Annotation of embedaddon/libxml2/test/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:
4: <!-- LAST TOUCHED BY: Tim Bray, 8 February 1997 -->
5:
6: <!-- The words 'FINAL EDIT' in comments mark places where changes
7: need to be made after approval of the document by the ERB, before
8: publication. -->
9:
10: <!ENTITY XML.version "1.0">
11: <!ENTITY doc.date "10 February 1998">
12: <!ENTITY iso6.doc.date "19980210">
13: <!ENTITY w3c.doc.date "02-Feb-1998">
14: <!ENTITY draft.day '10'>
15: <!ENTITY draft.month 'February'>
16: <!ENTITY draft.year '1998'>
17:
18: <!ENTITY WebSGML
19: 'WebSGML Adaptations Annex to ISO 8879'>
20:
21: <!ENTITY lt "<">
22: <!ENTITY gt ">">
23: <!ENTITY xmlpio "'<?xml'">
24: <!ENTITY pic "'?>'">
25: <!ENTITY br "\n">
26: <!ENTITY cellback '#c0d9c0'>
27: <!ENTITY mdash "--"> <!-- —, but nsgmls doesn't grok hex -->
28: <!ENTITY com "--">
29: <!ENTITY como "--">
30: <!ENTITY comc "--">
31: <!ENTITY hcro "&#x">
32: <!-- <!ENTITY nbsp " "> -->
33: <!ENTITY nbsp " ">
34: <!ENTITY magicents "<code>amp</code>,
35: <code>lt</code>,
36: <code>gt</code>,
37: <code>apos</code>,
38: <code>quot</code>">
39:
40: <!-- audience and distribution status: for use at publication time -->
41: <!ENTITY doc.audience "public review and discussion">
42: <!ENTITY doc.distribution "may be distributed freely, as long as
43: all text and legal notices remain intact">
44:
45: ]>
46:
47: <!-- for Panorama *-->
48: <?VERBATIM "eg" ?>
49:
50: <spec>
51: <header>
52: <title>Extensible Markup Language (XML) 1.0</title>
53: <version></version>
54: <w3c-designation>REC-xml-&iso6.doc.date;</w3c-designation>
55: <w3c-doctype>W3C Recommendation</w3c-doctype>
56: <pubdate><day>&draft.day;</day><month>&draft.month;</month><year>&draft.year;</year></pubdate>
57:
58: <publoc>
59: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;">
60: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;</loc>
61: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.xml">
62: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.xml</loc>
63: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.html">
64: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.html</loc>
65: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.pdf">
66: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.pdf</loc>
67: <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.ps">
68: http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.ps</loc>
69: </publoc>
70: <latestloc>
71: <loc href="http://www.w3.org/TR/REC-xml">
72: http://www.w3.org/TR/REC-xml</loc>
73: </latestloc>
74: <prevlocs>
75: <loc href="http://www.w3.org/TR/PR-xml-971208">
76: http://www.w3.org/TR/PR-xml-971208</loc>
77: <!--
78: <loc href='http://www.w3.org/TR/WD-xml-961114'>
79: http://www.w3.org/TR/WD-xml-961114</loc>
80: <loc href='http://www.w3.org/TR/WD-xml-lang-970331'>
81: http://www.w3.org/TR/WD-xml-lang-970331</loc>
82: <loc href='http://www.w3.org/TR/WD-xml-lang-970630'>
83: http://www.w3.org/TR/WD-xml-lang-970630</loc>
84: <loc href='http://www.w3.org/TR/WD-xml-970807'>
85: http://www.w3.org/TR/WD-xml-970807</loc>
86: <loc href='http://www.w3.org/TR/WD-xml-971117'>
87: http://www.w3.org/TR/WD-xml-971117</loc>-->
88: </prevlocs>
89: <authlist>
90: <author><name>Tim Bray</name>
91: <affiliation>Textuality and Netscape</affiliation>
92: <email
93: href="mailto:tbray@textuality.com">tbray@textuality.com</email></author>
94: <author><name>Jean Paoli</name>
95: <affiliation>Microsoft</affiliation>
96: <email href="mailto:jeanpa@microsoft.com">jeanpa@microsoft.com</email></author>
97: <author><name>C. M. Sperberg-McQueen</name>
98: <affiliation>University of Illinois at Chicago</affiliation>
99: <email href="mailto:cmsmcq@uic.edu">cmsmcq@uic.edu</email></author>
100: </authlist>
101: <abstract>
102: <p>The Extensible Markup Language (XML) is a subset of
103: SGML that is completely described in this document. Its goal is to
104: enable generic SGML to be served, received, and processed on the Web
105: in the way that is now possible with HTML. XML has been designed for
106: ease of implementation and for interoperability with both SGML and
107: HTML.</p>
108: </abstract>
109: <status>
110: <p>This document has been reviewed by W3C Members and
111: other interested parties and has been endorsed by the
112: Director as a W3C Recommendation. It is a stable
113: document and may be used as reference material or cited
114: as a normative reference from another document. W3C's
115: role in making the Recommendation is to draw attention
116: to the specification and to promote its widespread
117: deployment. This enhances the functionality and
118: interoperability of the Web.</p>
119: <p>
120: This document specifies a syntax created by subsetting an existing,
121: widely used international text processing standard (Standard
122: Generalized Markup Language, ISO 8879:1986(E) as amended and
123: corrected) for use on the World Wide Web. It is a product of the W3C
124: XML Activity, details of which can be found at <loc
125: href='http://www.w3.org/XML'>http://www.w3.org/XML</loc>. A list of
126: current W3C Recommendations and other technical documents can be found
127: at <loc href='http://www.w3.org/TR'>http://www.w3.org/TR</loc>.
128: </p>
129: <p>This specification uses the term URI, which is defined by <bibref
130: ref="Berners-Lee"/>, a work in progress expected to update <bibref
131: ref="RFC1738"/> and <bibref ref="RFC1808"/>.
132: </p>
133: <p>The list of known errors in this specification is
134: available at
135: <loc href='http://www.w3.org/XML/xml-19980210-errata'>http://www.w3.org/XML/xml-19980210-errata</loc>.</p>
136: <p>Please report errors in this document to
137: <loc href='mailto:xml-editor@w3.org'>xml-editor@w3.org</loc>.
