirement to validating
233: parsers).
234: Tag definition of validating processor and link to it.
235: Add colon as name character.
236: Change def of %operator.
237: Change standard definitions of lt, gt, amp.
238: Strip leading zeros from #x00nn forms.</sitem>
239: <sitem>1997-04-02 : CMSMcQ : final corrections of editorial errors
240: found in last night's proofreading. Reverse course once more on
241: well-formed: Webster's Second hyphenates it, and that's enough
242: for me.</sitem>
243: <sitem>1997-04-01 : CMSMcQ : corrections from JJC, EM, HT, and self</sitem>
244: <sitem>1997-03-31 : Tim Bray : many changes</sitem>
245: <sitem>1997-03-29 : CMSMcQ : some Henry Thompson (on entity handling),
246: some Charles Goldfarb, some ERB decisions (PE handling in miscellaneous
247: declarations. Changed Ident element to accept def attribute.
248: Allow normalization of Unicode characters. move def of systemliteral
249: into section on literals.</sitem>
250: <sitem>1997-03-28 : CMSMcQ : make as many corrections as possible, from
251: Terry Allen, Norbert Mikula, James Clark, Jon Bosak, Henry Thompson,
252: Paul Grosso, and self. Among other things: give in on "well formed"
253: (Terry is right), tentatively rename QuotedCData as AttValue
254: and Literal as EntityValue to be more informative, since attribute
255: values are the <emph>only</emph> place QuotedCData was used, and
256: vice versa for entity text and Literal. (I'd call it Entity Text,
257: but 8879 uses that name for both internal and external entities.)</sitem>
258: <sitem>1997-03-26 : CMSMcQ : resynch the two forks of this draft, reapply
259: my changes dated 03-20 and 03-21. Normalize old 'may not' to 'must not'
260: except in the one case where it meant 'may or may not'.</sitem>
261: <sitem>1997-03-21 : TB : massive changes on plane flight from Chicago
262: to Vancouver</sitem>
263: <sitem>1997-03-21 : CMSMcQ : correct as many reported errors as possible.
264: </sitem>
265: <sitem>1997-03-20 : CMSMcQ : correct typos listed in CMSMcQ hand copy of spec.</sitem>
266: <sitem>1997-03-20 : CMSMcQ : cosmetic changes preparatory to revision for
267: WWW conference April 1997: restore some of the internal entity
268: references (e.g. to docdate, etc.), change character xA0 to &nbsp;
269: and define nbsp as &#160;, and refill a lot of paragraphs for
270: legibility.</sitem>
271: <sitem>1996-11-12 : CMSMcQ : revise using Tim's edits:
272: Add list type of NUMBERED and change most lists either to
273: BULLETS or to NUMBERED.
274: Suppress QuotedNames, Names (not used).
275: Correct trivial-grammar doc type decl.
276: Rename 'marked section' as 'CDATA section' passim.
277: Also edits from James Clark:
278: Define the set of characters from which [^abc] subtracts.
279: Charref should use just [0-9] not Digit.
280: Location info needs cleaner treatment: remove? (ERB
281: question).
282: One example of a PI has wrong pic.
283: Clarify discussion of encoding names.
284: Encoding failure should lead to unspecified results; don't
285: prescribe error recovery.
286: Don't require exposure of entity boundaries.
287: Ignore white space in element content.
288: Reserve entity names of the form u-NNNN.
289: Clarify relative URLs.
290: And some of my own:
291: Correct productions for content model: model cannot
292: consist of a name, so "elements ::= cp" is no good.
293: </sitem>
294: <sitem>1996-11-11 : CMSMcQ : revise for style.
295: Add new rhs to entity declaration, for parameter entities.</sitem>
296: <sitem>1996-11-10 : CMSMcQ : revise for style.
297: Fix / complete section on names, characters.
298: Add sections on parameter entities, conditional sections.
299: Still to do: Add compatibility note on deterministic content models.
300: Finish stylistic revision.</sitem>
301: <sitem>1996-10-31 : TB : Add Entity Handling section</sitem>
302: <sitem>1996-10-30 : TB : Clean up term & termdef. Slip in
303: ERB decision re EMPTY.</sitem>
304: <sitem>1996-10-28 : TB : Change DTD. Implement some of Michael's
305: suggestions. Change comments back to //. Introduce language for
306: XML namespace reservation. Add section on white-space handling.
307: Lots more cleanup.</sitem>
308: <sitem>1996-10-24 : CMSMcQ : quick tweaks, implement some ERB
309: decisions. Characters are not integers. Comments are /* */ not //.
310: Add bibliographic refs to 10646, HyTime, Unicode.
311: Rename old Cdata as MsData since it's <emph>only</emph> seen
312: in marked sections. Call them attribute-value pairs not
313: name-value pairs, except once. Internal subset is optional, needs
314: '?'. Implied attributes should be signaled to the app, not
315: have values supplied by processor.</sitem>
316: <sitem>1996-10-16 : TB : track down & excise all DSD references;
317: introduce some EBNF for entity declarations.</sitem>
318: <sitem>1996-10-?? : TB : consistency check, fix up scraps so
319: they all parse, get formatter working, correct a few productions.</sitem>
320: <sitem>1996-10-10/11 : CMSMcQ : various maintenance, stylistic, and
321: organizational changes:
322: Replace a few literals with xmlpio and
323: pic entities, to make them consistent and ensure we can change pic
324: reliably when the ERB votes.
325: Drop paragraph on recognizers from notation section.
326: Add match, exact match to terminology.
327: Move old 2.2 XML Processors and Apps into intro.
328: Mention comments, PIs, and marked sections in discussion of
329: delimiter escaping.
330: Streamline discussion of doctype decl syntax.
331: Drop old section of 'PI syntax' for doctype decl, and add
332: section on partial-DTD summary PIs to end of Logical Structures
333: section.
334: Revise DSD syntax section to use Tim's subset-in-a-PI
335: mechanism.</sitem>
336: <sitem>1996-10-10 : TB : eliminate name recognizers (and more?)</sitem>
337: <sitem>1996-10-09 : CMSMcQ : revise for style, consistency through 2.3
338: (Characters)</sitem>
339: <sitem>1996-10-09 : CMSMcQ : re-unite everything for convenience,
340: at least temporarily, and revise quickly</sitem>
341: <sitem>1996-10-08 : TB : first major homogenization pass</sitem>
342: <sitem>1996-10-08 : TB : turn "current" attribute on div type into
343: CDATA</sitem>
344: <sitem>1996-10-02 : TB : remould into skeleton + entities</sitem>
345: <sitem>1996-09-30 : CMSMcQ : add a few more sections prior to exchange
346: with Tim.</sitem>
347: <sitem>1996-09-20 : CMSMcQ : finish transcribing notes.</sitem>
348: <sitem>1996-09-19 : CMSMcQ : begin transcribing notes for draft.</sitem>
349: <sitem>1996-09-13 : CMSMcQ : made outline from notes of 09-06,
350: do some housekeeping</sitem>
351: </slist>
352: </revisiondesc>
353: </header>
354: <body>
355: <div1 id="sec-intro">
356: <head>Introduction</head>
357: <p>Extensible Markup Language, abbreviated XML, describes a class of
358: data objects called <termref def="dt-xml-doc">XML documents</termref> and
359: partially describes the behavior of
360: computer programs which process them. XML is an application profile or
361: restricted form of SGML, the Standard Generalized Markup
362: Language <bibref ref="ISO8879"/>.
363: By construction, XML documents
364: are conforming SGML documents.
365: </p>
366: <p>XML documents are made up of storage units called <termref def="dt-entity">entities</termref>, which contain either parsed
367: or unparsed data.
368: Parsed data is made up of <termref def="dt-character">characters</termref>,
369: some
370: of which form <termref def="dt-chardata">character data</termref>,
371: and some of which form <termref def="dt-markup">markup</termref>.
372: Markup encodes a description of the document's storage layout and
373: logical structure. XML provides a mechanism to impose constraints on
374: the storage layout and logical structure.</p>
375: <p><termdef id="dt-xml-proc" term="XML Processor">A software module
376: called an <term>XML processor</term> is used to read XML documents
377: and provide access to their content and structure.</termdef> <termdef id="dt-app" term="Application">It is assumed that an XML processor is
378: doing its work on behalf of another module, called the
379: <term>application</term>.</termdef> This specification describes the
380: required behavior of an XML processor in terms of how it must read XML
381: data and the information it must provide to the application.</p>
382:
383: <div2 id="sec-origin-goals">
384: <head>Origin and Goals</head>
385: <p>XML was developed by an XML Working Group (originally known as the
386: SGML Editorial Review Board) formed under the auspices of the World
387: Wide Web Consortium (W3C) in 1996.
388: It was chaired by Jon Bosak of Sun
389: Microsystems with the active participation of an XML Special
390: Interest Group (previously known as the SGML Working Group) also
391: organized by the W3C. The membership of the XML Working Group is given
392: in an appendix. Dan Connolly served as the WG's contact with the W3C.
393: </p>
394: <p>The design goals for XML are:<olist>
395: <item><p>XML shall be straightforwardly usable over the
396: Internet.</p></item>
397: <item><p>XML shall support a wide variety of applications.</p></item>
398: <item><p>XML shall be compatible with SGML.</p></item>
399: <item><p>It shall be easy to write programs which process XML
400: documents.</p></item>
401: <item><p>The number of optional features in XML is to be kept to the
402: absolute minimum, ideally zero.</p></item>
403: <item><p>XML documents should be human-legible and reasonably
404: clear.</p></item>
405: <item><p>The XML design should be prepared quickly.</p></item>
406: <item><p>The design of XML shall be formal and concise.</p></item>
407: <item><p>XML documents shall be easy to create.</p></item>
408: <item><p>Terseness in XML markup is of minimal importance.</p></item></olist>
409: </p>
410: <p>This specification,
411: together with associated standards
412: (Unicode and ISO/IEC 10646 for characters,
413: Internet RFC 1766 for language identification tags,
414: ISO 639 for language name codes, and
415: ISO 3166 for country name codes),
416: provides all the information necessary to understand
417: XML Version &XML.version;
418: and construct computer programs to process it.</p>
419: <p>This version of the XML specification
420: <!-- is for &doc.audience;.-->
421: &doc.distribution;.</p>
422:
423: </div2>
424:
425:
426:
427:
428: <div2 id="sec-terminology">
429: <head>Terminology</head>
430:
431: <p>The terminology used to describe XML documents is defined in the body of
432: this specification.
433: The terms defined in the following list are used in building those
434: definitions and in describing the actions of an XML processor:
435: <glist>
436: <gitem>
437: <label>may</label>
438: <def><p><termdef id="dt-may" term="May">Conforming documents and XML
439: processors are permitted to but need not behave as
440: described.</termdef></p></def>
441: </gitem>
442: <gitem>
443: <label>must</label>
444: <def><p>Conforming documents and XML processors
445: are required to behave as described; otherwise they are in error.
446: <!-- do NOT change this! this is what defines a violation of
447: a 'must' clause as 'an error'. -MSM -->
448: </p></def>
449: </gitem>
450: <gitem>
451: <label>error</label>
452: <def><p><termdef id="dt-error" term="Error">A violation of the rules of this
453: specification; results are
454: undefined. Conforming software may detect and report an error and may
455: recover from it.</termdef></p></def>
456: </gitem>
457: <gitem>
458: <label>fatal error</label>
459: <def><p><termdef id="dt-fatal" term="Fatal Error">An error
460: which a conforming <termref def="dt-xml-proc">XML processor</termref>
461: must detect and report to the application.
462: After encountering a fatal error, the
463: processor may continue
464: processing the data to search for further errors and may report such
465: errors to the application. In order to support correction of errors,
466: the processor may make unprocessed data from the document (with
467: intermingled character data and markup) available to the application.
468: Once a fatal error is detected, however, the processor must not
469: continue normal processing (i.e., it must not
470: continue to pass character data and information about the document's
471: logical structure to the application in the normal way).
472: </termdef></p></def>
473: </gitem>
474: <gitem>
475: <label>at user option</label>
476: <def><p>Conforming software may or must (depending on the modal verb in the
477: sentence) behave as described; if it does, it must
478: provide users a means to enable or disable the behavior
479: described.</p></def>
480: </gitem>
481: <gitem>
482: <label>validity constraint</label>
483: <def><p>A rule which applies to all
484: <termref def="dt-valid">valid</termref> XML documents.
485: Violations of validity constraints are errors; they must, at user option,
486: be reported by
487: <termref def="dt-validating">validating XML processors</termref>.</p></def>
488: </gitem>
489: <gitem>
490: <label>well-formedness constraint</label>
491: <def><p>A rule which applies to all <termref def="dt-wellformed">well-formed</termref> XML documents.
492: Violations of well-formedness constraints are
493: <termref def="dt-fatal">fatal errors</termref>.</p></def>
494: </gitem>
495:
496: <gitem>
497: <label>match</label>
498: <def><p><termdef id="dt-match" term="match">(Of strings or names:)
499: Two strings or names being compared must be identical.
500: Characters with multiple possible representations in ISO/IEC 10646 (e.g.
501: characters with
502: both precomposed and base+diacritic forms) match only if they have the
503: same representation in both strings.
504: At user option, processors may normalize such characters to
505: some canonical form.
506: No case folding is performed.
507: (Of strings and rules in the grammar:)
508: A string matches a grammatical production if it belongs to the
509: language generated by that production.
510: (Of content and content models:)
511: An element matches its declaration when it conforms
512: in the fashion described in the constraint
513: <specref ref="elementvalid"/>.
514: </termdef>
515: </p></def>
516: </gitem>
517: <gitem>
518: <label>for compatibility</label>
519: <def><p><termdef id="dt-compat" term="For Compatibility">A feature of
520: XML included solely to ensure that XML remains compatible with SGML.
521: </termdef></p></def>
522: </gitem>
523: <gitem>
524: <label>for interoperability</label>
525: <def><p><termdef id="dt-interop" term="For interoperability">A
526: non-binding recommendation included to increase the chances that XML
527: documents can be processed by the existing installed base of SGML
528: processors which predate the
529: &WebSGML;.</termdef></p></def>
530: </gitem>
531: </glist>
532: </p>
533: </div2>
534:
535:
536: </div1>
537: <!-- &Docs; -->
538:
539: <div1 id="sec-documents">
540: <head>Documents</head>
541:
542: <p><termdef id="dt-xml-doc" term="XML Document">
543: A data object is an
544: <term>XML document</term> if it is
545: <termref def="dt-wellformed">well-formed</termref>, as
546: defined in this specification.
547: A well-formed XML document may in addition be
548: <termref def="dt-valid">valid</termref> if it meets certain further
549: constraints.</termdef></p>
550:
551: <p>Each XML document has both a logical and a physical structure.
552: Physically, the document is composed of units called <termref def="dt-entity">entities</termref>. An entity may <termref def="dt-entref">refer</termref> to other entities to cause their
553: inclusion in the document. A document begins in a "root" or <termref def="dt-docent">document entity</termref>.
554: Logically, the document is composed of declarations, elements,
555: comments,
556: character references, and
557: processing
558: instructions, all of which are indicated in the document by explicit
559: markup.
560: The logical and physical structures must nest properly, as described
561: in <specref ref="wf-entities"/>.
562: </p>
563:
564: <div2 id="sec-well-formed">
565: <head>Well-Formed XML Documents</head>
566:
567: <p><termdef id="dt-wellformed" term="Well-Formed">
568: A textual object is
569: a well-formed XML document if:</termdef>
570: <olist>
571: <item><p>Taken as a whole, it
572: matches the production labeled <nt def="NT-document">document</nt>.</p></item>
573: <item><p>It
574: meets all the well-formedness constraints given in this specification.</p>
575: </item>
576: <item><p>Each of the <termref def="dt-parsedent">parsed entities</termref>
577: which is referenced directly or indirectly within the document is
578: <titleref href="wf-entities">well-formed</titleref>.</p></item>
579: </olist></p>
580: <p>
581: <scrap lang="ebnf" id="document">
582: <head>Document</head>
583: <prod id="NT-document"><lhs>document</lhs>
584: <rhs><nt def="NT-prolog">prolog</nt>
585: <nt def="NT-element">element</nt>
586: <nt def="NT-Misc">Misc</nt>*</rhs></prod>
587: </scrap>
588: </p>
589: <p>Matching the <nt def="NT-document">document</nt> production
590: implies that:
591: <olist>
592: <item><p>It contains one or more
593: <termref def="dt-element">elements</termref>.</p>
594: </item>
595: <!--* N.B. some readers (notably JC) find the following
596: paragraph awkward and redundant. I agree it's logically redundant:
597: it *says* it is summarizing the logical implications of
598: matching the grammar, and that means by definition it's
599: logically redundant. I don't think it's rhetorically
600: redundant or unnecessary, though, so I'm keeping it. It
601: could however use some recasting when the editors are feeling
602: stronger. -MSM *-->
603: <item><p><termdef id="dt-root" term="Root Element">There is exactly
604: one element, called the <term>root</term>, or document element, no
605: part of which appears in the <termref def="dt-content">content</termref> of any other element.</termdef>
606: For all other elements, if the start-tag is in the content of another
607: element, the end-tag is in the content of the same element. More
608: simply stated, the elements, delimited by start- and end-tags, nest
609: properly within each other.
610: </p></item>
611: </olist>
612: </p>
613: <p><termdef id="dt-parentchild" term="Parent/Child">As a consequence
614: of this,
615: for each non-root element
616: <code>C</code> in the document, there is one other element <code>P</code>
617: in the document such that
618: <code>C</code> is in the content of <code>P</code>, but is not in
619: the content of any other element that is in the content of
620: <code>P</code>.
621: <code>P</code> is referred to as the
622: <term>parent</term> of <code>C</code>, and <code>C</code> as a
623: <term>child</term> of <code>P</code>.</termdef></p></div2>
624:
625: <div2 id="charsets">
626: <head>Characters</head>
627:
628: <p><termdef id="dt-text" term="Text">A parsed entity contains
629: <term>text</term>, a sequence of
630: <termref def="dt-character">characters</termref>,
631: which may represent markup or character data.</termdef>
632: <termdef id="dt-character" term="Character">A <term>character</term>
633: is an atomic unit of text as specified by
634: ISO/IEC 10646 <bibref ref="ISO10646"/>.
635: Legal characters are tab, carriage return, line feed, and the legal
636: graphic characters of Unicode and ISO/IEC 10646.
637: The use of "compatibility characters", as defined in section 6.8
638: of <bibref ref="Unicode"/>, is discouraged.
639: </termdef>
640: <scrap lang="ebnf" id="char32">
641: <head>Character Range</head>
642: <prodgroup pcw2="4" pcw4="17.5" pcw5="11">
643: <prod id="NT-Char"><lhs>Char</lhs>
644: <rhs>#x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD]
645: | [#x10000-#x10FFFF]</rhs>
646: <com>any Unicode character, excluding the
647: surrogate blocks, FFFE, and FFFF.</com> </prod>
648: </prodgroup>
649: </scrap>
650: </p>
651:
652: <p>The mechanism for encoding character code points into bit patterns may
653: vary from entity to entity. All XML processors must accept the UTF-8
654: and UTF-16 encodings of 10646; the mechanisms for signaling which of
655: the two is in use, or for bringing other encodings into play, are
656: discussed later, in <specref ref="charencoding"/>.
657: </p>
658: <!--
659: <p>Regardless of the specific encoding used, any character in the ISO/IEC
660: 10646 character set may be referred to by the decimal or hexadecimal
661: equivalent of its
662: UCS-4 code value.
663: </p>-->
664: </div2>
665:
666: <div2 id="sec-common-syn">
667: <head>Common Syntactic Constructs</head>
668:
669: <p>This section defines some symbols used widely in the grammar.</p>
670: <p><nt def="NT-S">S</nt> (white space) consists of one or more space (#x20)
671: characters, carriage returns, line feeds, or tabs.
672:
673: <scrap lang="ebnf" id="white">
674: <head>White Space</head>
675: <prodgroup pcw2="4" pcw4="17.5" pcw5="11">
676: <prod id="NT-S"><lhs>S</lhs>
677: <rhs>(#x20 | #x9 | #xD | #xA)+</rhs>
678: </prod>
679: </prodgroup>
680: </scrap></p>
681: <p>Characters are classified for convenience as letters, digits, or other
682: characters. Letters consist of an alphabetic or syllabic
683: base character possibly
684: followed by one or more combining characters, or of an ideographic
685: character.
686: Full definitions of the specific characters in each class
687: are given in <specref ref="CharClasses"/>.</p>
688: <p><termdef id="dt-name" term="Name">A <term>Name</term> is a token
689: beginning with a letter or one of a few punctuation characters, and continuing
690: with letters, digits, hyphens, underscores, colons, or full stops, together
691: known as name characters.</termdef>
692: Names beginning with the string "<code>xml</code>", or any string
693: which would match <code>(('X'|'x') ('M'|'m') ('L'|'l'))</code>, are
694: reserved for standardization in this or future versions of this
695: specification.
696: </p>
697: <note>
698: <p>The colon character within XML names is reserved for experimentation with
699: name spaces.
700: Its meaning is expected to be
701: standardized at some future point, at which point those documents
702: using the colon for experimental purposes may need to be updated.
703: (There is no guarantee that any name-space mechanism
704: adopted for XML will in fact use the colon as a name-space delimiter.)
705: In practice, this means that authors should not use the colon in XML
706: names except as part of name-space experiments, but that XML processors
707: should accept the colon as a name character.</p>
708: </note>
709: <p>An
710: <nt def="NT-Nmtoken">Nmtoken</nt> (name token) is any mixture of
711: name characters.
712: <scrap lang="ebnf">
713: <head>Names and Tokens</head>
714: <prod id="NT-NameChar"><lhs>NameChar</lhs>
715: <rhs><nt def="NT-Letter">Letter</nt>
716: | <nt def="NT-Digit">Digit</nt>
717: | '.' | '-' | '_' | ':'
718: | <nt def="NT-CombiningChar">CombiningChar</nt>
719: | <nt def="NT-Extender">Extender</nt></rhs>
720: </prod>
721: <prod id="NT-Name"><lhs>Name</lhs>
722: <rhs>(<nt def="NT-Letter">Letter</nt> | '_' | ':')
723: (<nt def="NT-NameChar">NameChar</nt>)*</rhs></prod>
724: <prod id="NT-Names"><lhs>Names</lhs>
725: <rhs><nt def="NT-Name">Name</nt>
726: (<nt def="NT-S">S</nt> <nt def="NT-Name">Name</nt>)*</rhs></prod>
727: <prod id="NT-Nmtoken"><lhs>Nmtoken</lhs>
728: <rhs>(<nt def="NT-NameChar">NameChar</nt>)+</rhs></prod>
729: <prod id="NT-Nmtokens"><lhs>Nmtokens</lhs>
730: <rhs><nt def="NT-Nmtoken">Nmtoken</nt> (<nt def="NT-S">S</nt> <nt def="NT-Nmtoken">Nmtoken</nt>)*</rhs></prod>
731: </scrap>
732: </p>
733: <p>Literal data is any quoted string not containing
734: the quotation mark used as a delimiter for that string.