138: </p>
139: </status>
140:
141:
142: <pubstmt>
143: <p>Chicago, Vancouver, Mountain View, et al.:
144: World-Wide Web Consortium, XML Working Group, 1996, 1997.</p>
145: </pubstmt>
146: <sourcedesc>
147: <p>Created in electronic form.</p>
148: </sourcedesc>
149: <langusage>
150: <language id='EN'>English</language>
151: <language id='ebnf'>Extended Backus-Naur Form (formal grammar)</language>
152: </langusage>
153: <revisiondesc>
154: <slist>
155: <sitem>1997-12-03 : CMSMcQ : yet further changes</sitem>
156: <sitem>1997-12-02 : TB : further changes (see TB to XML WG,
157: 2 December 1997)</sitem>
158: <sitem>1997-12-02 : CMSMcQ : deal with as many corrections and
159: comments from the proofreaders as possible:
160: entify hard-coded document date in pubdate element,
161: change expansion of entity WebSGML,
162: update status description as per Dan Connolly (am not sure
163: about refernece to Berners-Lee et al.),
164: add 'The' to abstract as per WG decision,
165: move Relationship to Existing Standards to back matter and
166: combine with References,
167: re-order back matter so normative appendices come first,
168: re-tag back matter so informative appendices are tagged informdiv1,
169: remove XXX XXX from list of 'normative' specs in prose,
170: move some references from Other References to Normative References,
171: add RFC 1738, 1808, and 2141 to Other References (they are not
172: normative since we do not require the processor to enforce any
173: rules based on them),
174: add reference to 'Fielding draft' (Berners-Lee et al.),
175: move notation section to end of body,
176: drop URIchar non-terminal and use SkipLit instead,
177: lose stray reference to defunct nonterminal 'markupdecls',
178: move reference to Aho et al. into appendix (Tim's right),
179: add prose note saying that hash marks and fragment identifiers are
180: NOT part of the URI formally speaking, and are NOT legal in
181: system identifiers (processor 'may' signal an error).
182: Work through:
183: Tim Bray reacting to James Clark,
184: Tim Bray on his own,
185: Eve Maler,
186:
187: NOT DONE YET:
188: change binary / text to unparsed / parsed.
189: handle James's suggestion about < in attriubte values
190: uppercase hex characters,
191: namechar list,
192: </sitem>
193: <sitem>1997-12-01 : JB : add some column-width parameters</sitem>
194: <sitem>1997-12-01 : CMSMcQ : begin round of changes to incorporate
195: recent WG decisions and other corrections:
196: binding sources of character encoding info (27 Aug / 3 Sept),
197: correct wording of Faust quotation (restore dropped line),
198: drop SDD from EncodingDecl,
199: change text at version number 1.0,
200: drop misleading (wrong!) sentence about ignorables and extenders,
201: modify definition of PCData to make bar on msc grammatical,
202: change grammar's handling of internal subset (drop non-terminal markupdecls),
203: change definition of includeSect to allow conditional sections,
204: add integral-declaration constraint on internal subset,
205: drop misleading / dangerous sentence about relationship of
206: entities with system storage objects,
207: change table body tag to htbody as per EM change to DTD,
208: add rule about space normalization in public identifiers,
209: add description of how to generate our name-space rules from
210: Unicode character database (needs further work!).
211: </sitem>
212: <sitem>1997-10-08 : TB : Removed %-constructs again, new rules
213: for PE appearance.</sitem>
214: <sitem>1997-10-01 : TB : Case-sensitive markup; cleaned up
215: element-type defs, lotsa little edits for style</sitem>
216: <sitem>1997-09-25 : TB : Change to elm's new DTD, with
217: substantial detail cleanup as a side-effect</sitem>
218: <sitem>1997-07-24 : CMSMcQ : correct error (lost *) in definition
219: of ignoreSectContents (thanks to Makoto Murata)</sitem>
220: <sitem>Allow all empty elements to have end-tags, consistent with
221: SGML TC (as per JJC).</sitem>
222: <sitem>1997-07-23 : CMSMcQ : pre-emptive strike on pending corrections:
223: introduce the term 'empty-element tag', note that all empty elements
224: may use it, and elements declared EMPTY must use it.
225: Add WFC requiring encoding decl to come first in an entity.
226: Redefine notations to point to PIs as well as binary entities.
227: Change autodetection table by removing bytes 3 and 4 from
228: examples with Byte Order Mark.
229: Add content model as a term and clarify that it applies to both
230: mixed and element content.
231: </sitem>
232: <sitem>1997-06-30 : CMSMcQ : change date, some cosmetic changes,
233: changes to productions for choice, seq, Mixed, NotationType,
234: Enumeration. Follow James Clark's suggestion and prohibit
235: conditional sections in internal subset. TO DO: simplify
236: production for ignored sections as a result, since we don't
237: need to worry about parsers which don't expand PErefs finding
238: a conditional section.</sitem>
239: <sitem>1997-06-29 : TB : various edits</sitem>
240: <sitem>1997-06-29 : CMSMcQ : further changes:
241: Suppress old FINAL EDIT comments and some dead material.
242: Revise occurrences of % in grammar to exploit Henry Thompson's pun,
243: especially markupdecl and attdef.
244: Remove RMD requirement relating to element content (?).
245: </sitem>
246: <sitem>1997-06-28 : CMSMcQ : Various changes for 1 July draft:
247: Add text for draconian error handling (introduce
248: the term Fatal Error).
249: RE deleta est (changing wording from
250: original announcement to restrict the requirement to validating
251: parsers).
252: Tag definition of validating processor and link to it.
253: Add colon as name character.
254: Change def of %operator.
255: Change standard definitions of lt, gt, amp.
256: Strip leading zeros from #x00nn forms.</sitem>
257: <sitem>1997-04-02 : CMSMcQ : final corrections of editorial errors
258: found in last night's proofreading. Reverse course once more on
259: well-formed: Webster's Second hyphenates it, and that's enough
260: for me.</sitem>
261: <sitem>1997-04-01 : CMSMcQ : corrections from JJC, EM, HT, and self</sitem>
262: <sitem>1997-03-31 : Tim Bray : many changes</sitem>
263: <sitem>1997-03-29 : CMSMcQ : some Henry Thompson (on entity handling),
264: some Charles Goldfarb, some ERB decisions (PE handling in miscellaneous
265: declarations. Changed Ident element to accept def attribute.
266: Allow normalization of Unicode characters. move def of systemliteral
267: into section on literals.</sitem>
268: <sitem>1997-03-28 : CMSMcQ : make as many corrections as possible, from
269: Terry Allen, Norbert Mikula, James Clark, Jon Bosak, Henry Thompson,
270: Paul Grosso, and self. Among other things: give in on "well formed"
271: (Terry is right), tentatively rename QuotedCData as AttValue
272: and Literal as EntityValue to be more informative, since attribute
273: values are the <emph>only</emph> place QuotedCData was used, and
274: vice versa for entity text and Literal. (I'd call it Entity Text,
275: but 8879 uses that name for both internal and external entities.)</sitem>
276: <sitem>1997-03-26 : CMSMcQ : resynch the two forks of this draft, reapply
277: my changes dated 03-20 and 03-21. Normalize old 'may not' to 'must not'
278: except in the one case where it meant 'may or may not'.</sitem>
279: <sitem>1997-03-21 : TB : massive changes on plane flight from Chicago
280: to Vancouver</sitem>
281: <sitem>1997-03-21 : CMSMcQ : correct as many reported errors as possible.
282: </sitem>
283: <sitem>1997-03-20 : CMSMcQ : correct typos listed in CMSMcQ hand copy of spec.</sitem>
284: <sitem>1997-03-20 : CMSMcQ : cosmetic changes preparatory to revision for
285: WWW conference April 1997: restore some of the internal entity
286: references (e.g. to docdate, etc.), change character xA0 to &nbsp;
287: and define nbsp as &#160;, and refill a lot of paragraphs for
288: legibility.</sitem>
289: <sitem>1996-11-12 : CMSMcQ : revise using Tim's edits:
290: Add list type of NUMBERED and change most lists either to
291: BULLETS or to NUMBERED.
292: Suppress QuotedNames, Names (not used).
293: Correct trivial-grammar doc type decl.
294: Rename 'marked section' as 'CDATA section' passim.
295: Also edits from James Clark:
296: Define the set of characters from which [^abc] subtracts.
297: Charref should use just [0-9] not Digit.
298: Location info needs cleaner treatment: remove? (ERB
299: question).
300: One example of a PI has wrong pic.
301: Clarify discussion of encoding names.
302: Encoding failure should lead to unspecified results; don't
303: prescribe error recovery.
304: Don't require exposure of entity boundaries.
305: Ignore white space in element content.
306: Reserve entity names of the form u-NNNN.
307: Clarify relative URLs.
308: And some of my own:
309: Correct productions for content model: model cannot
310: consist of a name, so "elements ::= cp" is no good.
311: </sitem>
312: <sitem>1996-11-11 : CMSMcQ : revise for style.
313: Add new rhs to entity declaration, for parameter entities.</sitem>
314: <sitem>1996-11-10 : CMSMcQ : revise for style.
315: Fix / complete section on names, characters.
316: Add sections on parameter entities, conditional sections.
317: Still to do: Add compatibility note on deterministic content models.
318: Finish stylistic revision.</sitem>
319: <sitem>1996-10-31 : TB : Add Entity Handling section</sitem>
320: <sitem>1996-10-30 : TB : Clean up term & termdef. Slip in
321: ERB decision re EMPTY.</sitem>
322: <sitem>1996-10-28 : TB : Change DTD. Implement some of Michael's
323: suggestions. Change comments back to //. Introduce language for
324: XML namespace reservation. Add section on white-space handling.
325: Lots more cleanup.</sitem>
326: <sitem>1996-10-24 : CMSMcQ : quick tweaks, implement some ERB
327: decisions. Characters are not integers. Comments are /* */ not //.
328: Add bibliographic refs to 10646, HyTime, Unicode.
329: Rename old Cdata as MsData since it's <emph>only</emph> seen
330: in marked sections. Call them attribute-value pairs not
331: name-value pairs, except once. Internal subset is optional, needs
332: '?'. Implied attributes should be signaled to the app, not
333: have values supplied by processor.</sitem>
334: <sitem>1996-10-16 : TB : track down & excise all DSD references;
335: introduce some EBNF for entity declarations.</sitem>
336: <sitem>1996-10-?? : TB : consistency check, fix up scraps so
337: they all parse, get formatter working, correct a few productions.</sitem>
338: <sitem>1996-10-10/11 : CMSMcQ : various maintenance, stylistic, and
339: organizational changes:
340: Replace a few literals with xmlpio and
341: pic entities, to make them consistent and ensure we can change pic
342: reliably when the ERB votes.
343: Drop paragraph on recognizers from notation section.
344: Add match, exact match to terminology.
345: Move old 2.2 XML Processors and Apps into intro.
346: Mention comments, PIs, and marked sections in discussion of
347: delimiter escaping.
348: Streamline discussion of doctype decl syntax.
349: Drop old section of 'PI syntax' for doctype decl, and add
350: section on partial-DTD summary PIs to end of Logical Structures
351: section.
352: Revise DSD syntax section to use Tim's subset-in-a-PI
353: mechanism.</sitem>
354: <sitem>1996-10-10 : TB : eliminate name recognizers (and more?)</sitem>
355: <sitem>1996-10-09 : CMSMcQ : revise for style, consistency through 2.3
356: (Characters)</sitem>
357: <sitem>1996-10-09 : CMSMcQ : re-unite everything for convenience,
358: at least temporarily, and revise quickly</sitem>
359: <sitem>1996-10-08 : TB : first major homogenization pass</sitem>
360: <sitem>1996-10-08 : TB : turn "current" attribute on div type into
361: CDATA</sitem>
362: <sitem>1996-10-02 : TB : remould into skeleton + entities</sitem>
363: <sitem>1996-09-30 : CMSMcQ : add a few more sections prior to exchange
364: with Tim.</sitem>
365: <sitem>1996-09-20 : CMSMcQ : finish transcribing notes.</sitem>
366: <sitem>1996-09-19 : CMSMcQ : begin transcribing notes for draft.</sitem>
367: <sitem>1996-09-13 : CMSMcQ : made outline from notes of 09-06,
368: do some housekeeping</sitem>
369: </slist>
370: </revisiondesc>
371: </header>
372: <body>
373: <div1 id='sec-intro'>
374: <head>Introduction</head>
375: <p>Extensible Markup Language, abbreviated XML, describes a class of
376: data objects called <termref def="dt-xml-doc">XML documents</termref> and
377: partially describes the behavior of
378: computer programs which process them. XML is an application profile or
379: restricted form of SGML, the Standard Generalized Markup
380: Language <bibref ref='ISO8879'/>.
381: By construction, XML documents
382: are conforming SGML documents.
383: </p>
384: <p>XML documents are made up of storage units called <termref
385: def="dt-entity">entities</termref>, which contain either parsed
386: or unparsed data.
387: Parsed data is made up of <termref def="dt-character">characters</termref>,
388: some
389: of which form <termref def="dt-chardata">character data</termref>,
390: and some of which form <termref def="dt-markup">markup</termref>.
391: Markup encodes a description of the document's storage layout and
392: logical structure. XML provides a mechanism to impose constraints on
393: the storage layout and logical structure.</p>
394: <p><termdef id="dt-xml-proc" term="XML Processor">A software module
395: called an <term>XML processor</term> is used to read XML documents
396: and provide access to their content and structure.</termdef> <termdef
397: id="dt-app" term="Application">It is assumed that an XML processor is
398: doing its work on behalf of another module, called the
399: <term>application</term>.</termdef> This specification describes the
400: required behavior of an XML processor in terms of how it must read XML
401: data and the information it must provide to the application.</p>
402:
403: <div2 id='sec-origin-goals'>
404: <head>Origin and Goals</head>
405: <p>XML was developed by an XML Working Group (originally known as the
406: SGML Editorial Review Board) formed under the auspices of the World
407: Wide Web Consortium (W3C) in 1996.
408: It was chaired by Jon Bosak of Sun
409: Microsystems with the active participation of an XML Special
410: Interest Group (previously known as the SGML Working Group) also
411: organized by the W3C. The membership of the XML Working Group is given
412: in an appendix. Dan Connolly served as the WG's contact with the W3C.