735: Literals are used
736: for specifying the content of internal entities
737: (<nt def="NT-EntityValue">EntityValue</nt>),
738: the values of attributes (<nt def="NT-AttValue">AttValue</nt>),
739: and external identifiers
740: (<nt def="NT-SystemLiteral">SystemLiteral</nt>).
741: Note that a <nt def="NT-SystemLiteral">SystemLiteral</nt>
742: can be parsed without scanning for markup.
743: <scrap lang="ebnf">
744: <head>Literals</head>
745: <prod id="NT-EntityValue"><lhs>EntityValue</lhs>
746: <rhs>'"'
747: ([^%&"]
748: | <nt def="NT-PEReference">PEReference</nt>
749: | <nt def="NT-Reference">Reference</nt>)*
750: '"'
751: </rhs>
752: <rhs>|
753: "'"
754: ([^%&']
755: | <nt def="NT-PEReference">PEReference</nt>
756: | <nt def="NT-Reference">Reference</nt>)*
757: "'"</rhs>
758: </prod>
759: <prod id="NT-AttValue"><lhs>AttValue</lhs>
760: <rhs>'"'
761: ([^<&"]
762: | <nt def="NT-Reference">Reference</nt>)*
763: '"'
764: </rhs>
765: <rhs>|
766: "'"
767: ([^<&']
768: | <nt def="NT-Reference">Reference</nt>)*
769: "'"</rhs>
770: </prod>
771: <prod id="NT-SystemLiteral"><lhs>SystemLiteral</lhs>
772: <rhs>('"' [^"]* '"') | ("'" [^']* "'")
773: </rhs>
774: </prod>
775: <prod id="NT-PubidLiteral"><lhs>PubidLiteral</lhs>
776: <rhs>'"' <nt def="NT-PubidChar">PubidChar</nt>*
777: '"'
778: | "'" (<nt def="NT-PubidChar">PubidChar</nt> - "'")* "'"</rhs>
779: </prod>
780: <prod id="NT-PubidChar"><lhs>PubidChar</lhs>
781: <rhs>#x20 | #xD | #xA
782: | [a-zA-Z0-9]
783: | [-'()+,./:=?;!*#@$_%]</rhs>
784: </prod>
785: </scrap>
786: </p>
787:
788: </div2>
789:
790: <div2 id="syntax">
791: <head>Character Data and Markup</head>
792:
793: <p><termref def="dt-text">Text</termref> consists of intermingled
794: <termref def="dt-chardata">character
795: data</termref> and markup.
796: <termdef id="dt-markup" term="Markup"><term>Markup</term> takes the form of
797: <termref def="dt-stag">start-tags</termref>,
798: <termref def="dt-etag">end-tags</termref>,
799: <termref def="dt-empty">empty-element tags</termref>,
800: <termref def="dt-entref">entity references</termref>,
801: <termref def="dt-charref">character references</termref>,
802: <termref def="dt-comment">comments</termref>,
803: <termref def="dt-cdsection">CDATA section</termref> delimiters,
804: <termref def="dt-doctype">document type declarations</termref>, and
805: <termref def="dt-pi">processing instructions</termref>.
806: </termdef>
807: </p>
808: <p><termdef id="dt-chardata" term="Character Data">All text that is not markup
809: constitutes the <term>character data</term> of
810: the document.</termdef></p>
811: <p>The ampersand character (&) and the left angle bracket (<)
812: may appear in their literal form <emph>only</emph> when used as markup
813: delimiters, or within a <termref def="dt-comment">comment</termref>, a
814: <termref def="dt-pi">processing instruction</termref>,
815: or a <termref def="dt-cdsection">CDATA section</termref>.
816:
817: They are also legal within the <termref def="dt-litentval">literal entity
818: value</termref> of an internal entity declaration; see
819: <specref ref="wf-entities"/>.
820: <!-- FINAL EDIT: restore internal entity decl or leave it out. -->
821: If they are needed elsewhere,
822: they must be <termref def="dt-escape">escaped</termref>
823: using either <termref def="dt-charref">numeric character references</termref>
824: or the strings
825: "<code>&amp;</code>" and "<code>&lt;</code>" respectively.
826: The right angle
827: bracket (>) may be represented using the string
828: "<code>&gt;</code>", and must, <termref def="dt-compat">for
829: compatibility</termref>,
830: be escaped using
831: "<code>&gt;</code>" or a character reference
832: when it appears in the string
833: "<code>]]></code>"
834: in content,
835: when that string is not marking the end of
836: a <termref def="dt-cdsection">CDATA section</termref>.
837: </p>
838: <p>
839: In the content of elements, character data
840: is any string of characters which does
841: not contain the start-delimiter of any markup.
842: In a CDATA section, character data
843: is any string of characters not including the CDATA-section-close
844: delimiter, "<code>]]></code>".</p>
845: <p>
846: To allow attribute values to contain both single and double quotes, the
847: apostrophe or single-quote character (') may be represented as
848: "<code>&apos;</code>", and the double-quote character (") as
849: "<code>&quot;</code>".
850: <scrap lang="ebnf">
851: <head>Character Data</head>
852: <prod id="NT-CharData">
853: <lhs>CharData</lhs>
854: <rhs>[^<&]* - ([^<&]* ']]>' [^<&]*)</rhs>
855: </prod>
856: </scrap>
857: </p>
858: </div2>
859:
860: <div2 id="sec-comments">
861: <head>Comments</head>
862:
863: <p><termdef id="dt-comment" term="Comment"><term>Comments</term> may
864: appear anywhere in a document outside other
865: <termref def="dt-markup">markup</termref>; in addition,
866: they may appear within the document type declaration
867: at places allowed by the grammar.
868: They are not part of the document's <termref def="dt-chardata">character
869: data</termref>; an XML
870: processor may, but need not, make it possible for an application to
871: retrieve the text of comments.
872: <termref def="dt-compat">For compatibility</termref>, the string
873: "<code>--</code>" (double-hyphen) must not occur within
874: comments.
875: <scrap lang="ebnf">
876: <head>Comments</head>
877: <prod id="NT-Comment"><lhs>Comment</lhs>
878: <rhs>'<!--'
879: ((<nt def="NT-Char">Char</nt> - '-')
880: | ('-' (<nt def="NT-Char">Char</nt> - '-')))*
881: '-->'</rhs>
882: </prod>
883: </scrap>
884: </termdef></p>
885: <p>An example of a comment:
886: <eg><!&como; declarations for <head> & <body> &comc;></eg>
887: </p>
888: </div2>
889:
890: <div2 id="sec-pi">
891: <head>Processing Instructions</head>
892:
893: <p><termdef id="dt-pi" term="Processing instruction"><term>Processing
894: instructions</term> (PIs) allow documents to contain instructions
895: for applications.
896:
897: <scrap lang="ebnf">
898: <head>Processing Instructions</head>
899: <prod id="NT-PI"><lhs>PI</lhs>
900: <rhs>'<?' <nt def="NT-PITarget">PITarget</nt>
901: (<nt def="NT-S">S</nt>
902: (<nt def="NT-Char">Char</nt>* -
903: (<nt def="NT-Char">Char</nt>* &pic; <nt def="NT-Char">Char</nt>*)))?
904: &pic;</rhs></prod>
905: <prod id="NT-PITarget"><lhs>PITarget</lhs>
906: <rhs><nt def="NT-Name">Name</nt> -
907: (('X' | 'x') ('M' | 'm') ('L' | 'l'))</rhs>
908: </prod>
909: </scrap></termdef>
910: PIs are not part of the document's <termref def="dt-chardata">character
911: data</termref>, but must be passed through to the application. The
912: PI begins with a target (<nt def="NT-PITarget">PITarget</nt>) used
913: to identify the application to which the instruction is directed.
914: The target names "<code>XML</code>", "<code>xml</code>", and so on are
915: reserved for standardization in this or future versions of this
916: specification.
917: The
918: XML <termref def="dt-notation">Notation</termref> mechanism
919: may be used for
920: formal declaration of PI targets.
921: </p>
922: </div2>
923:
924: <div2 id="sec-cdata-sect">
925: <head>CDATA Sections</head>
926:
927: <p><termdef id="dt-cdsection" term="CDATA Section"><term>CDATA sections</term>
928: may occur
929: anywhere character data may occur; they are
930: used to escape blocks of text containing characters which would
931: otherwise be recognized as markup. CDATA sections begin with the
932: string "<code><![CDATA[</code>" and end with the string
933: "<code>]]></code>":
934: <scrap lang="ebnf">
935: <head>CDATA Sections</head>
936: <prod id="NT-CDSect"><lhs>CDSect</lhs>
937: <rhs><nt def="NT-CDStart">CDStart</nt>
938: <nt def="NT-CData">CData</nt>
939: <nt def="NT-CDEnd">CDEnd</nt></rhs></prod>
940: <prod id="NT-CDStart"><lhs>CDStart</lhs>
941: <rhs>'<![CDATA['</rhs>
942: </prod>
943: <prod id="NT-CData"><lhs>CData</lhs>
944: <rhs>(<nt def="NT-Char">Char</nt>* -
945: (<nt def="NT-Char">Char</nt>* ']]>' <nt def="NT-Char">Char</nt>*))
946: </rhs>
947: </prod>
948: <prod id="NT-CDEnd"><lhs>CDEnd</lhs>
949: <rhs>']]>'</rhs>
950: </prod>
951: </scrap>
952:
953: Within a CDATA section, only the <nt def="NT-CDEnd">CDEnd</nt> string is
954: recognized as markup, so that left angle brackets and ampersands may occur in
955: their literal form; they need not (and cannot) be escaped using
956: "<code>&lt;</code>" and "<code>&amp;</code>". CDATA sections
957: cannot nest.</termdef>
958: </p>
959:
960: <p>An example of a CDATA section, in which "<code><greeting></code>" and
961: "<code></greeting></code>"
962: are recognized as <termref def="dt-chardata">character data</termref>, not
963: <termref def="dt-markup">markup</termref>:
964: <eg><![CDATA[<greeting>Hello, world!</greeting>]]></eg>
965: </p>
966: </div2>
967:
968: <div2 id="sec-prolog-dtd">
969: <head>Prolog and Document Type Declaration</head>
970:
971: <p><termdef id="dt-xmldecl" term="XML Declaration">XML documents
972: may, and should,
973: begin with an <term>XML declaration</term> which specifies
974: the version of
975: XML being used.</termdef>
976: For example, the following is a complete XML document, <termref def="dt-wellformed">well-formed</termref> but not
977: <termref def="dt-valid">valid</termref>:
978: <eg><![CDATA[<?xml version="1.0"?>
979: <greeting>Hello, world!</greeting>
980: ]]></eg>
981: and so is this:
982: <eg><![CDATA[<greeting>Hello, world!</greeting>
983: ]]></eg>
984: </p>
985:
986: <p>The version number "<code>1.0</code>" should be used to indicate
987: conformance to this version of this specification; it is an error
988: for a document to use the value "<code>1.0</code>"
989: if it does not conform to this version of this specification.
990: It is the intent
991: of the XML working group to give later versions of this specification
992: numbers other than "<code>1.0</code>", but this intent does not
993: indicate a
994: commitment to produce any future versions of XML, nor if any are produced, to
995: use any particular numbering scheme.
996: Since future versions are not ruled out, this construct is provided
997: as a means to allow the possibility of automatic version recognition, should
998: it become necessary.
999: Processors may signal an error if they receive documents labeled with
1000: versions they do not support.
1001: </p>
1002: <p>The function of the markup in an XML document is to describe its
1003: storage and logical structure and to associate attribute-value pairs
1004: with its logical structures. XML provides a mechanism, the <termref def="dt-doctype">document type declaration</termref>, to define
1005: constraints on the logical structure and to support the use of
1006: predefined storage units.
1007:
1008: <termdef id="dt-valid" term="Validity">An XML document is
1009: <term>valid</term> if it has an associated document type
1010: declaration and if the document
1011: complies with the constraints expressed in it.</termdef></p>
1012: <p>The document type declaration must appear before
1013: the first <termref def="dt-element">element</termref> in the document.
1014: <scrap lang="ebnf" id="xmldoc">
1015: <head>Prolog</head>
1016: <prodgroup pcw2="6" pcw4="17.5" pcw5="9">
1017: <prod id="NT-prolog"><lhs>prolog</lhs>
1018: <rhs><nt def="NT-XMLDecl">XMLDecl</nt>?
1019: <nt def="NT-Misc">Misc</nt>*
1020: (<nt def="NT-doctypedecl">doctypedecl</nt>
1021: <nt def="NT-Misc">Misc</nt>*)?</rhs></prod>
1022: <prod id="NT-XMLDecl"><lhs>XMLDecl</lhs>
1023: <rhs>&xmlpio;
1024: <nt def="NT-VersionInfo">VersionInfo</nt>
1025: <nt def="NT-EncodingDecl">EncodingDecl</nt>?
1026: <nt def="NT-SDDecl">SDDecl</nt>?
1027: <nt def="NT-S">S</nt>?
1028: &pic;</rhs>
1029: </prod>
1030: <prod id="NT-VersionInfo"><lhs>VersionInfo</lhs>
1031: <rhs><nt def="NT-S">S</nt> 'version' <nt def="NT-Eq">Eq</nt>
1032: (' <nt def="NT-VersionNum">VersionNum</nt> '
1033: | " <nt def="NT-VersionNum">VersionNum</nt> ")</rhs>
1034: </prod>
1035: <prod id="NT-Eq"><lhs>Eq</lhs>
1036: <rhs><nt def="NT-S">S</nt>? '=' <nt def="NT-S">S</nt>?</rhs></prod>
1037: <prod id="NT-VersionNum">
1038: <lhs>VersionNum</lhs>
1039: <rhs>([a-zA-Z0-9_.:] | '-')+</rhs>
1040: </prod>
1041: <prod id="NT-Misc"><lhs>Misc</lhs>
1042: <rhs><nt def="NT-Comment">Comment</nt> | <nt def="NT-PI">PI</nt> |
1043: <nt def="NT-S">S</nt></rhs></prod>
1044: </prodgroup>
1045: </scrap></p>
1046:
1047: <p><termdef id="dt-doctype" term="Document Type Declaration">The XML
1048: <term>document type declaration</term>
1049: contains or points to
1050: <termref def="dt-markupdecl">markup declarations</termref>
1051: that provide a grammar for a
1052: class of documents.
1053: This grammar is known as a document type definition,
1054: or <term>DTD</term>.
1055: The document type declaration can point to an external subset (a
1056: special kind of
1057: <termref def="dt-extent">external entity</termref>) containing markup
1058: declarations, or can
1059: contain the markup declarations directly in an internal subset, or can do
1060: both.
1061: The DTD for a document consists of both subsets taken
1062: together.</termdef>
1063: </p>
1064: <p><termdef id="dt-markupdecl" term="markup declaration">
1065: A <term>markup declaration</term> is
1066: an <termref def="dt-eldecl">element type declaration</termref>,
1067: an <termref def="dt-attdecl">attribute-list declaration</termref>,
1068: an <termref def="dt-entdecl">entity declaration</termref>, or
1069: a <termref def="dt-notdecl">notation declaration</termref>.
1070: </termdef>
1071: These declarations may be contained in whole or in part
1072: within <termref def="dt-PE">parameter entities</termref>,
1073: as described in the well-formedness and validity constraints below.
1074: For fuller information, see
1075: <specref ref="sec-physical-struct"/>.</p>
1076: <scrap lang="ebnf" id="dtd">
1077: <head>Document Type Definition</head>
1078: <prodgroup pcw2="6" pcw4="17.5" pcw5="9">
1079: <prod id="NT-doctypedecl"><lhs>doctypedecl</lhs>
1080: <rhs>'<!DOCTYPE' <nt def="NT-S">S</nt>
1081: <nt def="NT-Name">Name</nt> (<nt def="NT-S">S</nt>
1082: <nt def="NT-ExternalID">ExternalID</nt>)?
1083: <nt def="NT-S">S</nt>? ('['
1084: (<nt def="NT-markupdecl">markupdecl</nt>
1085: | <nt def="NT-PEReference">PEReference</nt>
1086: | <nt def="NT-S">S</nt>)*
1087: ']'
1088: <nt def="NT-S">S</nt>?)? '>'</rhs>
1089: <vc def="vc-roottype"/>
1090: </prod>
1091: <prod id="NT-markupdecl"><lhs>markupdecl</lhs>
1092: <rhs><nt def="NT-elementdecl">elementdecl</nt>
1093: | <nt def="NT-AttlistDecl">AttlistDecl</nt>
1094: | <nt def="NT-EntityDecl">EntityDecl</nt>
1095: | <nt def="NT-NotationDecl">NotationDecl</nt>
1096: | <nt def="NT-PI">PI</nt>
1097: | <nt def="NT-Comment">Comment</nt>
1098: </rhs>
1099: <vc def="vc-PEinMarkupDecl"/>
1100: <wfc def="wfc-PEinInternalSubset"/>
1101: </prod>
1102:
1103: </prodgroup>
1104: </scrap>
1105:
1106: <p>The markup declarations may be made up in whole or in part of
1107: the <termref def="dt-repltext">replacement text</termref> of
1108: <termref def="dt-PE">parameter entities</termref>.
1109: The productions later in this specification for
1110: individual nonterminals (<nt def="NT-elementdecl">elementdecl</nt>,
1111: <nt def="NT-AttlistDecl">AttlistDecl</nt>, and so on) describe
1112: the declarations <emph>after</emph> all the parameter entities have been
1113: <termref def="dt-include">included</termref>.</p>
1114:
1115: <vcnote id="vc-roottype">
1116: <head>Root Element Type</head>
1117: <p>
1118: The <nt def="NT-Name">Name</nt> in the document type declaration must
1119: match the element type of the <termref def="dt-root">root element</termref>.
1120: </p>
1121: </vcnote>
1122:
1123: <vcnote id="vc-PEinMarkupDecl">
1124: <head>Proper Declaration/PE Nesting</head>
1125: <p>Parameter-entity
1126: <termref def="dt-repltext">replacement text</termref> must be properly nested
1127: with markup declarations.
1128: That is to say, if either the first character
1129: or the last character of a markup
1130: declaration (<nt def="NT-markupdecl">markupdecl</nt> above)
1131: is contained in the replacement text for a
1132: <termref def="dt-PERef">parameter-entity reference</termref>,
1133: both must be contained in the same replacement text.</p>
1134: </vcnote>
1135: <wfcnote id="wfc-PEinInternalSubset">
1136: <head>PEs in Internal Subset</head>
1137: <p>In the internal DTD subset,
1138: <termref def="dt-PERef">parameter-entity references</termref>
1139: can occur only where markup declarations can occur, not
1140: within markup declarations. (This does not apply to
1141: references that occur in
1142: external parameter entities or to the external subset.)
1143: </p>
1144: </wfcnote>
1145: <p>
1146: Like the internal subset, the external subset and
1147: any external parameter entities referred to in the DTD
1148: must consist of a series of complete markup declarations of the types
1149: allowed by the non-terminal symbol
1150: <nt def="NT-markupdecl">markupdecl</nt>, interspersed with white space
1151: or <termref def="dt-PERef">parameter-entity references</termref>.
1152: However, portions of the contents
1153: of the
1154: external subset or of external parameter entities may conditionally be ignored
1155: by using
1156: the <termref def="dt-cond-section">conditional section</termref>
1157: construct; this is not allowed in the internal subset.
1158:
1159: <scrap id="ext-Subset">
1160: <head>External Subset</head>
1161: <prodgroup pcw2="6" pcw4="17.5" pcw5="9">
1162: <prod id="NT-extSubset"><lhs>extSubset</lhs>
1163: <rhs><nt def="NT-TextDecl">TextDecl</nt>?
1164: <nt def="NT-extSubsetDecl">extSubsetDecl</nt></rhs></prod>
1165: <prod id="NT-extSubsetDecl"><lhs>extSubsetDecl</lhs>
1166: <rhs>(
1167: <nt def="NT-markupdecl">markupdecl</nt>
1168: | <nt def="NT-conditionalSect">conditionalSect</nt>
1169: | <nt def="NT-PEReference">PEReference</nt>
1170: | <nt def="NT-S">S</nt>
1171: )*</rhs>
1172: </prod>
1173: </prodgroup>
1174: </scrap></p>
1175: <p>The external subset and external parameter entities also differ
1176: from the internal subset in that in them,
1177: <termref def="dt-PERef">parameter-entity references</termref>
1178: are permitted <emph>within</emph> markup declarations,
1179: not only <emph>between</emph> markup declarations.</p>
1180: <p>An example of an XML document with a document type declaration:
1181: <eg><![CDATA[<?xml version="1.0"?>
1182: <!DOCTYPE greeting SYSTEM "hello.dtd">
1183: <greeting>Hello, world!</greeting>
1184: ]]></eg>
1185: The <termref def="dt-sysid">system identifier</termref>
1186: "<code>hello.dtd</code>" gives the URI of a DTD for the document.</p>
1187: <p>The declarations can also be given locally, as in this
1188: example:
1189: <eg><![CDATA[<?xml version="1.0" encoding="UTF-8" ?>
1190: <!DOCTYPE greeting [
1191: <!ELEMENT greeting (#PCDATA)>
1192: ]>
1193: <greeting>Hello, world!</greeting>
1194: ]]></eg>
1195: If both the external and internal subsets are used, the
1196: internal subset is considered to occur before the external subset.
1197: <!-- 'is considered to'? boo. whazzat mean? -->
1198: This has the effect that entity and attribute-list declarations in the
1199: internal subset take precedence over those in the external subset.
1200: </p>
1201: </div2>
1202:
1203: <div2 id="sec-rmd">
1204: <head>Standalone Document Declaration</head>
1205: <p>Markup declarations can affect the content of the document,
1206: as passed from an <termref def="dt-xml-proc">XML processor</termref>
1207: to an application; examples are attribute defaults and entity
1208: declarations.
1209: The standalone document declaration,
1210: which may appear as a component of the XML declaration, signals
1211: whether or not there are such declarations which appear external to
1212: the <termref def="dt-docent">document entity</termref>.