413: </p>
414: <p>The design goals for XML are:<olist>
415: <item><p>XML shall be straightforwardly usable over the
416: Internet.</p></item>
417: <item><p>XML shall support a wide variety of applications.</p></item>
418: <item><p>XML shall be compatible with SGML.</p></item>
419: <item><p>It shall be easy to write programs which process XML
420: documents.</p></item>
421: <item><p>The number of optional features in XML is to be kept to the
422: absolute minimum, ideally zero.</p></item>
423: <item><p>XML documents should be human-legible and reasonably
424: clear.</p></item>
425: <item><p>The XML design should be prepared quickly.</p></item>
426: <item><p>The design of XML shall be formal and concise.</p></item>
427: <item><p>XML documents shall be easy to create.</p></item>
428: <item><p>Terseness in XML markup is of minimal importance.</p></item></olist>
429: </p>
430: <p>This specification,
431: together with associated standards
432: (Unicode and ISO/IEC 10646 for characters,
433: Internet RFC 1766 for language identification tags,
434: ISO 639 for language name codes, and
435: ISO 3166 for country name codes),
436: provides all the information necessary to understand
437: XML Version &XML.version;
438: and construct computer programs to process it.</p>
439: <p>This version of the XML specification
440: <!-- is for &doc.audience;.-->
441: &doc.distribution;.</p>
442:
443: </div2>
444:
445:
446:
447:
448: <div2 id='sec-terminology'>
449: <head>Terminology</head>
450:
451: <p>The terminology used to describe XML documents is defined in the body of
452: this specification.
453: The terms defined in the following list are used in building those
454: definitions and in describing the actions of an XML processor:
455: <glist>
456: <gitem>
457: <label>may</label>
458: <def><p><termdef id="dt-may" term="May">Conforming documents and XML
459: processors are permitted to but need not behave as
460: described.</termdef></p></def>
461: </gitem>
462: <gitem>
463: <label>must</label>
464: <def><p>Conforming documents and XML processors
465: are required to behave as described; otherwise they are in error.
466: <!-- do NOT change this! this is what defines a violation of
467: a 'must' clause as 'an error'. -MSM -->
468: </p></def>
469: </gitem>
470: <gitem>
471: <label>error</label>
472: <def><p><termdef id='dt-error' term='Error'
473: >A violation of the rules of this
474: specification; results are
475: undefined. Conforming software may detect and report an error and may
476: recover from it.</termdef></p></def>
477: </gitem>
478: <gitem>
479: <label>fatal error</label>
480: <def><p><termdef id="dt-fatal" term="Fatal Error">An error
481: which a conforming <termref def="dt-xml-proc">XML processor</termref>
482: must detect and report to the application.
483: After encountering a fatal error, the
484: processor may continue
485: processing the data to search for further errors and may report such
486: errors to the application. In order to support correction of errors,
487: the processor may make unprocessed data from the document (with
488: intermingled character data and markup) available to the application.
489: Once a fatal error is detected, however, the processor must not
490: continue normal processing (i.e., it must not
491: continue to pass character data and information about the document's
492: logical structure to the application in the normal way).
493: </termdef></p></def>
494: </gitem>
495: <gitem>
496: <label>at user option</label>
497: <def><p>Conforming software may or must (depending on the modal verb in the
498: sentence) behave as described; if it does, it must
499: provide users a means to enable or disable the behavior
500: described.</p></def>
501: </gitem>
502: <gitem>
503: <label>validity constraint</label>
504: <def><p>A rule which applies to all
505: <termref def="dt-valid">valid</termref> XML documents.
506: Violations of validity constraints are errors; they must, at user option,
507: be reported by
508: <termref def="dt-validating">validating XML processors</termref>.</p></def>
509: </gitem>
510: <gitem>
511: <label>well-formedness constraint</label>
512: <def><p>A rule which applies to all <termref
513: def="dt-wellformed">well-formed</termref> XML documents.
514: Violations of well-formedness constraints are
515: <termref def="dt-fatal">fatal errors</termref>.</p></def>
516: </gitem>
517:
518: <gitem>
519: <label>match</label>
520: <def><p><termdef id="dt-match" term="match">(Of strings or names:)
521: Two strings or names being compared must be identical.
522: Characters with multiple possible representations in ISO/IEC 10646 (e.g.
523: characters with
524: both precomposed and base+diacritic forms) match only if they have the
525: same representation in both strings.
526: At user option, processors may normalize such characters to
527: some canonical form.
528: No case folding is performed.
529: (Of strings and rules in the grammar:)
530: A string matches a grammatical production if it belongs to the
531: language generated by that production.
532: (Of content and content models:)
533: An element matches its declaration when it conforms
534: in the fashion described in the constraint
535: <specref ref='elementvalid'/>.
536: </termdef>
537: </p></def>
538: </gitem>
539: <gitem>
540: <label>for compatibility</label>
541: <def><p><termdef id="dt-compat" term="For Compatibility">A feature of
542: XML included solely to ensure that XML remains compatible with SGML.
543: </termdef></p></def>
544: </gitem>
545: <gitem>
546: <label>for interoperability</label>
547: <def><p><termdef id="dt-interop" term="For interoperability">A
548: non-binding recommendation included to increase the chances that XML
549: documents can be processed by the existing installed base of SGML
550: processors which predate the
551: &WebSGML;.</termdef></p></def>
552: </gitem>
553: </glist>
554: </p>
555: </div2>
556:
557:
558: </div1>
559: <!-- &Docs; -->
560:
561: <div1 id='sec-documents'>
562: <head>Documents</head>
563:
564: <p><termdef id="dt-xml-doc" term="XML Document">
565: A data object is an
566: <term>XML document</term> if it is
567: <termref def="dt-wellformed">well-formed</termref>, as
568: defined in this specification.
569: A well-formed XML document may in addition be
570: <termref def="dt-valid">valid</termref> if it meets certain further
571: constraints.</termdef></p>
572:
573: <p>Each XML document has both a logical and a physical structure.
574: Physically, the document is composed of units called <termref
575: def="dt-entity">entities</termref>. An entity may <termref
576: def="dt-entref">refer</termref> to other entities to cause their
577: inclusion in the document. A document begins in a "root" or <termref
578: def="dt-docent">document entity</termref>.
579: Logically, the document is composed of declarations, elements,
580: comments,
581: character references, and
582: processing
583: instructions, all of which are indicated in the document by explicit
584: markup.
585: The logical and physical structures must nest properly, as described
586: in <specref ref='wf-entities'/>.