1213: <scrap lang="ebnf" id="fulldtd">
1214: <head>Standalone Document Declaration</head>
1215: <prodgroup pcw2="4" pcw4="19.5" pcw5="9">
1216: <prod id="NT-SDDecl"><lhs>SDDecl</lhs>
1217: <rhs>
1218: <nt def="NT-S">S</nt>
1219: 'standalone' <nt def="NT-Eq">Eq</nt>
1220: (("'" ('yes' | 'no') "'") | ('"' ('yes' | 'no') '"'))
1221: </rhs>
1222: <vc def="vc-check-rmd"/></prod>
1223: </prodgroup>
1224: </scrap></p>
1225: <p>
1226: In a standalone document declaration, the value "<code>yes</code>" indicates
1227: that there
1228: are no markup declarations external to the <termref def="dt-docent">document
1229: entity</termref> (either in the DTD external subset, or in an
1230: external parameter entity referenced from the internal subset)
1231: which affect the information passed from the XML processor to
1232: the application.
1233: The value "<code>no</code>" indicates that there are or may be such
1234: external markup declarations.
1235: Note that the standalone document declaration only
1236: denotes the presence of external <emph>declarations</emph>; the presence, in a
1237: document, of
1238: references to external <emph>entities</emph>, when those entities are
1239: internally declared,
1240: does not change its standalone status.</p>
1241: <p>If there are no external markup declarations, the standalone document
1242: declaration has no meaning.
1243: If there are external markup declarations but there is no standalone
1244: document declaration, the value "<code>no</code>" is assumed.</p>
1245: <p>Any XML document for which <code>standalone="no"</code> holds can
1246: be converted algorithmically to a standalone document,
1247: which may be desirable for some network delivery applications.</p>
1248: <vcnote id="vc-check-rmd">
1249: <head>Standalone Document Declaration</head>
1250: <p>The standalone document declaration must have
1251: the value "<code>no</code>" if any external markup declarations
1252: contain declarations of:</p><ulist>
1253: <item><p>attributes with <termref def="dt-default">default</termref> values, if
1254: elements to which
1255: these attributes apply appear in the document without
1256: specifications of values for these attributes, or</p></item>
1257: <item><p>entities (other than &magicents;),
1258: if <termref def="dt-entref">references</termref> to those
1259: entities appear in the document, or</p>
1260: </item>
1261: <item><p>attributes with values subject to
1262: <titleref href="AVNormalize">normalization</titleref>, where the
1263: attribute appears in the document with a value which will
1264: change as a result of normalization, or</p>
1265: </item>
1266: <item>
1267: <p>element types with <termref def="dt-elemcontent">element content</termref>,
1268: if white space occurs
1269: directly within any instance of those types.
1270: </p></item>
1271: </ulist>
1272:
1273: </vcnote>
1274: <p>An example XML declaration with a standalone document declaration:<eg><?xml version="&XML.version;" standalone='yes'?></eg></p>
1275: </div2>
1276: <div2 id="sec-white-space">
1277: <head>White Space Handling</head>
1278:
1279: <p>In editing XML documents, it is often convenient to use "white space"
1280: (spaces, tabs, and blank lines, denoted by the nonterminal
1281: <nt def="NT-S">S</nt> in this specification) to
1282: set apart the markup for greater readability. Such white space is typically
1283: not intended for inclusion in the delivered version of the document.
1284: On the other hand, "significant" white space that should be preserved in the
1285: delivered version is common, for example in poetry and
1286: source code.</p>
1287: <p>An <termref def="dt-xml-proc">XML processor</termref>
1288: must always pass all characters in a document that are not
1289: markup through to the application. A <termref def="dt-validating">
1290: validating XML processor</termref> must also inform the application
1291: which of these characters constitute white space appearing
1292: in <termref def="dt-elemcontent">element content</termref>.
1293: </p>
1294: <p>A special <termref def="dt-attr">attribute</termref>
1295: named <kw>xml:space</kw> may be attached to an element
1296: to signal an intention that in that element,
1297: white space should be preserved by applications.
1298: In valid documents, this attribute, like any other, must be
1299: <termref def="dt-attdecl">declared</termref> if it is used.
1300: When declared, it must be given as an
1301: <termref def="dt-enumerated">enumerated type</termref> whose only
1302: possible values are "<code>default</code>" and "<code>preserve</code>".
1303: For example:<eg><![CDATA[ <!ATTLIST poem xml:space (default|preserve) 'preserve'>]]></eg></p>
1304: <p>The value "<code>default</code>" signals that applications'
1305: default white-space processing modes are acceptable for this element; the
1306: value "<code>preserve</code>" indicates the intent that applications preserve
1307: all the white space.
1308: This declared intent is considered to apply to all elements within the content
1309: of the element where it is specified, unless overriden with another instance
1310: of the <kw>xml:space</kw> attribute.
1311: </p>
1312: <p>The <termref def="dt-root">root element</termref> of any document
1313: is considered to have signaled no intentions as regards application space
1314: handling, unless it provides a value for
1315: this attribute or the attribute is declared with a default value.
1316: </p>
1317:
1318: </div2>
1319: <div2 id="sec-line-ends">
1320: <head>End-of-Line Handling</head>
1321: <p>XML <termref def="dt-parsedent">parsed entities</termref> are often stored in
1322: computer files which, for editing convenience, are organized into lines.
1323: These lines are typically separated by some combination of the characters
1324: carriage-return (#xD) and line-feed (#xA).</p>
1325: <p>To simplify the tasks of <termref def="dt-app">applications</termref>,
1326: wherever an external parsed entity or the literal entity value
1327: of an internal parsed entity contains either the literal
1328: two-character sequence "#xD#xA" or a standalone literal
1329: #xD, an <termref def="dt-xml-proc">XML processor</termref> must
1330: pass to the application the single character #xA.
1331: (This behavior can
1332: conveniently be produced by normalizing all
1333: line breaks to #xA on input, before parsing.)
1334: </p>
1335: </div2>
1336: <div2 id="sec-lang-tag">
1337: <head>Language Identification</head>
1338: <p>In document processing, it is often useful to
1339: identify the natural or formal language
1340: in which the content is
1341: written.
1342: A special <termref def="dt-attr">attribute</termref> named
1343: <kw>xml:lang</kw> may be inserted in
1344: documents to specify the
1345: language used in the contents and attribute values
1346: of any element in an XML document.
1347: In valid documents, this attribute, like any other, must be
1348: <termref def="dt-attdecl">declared</termref> if it is used.
1349: The values of the attribute are language identifiers as defined
1350: by <bibref ref="RFC1766"/>, "Tags for the Identification of Languages":
1351: <scrap lang="ebnf">
1352: <head>Language Identification</head>
1353: <prod id="NT-LanguageID"><lhs>LanguageID</lhs>
1354: <rhs><nt def="NT-Langcode">Langcode</nt>
1355: ('-' <nt def="NT-Subcode">Subcode</nt>)*</rhs></prod>
1356: <prod id="NT-Langcode"><lhs>Langcode</lhs>
1357: <rhs><nt def="NT-ISO639Code">ISO639Code</nt> |
1358: <nt def="NT-IanaCode">IanaCode</nt> |
1359: <nt def="NT-UserCode">UserCode</nt></rhs>
1360: </prod>
1361: <prod id="NT-ISO639Code"><lhs>ISO639Code</lhs>
1362: <rhs>([a-z] | [A-Z]) ([a-z] | [A-Z])</rhs></prod>
1363: <prod id="NT-IanaCode"><lhs>IanaCode</lhs>
1364: <rhs>('i' | 'I') '-' ([a-z] | [A-Z])+</rhs></prod>
1365: <prod id="NT-UserCode"><lhs>UserCode</lhs>
1366: <rhs>('x' | 'X') '-' ([a-z] | [A-Z])+</rhs></prod>
1367: <prod id="NT-Subcode"><lhs>Subcode</lhs>
1368: <rhs>([a-z] | [A-Z])+</rhs></prod>
1369: </scrap>
1370: The <nt def="NT-Langcode">Langcode</nt> may be any of the following:
1371: <ulist>
1372: <item><p>a two-letter language code as defined by
1373: <bibref ref="ISO639"/>, "Codes
1374: for the representation of names of languages"</p></item>
1375: <item><p>a language identifier registered with the Internet
1376: Assigned Numbers Authority <bibref ref="IANA"/>; these begin with the
1377: prefix "<code>i-</code>" (or "<code>I-</code>")</p></item>
1378: <item><p>a language identifier assigned by the user, or agreed on
1379: between parties in private use; these must begin with the
1380: prefix "<code>x-</code>" or "<code>X-</code>" in order to ensure that they do not conflict
1381: with names later standardized or registered with IANA</p></item>
1382: </ulist></p>
1383: <p>There may be any number of <nt def="NT-Subcode">Subcode</nt> segments; if
1384: the first
1385: subcode segment exists and the Subcode consists of two
1386: letters, then it must be a country code from
1387: <bibref ref="ISO3166"/>, "Codes
1388: for the representation of names of countries."
1389: If the first
1390: subcode consists of more than two letters, it must be
1391: a subcode for the language in question registered with IANA,
1392: unless the <nt def="NT-Langcode">Langcode</nt> begins with the prefix
1393: "<code>x-</code>" or
1394: "<code>X-</code>". </p>
1395: <p>It is customary to give the language code in lower case, and
1396: the country code (if any) in upper case.
1397: Note that these values, unlike other names in XML documents,
1398: are case insensitive.</p>
1399: <p>For example:
1400: <eg><![CDATA[<p xml:lang="en">The quick brown fox jumps over the lazy dog.</p>
1401: <p xml:lang="en-GB">What colour is it?</p>
1402: <p xml:lang="en-US">What color is it?</p>
1403: <sp who="Faust" desc='leise' xml:lang="de">
1404: <l>Habe nun, ach! Philosophie,</l>
1405: <l>Juristerei, und Medizin</l>
1406: <l>und leider auch Theologie</l>
1407: <l>durchaus studiert mit heißem Bemüh'n.</l>
1408: </sp>]]></eg></p>
1409: <!--<p>The xml:lang value is considered to apply both to the contents of an
1410: element and
1411: (unless otherwise via attribute default values) to the
1412: values of all of its attributes with free-text (CDATA) values. -->
1413: <p>The intent declared with <kw>xml:lang</kw> is considered to apply to
1414: all attributes and content of the element where it is specified,
1415: unless overridden with an instance of <kw>xml:lang</kw>
1416: on another element within that content.</p>
1417: <!--
1418: If no
1419: value is specified for xml:lang on an element, and no default value is
1420: defined for it in the DTD, then the xml:lang attribute of any element
1421: takes the same value it has in the parent element, if any. The two
1422: technical terms in the following example both have the same effective
1423: value for xml:lang:
1424:
1425: <p xml:lang="en">Here the keywords are
1426: <term xml:lang="en">shift</term> and
1427: <term>reduce</term>. ...</p>
1428:
1429: The application, not the XML processor, is responsible for this '
1430: inheritance' of attribute values.
1431: -->
1432: <p>A simple declaration for <kw>xml:lang</kw> might take
1433: the form
1434: <eg>xml:lang NMTOKEN #IMPLIED</eg>
1435: but specific default values may also be given, if appropriate. In a
1436: collection of French poems for English students, with glosses and
1437: notes in English, the xml:lang attribute might be declared this way:
1438: <eg><![CDATA[ <!ATTLIST poem xml:lang NMTOKEN 'fr'>
1439: <!ATTLIST gloss xml:lang NMTOKEN 'en'>
1440: <!ATTLIST note xml:lang NMTOKEN 'en'>]]></eg>
1441: </p>
1442:
1443: </div2>
1444: </div1>
1445: <!-- &Elements; -->
1446:
1447: <div1 id="sec-logical-struct">
1448: <head>Logical Structures</head>
1449:
1450: <p><termdef id="dt-element" term="Element">Each <termref def="dt-xml-doc">XML document</termref> contains one or more
1451: <term>elements</term>, the boundaries of which are
1452: either delimited by <termref def="dt-stag">start-tags</termref>
1453: and <termref def="dt-etag">end-tags</termref>, or, for <termref def="dt-empty">empty</termref> elements, by an <termref def="dt-eetag">empty-element tag</termref>. Each element has a type,
1454: identified by name, sometimes called its "generic
1455: identifier" (GI), and may have a set of
1456: attribute specifications.</termdef> Each attribute specification
1457: has a <termref def="dt-attrname">name</termref> and a <termref def="dt-attrval">value</termref>.
1458: </p>
1459: <scrap lang="ebnf"><head>Element</head>
1460: <prod id="NT-element"><lhs>element</lhs>
1461: <rhs><nt def="NT-EmptyElemTag">EmptyElemTag</nt></rhs>
1462: <rhs>| <nt def="NT-STag">STag</nt> <nt def="NT-content">content</nt>
1463: <nt def="NT-ETag">ETag</nt></rhs>
1464: <wfc def="GIMatch"/>
1465: <vc def="elementvalid"/>
1466: </prod>
1467: </scrap>
1468: <p>This specification does not constrain the semantics, use, or (beyond
1469: syntax) names of the element types and attributes, except that names
1470: beginning with a match to <code>(('X'|'x')('M'|'m')('L'|'l'))</code>
1471: are reserved for standardization in this or future versions of this
1472: specification.
1473: </p>
1474: <wfcnote id="GIMatch">
1475: <head>Element Type Match</head>
1476: <p>
1477: The <nt def="NT-Name">Name</nt> in an element's end-tag must match
1478: the element type in
1479: the start-tag.
1480: </p>
1481: </wfcnote>
1482: <vcnote id="elementvalid">
1483: <head>Element Valid</head>
1484: <p>An element is
1485: valid if
1486: there is a declaration matching
1487: <nt def="NT-elementdecl">elementdecl</nt> where the
1488: <nt def="NT-Name">Name</nt> matches the element type, and
1489: one of the following holds:</p>
1490: <olist>
1491: <item><p>The declaration matches <kw>EMPTY</kw> and the element has no
1492: <termref def="dt-content">content</termref>.</p></item>
1493: <item><p>The declaration matches <nt def="NT-children">children</nt> and
1494: the sequence of
1495: <termref def="dt-parentchild">child elements</termref>
1496: belongs to the language generated by the regular expression in
1497: the content model, with optional white space (characters
1498: matching the nonterminal <nt def="NT-S">S</nt>) between each pair
1499: of child elements.</p></item>
1500: <item><p>The declaration matches <nt def="NT-Mixed">Mixed</nt> and
1501: the content consists of <termref def="dt-chardata">character
1502: data</termref> and <termref def="dt-parentchild">child elements</termref>
1503: whose types match names in the content model.</p></item>
1504: <item><p>The declaration matches <kw>ANY</kw>, and the types
1505: of any <termref def="dt-parentchild">child elements</termref> have
1506: been declared.</p></item>
1507: </olist>
1508: </vcnote>
1509:
1510: <div2 id="sec-starttags">
1511: <head>Start-Tags, End-Tags, and Empty-Element Tags</head>
1512:
1513: <p><termdef id="dt-stag" term="Start-Tag">The beginning of every
1514: non-empty XML element is marked by a <term>start-tag</term>.
1515: <scrap lang="ebnf">
1516: <head>Start-tag</head>
1517: <prodgroup pcw2="6" pcw4="15" pcw5="11.5">
1518: <prod id="NT-STag"><lhs>STag</lhs>
1519: <rhs>'<' <nt def="NT-Name">Name</nt>
1520: (<nt def="NT-S">S</nt> <nt def="NT-Attribute">Attribute</nt>)*
1521: <nt def="NT-S">S</nt>? '>'</rhs>
1522: <wfc def="uniqattspec"/>
1523: </prod>
1524: <prod id="NT-Attribute"><lhs>Attribute</lhs>
1525: <rhs><nt def="NT-Name">Name</nt> <nt def="NT-Eq">Eq</nt>
1526: <nt def="NT-AttValue">AttValue</nt></rhs>
1527: <vc def="ValueType"/>
1528: <wfc def="NoExternalRefs"/>
1529: <wfc def="CleanAttrVals"/></prod>
1530: </prodgroup>
1531: </scrap>
1532: The <nt def="NT-Name">Name</nt> in
1533: the start- and end-tags gives the
1534: element's <term>type</term>.</termdef>
1535: <termdef id="dt-attr" term="Attribute">
1536: The <nt def="NT-Name">Name</nt>-<nt def="NT-AttValue">AttValue</nt> pairs are
1537: referred to as
1538: the <term>attribute specifications</term> of the element</termdef>,
1539: <termdef id="dt-attrname" term="Attribute Name">with the
1540: <nt def="NT-Name">Name</nt> in each pair
1541: referred to as the <term>attribute name</term></termdef> and
1542: <termdef id="dt-attrval" term="Attribute Value">the content of the
1543: <nt def="NT-AttValue">AttValue</nt> (the text between the
1544: <code>'</code> or <code>"</code> delimiters)
1545: as the <term>attribute value</term>.</termdef>
1546: </p>
1547: <wfcnote id="uniqattspec">
1548: <head>Unique Att Spec</head>
1549: <p>
1550: No attribute name may appear more than once in the same start-tag
1551: or empty-element tag.
1552: </p>
1553: </wfcnote>
1554: <vcnote id="ValueType">
1555: <head>Attribute Value Type</head>
1556: <p>
1557: The attribute must have been declared; the value must be of the type
1558: declared for it.
1559: (For attribute types, see <specref ref="attdecls"/>.)
1560: </p>
1561: </vcnote>
1562: <wfcnote id="NoExternalRefs">
1563: <head>No External Entity References</head>
1564: <p>
1565: Attribute values cannot contain direct or indirect entity references
1566: to external entities.
1567: </p>
1568: </wfcnote>
1569: <wfcnote id="CleanAttrVals">
1570: <head>No <code><</code> in Attribute Values</head>
1571: <p>The <termref def="dt-repltext">replacement text</termref> of any entity
1572: referred to directly or indirectly in an attribute
1573: value (other than "<code>&lt;</code>") must not contain
1574: a <code><</code>.
1575: </p></wfcnote>
1576: <p>An example of a start-tag:
1577: <eg><termdef id="dt-dog" term="dog"></eg></p>
1578: <p><termdef id="dt-etag" term="End Tag">The end of every element
1579: that begins with a start-tag must
1580: be marked by an <term>end-tag</term>
1581: containing a name that echoes the element's type as given in the
1582: start-tag:
1583: <scrap lang="ebnf">
1584: <head>End-tag</head>
1585: <prodgroup pcw2="6" pcw4="15" pcw5="11.5">
1586: <prod id="NT-ETag"><lhs>ETag</lhs>
1587: <rhs>'</' <nt def="NT-Name">Name</nt>
1588: <nt def="NT-S">S</nt>? '>'</rhs></prod>
1589: </prodgroup>
1590: </scrap>
1591: </termdef></p>
1592: <p>An example of an end-tag:<eg></termdef></eg></p>
1593: <p><termdef id="dt-content" term="Content">The
1594: <termref def="dt-text">text</termref> between the start-tag and
1595: end-tag is called the element's
1596: <term>content</term>:
1597: <scrap lang="ebnf">
1598: <head>Content of Elements</head>
1599: <prodgroup pcw2="6" pcw4="15" pcw5="11.5">
1600: <prod id="NT-content"><lhs>content</lhs>
1601: <rhs>(<nt def="NT-element">element</nt> | <nt def="NT-CharData">CharData</nt>
1602: | <nt def="NT-Reference">Reference</nt> | <nt def="NT-CDSect">CDSect</nt>
1603: | <nt def="NT-PI">PI</nt> | <nt def="NT-Comment">Comment</nt>)*</rhs>
1604: </prod>
1605: </prodgroup>
1606: </scrap>
1607: </termdef></p>
1608: <p><termdef id="dt-empty" term="Empty">If an element is <term>empty</term>,
1609: it must be represented either by a start-tag immediately followed
1610: by an end-tag or by an empty-element tag.</termdef>
1611: <termdef id="dt-eetag" term="empty-element tag">An
1612: <term>empty-element tag</term> takes a special form:
1613: <scrap lang="ebnf">
1614: <head>Tags for Empty Elements</head>
1615: <prodgroup pcw2="6" pcw4="15" pcw5="11.5">
1616: <prod id="NT-EmptyElemTag"><lhs>EmptyElemTag</lhs>
1617: <rhs>'<' <nt def="NT-Name">Name</nt> (<nt def="NT-S">S</nt>
1618: <nt def="NT-Attribute">Attribute</nt>)* <nt def="NT-S">S</nt>?
1619: '/>'</rhs>
1620: <wfc def="uniqattspec"/>
1621: </prod>
1622: </prodgroup>
1623: </scrap>
1624: </termdef></p>
1625: <p>Empty-element tags may be used for any element which has no
1626: content, whether or not it is declared using the keyword
1627: <kw>EMPTY</kw>.
1628: <termref def="dt-interop">For interoperability</termref>, the empty-element
1629: tag must be used, and can only be used, for elements which are
1630: <termref def="dt-eldecl">declared</termref> <kw>EMPTY</kw>.</p>
1631: <p>Examples of empty elements:
1632: <eg><IMG align="left"
1633: src="http://www.w3.org/Icons/WWW/w3c_home" />
1634: <br></br>
1635: <br/></eg></p>
1636: </div2>
1637:
1638: <div2 id="elemdecls">
1639: <head>Element Type Declarations</head>
1640:
1641: <p>The <termref def="dt-element">element</termref> structure of an
1642: <termref def="dt-xml-doc">XML document</termref> may, for
1643: <termref def="dt-valid">validation</termref> purposes,
1644: be constrained
1645: using element type and attribute-list declarations.
1646: An element type declaration constrains the element's
1647: <termref def="dt-content">content</termref>.
1648: </p>
1649:
1650: <p>Element type declarations often constrain which element types can
1651: appear as <termref def="dt-parentchild">children</termref> of the element.
1652: At user option, an XML processor may issue a warning
1653: when a declaration mentions an element type for which no declaration
1654: is provided, but this is not an error.</p>
1655: <p><termdef id="dt-eldecl" term="Element Type declaration">An <term>element
1656: type declaration</term> takes the form:
1657: <scrap lang="ebnf">
1658: <head>Element Type Declaration</head>
1659: <prodgroup pcw2="5.5" pcw4="18" pcw5="9">
1660: <prod id="NT-elementdecl"><lhs>elementdecl</lhs>
1661: <rhs>'<!ELEMENT' <nt def="NT-S">S</nt>
1662: <nt def="NT-Name">Name</nt>
1663: <nt def="NT-S">S</nt>
1664: <nt def="NT-contentspec">contentspec</nt>
1665: <nt def="NT-S">S</nt>? '>'</rhs>
1666: <vc def="EDUnique"/></prod>
1667: <prod id="NT-contentspec"><lhs>contentspec</lhs>
1668: <rhs>'EMPTY'
1669: | 'ANY'
1670: | <nt def="NT-Mixed">Mixed</nt>
1671: | <nt def="NT-children">children</nt>
1672: </rhs>
1673: </prod>
1674: </prodgroup>
1675: </scrap>
1676: where the <nt def="NT-Name">Name</nt> gives the element type
1677: being declared.</termdef>
1678: </p>
1679:
1680: <vcnote id="EDUnique">
1681: <head>Unique Element Type Declaration</head>
1682: <p>
1683: No element type may be declared more than once.
1684: </p>
1685: </vcnote>
1686:
1687: <p>Examples of element type declarations:
1688: <eg><!ELEMENT br EMPTY>
1689: <!ELEMENT p (#PCDATA|emph)* >
1690: <!ELEMENT %name.para; %content.para; >
1691: <!ELEMENT container ANY></eg></p>
1692:
1693: <div3 id="sec-element-content">
1694: <head>Element Content</head>
1695:
1696: <p><termdef id="dt-elemcontent" term="Element content">An element <termref def="dt-stag">type</termref> has
1697: <term>element content</term> when elements of that
1698: type must contain only <termref def="dt-parentchild">child</termref>
1699: elements (no character data), optionally separated by
1700: white space (characters matching the nonterminal
1701: <nt def="NT-S">S</nt>).
1702: </termdef>
1703: In this case, the
1704: constraint includes a content model, a simple grammar governing
1705: the allowed types of the child
1706: elements and the order in which they are allowed to appear.
1707: The grammar is built on
1708: content particles (<nt def="NT-cp">cp</nt>s), which consist of names,
1709: choice lists of content particles, or
1710: sequence lists of content particles:
1711: <scrap lang="ebnf">
1712: <head>Element-content Models</head>
1713: <prodgroup pcw2="5.5" pcw4="16" pcw5="11">
1714: <prod id="NT-children"><lhs>children</lhs>
1715: <rhs>(<nt def="NT-choice">choice</nt>
1716: | <nt def="NT-seq">seq</nt>)
1717: ('?' | '*' | '+')?</rhs></prod>
1718: <prod id="NT-cp"><lhs>cp</lhs>
1719: <rhs>(<nt def="NT-Name">Name</nt>
1720: | <nt def="NT-choice">choice</nt>
1721: | <nt def="NT-seq">seq</nt>)
1722: ('?' | '*' | '+')?</rhs></prod>
1723: <prod id="NT-choice"><lhs>choice</lhs>
1724: <rhs>'(' <nt def="NT-S">S</nt>? cp
1725: ( <nt def="NT-S">S</nt>? '|' <nt def="NT-S">S</nt>? <nt def="NT-cp">cp</nt> )*
1726: <nt def="NT-S">S</nt>? ')'</rhs>
1727: <vc def="vc-PEinGroup"/></prod>
1728: <prod id="NT-seq"><lhs>seq</lhs>
1729: <rhs>'(' <nt def="NT-S">S</nt>? cp
1730: ( <nt def="NT-S">S</nt>? ',' <nt def="NT-S">S</nt>? <nt def="NT-cp">cp</nt> )*
1731: <nt def="NT-S">S</nt>? ')'</rhs>
1732: <vc def="vc-PEinGroup"/></prod>
1733:
1734: </prodgroup>
1735: </scrap>
1736: where each <nt def="NT-Name">Name</nt> is the type of an element which may
1737: appear as a <termref def="dt-parentchild">child</termref>.
1738: Any content
1739: particle in a choice list may appear in the <termref def="dt-elemcontent">element content</termref> at the location where
1740: the choice list appears in the grammar;
1741: content particles occurring in a sequence list must each
1742: appear in the <termref def="dt-elemcontent">element content</termref> in the
1743: order given in the list.
1744: The optional character following a name or list governs
1745: whether the element or the content particles in the list may occur one
1746: or more (<code>+</code>), zero or more (<code>*</code>), or zero or
1747: one times (<code>?</code>).
1748: The absence of such an operator means that the element or content particle
1749: must appear exactly once.
1750: This syntax
1751: and meaning are identical to those used in the productions in this
1752: specification.</p>
1753: <p>
1754: The content of an element matches a content model if and only if it is
1755: possible to trace out a path through the content model, obeying the
1756: sequence, choice, and repetition operators and matching each element in
1757: the content against an element type in the content model. <termref def="dt-compat">For compatibility</termref>, it is an error
1758: if an element in the document can
1759: match more than one occurrence of an element type in the content model.
1760: For more information, see <specref ref="determinism"/>.
1761: <!-- appendix <specref ref="determinism"/>. -->
1762: <!-- appendix on deterministic content models. -->
1763: </p>
1764: <vcnote id="vc-PEinGroup">
1765: <head>Proper Group/PE Nesting</head>
1766: <p>Parameter-entity
1767: <termref def="dt-repltext">replacement text</termref> must be properly nested
1768: with parenthetized groups.
1769: That is to say, if either of the opening or closing parentheses
1770: in a <nt def="NT-choice">choice</nt>, <nt def="NT-seq">seq</nt>, or
1771: <nt def="NT-Mixed">Mixed</nt> construct
1772: is contained in the replacement text for a
1773: <termref def="dt-PERef">parameter entity</termref>,
1774: both must be contained in the same replacement text.</p>
1775: <p><termref def="dt-interop">For interoperability</termref>,
1776: if a parameter-entity reference appears in a
1777: <nt def="NT-choice">choice</nt>, <nt def="NT-seq">seq</nt>, or
1778: <nt def="NT-Mixed">Mixed</nt> construct, its replacement text
1779: should not be empty, and
1780: neither the first nor last non-blank
1781: character of the replacement text should be a connector
1782: (<code>|</code> or <code>,</code>).
1783: </p>
1784: </vcnote>
1785: <p>Examples of element-content models:
1786: <eg><!ELEMENT spec (front, body, back?)>
1787: <!ELEMENT div1 (head, (p | list | note)*, div2*)>
1788: <!ELEMENT dictionary-body (%div.mix; | %dict.mix;)*></eg></p>
1789: </div3>
1790:
1791: <div3 id="sec-mixed-content">
1792: <head>Mixed Content</head>
1793:
1794: <p><termdef id="dt-mixed" term="Mixed Content">An element
1795: <termref def="dt-stag">type</termref> has
1796: <term>mixed content</term> when elements of that type may contain
1797: character data, optionally interspersed with
1798: <termref def="dt-parentchild">child</termref> elements.</termdef>
1799: In this case, the types of the child elements
1800: may be constrained, but not their order or their number of occurrences:
1801: <scrap lang="ebnf">
1802: <head>Mixed-content Declaration</head>
1803: <prodgroup pcw2="5.5" pcw4="16" pcw5="11">
1804: <prod id="NT-Mixed"><lhs>Mixed</lhs>
1805: <rhs>'(' <nt def="NT-S">S</nt>?
1806: '#PCDATA'
1807: (<nt def="NT-S">S</nt>?
1808: '|'
1809: <nt def="NT-S">S</nt>?
1810: <nt def="NT-Name">Name</nt>)*
1811: <nt def="NT-S">S</nt>?
1812: ')*' </rhs>
1813: <rhs>| '(' <nt def="NT-S">S</nt>? '#PCDATA' <nt def="NT-S">S</nt>? ')'
1814: </rhs><vc def="vc-PEinGroup"/>
1815: <vc def="vc-MixedChildrenUnique"/>
1816: </prod>
1817:
1818: </prodgroup>
1819: </scrap>
1820: where the <nt def="NT-Name">Name</nt>s give the types of elements
1821: that may appear as children.
1822: </p>
1823: <vcnote id="vc-MixedChildrenUnique">
1824: <head>No Duplicate Types</head>
1825: <p>The same name must not appear more than once in a single mixed-content
1826: declaration.
1827: </p></vcnote>
1828: <p>Examples of mixed content declarations:
1829: <eg><!ELEMENT p (#PCDATA|a|ul|b|i|em)*>
1830: <!ELEMENT p (#PCDATA | %font; | %phrase; | %special; | %form;)* >
1831: <!ELEMENT b (#PCDATA)></eg></p>
1832: </div3>
1833: </div2>
1834:
1835: <div2 id="attdecls">
1836: <head>Attribute-List Declarations</head>
1837:
1838: <p><termref def="dt-attr">Attributes</termref> are used to associate
1839: name-value pairs with <termref def="dt-element">elements</termref>.
1840: Attribute specifications may appear only within <termref def="dt-stag">start-tags</termref>
1841: and <termref def="dt-eetag">empty-element tags</termref>;
1842: thus, the productions used to
1843: recognize them appear in <specref ref="sec-starttags"/>.
1844: Attribute-list
1845: declarations may be used:
1846: <ulist>
1847: <item><p>To define the set of attributes pertaining to a given
1848: element type.</p></item>
1849: <item><p>To establish type constraints for these
1850: attributes.</p></item>
1851: <item><p>To provide <termref def="dt-default">default values</termref>
1852: for attributes.</p></item>
1853: </ulist>
1854: </p>
1855: <p><termdef id="dt-attdecl" term="Attribute-List Declaration">
1856: <term>Attribute-list declarations</term> specify the name, data type, and default
1857: value (if any) of each attribute associated with a given element type:
1858: <scrap lang="ebnf">
1859: <head>Attribute-list Declaration</head>
1860: <prod id="NT-AttlistDecl"><lhs>AttlistDecl</lhs>
1861: <rhs>'<!ATTLIST' <nt def="NT-S">S</nt>
1862: <nt def="NT-Name">Name</nt>
1863: <nt def="NT-AttDef">AttDef</nt>*
1864: <nt def="NT-S">S</nt>? '>'</rhs>
1865: </prod>
1866: <prod id="NT-AttDef"><lhs>AttDef</lhs>
1867: <rhs><nt def="NT-S">S</nt> <nt def="NT-Name">Name</nt>
1868: <nt def="NT-S">S</nt> <nt def="NT-AttType">AttType</nt>
1869: <nt def="NT-S">S</nt> <nt def="NT-DefaultDecl">DefaultDecl</nt></rhs>
1870: </prod>
1871: </scrap>
1872: The <nt def="NT-Name">Name</nt> in the
1873: <nt def="NT-AttlistDecl">AttlistDecl</nt> rule is the type of an element. At
1874: user option, an XML processor may issue a warning if attributes are
1875: declared for an element type not itself declared, but this is not an
1876: error. The <nt def="NT-Name">Name</nt> in the
1877: <nt def="NT-AttDef">AttDef</nt> rule is
1878: the name of the attribute.</termdef></p>
1879: <p>
1880: When more than one <nt def="NT-AttlistDecl">AttlistDecl</nt> is provided for a
1881: given element type, the contents of all those provided are merged. When
1882: more than one definition is provided for the same attribute of a
1883: given element type, the first declaration is binding and later
1884: declarations are ignored.
1885: <termref def="dt-interop">For interoperability,</termref> writers of DTDs
1886: may choose to provide at most one attribute-list declaration
1887: for a given element type, at most one attribute definition
1888: for a given attribute name, and at least one attribute definition
1889: in each attribute-list declaration.
1890: For interoperability, an XML processor may at user option
1891: issue a warning when more than one attribute-list declaration is
1892: provided for a given element type, or more than one attribute definition
1893: is provided
1894: for a given attribute, but this is not an error.
1895: </p>
1896:
1897: <div3 id="sec-attribute-types">
1898: <head>Attribute Types</head>
1899:
1900: <p>XML attribute types are of three kinds: a string type, a
1901: set of tokenized types, and enumerated types. The string type may take
1902: any literal string as a value; the tokenized types have varying lexical
1903: and semantic constraints, as noted:
1904: <scrap lang="ebnf">
1905: <head>Attribute Types</head>
1906: <prodgroup pcw4="14" pcw5="11.5">
1907: <prod id="NT-AttType"><lhs>AttType</lhs>
1908: <rhs><nt def="NT-StringType">StringType</nt>
1909: | <nt def="NT-TokenizedType">TokenizedType</nt>
1910: | <nt def="NT-EnumeratedType">EnumeratedType</nt>
1911: </rhs>
1912: </prod>
1913: <prod id="NT-StringType"><lhs>StringType</lhs>
1914: <rhs>'CDATA'</rhs>
1915: </prod>
1916: <prod id="NT-TokenizedType"><lhs>TokenizedType</lhs>
1917: <rhs>'ID'</rhs>
1918: <vc def="id"/>
1919: <vc def="one-id-per-el"/>
1920: <vc def="id-default"/>
1921: <rhs>| 'IDREF'</rhs>
1922: <vc def="idref"/>
1923: <rhs>| 'IDREFS'</rhs>
1924: <vc def="idref"/>
1925: <rhs>| 'ENTITY'</rhs>
1926: <vc def="entname"/>
1927: <rhs>| 'ENTITIES'</rhs>
1928: <vc def="entname"/>
1929: <rhs>| 'NMTOKEN'</rhs>
1930: <vc def="nmtok"/>
1931: <rhs>| 'NMTOKENS'</rhs>
1932: <vc def="nmtok"/></prod>
1933: </prodgroup>
1934: </scrap>
1935: </p>
1936: <vcnote id="id">
1937: <head>ID</head>
1938: <p>
1939: Values of type <kw>ID</kw> must match the
1940: <nt def="NT-Name">Name</nt> production.
1941: A name must not appear more than once in
1942: an XML document as a value of this type; i.e., ID values must uniquely
1943: identify the elements which bear them.
1944: </p>
1945: </vcnote>
1946: <vcnote id="one-id-per-el">
1947: <head>One ID per Element Type</head>
1948: <p>No element type may have more than one ID attribute specified.</p>
1949: </vcnote>
1950: <vcnote id="id-default">
1951: <head>ID Attribute Default</head>
1952: <p>An ID attribute must have a declared default of <kw>#IMPLIED</kw> or
1953: <kw>#REQUIRED</kw>.</p>
1954: </vcnote>
1955: <vcnote id="idref">
1956: <head>IDREF</head>
1957: <p>
1958: Values of type <kw>IDREF</kw> must match
1959: the <nt def="NT-Name">Name</nt> production, and
1960: values of type <kw>IDREFS</kw> must match
1961: <nt def="NT-Names">Names</nt>;
1962: each <nt def="NT-Name">Name</nt> must match the value of an ID attribute on
1963: some element in the XML document; i.e. <kw>IDREF</kw> values must
1964: match the value of some ID attribute.
1965: </p>
1966: </vcnote>
1967: <vcnote id="entname">
1968: <head>Entity Name</head>
1969: <p>
1970: Values of type <kw>ENTITY</kw>
1971: must match the <nt def="NT-Name">Name</nt> production,
1972: values of type <kw>ENTITIES</kw> must match
1973: <nt def="NT-Names">Names</nt>;
1974: each <nt def="NT-Name">Name</nt> must
1975: match the
1976: name of an <termref def="dt-unparsed">unparsed entity</termref> declared in the
1977: <termref def="dt-doctype">DTD</termref>.
1978: </p>
1979: </vcnote>
1980: <vcnote id="nmtok">
1981: <head>Name Token</head>
1982: <p>
1983: Values of type <kw>NMTOKEN</kw> must match the
1984: <nt def="NT-Nmtoken">Nmtoken</nt> production;
1985: values of type <kw>NMTOKENS</kw> must
1986: match <termref def="NT-Nmtokens">Nmtokens</termref>.
1987: </p>
1988: </vcnote>
1989: <!-- why?
1990: <p>The XML processor must normalize attribute values before
1991: passing them to the application, as described in
1992: <specref ref="AVNormalize"/>.</p>-->
1993: <p><termdef id="dt-enumerated" term="Enumerated Attribute Values"><term>Enumerated attributes</term> can take one
1994: of a list of values provided in the declaration</termdef>. There are two
1995: kinds of enumerated types:
1996: <scrap lang="ebnf">
1997: <head>Enumerated Attribute Types</head>
1998: <prod id="NT-EnumeratedType"><lhs>EnumeratedType</lhs>
1999: <rhs><nt def="NT-NotationType">NotationType</nt>
2000: | <nt def="NT-Enumeration">Enumeration</nt>
2001: </rhs></prod>
2002: <prod id="NT-NotationType"><lhs>NotationType</lhs>
2003: <rhs>'NOTATION'
2004: <nt def="NT-S">S</nt>
2005: '('
2006: <nt def="NT-S">S</nt>?
2007: <nt def="NT-Name">Name</nt>
2008: (<nt def="NT-S">S</nt>? '|' <nt def="NT-S">S</nt>?
2009: <nt def="NT-Name">Name</nt>)*
2010: <nt def="NT-S">S</nt>? ')'
2011: </rhs>
2012: <vc def="notatn"/></prod>
2013: <prod id="NT-Enumeration"><lhs>Enumeration</lhs>
2014: <rhs>'(' <nt def="NT-S">S</nt>?
2015: <nt def="NT-Nmtoken">Nmtoken</nt>
2016: (<nt def="NT-S">S</nt>? '|'
2017: <nt def="NT-S">S</nt>?
2018: <nt def="NT-Nmtoken">Nmtoken</nt>)*
2019: <nt def="NT-S">S</nt>?
2020: ')'</rhs>
2021: <vc def="enum"/></prod>
2022: </scrap>
2023: A <kw>NOTATION</kw> attribute identifies a
2024: <termref def="dt-notation">notation</termref>, declared in the
2025: DTD with associated system and/or public identifiers, to
2026: be used in interpreting the element to which the attribute
2027: is attached.
2028: </p>
2029:
2030: <vcnote id="notatn">
2031: <head>Notation Attributes</head>
2032: <p>
2033: Values of this type must match
2034: one of the <titleref href="Notations">notation</titleref> names included in
2035: the declaration; all notation names in the declaration must
2036: be declared.
2037: </p>
2038: </vcnote>
2039: <vcnote id="enum">
2040: <head>Enumeration</head>
2041: <p>
2042: Values of this type
2043: must match one of the <nt def="NT-Nmtoken">Nmtoken</nt> tokens in the
2044: declaration.
2045: </p>
2046: </vcnote>
2047: <p><termref def="dt-interop">For interoperability,</termref> the same
2048: <nt def="NT-Nmtoken">Nmtoken</nt> should not occur more than once in the
2049: enumerated attribute types of a single element type.
2050: </p>
2051: </div3>
2052:
2053: <div3 id="sec-attr-defaults">
2054: <head>Attribute Defaults</head>
2055:
2056: <p>An <termref def="dt-attdecl">attribute declaration</termref> provides
2057: information on whether
2058: the attribute's presence is required, and if not, how an XML processor should
2059: react if a declared attribute is absent in a document.
2060: <scrap lang="ebnf">
2061: <head>Attribute Defaults</head>
2062: <prodgroup pcw4="14" pcw5="11.5">
2063: <prod id="NT-DefaultDecl"><lhs>DefaultDecl</lhs>
2064: <rhs>'#REQUIRED'
2065: | '#IMPLIED' </rhs>
2066: <rhs>| (('#FIXED' S)? <nt def="NT-AttValue">AttValue</nt>)</rhs>
2067: <vc def="RequiredAttr"/>
2068: <vc def="defattrvalid"/>
2069: <wfc def="CleanAttrVals"/>
2070: <vc def="FixedAttr"/>
2071: </prod>
2072: </prodgroup>
2073: </scrap>
2074:
2075: </p>
2076: <p>In an attribute declaration, <kw>#REQUIRED</kw> means that the
2077: attribute must always be provided, <kw>#IMPLIED</kw> that no default
2078: value is provided.
2079: <!-- not any more!!
2080: <kw>#IMPLIED</kw> means that if the attribute is omitted
2081: from an element of this type,
2082: the XML processor must inform the application
2083: that no value was specified; no constraint is placed on the behavior
2084: of the application. -->
2085: <termdef id="dt-default" term="Attribute Default">If the
2086: declaration
2087: is neither <kw>#REQUIRED</kw> nor <kw>#IMPLIED</kw>, then the
2088: <nt def="NT-AttValue">AttValue</nt> value contains the declared
2089: <term>default</term> value; the <kw>#FIXED</kw> keyword states that
2090: the attribute must always have the default value.
2091: If a default value
2092: is declared, when an XML processor encounters an omitted attribute, it
2093: is to behave as though the attribute were present with
2094: the declared default value.</termdef></p>
2095: <vcnote id="RequiredAttr">
2096: <head>Required Attribute</head>
2097: <p>If the default declaration is the keyword <kw>#REQUIRED</kw>, then
2098: the attribute must be specified for
2099: all elements of the type in the attribute-list declaration.
2100: </p></vcnote>
2101: <vcnote id="defattrvalid">
2102: <head>Attribute Default Legal</head>
2103: <p>
2104: The declared
2105: default value must meet the lexical constraints of the declared attribute type.
2106: </p>
2107: </vcnote>
2108: <vcnote id="FixedAttr">
2109: <head>Fixed Attribute Default</head>
2110: <p>If an attribute has a default value declared with the
2111: <kw>#FIXED</kw> keyword, instances of that attribute must
2112: match the default value.
2113: </p></vcnote>
2114:
2115: <p>Examples of attribute-list declarations:
2116: <eg><!ATTLIST termdef
2117: id ID #REQUIRED
2118: name CDATA #IMPLIED>
2119: <!ATTLIST list
2120: type (bullets|ordered|glossary) "ordered">
2121: <!ATTLIST form
2122: method CDATA #FIXED "POST"></eg></p>
2123: </div3>
2124: <div3 id="AVNormalize">
2125: <head>Attribute-Value Normalization</head>
2126: <p>Before the value of an attribute is passed to the application
2127: or checked for validity, the
2128: XML processor must normalize it as follows:
2129: <ulist>
2130: <item><p>a character reference is processed by appending the referenced
2131: character to the attribute value</p></item>
2132: <item><p>an entity reference is processed by recursively processing the
2133: replacement text of the entity</p></item>
2134: <item><p>a whitespace character (#x20, #xD, #xA, #x9) is processed by
2135: appending #x20 to the normalized value, except that only a single #x20
2136: is appended for a "#xD#xA" sequence that is part of an external
2137: parsed entity or the literal entity value of an internal parsed
2138: entity</p></item>
2139: <item><p>other characters are processed by appending them to the normalized
2140: value</p>
2141: </item></ulist>
2142: </p>
2143: <p>If the declared value is not CDATA, then the XML processor must
2144: further process the normalized attribute value by discarding any
2145: leading and trailing space (#x20) characters, and by replacing
2146: sequences of space (#x20) characters by a single space (#x20)
2147: character.</p>
2148: <p>
2149: All attributes for which no declaration has been read should be treated
2150: by a non-validating parser as if declared
2151: <kw>CDATA</kw>.