587: </p>
588:
589: <div2 id='sec-well-formed'>
590: <head>Well-Formed XML Documents</head>
591:
592: <p><termdef id="dt-wellformed" term="Well-Formed">
593: A textual object is
594: a well-formed XML document if:</termdef>
595: <olist>
596: <item><p>Taken as a whole, it
597: matches the production labeled <nt def='NT-document'>document</nt>.</p></item>
598: <item><p>It
599: meets all the well-formedness constraints given in this specification.</p>
600: </item>
601: <item><p>Each of the <termref def='dt-parsedent'>parsed entities</termref>
602: which is referenced directly or indirectly within the document is
603: <titleref href='wf-entities'>well-formed</titleref>.</p></item>
604: </olist></p>
605: <p>
606: <scrap lang='ebnf' id='document'>
607: <head>Document</head>
608: <prod id='NT-document'><lhs>document</lhs>
609: <rhs><nt def='NT-prolog'>prolog</nt>
610: <nt def='NT-element'>element</nt>
611: <nt def='NT-Misc'>Misc</nt>*</rhs></prod>
612: </scrap>
613: </p>
614: <p>Matching the <nt def="NT-document">document</nt> production
615: implies that:
616: <olist>
617: <item><p>It contains one or more
618: <termref def="dt-element">elements</termref>.</p>
619: </item>
620: <!--* N.B. some readers (notably JC) find the following
621: paragraph awkward and redundant. I agree it's logically redundant:
622: it *says* it is summarizing the logical implications of
623: matching the grammar, and that means by definition it's
624: logically redundant. I don't think it's rhetorically
625: redundant or unnecessary, though, so I'm keeping it. It
626: could however use some recasting when the editors are feeling
627: stronger. -MSM *-->
628: <item><p><termdef id="dt-root" term="Root Element">There is exactly
629: one element, called the <term>root</term>, or document element, no
630: part of which appears in the <termref
631: def="dt-content">content</termref> of any other element.</termdef>
632: For all other elements, if the start-tag is in the content of another
633: element, the end-tag is in the content of the same element. More
634: simply stated, the elements, delimited by start- and end-tags, nest
635: properly within each other.
636: </p></item>
637: </olist>
638: </p>
639: <p><termdef id="dt-parentchild" term="Parent/Child">As a consequence
640: of this,
641: for each non-root element
642: <code>C</code> in the document, there is one other element <code>P</code>
643: in the document such that
644: <code>C</code> is in the content of <code>P</code>, but is not in
645: the content of any other element that is in the content of
646: <code>P</code>.
647: <code>P</code> is referred to as the
648: <term>parent</term> of <code>C</code>, and <code>C</code> as a
649: <term>child</term> of <code>P</code>.</termdef></p></div2>
650:
651: <div2 id="charsets">
652: <head>Characters</head>
653:
654: <p><termdef id="dt-text" term="Text">A parsed entity contains
655: <term>text</term>, a sequence of
656: <termref def="dt-character">characters</termref>,
657: which may represent markup or character data.</termdef>
658: <termdef id="dt-character" term="Character">A <term>character</term>
659: is an atomic unit of text as specified by
660: ISO/IEC 10646 <bibref ref="ISO10646"/>.
661: Legal characters are tab, carriage return, line feed, and the legal
662: graphic characters of Unicode and ISO/IEC 10646.
663: The use of "compatibility characters", as defined in section 6.8
664: of <bibref ref='Unicode'/>, is discouraged.
665: </termdef>
666: <scrap lang="ebnf" id="char32">
667: <head>Character Range</head>
668: <prodgroup pcw2="4" pcw4="17.5" pcw5="11">
669: <prod id="NT-Char"><lhs>Char</lhs>
670: <rhs>#x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD]
671: | [#x10000-#x10FFFF]</rhs>
672: <com>any Unicode character, excluding the
673: surrogate blocks, FFFE, and FFFF.</com> </prod>
674: </prodgroup>
675: </scrap>
676: </p>
677:
678: <p>The mechanism for encoding character code points into bit patterns may
679: vary from entity to entity. All XML processors must accept the UTF-8
680: and UTF-16 encodings of 10646; the mechanisms for signaling which of
681: the two is in use, or for bringing other encodings into play, are
682: discussed later, in <specref ref='charencoding'/>.
683: </p>
684: <!--
685: <p>Regardless of the specific encoding used, any character in the ISO/IEC
686: 10646 character set may be referred to by the decimal or hexadecimal
687: equivalent of its
688: UCS-4 code value.
689: </p>-->
690: </div2>
691:
692: <div2 id='sec-common-syn'>
693: <head>Common Syntactic Constructs</head>
694:
695: <p>This section defines some symbols used widely in the grammar.</p>
696: <p><nt def="NT-S">S</nt> (white space) consists of one or more space (#x20)
697: characters, carriage returns, line feeds, or tabs.
698:
699: <scrap lang="ebnf" id='white'>
700: <head>White Space</head>
701: <prodgroup pcw2="4" pcw4="17.5" pcw5="11">
702: <prod id='NT-S'><lhs>S</lhs>
703: <rhs>(#x20 | #x9 | #xD | #xA)+</rhs>
704: </prod>
705: </prodgroup>
706: </scrap></p>
707: <p>Characters are classified for convenience as letters, digits, or other
708: characters. Letters consist of an alphabetic or syllabic
709: base character possibly
710: followed by one or more combining characters, or of an ideographic
711: character.
712: Full definitions of the specific characters in each class
713: are given in <specref ref='CharClasses'/>.</p>
714: <p><termdef id="dt-name" term="Name">A <term>Name</term> is a token
715: beginning with a letter or one of a few punctuation characters, and continuing
716: with letters, digits, hyphens, underscores, colons, or full stops, together
717: known as name characters.</termdef>
718: Names beginning with the string "<code>xml</code>", or any string
719: which would match <code>(('X'|'x') ('M'|'m') ('L'|'l'))</code>, are
720: reserved for standardization in this or future versions of this
721: specification.
722: </p>
723: <note>
724: <p>The colon character within XML names is reserved for experimentation with
725: name spaces.
726: Its meaning is expected to be
727: standardized at some future point, at which point those documents
728: using the colon for experimental purposes may need to be updated.
729: (There is no guarantee that any name-space mechanism
730: adopted for XML will in fact use the colon as a name-space delimiter.)
731: In practice, this means that authors should not use the colon in XML
732: names except as part of name-space experiments, but that XML processors
733: should accept the colon as a name character.</p>
734: </note>
735: <p>An
736: <nt def='NT-Nmtoken'>Nmtoken</nt> (name token) is any mixture of
737: name characters.
738: <scrap lang='ebnf'>
739: <head>Names and Tokens</head>
740: <prod id='NT-NameChar'><lhs>NameChar</lhs>
741: <rhs><nt def="NT-Letter">Letter</nt>
742: | <nt def='NT-Digit'>Digit</nt>
743: | '.' | '-' | '_' | ':'
744: | <nt def='NT-CombiningChar'>CombiningChar</nt>
745: | <nt def='NT-Extender'>Extender</nt></rhs>
746: </prod>
747: <prod id='NT-Name'><lhs>Name</lhs>
748: <rhs>(<nt def='NT-Letter'>Letter</nt> | '_' | ':')
749: (<nt def='NT-NameChar'>NameChar</nt>)*</rhs></prod>
750: <prod id='NT-Names'><lhs>Names</lhs>
751: <rhs><nt def='NT-Name'>Name</nt>
752: (<nt def='NT-S'>S</nt> <nt def='NT-Name'>Name</nt>)*</rhs></prod>
753: <prod id='NT-Nmtoken'><lhs>Nmtoken</lhs>
754: <rhs>(<nt def='NT-NameChar'>NameChar</nt>)+</rhs></prod>
755: <prod id='NT-Nmtokens'><lhs>Nmtokens</lhs>
756: <rhs><nt def='NT-Nmtoken'>Nmtoken</nt> (<nt def='NT-S'>S</nt> <nt def='NT-Nmtoken'>Nmtoken</nt>)*</rhs></prod>
757: </scrap>
758: </p>
759: <p>Literal data is any quoted string not containing
760: the quotation mark used as a delimiter for that string.
761: Literals are used
762: for specifying the content of internal entities
763: (<nt def='NT-EntityValue'>EntityValue</nt>),
764: the values of attributes (<nt def='NT-AttValue'>AttValue</nt>),
765: and external identifiers
766: (<nt def="NT-SystemLiteral">SystemLiteral</nt>).
767: Note that a <nt def='NT-SystemLiteral'>SystemLiteral</nt>
768: can be parsed without scanning for markup.
769: <scrap lang='ebnf'>
770: <head>Literals</head>
771: <prod id='NT-EntityValue'><lhs>EntityValue</lhs>
772: <rhs>'"'
773: ([^%&"]
774: | <nt def='NT-PEReference'>PEReference</nt>
775: | <nt def='NT-Reference'>Reference</nt>)*
776: '"'
777: </rhs>
778: <rhs>|
779: "'"
780: ([^%&']
781: | <nt def='NT-PEReference'>PEReference</nt>
782: | <nt def='NT-Reference'>Reference</nt>)*
783: "'"</rhs>
784: </prod>
785: <prod id='NT-AttValue'><lhs>AttValue</lhs>
786: <rhs>'"'
787: ([^<&"]
788: | <nt def='NT-Reference'>Reference</nt>)*
789: '"'
790: </rhs>
791: <rhs>|
792: "'"
793: ([^<&']
794: | <nt def='NT-Reference'>Reference</nt>)*
795: "'"</rhs>
796: </prod>
797: <prod id="NT-SystemLiteral"><lhs>SystemLiteral</lhs>
798: <rhs>('"' [^"]* '"') | ("'" [^']* "'")
799: </rhs>
800: </prod>
801: <prod id="NT-PubidLiteral"><lhs>PubidLiteral</lhs>
802: <rhs>'"' <nt def='NT-PubidChar'>PubidChar</nt>*
803: '"'
804: | "'" (<nt def='NT-PubidChar'>PubidChar</nt> - "'")* "'"</rhs>
805: </prod>
806: <prod id="NT-PubidChar"><lhs>PubidChar</lhs>
807: <rhs>#x20 | #xD | #xA
808: | [a-zA-Z0-9]
809: | [-'()+,./:=?;!*#@$_%]</rhs>
810: </prod>
811: </scrap>
812: </p>
813:
814: </div2>
815:
816: <div2 id='syntax'>
817: <head>Character Data and Markup</head>
818:
819: <p><termref def='dt-text'>Text</termref> consists of intermingled
820: <termref def="dt-chardata">character
821: data</termref> and markup.
822: <termdef id="dt-markup" term="Markup"><term>Markup</term> takes the form of
823: <termref def="dt-stag">start-tags</termref>,
824: <termref def="dt-etag">end-tags</termref>,
825: <termref def="dt-empty">empty-element tags</termref>,
826: <termref def="dt-entref">entity references</termref>,
827: <termref def="dt-charref">character references</termref>,
828: <termref def="dt-comment">comments</termref>,
829: <termref def="dt-cdsection">CDATA section</termref> delimiters,
830: <termref def="dt-doctype">document type declarations</termref>, and
831: <termref def="dt-pi">processing instructions</termref>.
832: </termdef>
833: </p>
834: <p><termdef id="dt-chardata" term="Character Data">All text that is not markup
835: constitutes the <term>character data</term> of
836: the document.</termdef></p>
837: <p>The ampersand character (&) and the left angle bracket (<)
838: may appear in their literal form <emph>only</emph> when used as markup
839: delimiters, or within a <termref def="dt-comment">comment</termref>, a
840: <termref def="dt-pi">processing instruction</termref>,
841: or a <termref def="dt-cdsection">CDATA section</termref>.
842:
843: They are also legal within the <termref def='dt-litentval'>literal entity
844: value</termref> of an internal entity declaration; see
845: <specref ref='wf-entities'/>.
846: <!-- FINAL EDIT: restore internal entity decl or leave it out. -->
847: If they are needed elsewhere,
848: they must be <termref def="dt-escape">escaped</termref>
849: using either <termref def='dt-charref'>numeric character references</termref>
850: or the strings
851: "<code>&amp;</code>" and "<code>&lt;</code>" respectively.
852: The right angle
853: bracket (>) may be represented using the string
854: "<code>&gt;</code>", and must, <termref def='dt-compat'>for
855: compatibility</termref>,
856: be escaped using
857: "<code>&gt;</code>" or a character reference
858: when it appears in the string
859: "<code>]]></code>"
860: in content,
861: when that string is not marking the end of
862: a <termref def="dt-cdsection">CDATA section</termref>.
863: </p>
864: <p>
865: In the content of elements, character data
866: is any string of characters which does
867: not contain the start-delimiter of any markup.
868: In a CDATA section, character data
869: is any string of characters not including the CDATA-section-close
870: delimiter, "<code>]]></code>".</p>
871: <p>
872: To allow attribute values to contain both single and double quotes, the
873: apostrophe or single-quote character (') may be represented as
874: "<code>&apos;</code>", and the double-quote character (") as
875: "<code>&quot;</code>".
876: <scrap lang="ebnf">
877: <head>Character Data</head>
878: <prod id='NT-CharData'>
879: <lhs>CharData</lhs>
880: <rhs>[^<&]* - ([^<&]* ']]>' [^<&]*)</rhs>
881: </prod>
882: </scrap>
883: </p>
884: </div2>
885:
886: <div2 id='sec-comments'>
887: <head>Comments</head>
888:
889: <p><termdef id="dt-comment" term="Comment"><term>Comments</term> may
890: appear anywhere in a document outside other
891: <termref def='dt-markup'>markup</termref>; in addition,
892: they may appear within the document type declaration
893: at places allowed by the grammar.
894: They are not part of the document's <termref def="dt-chardata">character
895: data</termref>; an XML
896: processor may, but need not, make it possible for an application to
897: retrieve the text of comments.
898: <termref def="dt-compat">For compatibility</termref>, the string
899: "<code>--</code>" (double-hyphen) must not occur within
900: comments.