2152: </p>
2153: </div3>
2154: </div2>
2155: <div2 id="sec-condition-sect">
2156: <head>Conditional Sections</head>
2157: <p><termdef id="dt-cond-section" term="conditional section">
2158: <term>Conditional sections</term> are portions of the
2159: <termref def="dt-doctype">document type declaration external subset</termref>
2160: which are
2161: included in, or excluded from, the logical structure of the DTD based on
2162: the keyword which governs them.</termdef>
2163: <scrap lang="ebnf">
2164: <head>Conditional Section</head>
2165: <prodgroup pcw2="9" pcw4="14.5">
2166: <prod id="NT-conditionalSect"><lhs>conditionalSect</lhs>
2167: <rhs><nt def="NT-includeSect">includeSect</nt>
2168: | <nt def="NT-ignoreSect">ignoreSect</nt>
2169: </rhs>
2170: </prod>
2171: <prod id="NT-includeSect"><lhs>includeSect</lhs>
2172: <rhs>'<![' S? 'INCLUDE' S? '['
2173:
2174: <nt def="NT-extSubsetDecl">extSubsetDecl</nt>
2175: ']]>'
2176: </rhs>
2177: </prod>
2178: <prod id="NT-ignoreSect"><lhs>ignoreSect</lhs>
2179: <rhs>'<![' S? 'IGNORE' S? '['
2180: <nt def="NT-ignoreSectContents">ignoreSectContents</nt>*
2181: ']]>'</rhs>
2182: </prod>
2183:
2184: <prod id="NT-ignoreSectContents"><lhs>ignoreSectContents</lhs>
2185: <rhs><nt def="NT-Ignore">Ignore</nt>
2186: ('<![' <nt def="NT-ignoreSectContents">ignoreSectContents</nt> ']]>'
2187: <nt def="NT-Ignore">Ignore</nt>)*</rhs></prod>
2188: <prod id="NT-Ignore"><lhs>Ignore</lhs>
2189: <rhs><nt def="NT-Char">Char</nt>* -
2190: (<nt def="NT-Char">Char</nt>* ('<![' | ']]>')
2191: <nt def="NT-Char">Char</nt>*)
2192: </rhs></prod>
2193:
2194: </prodgroup>
2195: </scrap>
2196: </p>
2197: <p>Like the internal and external DTD subsets, a conditional section
2198: may contain one or more complete declarations,
2199: comments, processing instructions,
2200: or nested conditional sections, intermingled with white space.
2201: </p>
2202: <p>If the keyword of the
2203: conditional section is <kw>INCLUDE</kw>, then the contents of the conditional
2204: section are part of the DTD.
2205: If the keyword of the conditional
2206: section is <kw>IGNORE</kw>, then the contents of the conditional section are
2207: not logically part of the DTD.
2208: Note that for reliable parsing, the contents of even ignored
2209: conditional sections must be read in order to
2210: detect nested conditional sections and ensure that the end of the
2211: outermost (ignored) conditional section is properly detected.
2212: If a conditional section with a
2213: keyword of <kw>INCLUDE</kw> occurs within a larger conditional
2214: section with a keyword of <kw>IGNORE</kw>, both the outer and the
2215: inner conditional sections are ignored.</p>
2216: <p>If the keyword of the conditional section is a
2217: parameter-entity reference, the parameter entity must be replaced by its
2218: content before the processor decides whether to
2219: include or ignore the conditional section.</p>
2220: <p>An example:
2221: <eg><!ENTITY % draft 'INCLUDE' >
2222: <!ENTITY % final 'IGNORE' >
2223:
2224: <![%draft;[
2225: <!ELEMENT book (comments*, title, body, supplements?)>
2226: ]]>
2227: <![%final;[
2228: <!ELEMENT book (title, body, supplements?)>
2229: ]]>
2230: </eg>
2231: </p>
2232: </div2>
2233:
2234:
2235: <!--
2236: <div2 id='sec-pass-to-app'>
2237: <head>XML Processor Treatment of Logical Structure</head>
2238: <p>When an XML processor encounters a start-tag, it must make
2239: at least the following information available to the application:
2240: <ulist>
2241: <item>
2242: <p>the element type's generic identifier</p>
2243: </item>
2244: <item>
2245: <p>the names of attributes known to apply to this element type
2246: (validating processors must make available names of all attributes
2247: declared for the element type; non-validating processors must
2248: make available at least the names of the attributes for which
2249: values are specified.
2250: </p>
2251: </item>
2252: </ulist>
2253: </p>
2254: </div2>
2255: -->
2256:
2257: </div1>
2258: <!-- &Entities; -->
2259:
2260: <div1 id="sec-physical-struct">
2261: <head>Physical Structures</head>
2262:
2263: <p><termdef id="dt-entity" term="Entity">An XML document may consist
2264: of one or many storage units. These are called
2265: <term>entities</term>; they all have <term>content</term> and are all
2266: (except for the document entity, see below, and
2267: the <termref def="dt-doctype">external DTD subset</termref>)
2268: identified by <term>name</term>.
2269: </termdef>
2270: Each XML document has one entity
2271: called the <termref def="dt-docent">document entity</termref>, which serves
2272: as the starting point for the <termref def="dt-xml-proc">XML
2273: processor</termref> and may contain the whole document.</p>
2274: <p>Entities may be either parsed or unparsed.
2275: <termdef id="dt-parsedent" term="Text Entity">A <term>parsed entity's</term>
2276: contents are referred to as its
2277: <termref def="dt-repltext">replacement text</termref>;
2278: this <termref def="dt-text">text</termref> is considered an
2279: integral part of the document.</termdef></p>
2280:
2281: <p><termdef id="dt-unparsed" term="Unparsed Entity">An
2282: <term>unparsed entity</term>
2283: is a resource whose contents may or may not be
2284: <termref def="dt-text">text</termref>, and if text, may not be XML.
2285: Each unparsed entity
2286: has an associated <termref def="dt-notation">notation</termref>, identified by name.
2287: Beyond a requirement
2288: that an XML processor make the identifiers for the entity and
2289: notation available to the application,
2290: XML places no constraints on the contents of unparsed entities.</termdef>
2291: </p>
2292: <p>
2293: Parsed entities are invoked by name using entity references;
2294: unparsed entities by name, given in the value of <kw>ENTITY</kw>
2295: or <kw>ENTITIES</kw>
2296: attributes.</p>
2297: <p><termdef id="gen-entity" term="general entity"><term>General entities</term>
2298: are entities for use within the document content.
2299: In this specification, general entities are sometimes referred
2300: to with the unqualified term <emph>entity</emph> when this leads
2301: to no ambiguity.</termdef>
2302: <termdef id="dt-PE" term="Parameter entity">Parameter entities
2303: are parsed entities for use within the DTD.</termdef>
2304: These two types of entities use different forms of reference and
2305: are recognized in different contexts.
2306: Furthermore, they occupy different namespaces; a parameter entity and
2307: a general entity with the same name are two distinct entities.
2308: </p>
2309:
2310: <div2 id="sec-references">
2311: <head>Character and Entity References</head>
2312: <p><termdef id="dt-charref" term="Character Reference">
2313: A <term>character reference</term> refers to a specific character in the
2314: ISO/IEC 10646 character set, for example one not directly accessible from
2315: available input devices.
2316: <scrap lang="ebnf">
2317: <head>Character Reference</head>
2318: <prod id="NT-CharRef"><lhs>CharRef</lhs>
2319: <rhs>'&#' [0-9]+ ';' </rhs>
2320: <rhs>| '&hcro;' [0-9a-fA-F]+ ';'</rhs>
2321: <wfc def="wf-Legalchar"/>
2322: </prod>
2323: </scrap>
2324: <wfcnote id="wf-Legalchar">
2325: <head>Legal Character</head>
2326: <p>Characters referred to using character references must
2327: match the production for
2328: <termref def="NT-Char">Char</termref>.</p>
2329: </wfcnote>
2330: If the character reference begins with "<code>&#x</code>", the digits and
2331: letters up to the terminating <code>;</code> provide a hexadecimal
2332: representation of the character's code point in ISO/IEC 10646.
2333: If it begins just with "<code>&#</code>", the digits up to the terminating
2334: <code>;</code> provide a decimal representation of the character's
2335: code point.
2336: </termdef>
2337: </p>
2338: <p><termdef id="dt-entref" term="Entity Reference">An <term>entity
2339: reference</term> refers to the content of a named entity.</termdef>
2340: <termdef id="dt-GERef" term="General Entity Reference">References to
2341: parsed general entities
2342: use ampersand (<code>&</code>) and semicolon (<code>;</code>) as
2343: delimiters.</termdef>
2344: <termdef id="dt-PERef" term="Parameter-entity reference">
2345: <term>Parameter-entity references</term> use percent-sign (<code>%</code>) and
2346: semicolon
2347: (<code>;</code>) as delimiters.</termdef>
2348: </p>
2349: <scrap lang="ebnf">
2350: <head>Entity Reference</head>
2351: <prod id="NT-Reference"><lhs>Reference</lhs>
2352: <rhs><nt def="NT-EntityRef">EntityRef</nt>
2353: | <nt def="NT-CharRef">CharRef</nt></rhs></prod>
2354: <prod id="NT-EntityRef"><lhs>EntityRef</lhs>
2355: <rhs>'&' <nt def="NT-Name">Name</nt> ';'</rhs>
2356: <wfc def="wf-entdeclared"/>
2357: <vc def="vc-entdeclared"/>
2358: <wfc def="textent"/>
2359: <wfc def="norecursion"/>
2360: </prod>
2361: <prod id="NT-PEReference"><lhs>PEReference</lhs>
2362: <rhs>'%' <nt def="NT-Name">Name</nt> ';'</rhs>
2363: <vc def="vc-entdeclared"/>
2364: <wfc def="norecursion"/>
2365: <wfc def="indtd"/>
2366: </prod>
2367: </scrap>
2368:
2369: <wfcnote id="wf-entdeclared">
2370: <head>Entity Declared</head>
2371: <p>In a document without any DTD, a document with only an internal
2372: DTD subset which contains no parameter entity references, or a document with
2373: "<code>standalone='yes'</code>",
2374: the <nt def="NT-Name">Name</nt> given in the entity reference must
2375: <termref def="dt-match">match</termref> that in an
2376: <titleref href="sec-entity-decl">entity declaration</titleref>, except that
2377: well-formed documents need not declare
2378: any of the following entities: &magicents;.
2379: The declaration of a parameter entity must precede any reference to it.
2380: Similarly, the declaration of a general entity must precede any
2381: reference to it which appears in a default value in an attribute-list
2382: declaration.</p>
2383: <p>Note that if entities are declared in the external subset or in
2384: external parameter entities, a non-validating processor is
2385: <titleref href="include-if-valid">not obligated to</titleref> read
2386: and process their declarations; for such documents, the rule that
2387: an entity must be declared is a well-formedness constraint only
2388: if <titleref href="sec-rmd">standalone='yes'</titleref>.</p>
2389: </wfcnote>
2390: <vcnote id="vc-entdeclared">
2391: <head>Entity Declared</head>
2392: <p>In a document with an external subset or external parameter
2393: entities with "<code>standalone='no'</code>",
2394: the <nt def="NT-Name">Name</nt> given in the entity reference must <termref def="dt-match">match</termref> that in an
2395: <titleref href="sec-entity-decl">entity declaration</titleref>.
2396: For interoperability, valid documents should declare the entities
2397: &magicents;, in the form
2398: specified in <specref ref="sec-predefined-ent"/>.
2399: The declaration of a parameter entity must precede any reference to it.
2400: Similarly, the declaration of a general entity must precede any
2401: reference to it which appears in a default value in an attribute-list
2402: declaration.</p>
2403: </vcnote>
2404: <!-- FINAL EDIT: is this duplication too clumsy? -->
2405: <wfcnote id="textent">
2406: <head>Parsed Entity</head>
2407: <p>
2408: An entity reference must not contain the name of an <termref def="dt-unparsed">unparsed entity</termref>. Unparsed entities may be referred
2409: to only in <termref def="dt-attrval">attribute values</termref> declared to
2410: be of type <kw>ENTITY</kw> or <kw>ENTITIES</kw>.
2411: </p>
2412: </wfcnote>
2413: <wfcnote id="norecursion">
2414: <head>No Recursion</head>
2415: <p>
2416: A parsed entity must not contain a recursive reference to itself,
2417: either directly or indirectly.
2418: </p>
2419: </wfcnote>
2420: <wfcnote id="indtd">
2421: <head>In DTD</head>
2422: <p>
2423: Parameter-entity references may only appear in the
2424: <termref def="dt-doctype">DTD</termref>.
2425: </p>
2426: </wfcnote>
2427: <p>Examples of character and entity references:
2428: <eg>Type <key>less-than</key> (&hcro;3C;) to save options.
2429: This document was prepared on &docdate; and
2430: is classified &security-level;.</eg></p>
2431: <p>Example of a parameter-entity reference:
2432: <eg><![CDATA[<!-- declare the parameter entity "ISOLat2"... -->
2433: <!ENTITY % ISOLat2
2434: SYSTEM "http://www.xml.com/iso/isolat2-xml.entities" >
2435: <!-- ... now reference it. -->
2436: %ISOLat2;]]></eg></p>
2437: </div2>
2438:
2439: <div2 id="sec-entity-decl">
2440: <head>Entity Declarations</head>
2441:
2442: <p><termdef id="dt-entdecl" term="entity declaration">
2443: Entities are declared thus:
2444: <scrap lang="ebnf">
2445: <head>Entity Declaration</head>
2446: <prodgroup pcw2="5" pcw4="18.5">
2447: <prod id="NT-EntityDecl"><lhs>EntityDecl</lhs>
2448: <rhs><nt def="NT-GEDecl">GEDecl</nt><!--</rhs><com>General entities</com>
2449: <rhs>--> | <nt def="NT-PEDecl">PEDecl</nt></rhs>
2450: <!--<com>Parameter entities</com>-->
2451: </prod>
2452: <prod id="NT-GEDecl"><lhs>GEDecl</lhs>
2453: <rhs>'<!ENTITY' <nt def="NT-S">S</nt> <nt def="NT-Name">Name</nt>
2454: <nt def="NT-S">S</nt> <nt def="NT-EntityDef">EntityDef</nt>
2455: <nt def="NT-S">S</nt>? '>'</rhs>
2456: </prod>
2457: <prod id="NT-PEDecl"><lhs>PEDecl</lhs>
2458: <rhs>'<!ENTITY' <nt def="NT-S">S</nt> '%' <nt def="NT-S">S</nt>
2459: <nt def="NT-Name">Name</nt> <nt def="NT-S">S</nt>
2460: <nt def="NT-PEDef">PEDef</nt> <nt def="NT-S">S</nt>? '>'</rhs>
2461: <!--<com>Parameter entities</com>-->
2462: </prod>
2463: <prod id="NT-EntityDef"><lhs>EntityDef</lhs>
2464: <rhs><nt def="NT-EntityValue">EntityValue</nt>
2465: <!--</rhs>
2466: <rhs>-->| (<nt def="NT-ExternalID">ExternalID</nt>
2467: <nt def="NT-NDataDecl">NDataDecl</nt>?)</rhs>
2468: <!-- <nt def='NT-ExternalDef'>ExternalDef</nt></rhs> -->
2469: </prod>
2470: <!-- FINAL EDIT: what happened to WFs here? -->
2471: <prod id="NT-PEDef"><lhs>PEDef</lhs>
2472: <rhs><nt def="NT-EntityValue">EntityValue</nt>
2473: | <nt def="NT-ExternalID">ExternalID</nt></rhs></prod>
2474: </prodgroup>
2475: </scrap>
2476: The <nt def="NT-Name">Name</nt> identifies the entity in an
2477: <termref def="dt-entref">entity reference</termref> or, in the case of an
2478: unparsed entity, in the value of an <kw>ENTITY</kw> or <kw>ENTITIES</kw>
2479: attribute.
2480: If the same entity is declared more than once, the first declaration
2481: encountered is binding; at user option, an XML processor may issue a
2482: warning if entities are declared multiple times.</termdef>
2483: </p>
2484:
2485: <div3 id="sec-internal-ent">
2486: <head>Internal Entities</head>
2487:
2488: <p><termdef id="dt-internent" term="Internal Entity Replacement Text">If
2489: the entity definition is an
2490: <nt def="NT-EntityValue">EntityValue</nt>,
2491: the defined entity is called an <term>internal entity</term>.
2492: There is no separate physical
2493: storage object, and the content of the entity is given in the
2494: declaration. </termdef>
2495: Note that some processing of entity and character references in the
2496: <termref def="dt-litentval">literal entity value</termref> may be required to
2497: produce the correct <termref def="dt-repltext">replacement
2498: text</termref>: see <specref ref="intern-replacement"/>.
2499: </p>
2500: <p>An internal entity is a <termref def="dt-parsedent">parsed
2501: entity</termref>.</p>
2502: <p>Example of an internal entity declaration:
2503: <eg><!ENTITY Pub-Status "This is a pre-release of the
2504: specification."></eg></p>
2505: </div3>
2506:
2507: <div3 id="sec-external-ent">
2508: <head>External Entities</head>
2509:
2510: <p><termdef id="dt-extent" term="External Entity">If the entity is not
2511: internal, it is an <term>external
2512: entity</term>, declared as follows:
2513: <scrap lang="ebnf">
2514: <head>External Entity Declaration</head>
2515: <!--
2516: <prod id='NT-ExternalDef'><lhs>ExternalDef</lhs>
2517: <rhs></prod> -->
2518: <prod id="NT-ExternalID"><lhs>ExternalID</lhs>
2519: <rhs>'SYSTEM' <nt def="NT-S">S</nt>
2520: <nt def="NT-SystemLiteral">SystemLiteral</nt></rhs>
2521: <rhs>| 'PUBLIC' <nt def="NT-S">S</nt>
2522: <nt def="NT-PubidLiteral">PubidLiteral</nt>
2523: <nt def="NT-S">S</nt>
2524: <nt def="NT-SystemLiteral">SystemLiteral</nt>
2525: </rhs>
2526: </prod>
2527: <prod id="NT-NDataDecl"><lhs>NDataDecl</lhs>
2528: <rhs><nt def="NT-S">S</nt> 'NDATA' <nt def="NT-S">S</nt>
2529: <nt def="NT-Name">Name</nt></rhs>
2530: <vc def="not-declared"/></prod>
2531: </scrap>
2532: If the <nt def="NT-NDataDecl">NDataDecl</nt> is present, this is a
2533: general <termref def="dt-unparsed">unparsed
2534: entity</termref>; otherwise it is a parsed entity.</termdef></p>
2535: <vcnote id="not-declared">
2536: <head>Notation Declared</head>
2537: <p>
2538: The <nt def="NT-Name">Name</nt> must match the declared name of a
2539: <termref def="dt-notation">notation</termref>.
2540: </p>
2541: </vcnote>
2542: <p><termdef id="dt-sysid" term="System Identifier">The
2543: <nt def="NT-SystemLiteral">SystemLiteral</nt>
2544: is called the entity's <term>system identifier</term>. It is a URI,
2545: which may be used to retrieve the entity.</termdef>
2546: Note that the hash mark (<code>#</code>) and fragment identifier
2547: frequently used with URIs are not, formally, part of the URI itself;
2548: an XML processor may signal an error if a fragment identifier is
2549: given as part of a system identifier.
2550: Unless otherwise provided by information outside the scope of this
2551: specification (e.g. a special XML element type defined by a particular
2552: DTD, or a processing instruction defined by a particular application
2553: specification), relative URIs are relative to the location of the
2554: resource within which the entity declaration occurs.
2555: A URI might thus be relative to the
2556: <termref def="dt-docent">document entity</termref>, to the entity
2557: containing the <termref def="dt-doctype">external DTD subset</termref>,
2558: or to some other <termref def="dt-extent">external parameter entity</termref>.
2559: </p>
2560: <p>An XML processor should handle a non-ASCII character in a URI by
2561: representing the character in UTF-8 as one or more bytes, and then
2562: escaping these bytes with the URI escaping mechanism (i.e., by
2563: converting each byte to %HH, where HH is the hexadecimal notation of the
2564: byte value).</p>
2565: <p><termdef id="dt-pubid" term="Public identifier">
2566: In addition to a system identifier, an external identifier may
2567: include a <term>public identifier</term>.</termdef>
2568: An XML processor attempting to retrieve the entity's content may use the public
2569: identifier to try to generate an alternative URI. If the processor
2570: is unable to do so, it must use the URI specified in the system
2571: literal. Before a match is attempted, all strings
2572: of white space in the public identifier must be normalized to single space characters (#x20),
2573: and leading and trailing white space must be removed.</p>
2574: <p>Examples of external entity declarations:
2575: <eg><!ENTITY open-hatch
2576: SYSTEM "http://www.textuality.com/boilerplate/OpenHatch.xml">
2577: <!ENTITY open-hatch
2578: PUBLIC "-//Textuality//TEXT Standard open-hatch boilerplate//EN"
2579: "http://www.textuality.com/boilerplate/OpenHatch.xml">
2580: <!ENTITY hatch-pic
2581: SYSTEM "../grafix/OpenHatch.gif"
2582: NDATA gif ></eg></p>
2583: </div3>
2584:
2585: </div2>
2586:
2587: <div2 id="TextEntities">
2588: <head>Parsed Entities</head>
2589: <div3 id="sec-TextDecl">
2590: <head>The Text Declaration</head>
2591: <p>External parsed entities may each begin with a <term>text
2592: declaration</term>.
2593: <scrap lang="ebnf">
2594: <head>Text Declaration</head>
2595: <prodgroup pcw4="12.5" pcw5="13">
2596: <prod id="NT-TextDecl"><lhs>TextDecl</lhs>
2597: <rhs>&xmlpio;
2598: <nt def="NT-VersionInfo">VersionInfo</nt>?
2599: <nt def="NT-EncodingDecl">EncodingDecl</nt>
2600: <nt def="NT-S">S</nt>? &pic;</rhs>
2601: </prod>
2602: </prodgroup>
2603: </scrap>
2604: </p>
2605: <p>The text declaration must be provided literally, not
2606: by reference to a parsed entity.
2607: No text declaration may appear at any position other than the beginning of
2608: an external parsed entity.</p>
2609: </div3>
2610: <div3 id="wf-entities">
2611: <head>Well-Formed Parsed Entities</head>
2612: <p>The document entity is well-formed if it matches the production labeled
2613: <nt def="NT-document">document</nt>.
2614: An external general
2615: parsed entity is well-formed if it matches the production labeled
2616: <nt def="NT-extParsedEnt">extParsedEnt</nt>.
2617: An external parameter
2618: entity is well-formed if it matches the production labeled
2619: <nt def="NT-extPE">extPE</nt>.