901: <scrap lang="ebnf">
902: <head>Comments</head>
903: <prod id='NT-Comment'><lhs>Comment</lhs>
904: <rhs>'<!--'
905: ((<nt def='NT-Char'>Char</nt> - '-')
906: | ('-' (<nt def='NT-Char'>Char</nt> - '-')))*
907: '-->'</rhs>
908: </prod>
909: </scrap>
910: </termdef></p>
911: <p>An example of a comment:
912: <eg><!&como; declarations for <head> & <body> &comc;></eg>
913: </p>
914: </div2>
915:
916: <div2 id='sec-pi'>
917: <head>Processing Instructions</head>
918:
919: <p><termdef id="dt-pi" term="Processing instruction"><term>Processing
920: instructions</term> (PIs) allow documents to contain instructions
921: for applications.
922:
923: <scrap lang="ebnf">
924: <head>Processing Instructions</head>
925: <prod id='NT-PI'><lhs>PI</lhs>
926: <rhs>'<?' <nt def='NT-PITarget'>PITarget</nt>
927: (<nt def='NT-S'>S</nt>
928: (<nt def='NT-Char'>Char</nt>* -
929: (<nt def='NT-Char'>Char</nt>* &pic; <nt def='NT-Char'>Char</nt>*)))?
930: &pic;</rhs></prod>
931: <prod id='NT-PITarget'><lhs>PITarget</lhs>
932: <rhs><nt def='NT-Name'>Name</nt> -
933: (('X' | 'x') ('M' | 'm') ('L' | 'l'))</rhs>
934: </prod>
935: </scrap></termdef>
936: PIs are not part of the document's <termref def="dt-chardata">character
937: data</termref>, but must be passed through to the application. The
938: PI begins with a target (<nt def='NT-PITarget'>PITarget</nt>) used
939: to identify the application to which the instruction is directed.
940: The target names "<code>XML</code>", "<code>xml</code>", and so on are
941: reserved for standardization in this or future versions of this
942: specification.
943: The
944: XML <termref def='dt-notation'>Notation</termref> mechanism
945: may be used for
946: formal declaration of PI targets.
947: </p>
948: </div2>
949:
950: <div2 id='sec-cdata-sect'>
951: <head>CDATA Sections</head>
952:
953: <p><termdef id="dt-cdsection" term="CDATA Section"><term>CDATA sections</term>
954: may occur
955: anywhere character data may occur; they are
956: used to escape blocks of text containing characters which would
957: otherwise be recognized as markup. CDATA sections begin with the
958: string "<code><![CDATA[</code>" and end with the string
959: "<code>]]></code>":
960: <scrap lang="ebnf">
961: <head>CDATA Sections</head>
962: <prod id='NT-CDSect'><lhs>CDSect</lhs>
963: <rhs><nt def='NT-CDStart'>CDStart</nt>
964: <nt def='NT-CData'>CData</nt>
965: <nt def='NT-CDEnd'>CDEnd</nt></rhs></prod>
966: <prod id='NT-CDStart'><lhs>CDStart</lhs>
967: <rhs>'<![CDATA['</rhs>
968: </prod>
969: <prod id='NT-CData'><lhs>CData</lhs>
970: <rhs>(<nt def='NT-Char'>Char</nt>* -
971: (<nt def='NT-Char'>Char</nt>* ']]>' <nt def='NT-Char'>Char</nt>*))
972: </rhs>
973: </prod>
974: <prod id='NT-CDEnd'><lhs>CDEnd</lhs>
975: <rhs>']]>'</rhs>
976: </prod>
977: </scrap>
978:
979: Within a CDATA section, only the <nt def='NT-CDEnd'>CDEnd</nt> string is
980: recognized as markup, so that left angle brackets and ampersands may occur in
981: their literal form; they need not (and cannot) be escaped using
982: "<code>&lt;</code>" and "<code>&amp;</code>". CDATA sections
983: cannot nest.</termdef>
984: </p>
985:
986: <p>An example of a CDATA section, in which "<code><greeting></code>" and
987: "<code></greeting></code>"
988: are recognized as <termref def='dt-chardata'>character data</termref>, not
989: <termref def='dt-markup'>markup</termref>:
990: <eg><![CDATA[<greeting>Hello, world!</greeting>]]></eg>
991: </p>
992: </div2>
993:
994: <div2 id='sec-prolog-dtd'>
995: <head>Prolog and Document Type Declaration</head>
996:
997: <p><termdef id='dt-xmldecl' term='XML Declaration'>XML documents
998: may, and should,
999: begin with an <term>XML declaration</term> which specifies
1000: the version of
1001: XML being used.</termdef>
1002: For example, the following is a complete XML document, <termref
1003: def="dt-wellformed">well-formed</termref> but not
1004: <termref def="dt-valid">valid</termref>:
1005: <eg><![CDATA[<?xml version="1.0"?>
1006: <greeting>Hello, world!</greeting>
1007: ]]></eg>
1008: and so is this:
1009: <eg><![CDATA[<greeting>Hello, world!</greeting>
1010: ]]></eg>
1011: </p>
1012:
1013: <p>The version number "<code>1.0</code>" should be used to indicate
1014: conformance to this version of this specification; it is an error
1015: for a document to use the value "<code>1.0</code>"
1016: if it does not conform to this version of this specification.
1017: It is the intent
1018: of the XML working group to give later versions of this specification
1019: numbers other than "<code>1.0</code>", but this intent does not
1020: indicate a
1021: commitment to produce any future versions of XML, nor if any are produced, to
1022: use any particular numbering scheme.
1023: Since future versions are not ruled out, this construct is provided
1024: as a means to allow the possibility of automatic version recognition, should
1025: it become necessary.
1026: Processors may signal an error if they receive documents labeled with
1027: versions they do not support.
1028: </p>
1029: <p>The function of the markup in an XML document is to describe its
1030: storage and logical structure and to associate attribute-value pairs
1031: with its logical structures. XML provides a mechanism, the <termref
1032: def="dt-doctype">document type declaration</termref>, to define
1033: constraints on the logical structure and to support the use of
1034: predefined storage units.
1035:
1036: <termdef id="dt-valid" term="Validity">An XML document is
1037: <term>valid</term> if it has an associated document type
1038: declaration and if the document
1039: complies with the constraints expressed in it.</termdef></p>
1040: <p>The document type declaration must appear before
1041: the first <termref def="dt-element">element</termref> in the document.
1042: <scrap lang="ebnf" id='xmldoc'>
1043: <head>Prolog</head>
1044: <prodgroup pcw2="6" pcw4="17.5" pcw5="9">
1045: <prod id='NT-prolog'><lhs>prolog</lhs>
1046: <rhs><nt def='NT-XMLDecl'>XMLDecl</nt>?
1047: <nt def='NT-Misc'>Misc</nt>*
1048: (<nt def='NT-doctypedecl'>doctypedecl</nt>
1049: <nt def='NT-Misc'>Misc</nt>*)?</rhs></prod>
1050: <prod id='NT-XMLDecl'><lhs>XMLDecl</lhs>
1051: <rhs>&xmlpio;
1052: <nt def='NT-VersionInfo'>VersionInfo</nt>
1053: <nt def='NT-EncodingDecl'>EncodingDecl</nt>?