2620: <scrap lang="ebnf">
2621: <head>Well-Formed External Parsed Entity</head>
2622: <prod id="NT-extParsedEnt"><lhs>extParsedEnt</lhs>
2623: <rhs><nt def="NT-TextDecl">TextDecl</nt>?
2624: <nt def="NT-content">content</nt></rhs>
2625: </prod>
2626: <prod id="NT-extPE"><lhs>extPE</lhs>
2627: <rhs><nt def="NT-TextDecl">TextDecl</nt>?
2628: <nt def="NT-extSubsetDecl">extSubsetDecl</nt></rhs>
2629: </prod>
2630: </scrap>
2631: An internal general parsed entity is well-formed if its replacement text
2632: matches the production labeled
2633: <nt def="NT-content">content</nt>.
2634: All internal parameter entities are well-formed by definition.
2635: </p>
2636: <p>A consequence of well-formedness in entities is that the logical
2637: and physical structures in an XML document are properly nested; no
2638: <termref def="dt-stag">start-tag</termref>,
2639: <termref def="dt-etag">end-tag</termref>,
2640: <termref def="dt-empty">empty-element tag</termref>,
2641: <termref def="dt-element">element</termref>,
2642: <termref def="dt-comment">comment</termref>,
2643: <termref def="dt-pi">processing instruction</termref>,
2644: <termref def="dt-charref">character
2645: reference</termref>, or
2646: <termref def="dt-entref">entity reference</termref>
2647: can begin in one entity and end in another.</p>
2648: </div3>
2649: <div3 id="charencoding">
2650: <head>Character Encoding in Entities</head>
2651:
2652: <p>Each external parsed entity in an XML document may use a different
2653: encoding for its characters. All XML processors must be able to read
2654: entities in either UTF-8 or UTF-16.
2655:
2656: </p>
2657: <p>Entities encoded in UTF-16 must
2658: begin with the Byte Order Mark described by ISO/IEC 10646 Annex E and
2659: Unicode Appendix B (the ZERO WIDTH NO-BREAK SPACE character, #xFEFF).
2660: This is an encoding signature, not part of either the markup or the
2661: character data of the XML document.
2662: XML processors must be able to use this character to
2663: differentiate between UTF-8 and UTF-16 encoded documents.</p>
2664: <p>Although an XML processor is required to read only entities in
2665: the UTF-8 and UTF-16 encodings, it is recognized that other encodings are
2666: used around the world, and it may be desired for XML processors
2667: to read entities that use them.
2668: Parsed entities which are stored in an encoding other than
2669: UTF-8 or UTF-16 must begin with a <titleref href="TextDecl">text
2670: declaration</titleref> containing an encoding declaration:
2671: <scrap lang="ebnf">
2672: <head>Encoding Declaration</head>
2673: <prod id="NT-EncodingDecl"><lhs>EncodingDecl</lhs>
2674: <rhs><nt def="NT-S">S</nt>
2675: 'encoding' <nt def="NT-Eq">Eq</nt>
2676: ('"' <nt def="NT-EncName">EncName</nt> '"' |
2677: "'" <nt def="NT-EncName">EncName</nt> "'" )
2678: </rhs>
2679: </prod>
2680: <prod id="NT-EncName"><lhs>EncName</lhs>
2681: <rhs>[A-Za-z] ([A-Za-z0-9._] | '-')*</rhs>
2682: <com>Encoding name contains only Latin characters</com>
2683: </prod>
2684: </scrap>
2685: In the <termref def="dt-docent">document entity</termref>, the encoding
2686: declaration is part of the <termref def="dt-xmldecl">XML declaration</termref>.
2687: The <nt def="NT-EncName">EncName</nt> is the name of the encoding used.
2688: </p>
2689: <!-- FINAL EDIT: check name of IANA and charset names -->
2690: <p>In an encoding declaration, the values
2691: "<code>UTF-8</code>",
2692: "<code>UTF-16</code>",
2693: "<code>ISO-10646-UCS-2</code>", and
2694: "<code>ISO-10646-UCS-4</code>" should be
2695: used for the various encodings and transformations of Unicode /
2696: ISO/IEC 10646, the values
2697: "<code>ISO-8859-1</code>",
2698: "<code>ISO-8859-2</code>", ...
2699: "<code>ISO-8859-9</code>" should be used for the parts of ISO 8859, and
2700: the values
2701: "<code>ISO-2022-JP</code>",
2702: "<code>Shift_JIS</code>", and
2703: "<code>EUC-JP</code>"
2704: should be used for the various encoded forms of JIS X-0208-1997. XML
2705: processors may recognize other encodings; it is recommended that
2706: character encodings registered (as <emph>charset</emph>s)
2707: with the Internet Assigned Numbers
2708: Authority <bibref ref="IANA"/>, other than those just listed, should be
2709: referred to
2710: using their registered names.
2711: Note that these registered names are defined to be
2712: case-insensitive, so processors wishing to match against them
2713: should do so in a case-insensitive
2714: way.</p>
2715: <p>In the absence of information provided by an external
2716: transport protocol (e.g. HTTP or MIME),
2717: it is an <termref def="dt-error">error</termref> for an entity including
2718: an encoding declaration to be presented to the XML processor
2719: in an encoding other than that named in the declaration,
2720: for an encoding declaration to occur other than at the beginning
2721: of an external entity, or for
2722: an entity which begins with neither a Byte Order Mark nor an encoding
2723: declaration to use an encoding other than UTF-8.
2724: Note that since ASCII
2725: is a subset of UTF-8, ordinary ASCII entities do not strictly need
2726: an encoding declaration.</p>
2727:
2728: <p>It is a <termref def="dt-fatal">fatal error</termref> when an XML processor
2729: encounters an entity with an encoding that it is unable to process.</p>
2730: <p>Examples of encoding declarations:
2731: <eg><?xml encoding='UTF-8'?>
2732: <?xml encoding='EUC-JP'?></eg></p>
2733: </div3>
2734: </div2>
2735: <div2 id="entproc">
2736: <head>XML Processor Treatment of Entities and References</head>
2737: <p>The table below summarizes the contexts in which character references,
2738: entity references, and invocations of unparsed entities might appear and the
2739: required behavior of an <termref def="dt-xml-proc">XML processor</termref> in
2740: each case.
2741: The labels in the leftmost column describe the recognition context:
2742: <glist>
2743: <gitem><label>Reference in Content</label>
2744: <def><p>as a reference
2745: anywhere after the <termref def="dt-stag">start-tag</termref> and
2746: before the <termref def="dt-etag">end-tag</termref> of an element; corresponds
2747: to the nonterminal <nt def="NT-content">content</nt>.</p></def>
2748: </gitem>
2749: <gitem>
2750: <label>Reference in Attribute Value</label>
2751: <def><p>as a reference within either the value of an attribute in a
2752: <termref def="dt-stag">start-tag</termref>, or a default
2753: value in an <termref def="dt-attdecl">attribute declaration</termref>;
2754: corresponds to the nonterminal
2755: <nt def="NT-AttValue">AttValue</nt>.</p></def></gitem>
2756: <gitem>
2757: <label>Occurs as Attribute Value</label>
2758: <def><p>as a <nt def="NT-Name">Name</nt>, not a reference, appearing either as
2759: the value of an
2760: attribute which has been declared as type <kw>ENTITY</kw>, or as one of
2761: the space-separated tokens in the value of an attribute which has been
2762: declared as type <kw>ENTITIES</kw>.</p>
2763: </def></gitem>
2764: <gitem><label>Reference in Entity Value</label>
2765: <def><p>as a reference
2766: within a parameter or internal entity's
2767: <termref def="dt-litentval">literal entity value</termref> in
2768: the entity's declaration; corresponds to the nonterminal
2769: <nt def="NT-EntityValue">EntityValue</nt>.</p></def></gitem>
2770: <gitem><label>Reference in DTD</label>
2771: <def><p>as a reference within either the internal or external subsets of the
2772: <termref def="dt-doctype">DTD</termref>, but outside
2773: of an <nt def="NT-EntityValue">EntityValue</nt> or
2774: <nt def="NT-AttValue">AttValue</nt>.</p></def>
2775: </gitem>
2776: </glist></p>
2777: <htable border="1" cellpadding="7" align="center">
2778: <htbody>
2779: <tr><td bgcolor="&cellback;" rowspan="2" colspan="1"/>
2780: <td bgcolor="&cellback;" align="center" valign="bottom" colspan="4">Entity Type</td>
2781: <td bgcolor="&cellback;" rowspan="2" align="center">Character</td>
2782: </tr>
2783: <tr align="center" valign="bottom">
2784: <td bgcolor="&cellback;">Parameter</td>
2785: <td bgcolor="&cellback;">Internal
2786: General</td>
2787: <td bgcolor="&cellback;">External Parsed
2788: General</td>
2789: <td bgcolor="&cellback;">Unparsed</td>
2790: </tr>
2791: <tr align="center" valign="middle">
2792:
2793: <td bgcolor="&cellback;" align="right">Reference
2794: in Content</td>
2795: <td bgcolor="&cellback;"><titleref href="not-recognized">Not recognized</titleref></td>
2796: <td bgcolor="&cellback;"><titleref href="included">Included</titleref></td>
2797: <td bgcolor="&cellback;"><titleref href="include-if-valid">Included if validating</titleref></td>
2798: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td>
2799: <td bgcolor="&cellback;"><titleref href="included">Included</titleref></td>
2800: </tr>
2801: <tr align="center" valign="middle">
2802: <td bgcolor="&cellback;" align="right">Reference
2803: in Attribute Value</td>
2804: <td bgcolor="&cellback;"><titleref href="not-recognized">Not recognized</titleref></td>
2805: <td bgcolor="&cellback;"><titleref href="inliteral">Included in literal</titleref></td>
2806: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td>
2807: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td>
2808: <td bgcolor="&cellback;"><titleref href="included">Included</titleref></td>
2809: </tr>
2810: <tr align="center" valign="middle">
2811: <td bgcolor="&cellback;" align="right">Occurs as
2812: Attribute Value</td>
2813: <td bgcolor="&cellback;"><titleref href="not-recognized">Not recognized</titleref></td>
2814: <td bgcolor="&cellback;"><titleref href="not-recognized">Forbidden</titleref></td>
2815: <td bgcolor="&cellback;"><titleref href="not-recognized">Forbidden</titleref></td>
2816: <td bgcolor="&cellback;"><titleref href="notify">Notify</titleref></td>
2817: <td bgcolor="&cellback;"><titleref href="not recognized">Not recognized</titleref></td>
2818: </tr>
2819: <tr align="center" valign="middle">
2820: <td bgcolor="&cellback;" align="right">Reference
2821: in EntityValue</td>
2822: <td bgcolor="&cellback;"><titleref href="inliteral">Included in literal</titleref></td>
2823: <td bgcolor="&cellback;"><titleref href="bypass">Bypassed</titleref></td>
2824: <td bgcolor="&cellback;"><titleref href="bypass">Bypassed</titleref></td>
2825: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td>
2826: <td bgcolor="&cellback;"><titleref href="included">Included</titleref></td>
2827: </tr>
2828: <tr align="center" valign="middle">
2829: <td bgcolor="&cellback;" align="right">Reference
2830: in DTD</td>
2831: <td bgcolor="&cellback;"><titleref href="as-PE">Included as PE</titleref></td>
2832: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td>
2833: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td>
2834: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td>
2835: <td bgcolor="&cellback;"><titleref href="forbidden">Forbidden</titleref></td>
2836: </tr>
2837: </htbody>
2838: </htable>
2839: <div3 id="not-recognized">
2840: <head>Not Recognized</head>
2841: <p>Outside the DTD, the <code>%</code> character has no
2842: special significance; thus, what would be parameter entity references in the
2843: DTD are not recognized as markup in <nt def="NT-content">content</nt>.
2844: Similarly, the names of unparsed entities are not recognized except
2845: when they appear in the value of an appropriately declared attribute.
2846: </p>
2847: </div3>
2848: <div3 id="included">
2849: <head>Included</head>
2850: <p><termdef id="dt-include" term="Include">An entity is
2851: <term>included</term> when its
2852: <termref def="dt-repltext">replacement text</termref> is retrieved
2853: and processed, in place of the reference itself,
2854: as though it were part of the document at the location the
2855: reference was recognized.
2856: The replacement text may contain both
2857: <termref def="dt-chardata">character data</termref>
2858: and (except for parameter entities) <termref def="dt-markup">markup</termref>,
2859: which must be recognized in
2860: the usual way, except that the replacement text of entities used to escape
2861: markup delimiters (the entities &magicents;) is always treated as
2862: data. (The string "<code>AT&amp;T;</code>" expands to
2863: "<code>AT&T;</code>" and the remaining ampersand is not recognized
2864: as an entity-reference delimiter.)
2865: A character reference is <term>included</term> when the indicated
2866: character is processed in place of the reference itself.
2867: </termdef></p>
2868: </div3>
2869: <div3 id="include-if-valid">
2870: <head>Included If Validating</head>
2871: <p>When an XML processor recognizes a reference to a parsed entity, in order
2872: to <termref def="dt-valid">validate</termref>
2873: the document, the processor must
2874: <termref def="dt-include">include</termref> its
2875: replacement text.
2876: If the entity is external, and the processor is not
2877: attempting to validate the XML document, the
2878: processor <termref def="dt-may">may</termref>, but need not,
2879: include the entity's replacement text.
2880: If a non-validating parser does not include the replacement text,
2881: it must inform the application that it recognized, but did not
2882: read, the entity.</p>
2883: <p>This rule is based on the recognition that the automatic inclusion
2884: provided by the SGML and XML entity mechanism, primarily designed
2885: to support modularity in authoring, is not necessarily
2886: appropriate for other applications, in particular document browsing.
2887: Browsers, for example, when encountering an external parsed entity reference,
2888: might choose to provide a visual indication of the entity's
2889: presence and retrieve it for display only on demand.
2890: </p>
2891: </div3>
2892: <div3 id="forbidden">
2893: <head>Forbidden</head>
2894: <p>The following are forbidden, and constitute
2895: <termref def="dt-fatal">fatal</termref> errors:
2896: <ulist>
2897: <item><p>the appearance of a reference to an
2898: <termref def="dt-unparsed">unparsed entity</termref>.
2899: </p></item>
2900: <item><p>the appearance of any character or general-entity reference in the
2901: DTD except within an <nt def="NT-EntityValue">EntityValue</nt> or
2902: <nt def="NT-AttValue">AttValue</nt>.</p></item>
2903: <item><p>a reference to an external entity in an attribute value.</p>
2904: </item>
2905: </ulist>
2906: </p>
2907: </div3>
2908: <div3 id="inliteral">
2909: <head>Included in Literal</head>
2910: <p>When an <termref def="dt-entref">entity reference</termref> appears in an
2911: attribute value, or a parameter entity reference appears in a literal entity
2912: value, its <termref def="dt-repltext">replacement text</termref> is
2913: processed in place of the reference itself as though it
2914: were part of the document at the location the reference was recognized,
2915: except that a single or double quote character in the replacement text
2916: is always treated as a normal data character and will not terminate the
2917: literal.
2918: For example, this is well-formed:
2919: <eg><![CDATA[<!ENTITY % YN '"Yes"' >
2920: <!ENTITY WhatHeSaid "He said &YN;" >]]></eg>
2921: while this is not:
2922: <eg><!ENTITY EndAttr "27'" >
2923: <element attribute='a-&EndAttr;></eg>
2924: </p></div3>
2925: <div3 id="notify">
2926: <head>Notify</head>
2927: <p>When the name of an <termref def="dt-unparsed">unparsed
2928: entity</termref> appears as a token in the
2929: value of an attribute of declared type <kw>ENTITY</kw> or <kw>ENTITIES</kw>,
2930: a validating processor must inform the
2931: application of the <termref def="dt-sysid">system</termref>
2932: and <termref def="dt-pubid">public</termref> (if any)
2933: identifiers for both the entity and its associated
2934: <termref def="dt-notation">notation</termref>.</p>
2935: </div3>
2936: <div3 id="bypass">
2937: <head>Bypassed</head>
2938: <p>When a general entity reference appears in the
2939: <nt def="NT-EntityValue">EntityValue</nt> in an entity declaration,
2940: it is bypassed and left as is.</p>
2941: </div3>
2942: <div3 id="as-PE">
2943: <head>Included as PE</head>
2944: <p>Just as with external parsed entities, parameter entities
2945: need only be <titleref href="include-if-valid">included if
2946: validating</titleref>.
2947: When a parameter-entity reference is recognized in the DTD
2948: and included, its
2949: <termref def="dt-repltext">replacement
2950: text</termref> is enlarged by the attachment of one leading and one following
2951: space (#x20) character; the intent is to constrain the replacement
2952: text of parameter
2953: entities to contain an integral number of grammatical tokens in the DTD.
2954: </p>
2955: </div3>
2956:
2957: </div2>
2958: <div2 id="intern-replacement">
2959: <head>Construction of Internal Entity Replacement Text</head>
2960: <p>In discussing the treatment
2961: of internal entities, it is
2962: useful to distinguish two forms of the entity's value.
2963: <termdef id="dt-litentval" term="Literal Entity Value">The <term>literal
2964: entity value</term> is the quoted string actually
2965: present in the entity declaration, corresponding to the
2966: non-terminal <nt def="NT-EntityValue">EntityValue</nt>.</termdef>
2967: <termdef id="dt-repltext" term="Replacement Text">The <term>replacement
2968: text</term> is the content of the entity, after
2969: replacement of character references and parameter-entity
2970: references.
2971: </termdef></p>
2972:
2973: <p>The literal entity value
2974: as given in an internal entity declaration
2975: (<nt def="NT-EntityValue">EntityValue</nt>) may contain character,
2976: parameter-entity, and general-entity references.
2977: Such references must be contained entirely within the
2978: literal entity value.
2979: The actual replacement text that is
2980: <termref def="dt-include">included</termref> as described above
2981: must contain the <emph>replacement text</emph> of any
2982: parameter entities referred to, and must contain the character
2983: referred to, in place of any character references in the
2984: literal entity value; however,
2985: general-entity references must be left as-is, unexpanded.
2986: For example, given the following declarations:
2987:
2988: <eg><![CDATA[<!ENTITY % pub "Éditions Gallimard" >
2989: <!ENTITY rights "All rights reserved" >
2990: <!ENTITY book "La Peste: Albert Camus,
2991: © 1947 %pub;. &rights;" >]]></eg>
2992: then the replacement text for the entity "<code>book</code>" is:
2993: <eg>La Peste: Albert Camus,
2994: © 1947 Éditions Gallimard. &rights;</eg>
2995: The general-entity reference "<code>&rights;</code>" would be expanded
2996: should the reference "<code>&book;</code>" appear in the document's
2997: content or an attribute value.</p>
2998: <p>These simple rules may have complex interactions; for a detailed
2999: discussion of a difficult example, see
3000: <specref ref="sec-entexpand"/>.
3001: </p>
3002:
3003: </div2>
3004: <div2 id="sec-predefined-ent">
3005: <head>Predefined Entities</head>
3006: <p><termdef id="dt-escape" term="escape">Entity and character
3007: references can both be used to <term>escape</term> the left angle bracket,
3008: ampersand, and other delimiters. A set of general entities
3009: (&magicents;) is specified for this purpose.
3010: Numeric character references may also be used; they are
3011: expanded immediately when recognized and must be treated as
3012: character data, so the numeric character references
3013: "<code>&#60;</code>" and "<code>&#38;</code>" may be used to
3014: escape <code><</code> and <code>&</code> when they occur
3015: in character data.</termdef></p>
3016: <p>All XML processors must recognize these entities whether they
3017: are declared or not.
3018: <termref def="dt-interop">For interoperability</termref>,
3019: valid XML documents should declare these
3020: entities, like any others, before using them.
3021: If the entities in question are declared, they must be declared
3022: as internal entities whose replacement text is the single
3023: character being escaped or a character reference to
3024: that character, as shown below.
3025: <eg><![CDATA[<!ENTITY lt "&#60;">
3026: <!ENTITY gt ">">
3027: <!ENTITY amp "&#38;">
3028: <!ENTITY apos "'">
3029: <!ENTITY quot """>
3030: ]]></eg>
3031: Note that the <code><</code> and <code>&</code> characters
3032: in the declarations of "<code>lt</code>" and "<code>amp</code>"
3033: are doubly escaped to meet the requirement that entity replacement
3034: be well-formed.
3035: </p>
3036: </div2>
3037:
3038: <div2 id="Notations">
3039: <head>Notation Declarations</head>
3040:
3041: <p><termdef id="dt-notation" term="Notation"><term>Notations</term> identify by
3042: name the format of <termref def="dt-extent">unparsed
3043: entities</termref>, the
3044: format of elements which bear a notation attribute,
3045: or the application to which
3046: a <termref def="dt-pi">processing instruction</termref> is
3047: addressed.</termdef></p>
3048: <p><termdef id="dt-notdecl" term="Notation Declaration">
3049: <term>Notation declarations</term>
3050: provide a name for the notation, for use in
3051: entity and attribute-list declarations and in attribute specifications,
3052: and an external identifier for the notation which may allow an XML
3053: processor or its client application to locate a helper application
3054: capable of processing data in the given notation.
3055: <scrap lang="ebnf">
3056: <head>Notation Declarations</head>
3057: <prod id="NT-NotationDecl"><lhs>NotationDecl</lhs>
3058: <rhs>'<!NOTATION' <nt def="NT-S">S</nt> <nt def="NT-Name">Name</nt>
3059: <nt def="NT-S">S</nt>
3060: (<nt def="NT-ExternalID">ExternalID</nt> |
3061: <nt def="NT-PublicID">PublicID</nt>)
3062: <nt def="NT-S">S</nt>? '>'</rhs></prod>
3063: <prod id="NT-PublicID"><lhs>PublicID</lhs>
3064: <rhs>'PUBLIC' <nt def="NT-S">S</nt>
3065: <nt def="NT-PubidLiteral">PubidLiteral</nt>
3066: </rhs></prod>
3067: </scrap>
3068: </termdef></p>
3069: <p>XML processors must provide applications with the name and external
3070: identifier(s) of any notation declared and referred to in an attribute
3071: value, attribute definition, or entity declaration. They may
3072: additionally resolve the external identifier into the
3073: <termref def="dt-sysid">system identifier</termref>,
3074: file name, or other information needed to allow the
3075: application to call a processor for data in the notation described. (It
3076: is not an error, however, for XML documents to declare and refer to
3077: notations for which notation-specific applications are not available on
3078: the system where the XML processor or application is running.)</p>
3079: </div2>
3080:
3081:
3082: <div2 id="sec-doc-entity">
3083: <head>Document Entity</head>
3084:
3085: <p><termdef id="dt-docent" term="Document Entity">The <term>document
3086: entity</term> serves as the root of the entity
3087: tree and a starting-point for an <termref def="dt-xml-proc">XML
3088: processor</termref>.</termdef>
3089: This specification does
3090: not specify how the document entity is to be located by an XML
3091: processor; unlike other entities, the document entity has no name and might
3092: well appear on a processor input stream
3093: without any identification at all.</p>
3094: </div2>
3095:
3096:
3097: </div1>
3098: <!-- &Conformance; -->
3099:
3100: <div1 id="sec-conformance">
3101: <head>Conformance</head>
3102:
3103: <div2 id="proc-types">
3104: <head>Validating and Non-Validating Processors</head>
3105: <p>Conforming <termref def="dt-xml-proc">XML processors</termref> fall into two
3106: classes: validating and non-validating.</p>
3107: <p>Validating and non-validating processors alike must report
3108: violations of this specification's well-formedness constraints
3109: in the content of the
3110: <termref def="dt-docent">document entity</termref> and any
3111: other <termref def="dt-parsedent">parsed entities</termref> that
3112: they read.</p>
3113: <p><termdef id="dt-validating" term="Validating Processor">
3114: <term>Validating processors</term> must report
3115: violations of the constraints expressed by the declarations in the
3116: <termref def="dt-doctype">DTD</termref>, and
3117: failures to fulfill the validity constraints given
3118: in this specification.
3119: </termdef>
3120: To accomplish this, validating XML processors must read and process the entire
3121: DTD and all external parsed entities referenced in the document.
3122: </p>
3123: <p>Non-validating processors are required to check only the
3124: <termref def="dt-docent">document entity</termref>, including
3125: the entire internal DTD subset, for well-formedness.
3126: <termdef id="dt-use-mdecl" term="Process Declarations">
3127: While they are not required to check the document for validity,
3128: they are required to
3129: <term>process</term> all the declarations they read in the
3130: internal DTD subset and in any parameter entity that they
3131: read, up to the first reference
3132: to a parameter entity that they do <emph>not</emph> read; that is to
3133: say, they must
3134: use the information in those declarations to
3135: <titleref href="AVNormalize">normalize</titleref> attribute values,
3136: <titleref href="included">include</titleref> the replacement text of
3137: internal entities, and supply
3138: <titleref href="sec-attr-defaults">default attribute values</titleref>.
3139: </termdef>
3140: They must not <termref def="dt-use-mdecl">process</termref>
3141: <termref def="dt-entdecl">entity declarations</termref> or
3142: <termref def="dt-attdecl">attribute-list declarations</termref>
3143: encountered after a reference to a parameter entity that is not
3144: read, since the entity may have contained overriding declarations.
3145: </p>
3146: </div2>
3147: <div2 id="safe-behavior">
3148: <head>Using XML Processors</head>
3149: <p>The behavior of a validating XML processor is highly predictable; it
3150: must read every piece of a document and report all well-formedness and
3151: validity violations.
3152: Less is required of a non-validating processor; it need not read any
3153: part of the document other than the document entity.
3154: This has two effects that may be important to users of XML processors:
3155: <ulist>
3156: <item><p>Certain well-formedness errors, specifically those that require
3157: reading external entities, may not be detected by a non-validating processor.
3158: Examples include the constraints entitled
3159: <titleref href="wf-entdeclared">Entity Declared</titleref>,
3160: <titleref href="wf-textent">Parsed Entity</titleref>, and
3161: <titleref href="wf-norecursion">No Recursion</titleref>, as well
3162: as some of the cases described as
3163: <titleref href="forbidden">forbidden</titleref> in
3164: <specref ref="entproc"/>.</p></item>
3165: <item><p>The information passed from the processor to the application may
3166: vary, depending on whether the processor reads
3167: parameter and external entities.
3168: For example, a non-validating processor may not
3169: <titleref href="AVNormalize">normalize</titleref> attribute values,
3170: <titleref href="included">include</titleref> the replacement text of
3171: internal entities, or supply
3172: <titleref href="sec-attr-defaults">default attribute values</titleref>,
3173: where doing so depends on having read declarations in
3174: external or parameter entities.</p></item>
3175: </ulist>
3176: </p>
3177: <p>For maximum reliability in interoperating between different XML
3178: processors, applications which use non-validating processors should not
3179: rely on any behaviors not required of such processors.
3180: Applications which require facilities such as the use of default
3181: attributes or internal entities which are declared in external
3182: entities should use validating XML processors.</p>
3183: </div2>
3184: </div1>
3185:
3186: <div1 id="sec-notation">
3187: <head>Notation</head>
3188:
3189: <p>The formal grammar of XML is given in this specification using a simple
3190: Extended Backus-Naur Form (EBNF) notation. Each rule in the grammar defines
3191: one symbol, in the form
3192: <eg>symbol ::= expression</eg></p>
3193: <p>Symbols are written with an initial capital letter if they are
3194: defined by a regular expression, or with an initial lower case letter
3195: otherwise.
3196: Literal strings are quoted.
3197:
3198: </p>
3199:
3200: <p>Within the expression on the right-hand side of a rule, the following
3201: expressions are used to match strings of one or more characters:
3202: <glist>
3203: <gitem>
3204: <label><code>#xN</code></label>
3205: <def><p>where <code>N</code> is a hexadecimal integer, the
3206: expression matches the character in ISO/IEC 10646 whose canonical
3207: (UCS-4)
3208: code value, when interpreted as an unsigned binary number, has
3209: the value indicated. The number of leading zeros in the
3210: <code>#xN</code> form is insignificant; the number of leading
3211: zeros in the corresponding code value
3212: is governed by the character
3213: encoding in use and is not significant for XML.</p></def>
3214: </gitem>
3215: <gitem>
3216: <label><code>[a-zA-Z]</code>, <code>[#xN-#xN]</code></label>
3217: <def><p>matches any <termref def="dt-character">character</termref>
3218: with a value in the range(s) indicated (inclusive).</p></def>
3219: </gitem>
3220: <gitem>
3221: <label><code>[^a-z]</code>, <code>[^#xN-#xN]</code></label>
3222: <def><p>matches any <termref def="dt-character">character</termref>
3223: with a value <emph>outside</emph> the
3224: range indicated.</p></def>
3225: </gitem>
3226: <gitem>
3227: <label><code>[^abc]</code>, <code>[^#xN#xN#xN]</code></label>
3228: <def><p>matches any <termref def="dt-character">character</termref>
3229: with a value not among the characters given.</p></def>
3230: </gitem>
3231: <gitem>
3232: <label><code>"string"</code></label>
3233: <def><p>matches a literal string <termref def="dt-match">matching</termref>
3234: that given inside the double quotes.</p></def>
3235: </gitem>
3236: <gitem>
3237: <label><code>'string'</code></label>
3238: <def><p>matches a literal string <termref def="dt-match">matching</termref>
3239: that given inside the single quotes.</p></def>
3240: </gitem>
3241: </glist>
3242: These symbols may be combined to match more complex patterns as follows,
3243: where <code>A</code> and <code>B</code> represent simple expressions:
3244: <glist>
3245: <gitem>
3246: <label>(<code>expression</code>)</label>
3247: <def><p><code>expression</code> is treated as a unit
3248: and may be combined as described in this list.</p></def>
3249: </gitem>
3250: <gitem>
3251: <label><code>A?</code></label>
3252: <def><p>matches <code>A</code> or nothing; optional <code>A</code>.</p></def>
3253: </gitem>
3254: <gitem>
3255: <label><code>A B</code></label>
3256: <def><p>matches <code>A</code> followed by <code>B</code>.</p></def>
3257: </gitem>
3258: <gitem>
3259: <label><code>A | B</code></label>
3260: <def><p>matches <code>A</code> or <code>B</code> but not both.</p></def>
3261: </gitem>
3262: <gitem>
3263: <label><code>A - B</code></label>
3264: <def><p>matches any string that matches <code>A</code> but does not match
3265: <code>B</code>.
3266: </p></def>
3267: </gitem>
3268: <gitem>
3269: <label><code>A+</code></label>
3270: <def><p>matches one or more occurrences of <code>A</code>.</p></def>
3271: </gitem>
3272: <gitem>
3273: <label><code>A*</code></label>
3274: <def><p>matches zero or more occurrences of <code>A</code>.</p></def>
3275: </gitem>
3276:
3277: </glist>
3278: Other notations used in the productions are:
3279: <glist>
3280: <gitem>
3281: <label><code>/* ... */</code></label>
3282: <def><p>comment.</p></def>
3283: </gitem>
3284: <gitem>
3285: <label><code>[ wfc: ... ]</code></label>
3286: <def><p>well-formedness constraint; this identifies by name a
3287: constraint on
3288: <termref def="dt-wellformed">well-formed</termref> documents
3289: associated with a production.</p></def>
3290: </gitem>
3291: <gitem>
3292: <label><code>[ vc: ... ]</code></label>
3293: <def><p>validity constraint; this identifies by name a constraint on
3294: <termref def="dt-valid">valid</termref> documents associated with
3295: a production.</p></def>
3296: </gitem>
3297: </glist>
3298: </p></div1>
3299:
3300: </body>
3301: <back>
3302: <!-- &SGML; -->
3303:
3304:
3305: <!-- &Biblio; -->
3306: <div1 id="sec-bibliography">
3307:
3308: <head>References</head>
3309: <div2 id="sec-existing-stds">
3310: <head>Normative References</head>
3311:
3312: <blist>
3313: <bibl id="IANA" key="IANA">
3314: (Internet Assigned Numbers Authority) <emph>Official Names for
3315: Character Sets</emph>,
3316: ed. Keld Simonsen et al.
3317: See <loc href="ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets">ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets</loc>.
3318: </bibl>
3319:
3320: <bibl id="RFC1766" key="IETF RFC 1766">
3321: IETF (Internet Engineering Task Force).
3322: <emph>RFC 1766: Tags for the Identification of Languages</emph>,
3323: ed. H. Alvestrand.
3324: 1995.
3325: </bibl>
3326:
3327: <bibl id="ISO639" key="ISO 639">
3328: (International Organization for Standardization).
3329: <emph>ISO 639:1988 (E).
3330: Code for the representation of names of languages.</emph>
3331: [Geneva]: International Organization for
3332: Standardization, 1988.</bibl>
3333:
3334: <bibl id="ISO3166" key="ISO 3166">
3335: (International Organization for Standardization).
3336: <emph>ISO 3166-1:1997 (E).
3337: Codes for the representation of names of countries and their subdivisions
3338: — Part 1: Country codes</emph>
3339: [Geneva]: International Organization for
3340: Standardization, 1997.</bibl>
3341:
3342: <bibl id="ISO10646" key="ISO/IEC 10646">ISO
3343: (International Organization for Standardization).
3344: <emph>ISO/IEC 10646-1993 (E). Information technology — Universal
3345: Multiple-Octet Coded Character Set (UCS) — Part 1:
3346: Architecture and Basic Multilingual Plane.</emph>
3347: [Geneva]: International Organization for
3348: Standardization, 1993 (plus amendments AM 1 through AM 7).
3349: </bibl>
3350:
3351: <bibl id="Unicode" key="Unicode">The Unicode Consortium.
3352: <emph>The Unicode Standard, Version 2.0.</emph>
3353: Reading, Mass.: Addison-Wesley Developers Press, 1996.</bibl>
3354:
3355: </blist>
3356:
3357: </div2>
3358:
3359: <div2><head>Other References</head>
3360:
3361: <blist>
3362:
3363: <bibl id="Aho" key="Aho/Ullman">Aho, Alfred V.,
3364: Ravi Sethi, and Jeffrey D. Ullman.
3365: <emph>Compilers: Principles, Techniques, and Tools</emph>.
3366: Reading: Addison-Wesley, 1986, rpt. corr. 1988.</bibl>
3367:
3368: <bibl id="Berners-Lee" xml-link="simple" key="Berners-Lee et al.">
3369: Berners-Lee, T., R. Fielding, and L. Masinter.
3370: <emph>Uniform Resource Identifiers (URI): Generic Syntax and
3371: Semantics</emph>.
3372: 1997.
3373: (Work in progress; see updates to RFC1738.)</bibl>
3374:
3375: <bibl id="ABK" key="Brüggemann-Klein">Brüggemann-Klein, Anne.
3376: <emph>Regular Expressions into Finite Automata</emph>.
3377: Extended abstract in I. Simon, Hrsg., LATIN 1992,
3378: S. 97-98. Springer-Verlag, Berlin 1992.
3379: Full Version in Theoretical Computer Science 120: 197-213, 1993.
3380:
3381: </bibl>
3382:
3383: <bibl id="ABKDW" key="Brüggemann-Klein and Wood">Brüggemann-Klein, Anne,
3384: and Derick Wood.
3385: <emph>Deterministic Regular Languages</emph>.
3386: Universität Freiburg, Institut für Informatik,
3387: Bericht 38, Oktober 1991.
3388: </bibl>
3389:
3390: <bibl id="Clark" key="Clark">James Clark.
3391: Comparison of SGML and XML. See
3392: <loc href="http://www.w3.org/TR/NOTE-sgml-xml-971215">http://www.w3.org/TR/NOTE-sgml-xml-971215</loc>.
3393: </bibl>
3394: <bibl id="RFC1738" xml-link="simple" key="IETF RFC1738">
3395: IETF (Internet Engineering Task Force).
3396: <emph>RFC 1738: Uniform Resource Locators (URL)</emph>,
3397: ed. T. Berners-Lee, L. Masinter, M. McCahill.
3398: 1994.
3399: </bibl>
3400:
3401: <bibl id="RFC1808" xml-link="simple" key="IETF RFC1808">
3402: IETF (Internet Engineering Task Force).
3403: <emph>RFC 1808: Relative Uniform Resource Locators</emph>,
3404: ed. R. Fielding.
3405: 1995.
3406: </bibl>
3407:
3408: <bibl id="RFC2141" xml-link="simple" key="IETF RFC2141">
3409: IETF (Internet Engineering Task Force).
3410: <emph>RFC 2141: URN Syntax</emph>,
3411: ed. R. Moats.
3412: 1997.
3413: </bibl>
3414:
3415: <bibl id="ISO8879" key="ISO 8879">ISO
3416: (International Organization for Standardization).
3417: <emph>ISO 8879:1986(E). Information processing — Text and Office
3418: Systems — Standard Generalized Markup Language (SGML).</emph> First
3419: edition — 1986-10-15. [Geneva]: International Organization for
3420: Standardization, 1986.
3421: </bibl>
3422:
3423:
3424: <bibl id="ISO10744" key="ISO/IEC 10744">ISO
3425: (International Organization for Standardization).
3426: <emph>ISO/IEC 10744-1992 (E). Information technology —
3427: Hypermedia/Time-based Structuring Language (HyTime).
3428: </emph>
3429: [Geneva]: International Organization for
3430: Standardization, 1992.
3431: <emph>Extended Facilities Annexe.</emph>
3432: [Geneva]: International Organization for
3433: Standardization, 1996.
3434: </bibl>
3435:
3436:
3437:
3438: </blist>
3439: </div2>
3440: </div1>
3441: <div1 id="CharClasses">
3442: <head>Character Classes</head>
3443: <p>Following the characteristics defined in the Unicode standard,
3444: characters are classed as base characters (among others, these
3445: contain the alphabetic characters of the Latin alphabet, without
3446: diacritics), ideographic characters, and combining characters (among
3447: others, this class contains most diacritics); these classes combine
3448: to form the class of letters. Digits and extenders are
3449: also distinguished.
3450: <scrap lang="ebnf" id="CHARACTERS">
3451: <head>Characters</head>
3452: <prodgroup pcw3="3" pcw4="15">
3453: <prod id="NT-Letter"><lhs>Letter</lhs>
3454: <rhs><nt def="NT-BaseChar">BaseChar</nt>
3455: | <nt def="NT-Ideographic">Ideographic</nt></rhs> </prod>
3456: <prod id="NT-BaseChar"><lhs>BaseChar</lhs>
3457: <rhs>[#x0041-#x005A]
3458: | [#x0061-#x007A]
3459: | [#x00C0-#x00D6]
3460: | [#x00D8-#x00F6]
3461: | [#x00F8-#x00FF]
3462: | [#x0100-#x0131]
3463: | [#x0134-#x013E]
3464: | [#x0141-#x0148]
3465: | [#x014A-#x017E]
3466: | [#x0180-#x01C3]
3467: | [#x01CD-#x01F0]
3468: | [#x01F4-#x01F5]
3469: | [#x01FA-#x0217]
3470: | [#x0250-#x02A8]
3471: | [#x02BB-#x02C1]
3472: | #x0386
3473: | [#x0388-#x038A]
3474: | #x038C
3475: | [#x038E-#x03A1]
3476: | [#x03A3-#x03CE]
3477: | [#x03D0-#x03D6]
3478: | #x03DA
3479: | #x03DC
3480: | #x03DE
3481: | #x03E0
3482: | [#x03E2-#x03F3]
3483: | [#x0401-#x040C]
3484: | [#x040E-#x044F]
3485: | [#x0451-#x045C]
3486: | [#x045E-#x0481]
3487: | [#x0490-#x04C4]
3488: | [#x04C7-#x04C8]
3489: | [#x04CB-#x04CC]
3490: | [#x04D0-#x04EB]
3491: | [#x04EE-#x04F5]
3492: | [#x04F8-#x04F9]
3493: | [#x0531-#x0556]
3494: | #x0559
3495: | [#x0561-#x0586]
3496: | [#x05D0-#x05EA]
3497: | [#x05F0-#x05F2]
3498: | [#x0621-#x063A]
3499: | [#x0641-#x064A]
3500: | [#x0671-#x06B7]
3501: | [#x06BA-#x06BE]
3502: | [#x06C0-#x06CE]
3503: | [#x06D0-#x06D3]
3504: | #x06D5
3505: | [#x06E5-#x06E6]
3506: | [#x0905-#x0939]
3507: | #x093D
3508: | [#x0958-#x0961]
3509: | [#x0985-#x098C]
3510: | [#x098F-#x0990]
3511: | [#x0993-#x09A8]
3512: | [#x09AA-#x09B0]
3513: | #x09B2
3514: | [#x09B6-#x09B9]
3515: | [#x09DC-#x09DD]
3516: | [#x09DF-#x09E1]
3517: | [#x09F0-#x09F1]
3518: | [#x0A05-#x0A0A]
3519: | [#x0A0F-#x0A10]
3520: | [#x0A13-#x0A28]
3521: | [#x0A2A-#x0A30]
3522: | [#x0A32-#x0A33]
3523: | [#x0A35-#x0A36]
3524: | [#x0A38-#x0A39]
3525: | [#x0A59-#x0A5C]
3526: | #x0A5E
3527: | [#x0A72-#x0A74]
3528: | [#x0A85-#x0A8B]
3529: | #x0A8D
3530: | [#x0A8F-#x0A91]
3531: | [#x0A93-#x0AA8]
3532: | [#x0AAA-#x0AB0]
3533: | [#x0AB2-#x0AB3]
3534: | [#x0AB5-#x0AB9]
3535: | #x0ABD
3536: | #x0AE0
3537: | [#x0B05-#x0B0C]
3538: | [#x0B0F-#x0B10]
3539: | [#x0B13-#x0B28]
3540: | [#x0B2A-#x0B30]
3541: | [#x0B32-#x0B33]
3542: | [#x0B36-#x0B39]
3543: | #x0B3D
3544: | [#x0B5C-#x0B5D]
3545: | [#x0B5F-#x0B61]
3546: | [#x0B85-#x0B8A]
3547: | [#x0B8E-#x0B90]
3548: | [#x0B92-#x0B95]
3549: | [#x0B99-#x0B9A]
3550: | #x0B9C
3551: | [#x0B9E-#x0B9F]
3552: | [#x0BA3-#x0BA4]
3553: | [#x0BA8-#x0BAA]
3554: | [#x0BAE-#x0BB5]
3555: | [#x0BB7-#x0BB9]
3556: | [#x0C05-#x0C0C]
3557: | [#x0C0E-#x0C10]
3558: | [#x0C12-#x0C28]
3559: | [#x0C2A-#x0C33]
3560: | [#x0C35-#x0C39]
3561: | [#x0C60-#x0C61]
3562: | [#x0C85-#x0C8C]
3563: | [#x0C8E-#x0C90]
3564: | [#x0C92-#x0CA8]
3565: | [#x0CAA-#x0CB3]
3566: | [#x0CB5-#x0CB9]
3567: | #x0CDE
3568: | [#x0CE0-#x0CE1]
3569: | [#x0D05-#x0D0C]
3570: | [#x0D0E-#x0D10]
3571: | [#x0D12-#x0D28]
3572: | [#x0D2A-#x0D39]
3573: | [#x0D60-#x0D61]
3574: | [#x0E01-#x0E2E]
3575: | #x0E30
3576: | [#x0E32-#x0E33]
3577: | [#x0E40-#x0E45]
3578: | [#x0E81-#x0E82]
3579: | #x0E84
3580: | [#x0E87-#x0E88]
3581: | #x0E8A
3582: | #x0E8D
3583: | [#x0E94-#x0E97]
3584: | [#x0E99-#x0E9F]
3585: | [#x0EA1-#x0EA3]
3586: | #x0EA5
3587: | #x0EA7
3588: | [#x0EAA-#x0EAB]
3589: | [#x0EAD-#x0EAE]
3590: | #x0EB0
3591: | [#x0EB2-#x0EB3]
3592: | #x0EBD
3593: | [#x0EC0-#x0EC4]
3594: | [#x0F40-#x0F47]
3595: | [#x0F49-#x0F69]
3596: | [#x10A0-#x10C5]
3597: | [#x10D0-#x10F6]
3598: | #x1100
3599: | [#x1102-#x1103]
3600: | [#x1105-#x1107]
3601: | #x1109
3602: | [#x110B-#x110C]
3603: | [#x110E-#x1112]
3604: | #x113C
3605: | #x113E
3606: | #x1140
3607: | #x114C
3608: | #x114E
3609: | #x1150
3610: | [#x1154-#x1155]
3611: | #x1159
3612: | [#x115F-#x1161]
3613: | #x1163
3614: | #x1165
3615: | #x1167
3616: | #x1169
3617: | [#x116D-#x116E]
3618: | [#x1172-#x1173]
3619: | #x1175
3620: | #x119E
3621: | #x11A8
3622: | #x11AB
3623: | [#x11AE-#x11AF]
3624: | [#x11B7-#x11B8]
3625: | #x11BA
3626: | [#x11BC-#x11C2]
3627: | #x11EB
3628: | #x11F0
3629: | #x11F9
3630: | [#x1E00-#x1E9B]
3631: | [#x1EA0-#x1EF9]
3632: | [#x1F00-#x1F15]
3633: | [#x1F18-#x1F1D]
3634: | [#x1F20-#x1F45]
3635: | [#x1F48-#x1F4D]
3636: | [#x1F50-#x1F57]
3637: | #x1F59
3638: | #x1F5B
3639: | #x1F5D
3640: | [#x1F5F-#x1F7D]
3641: | [#x1F80-#x1FB4]
3642: | [#x1FB6-#x1FBC]
3643: | #x1FBE
3644: | [#x1FC2-#x1FC4]
3645: | [#x1FC6-#x1FCC]
3646: | [#x1FD0-#x1FD3]
3647: | [#x1FD6-#x1FDB]
3648: | [#x1FE0-#x1FEC]
3649: | [#x1FF2-#x1FF4]
3650: | [#x1FF6-#x1FFC]
3651: | #x2126
3652: | [#x212A-#x212B]
3653: | #x212E
3654: | [#x2180-#x2182]
3655: | [#x3041-#x3094]
3656: | [#x30A1-#x30FA]
3657: | [#x3105-#x312C]
3658: | [#xAC00-#xD7A3]
3659: </rhs></prod>
3660: <prod id="NT-Ideographic"><lhs>Ideographic</lhs>
3661: <rhs>[#x4E00-#x9FA5]
3662: | #x3007
3663: | [#x3021-#x3029]
3664: </rhs></prod>
3665: <prod id="NT-CombiningChar"><lhs>CombiningChar</lhs>
3666: <rhs>[#x0300-#x0345]
3667: | [#x0360-#x0361]
3668: | [#x0483-#x0486]
3669: | [#x0591-#x05A1]
3670: | [#x05A3-#x05B9]
3671: | [#x05BB-#x05BD]
3672: | #x05BF
3673: | [#x05C1-#x05C2]
3674: | #x05C4
3675: | [#x064B-#x0652]
3676: | #x0670
3677: | [#x06D6-#x06DC]
3678: | [#x06DD-#x06DF]
3679: | [#x06E0-#x06E4]
3680: | [#x06E7-#x06E8]
3681: | [#x06EA-#x06ED]
3682: | [#x0901-#x0903]
3683: | #x093C
3684: | [#x093E-#x094C]
3685: | #x094D
3686: | [#x0951-#x0954]
3687: | [#x0962-#x0963]
3688: | [#x0981-#x0983]
3689: | #x09BC
3690: | #x09BE
3691: | #x09BF
3692: | [#x09C0-#x09C4]
3693: | [#x09C7-#x09C8]
3694: | [#x09CB-#x09CD]
3695: | #x09D7
3696: | [#x09E2-#x09E3]
3697: | #x0A02
3698: | #x0A3C
3699: | #x0A3E
3700: | #x0A3F
3701: | [#x0A40-#x0A42]
3702: | [#x0A47-#x0A48]
3703: | [#x0A4B-#x0A4D]
3704: | [#x0A70-#x0A71]
3705: | [#x0A81-#x0A83]
3706: | #x0ABC
3707: | [#x0ABE-#x0AC5]
3708: | [#x0AC7-#x0AC9]
3709: | [#x0ACB-#x0ACD]
3710: | [#x0B01-#x0B03]
3711: | #x0B3C
3712: | [#x0B3E-#x0B43]
3713: | [#x0B47-#x0B48]
3714: | [#x0B4B-#x0B4D]
3715: | [#x0B56-#x0B57]
3716: | [#x0B82-#x0B83]
3717: | [#x0BBE-#x0BC2]
3718: | [#x0BC6-#x0BC8]
3719: | [#x0BCA-#x0BCD]
3720: | #x0BD7
3721: | [#x0C01-#x0C03]
3722: | [#x0C3E-#x0C44]
3723: | [#x0C46-#x0C48]
3724: | [#x0C4A-#x0C4D]
3725: | [#x0C55-#x0C56]
3726: | [#x0C82-#x0C83]
3727: | [#x0CBE-#x0CC4]
3728: | [#x0CC6-#x0CC8]
3729: | [#x0CCA-#x0CCD]
3730: | [#x0CD5-#x0CD6]
3731: | [#x0D02-#x0D03]
3732: | [#x0D3E-#x0D43]
3733: | [#x0D46-#x0D48]
3734: | [#x0D4A-#x0D4D]
3735: | #x0D57
3736: | #x0E31
3737: | [#x0E34-#x0E3A]
3738: | [#x0E47-#x0E4E]
3739: | #x0EB1
3740: | [#x0EB4-#x0EB9]
3741: | [#x0EBB-#x0EBC]
3742: | [#x0EC8-#x0ECD]
3743: | [#x0F18-#x0F19]
3744: | #x0F35
3745: | #x0F37
3746: | #x0F39
3747: | #x0F3E
3748: | #x0F3F
3749: | [#x0F71-#x0F84]
3750: | [#x0F86-#x0F8B]
3751: | [#x0F90-#x0F95]
3752: | #x0F97
3753: | [#x0F99-#x0FAD]
3754: | [#x0FB1-#x0FB7]
3755: | #x0FB9
3756: | [#x20D0-#x20DC]
3757: | #x20E1
3758: | [#x302A-#x302F]
3759: | #x3099
3760: | #x309A
3761: </rhs></prod>
3762: <prod id="NT-Digit"><lhs>Digit</lhs>
3763: <rhs>[#x0030-#x0039]
3764: | [#x0660-#x0669]
3765: | [#x06F0-#x06F9]
3766: | [#x0966-#x096F]
3767: | [#x09E6-#x09EF]
3768: | [#x0A66-#x0A6F]
3769: | [#x0AE6-#x0AEF]
3770: | [#x0B66-#x0B6F]
3771: | [#x0BE7-#x0BEF]
3772: | [#x0C66-#x0C6F]
3773: | [#x0CE6-#x0CEF]
3774: | [#x0D66-#x0D6F]
3775: | [#x0E50-#x0E59]
3776: | [#x0ED0-#x0ED9]
3777: | [#x0F20-#x0F29]
3778: </rhs></prod>
3779: <prod id="NT-Extender"><lhs>Extender</lhs>
3780: <rhs>#x00B7
3781: | #x02D0
3782: | #x02D1
3783: | #x0387
3784: | #x0640
3785: | #x0E46
3786: | #x0EC6
3787: | #x3005
3788: | [#x3031-#x3035]
3789: | [#x309D-#x309E]
3790: | [#x30FC-#x30FE]
3791: </rhs></prod>
3792:
3793: </prodgroup>
3794: </scrap>
3795: </p>
3796: <p>The character classes defined here can be derived from the
3797: Unicode character database as follows:
3798: <ulist>
3799: <item>
3800: <p>Name start characters must have one of the categories Ll, Lu,
3801: Lo, Lt, Nl.</p>
3802: </item>
3803: <item>
3804: <p>Name characters other than Name-start characters
3805: must have one of the categories Mc, Me, Mn, Lm, or Nd.</p>
3806: </item>
3807: <item>
3808: <p>Characters in the compatibility area (i.e. with character code
3809: greater than #xF900 and less than #xFFFE) are not allowed in XML
3810: names.</p>
3811: </item>
3812: <item>
3813: <p>Characters which have a font or compatibility decomposition (i.e. those
3814: with a "compatibility formatting tag" in field 5 of the database --
3815: marked by field 5 beginning with a "<") are not allowed.</p>
3816: </item>
3817: <item>
3818: <p>The following characters are treated as name-start characters
3819: rather than name characters, because the property file classifies
3820: them as Alphabetic: [#x02BB-#x02C1], #x0559, #x06E5, #x06E6.</p>
3821: </item>
3822: <item>
3823: <p>Characters #x20DD-#x20E0 are excluded (in accordance with
3824: Unicode, section 5.14).</p>
3825: </item>
3826: <item>
3827: <p>Character #x00B7 is classified as an extender, because the
3828: property list so identifies it.</p>
3829: </item>
3830: <item>
3831: <p>Character #x0387 is added as a name character, because #x00B7
3832: is its canonical equivalent.</p>
3833: </item>
3834: <item>
3835: <p>Characters ':' and '_' are allowed as name-start characters.</p>
3836: </item>
3837: <item>
3838: <p>Characters '-' and '.' are allowed as name characters.</p>
3839: </item>
3840: </ulist>
3841: </p>
3842: </div1>
3843: <inform-div1 id="sec-xml-and-sgml">
3844: <head>XML and SGML</head>
3845:
3846: <p>XML is designed to be a subset of SGML, in that every
3847: <termref def="dt-valid">valid</termref> XML document should also be a
3848: conformant SGML document.
3849: For a detailed comparison of the additional restrictions that XML places on
3850: documents beyond those of SGML, see <bibref ref="Clark"/>.
3851: </p>
3852: </inform-div1>
3853: <inform-div1 id="sec-entexpand">
3854: <head>Expansion of Entity and Character References</head>
3855: <p>This appendix contains some examples illustrating the
3856: sequence of entity- and character-reference recognition and
3857: expansion, as specified in <specref ref="entproc"/>.</p>
3858: <p>
3859: If the DTD contains the declaration
3860: <eg><![CDATA[<!ENTITY example "<p>An ampersand (&#38;) may be escaped
3861: numerically (&#38;#38;) or with a general entity
3862: (&amp;).</p>" >
3863: ]]></eg>
3864: then the XML processor will recognize the character references
3865: when it parses the entity declaration, and resolve them before
3866: storing the following string as the
3867: value of the entity "<code>example</code>":
3868: <eg><![CDATA[<p>An ampersand (&) may be escaped
3869: numerically (&#38;) or with a general entity
3870: (&amp;).</p>
3871: ]]></eg>
3872: A reference in the document to "<code>&example;</code>"
3873: will cause the text to be reparsed, at which time the
3874: start- and end-tags of the "<code>p</code>" element will be recognized
3875: and the three references will be recognized and expanded,
3876: resulting in a "<code>p</code>" element with the following content
3877: (all data, no delimiters or markup):
3878: <eg><![CDATA[An ampersand (&) may be escaped
3879: numerically (&) or with a general entity
3880: (&).
3881: ]]></eg>
3882: </p>
3883: <p>A more complex example will illustrate the rules and their
3884: effects fully. In the following example, the line numbers are
3885: solely for reference.
3886: <eg><![CDATA[1 <?xml version='1.0'?>
3887: 2 <!DOCTYPE test [
3888: 3 <!ELEMENT test (#PCDATA) >
3889: 4 <!ENTITY % xx '%zz;'>
3890: 5 <!ENTITY % zz '<!ENTITY tricky "error-prone" >' >
3891: 6 %xx;
3892: 7 ]>
3893: 8 <test>This sample shows a &tricky; method.</test>
3894: ]]></eg>
3895: This produces the following:
3896: <ulist spacing="compact">
3897: <item><p>in line 4, the reference to character 37 is expanded immediately,
3898: and the parameter entity "<code>xx</code>" is stored in the symbol
3899: table with the value "<code>%zz;</code>". Since the replacement text
3900: is not rescanned, the reference to parameter entity "<code>zz</code>"
3901: is not recognized. (And it would be an error if it were, since
3902: "<code>zz</code>" is not yet declared.)</p></item>
3903: <item><p>in line 5, the character reference "<code>&#60;</code>" is
3904: expanded immediately and the parameter entity "<code>zz</code>" is
3905: stored with the replacement text
3906: "<code><!ENTITY tricky "error-prone" ></code>",
3907: which is a well-formed entity declaration.</p></item>
3908: <item><p>in line 6, the reference to "<code>xx</code>" is recognized,
3909: and the replacement text of "<code>xx</code>" (namely
3910: "<code>%zz;</code>") is parsed. The reference to "<code>zz</code>"
3911: is recognized in its turn, and its replacement text
3912: ("<code><!ENTITY tricky "error-prone" ></code>") is parsed.
3913: The general entity "<code>tricky</code>" has now been
3914: declared, with the replacement text "<code>error-prone</code>".</p></item>
3915: <item><p>
3916: in line 8, the reference to the general entity "<code>tricky</code>" is
3917: recognized, and it is expanded, so the full content of the
3918: "<code>test</code>" element is the self-describing (and ungrammatical) string
3919: <emph>This sample shows a error-prone method.</emph>
3920: </p></item>
3921: </ulist>
3922: </p>
3923: </inform-div1>
3924: <inform-div1 id="determinism">
3925: <head>Deterministic Content Models</head>
3926: <p><termref def="dt-compat">For compatibility</termref>, it is
3927: required
3928: that content models in element type declarations be deterministic.
3929: </p>
3930: <!-- FINAL EDIT: WebSGML allows ambiguity? -->
3931: <p>SGML
3932: requires deterministic content models (it calls them
3933: "unambiguous"); XML processors built using SGML systems may
3934: flag non-deterministic content models as errors.</p>
3935: <p>For example, the content model <code>((b, c) | (b, d))</code> is
3936: non-deterministic, because given an initial <code>b</code> the parser
3937: cannot know which <code>b</code> in the model is being matched without
3938: looking ahead to see which element follows the <code>b</code>.
3939: In this case, the two references to
3940: <code>b</code> can be collapsed
3941: into a single reference, making the model read
3942: <code>(b, (c | d))</code>. An initial <code>b</code> now clearly
3943: matches only a single name in the content model. The parser doesn't
3944: need to look ahead to see what follows; either <code>c</code> or
3945: <code>d</code> would be accepted.</p>
3946: <p>More formally: a finite state automaton may be constructed from the
3947: content model using the standard algorithms, e.g. algorithm 3.5
3948: in section 3.9
3949: of Aho, Sethi, and Ullman <bibref ref="Aho"/>.
3950: In many such algorithms, a follow set is constructed for each
3951: position in the regular expression (i.e., each leaf
3952: node in the
3953: syntax tree for the regular expression);
3954: if any position has a follow set in which
3955: more than one following position is
3956: labeled with the same element type name,
3957: then the content model is in error
3958: and may be reported as an error.
3959: </p>
3960: <p>Algorithms exist which allow many but not all non-deterministic
3961: content models to be reduced automatically to equivalent deterministic
3962: models; see Brüggemann-Klein 1991 <bibref ref="ABK"/>.</p>
3963: </inform-div1>
3964: <inform-div1 id="sec-guessing">
3965: <head>Autodetection of Character Encodings</head>
3966: <p>The XML encoding declaration functions as an internal label on each
3967: entity, indicating which character encoding is in use. Before an XML
3968: processor can read the internal label, however, it apparently has to
3969: know what character encoding is in use—which is what the internal label
3970: is trying to indicate. In the general case, this is a hopeless
3971: situation. It is not entirely hopeless in XML, however, because XML
3972: limits the general case in two ways: each implementation is assumed
3973: to support only a finite set of character encodings, and the XML
3974: encoding declaration is restricted in position and content in order to
3975: make it feasible to autodetect the character encoding in use in each
3976: entity in normal cases. Also, in many cases other sources of information
3977: are available in addition to the XML data stream itself.
3978: Two cases may be distinguished,
3979: depending on whether the XML entity is presented to the
3980: processor without, or with, any accompanying
3981: (external) information. We consider the first case first.
3982: </p>
3983: <p>
3984: Because each XML entity not in UTF-8 or UTF-16 format <emph>must</emph>
3985: begin with an XML encoding declaration, in which the first characters
3986: must be '<code><?xml</code>', any conforming processor can detect,
3987: after two to four octets of input, which of the following cases apply.
3988: In reading this list, it may help to know that in UCS-4, '<' is
3989: "<code>#x0000003C</code>" and '?' is "<code>#x0000003F</code>", and the Byte
3990: Order Mark required of UTF-16 data streams is "<code>#xFEFF</code>".</p>
3991: <p>
3992: <ulist>
3993: <item>
3994: <p><code>00 00 00 3C</code>: UCS-4, big-endian machine (1234 order)</p>
3995: </item>
3996: <item>
3997: <p><code>3C 00 00 00</code>: UCS-4, little-endian machine (4321 order)</p>
3998: </item>
3999: <item>
4000: <p><code>00 00 3C 00</code>: UCS-4, unusual octet order (2143)</p>
4001: </item>
4002: <item>
4003: <p><code>00 3C 00 00</code>: UCS-4, unusual octet order (3412)</p>
4004: </item>
4005: <item>
4006: <p><code>FE FF</code>: UTF-16, big-endian</p>
4007: </item>
4008: <item>
4009: <p><code>FF FE</code>: UTF-16, little-endian</p>
4010: </item>
4011: <item>
4012: <p><code>00 3C 00 3F</code>: UTF-16, big-endian, no Byte Order Mark
4013: (and thus, strictly speaking, in error)</p>
4014: </item>
4015: <item>
4016: <p><code>3C 00 3F 00</code>: UTF-16, little-endian, no Byte Order Mark
4017: (and thus, strictly speaking, in error)</p>
4018: </item>
4019: <item>
4020: <p><code>3C 3F 78 6D</code>: UTF-8, ISO 646, ASCII, some part of ISO 8859,
4021: Shift-JIS, EUC, or any other 7-bit, 8-bit, or mixed-width encoding
4022: which ensures that the characters of ASCII have their normal positions,
4023: width,
4024: and values; the actual encoding declaration must be read to
4025: detect which of these applies, but since all of these encodings
4026: use the same bit patterns for the ASCII characters, the encoding
4027: declaration itself may be read reliably
4028: </p>
4029: </item>
4030: <item>
4031: <p><code>4C 6F A7 94</code>: EBCDIC (in some flavor; the full
4032: encoding declaration must be read to tell which code page is in
4033: use)</p>
4034: </item>
4035: <item>
4036: <p>other: UTF-8 without an encoding declaration, or else
4037: the data stream is corrupt, fragmentary, or enclosed in
4038: a wrapper of some kind</p>
4039: </item>
4040: </ulist>
4041: </p>
4042: <p>
4043: This level of autodetection is enough to read the XML encoding
4044: declaration and parse the character-encoding identifier, which is
4045: still necessary to distinguish the individual members of each family
4046: of encodings (e.g. to tell UTF-8 from 8859, and the parts of 8859
4047: from each other, or to distinguish the specific EBCDIC code page in
4048: use, and so on).
4049: </p>
4050: <p>
4051: Because the contents of the encoding declaration are restricted to
4052: ASCII characters, a processor can reliably read the entire encoding
4053: declaration as soon as it has detected which family of encodings is in
4054: use. Since in practice, all widely used character encodings fall into
4055: one of the categories above, the XML encoding declaration allows
4056: reasonably reliable in-band labeling of character encodings, even when
4057: external sources of information at the operating-system or
4058: transport-protocol level are unreliable.
4059: </p>
4060: <p>
4061: Once the processor has detected the character encoding in use, it can
4062: act appropriately, whether by invoking a separate input routine for
4063: each case, or by calling the proper conversion function on each
4064: character of input.
4065: </p>
4066: <p>
4067: Like any self-labeling system, the XML encoding declaration will not
4068: work if any software changes the entity's character set or encoding
4069: without updating the encoding declaration. Implementors of
4070: character-encoding routines should be careful to ensure the accuracy
4071: of the internal and external information used to label the entity.
4072: </p>
4073: <p>The second possible case occurs when the XML entity is accompanied
4074: by encoding information, as in some file systems and some network
4075: protocols.
4076: When multiple sources of information are available,
4077:
4078: their relative
4079: priority and the preferred method of handling conflict should be
4080: specified as part of the higher-level protocol used to deliver XML.
4081: Rules for the relative priority of the internal label and the
4082: MIME-type label in an external header, for example, should be part of the
4083: RFC document defining the text/xml and application/xml MIME types. In
4084: the interests of interoperability, however, the following rules
4085: are recommended.
4086: <ulist>
4087: <item><p>If an XML entity is in a file, the Byte-Order Mark
4088: and encoding-declaration PI are used (if present) to determine the
4089: character encoding. All other heuristics and sources of information
4090: are solely for error recovery.
4091: </p></item>
4092: <item><p>If an XML entity is delivered with a
4093: MIME type of text/xml, then the <code>charset</code> parameter
4094: on the MIME type determines the
4095: character encoding method; all other heuristics and sources of
4096: information are solely for error recovery.
4097: </p></item>
4098: <item><p>If an XML entity is delivered
4099: with a
4100: MIME type of application/xml, then the Byte-Order Mark and
4101: encoding-declaration PI are used (if present) to determine the
4102: character encoding. All other heuristics and sources of
4103: information are solely for error recovery.
4104: </p></item>
4105: </ulist>
4106: These rules apply only in the absence of protocol-level documentation;
4107: in particular, when the MIME types text/xml and application/xml are
4108: defined, the recommendations of the relevant RFC will supersede
4109: these rules.
4110: </p>
4111:
4112: </inform-div1>
4113:
4114: <inform-div1 id="sec-xml-wg">
4115: <head>W3C XML Working Group</head>
4116:
4117: <p>This specification was prepared and approved for publication by the
4118: W3C XML Working Group (WG). WG approval of this specification does
4119: not necessarily imply that all WG members voted for its approval.
4120: The current and former members of the XML WG are:</p>
4121:
4122: <orglist>
4123: <member><name>Jon Bosak, Sun</name><role>Chair</role></member>
4124: <member><name>James Clark</name><role>Technical Lead</role></member>
4125: <member><name>Tim Bray, Textuality and Netscape</name><role>XML Co-editor</role></member>
4126: <member><name>Jean Paoli, Microsoft</name><role>XML Co-editor</role></member>
4127: <member><name>C. M. Sperberg-McQueen, U. of Ill.</name><role>XML
4128: Co-editor</role></member>
4129: <member><name>Dan Connolly, W3C</name><role>W3C Liaison</role></member>
4130: <member><name>Paula Angerstein, Texcel</name></member>
4131: <member><name>Steve DeRose, INSO</name></member>
4132: <member><name>Dave Hollander, HP</name></member>
4133: <member><name>Eliot Kimber, ISOGEN</name></member>
4134: <member><name>Eve Maler, ArborText</name></member>
4135: <member><name>Tom Magliery, NCSA</name></member>
4136: <member><name>Murray Maloney, Muzmo and Grif</name></member>
4137: <member><name>Makoto Murata, Fuji Xerox Information Systems</name></member>
4138: <member><name>Joel Nava, Adobe</name></member>
4139: <member><name>Conleth O'Connell, Vignette</name></member>
4140: <member><name>Peter Sharpe, SoftQuad</name></member>
4141: <member><name>John Tigue, DataChannel</name></member>
4142: </orglist>
4143:
4144: </inform-div1>
4145: </back>
4146: </spec>
4147: <!-- Keep this comment at the end of the file
4148: Local variables:
4149: mode: sgml
4150: sgml-default-dtd-file:"~/sgml/spec.ced"
4151: sgml-omittag:t
4152: sgml-shorttag:t
4153: End:
4154: -->
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