1054: <nt def='NT-SDDecl'>SDDecl</nt>?
1055: <nt def="NT-S">S</nt>?
1056: &pic;</rhs>
1057: </prod>
1058: <prod id='NT-VersionInfo'><lhs>VersionInfo</lhs>
1059: <rhs><nt def="NT-S">S</nt> 'version' <nt def='NT-Eq'>Eq</nt>
1060: (' <nt def="NT-VersionNum">VersionNum</nt> '
1061: | " <nt def="NT-VersionNum">VersionNum</nt> ")</rhs>
1062: </prod>
1063: <prod id='NT-Eq'><lhs>Eq</lhs>
1064: <rhs><nt def='NT-S'>S</nt>? '=' <nt def='NT-S'>S</nt>?</rhs></prod>
1065: <prod id="NT-VersionNum">
1066: <lhs>VersionNum</lhs>
1067: <rhs>([a-zA-Z0-9_.:] | '-')+</rhs>
1068: </prod>
1069: <prod id='NT-Misc'><lhs>Misc</lhs>
1070: <rhs><nt def='NT-Comment'>Comment</nt> | <nt def='NT-PI'>PI</nt> |
1071: <nt def='NT-S'>S</nt></rhs></prod>
1072: </prodgroup>
1073: </scrap></p>
1074:
1075: <p><termdef id="dt-doctype" term="Document Type Declaration">The XML
1076: <term>document type declaration</term>
1077: contains or points to
1078: <termref def='dt-markupdecl'>markup declarations</termref>
1079: that provide a grammar for a
1080: class of documents.
1081: This grammar is known as a document type definition,
1082: or <term>DTD</term>.
1083: The document type declaration can point to an external subset (a
1084: special kind of
1085: <termref def='dt-extent'>external entity</termref>) containing markup
1086: declarations, or can
1087: contain the markup declarations directly in an internal subset, or can do
1088: both.
1089: The DTD for a document consists of both subsets taken
1090: together.</termdef>
1091: </p>
1092: <p><termdef id="dt-markupdecl" term="markup declaration">
1093: A <term>markup declaration</term> is
1094: an <termref def="dt-eldecl">element type declaration</termref>,
1095: an <termref def="dt-attdecl">attribute-list declaration</termref>,
1096: an <termref def="dt-entdecl">entity declaration</termref>, or
1097: a <termref def="dt-notdecl">notation declaration</termref>.
1098: </termdef>
1099: These declarations may be contained in whole or in part
1100: within <termref def='dt-PE'>parameter entities</termref>,
1101: as described in the well-formedness and validity constraints below.
1102: For fuller information, see
1103: <specref ref="sec-physical-struct"/>.</p>
1104: <scrap lang="ebnf" id='dtd'>
1105: <head>Document Type Definition</head>
1106: <prodgroup pcw2="6" pcw4="17.5" pcw5="9">
1107: <prod id='NT-doctypedecl'><lhs>doctypedecl</lhs>
1108: <rhs>'<!DOCTYPE' <nt def='NT-S'>S</nt>
1109: <nt def='NT-Name'>Name</nt> (<nt def='NT-S'>S</nt>
1110: <nt def='NT-ExternalID'>ExternalID</nt>)?
1111: <nt def='NT-S'>S</nt>? ('['
1112: (<nt def='NT-markupdecl'>markupdecl</nt>
1113: | <nt def='NT-PEReference'>PEReference</nt>
1114: | <nt def='NT-S'>S</nt>)*
1115: ']'
1116: <nt def='NT-S'>S</nt>?)? '>'</rhs>
1117: <vc def="vc-roottype"/>
1118: </prod>
1119: <prod id='NT-markupdecl'><lhs>markupdecl</lhs>
1120: <rhs><nt def='NT-elementdecl'>elementdecl</nt>
1121: | <nt def='NT-AttlistDecl'>AttlistDecl</nt>
1122: | <nt def='NT-EntityDecl'>EntityDecl</nt>
1123: | <nt def='NT-NotationDecl'>NotationDecl</nt>
1124: | <nt def='NT-PI'>PI</nt>
1125: | <nt def='NT-Comment'>Comment</nt>
1126: </rhs>
1127: <vc def='vc-PEinMarkupDecl'/>
1128: <wfc def="wfc-PEinInternalSubset"/>
1129: </prod>
1130:
1131: </prodgroup>
1132: </scrap>
1133:
1134: <p>The markup declarations may be made up in whole or in part of
1135: the <termref def='dt-repltext'>replacement text</termref> of
1136: <termref def='dt-PE'>parameter entities</termref>.
1137: The productions later in this specification for
1138: individual nonterminals (<nt def='NT-elementdecl'>elementdecl</nt>,
1139: <nt def='NT-AttlistDecl'>AttlistDecl</nt>, and so on) describe
1140: the declarations <emph>after</emph> all the parameter entities have been
1141: <termref def='dt-include'>included</termref>.</p>
1142:
1143: <vcnote id="vc-roottype">
1144: <head>Root Element Type</head>
1145: <p>
1146: The <nt def='NT-Name'>Name</nt> in the document type declaration must
1147: match the element type of the <termref def='dt-root'>root element</termref>.
1148: </p>
1149: </vcnote>
1150:
1151: <vcnote id='vc-PEinMarkupDecl'>
1152: <head>Proper Declaration/PE Nesting</head>
1153: <p>Parameter-entity
1154: <termref def='dt-repltext'>replacement text</termref> must be properly nested
1155: with markup declarations.
1156: That is to say, if either the first character
1157: or the last character of a markup
1158: declaration (<nt def='NT-markupdecl'>markupdecl</nt> above)
1159: is contained in the replacement text for a
1160: <termref def='dt-PERef'>parameter-entity reference</termref>,
1161: both must be contained in the same replacement text.</p>
1162: </vcnote>
1163: <wfcnote id="wfc-PEinInternalSubset">
1164: <head>PEs in Internal Subset</head>
1165: <p>In the internal DTD subset,
1166: <termref def='dt-PERef'>parameter-entity references</termref>
1167: can occur only where markup declarations can occur, not
1168: within markup declarations. (This does not apply to
1169: references that occur in
1170: external parameter entities or to the external subset.)
1171: </p>
1172: </wfcnote>
1173: <p>
1174: Like the internal subset, the external subset and
1175: any external parameter entities referred to in the DTD
1176: must consist of a series of complete markup declarations of the types
1177: allowed by the non-terminal symbol
1178: <nt def="NT-markupdecl">markupdecl</nt>, interspersed with white space
1179: or <termref def="dt-PERef">parameter-entity references</termref>.
1180: However, portions of the contents
1181: of the
1182: external subset or of external parameter entities may conditionally be ignored
1183: by using
1184: the <termref def="dt-cond-section">conditional section</termref>
1185: construct; this is not allowed in the internal subset.
1186:
1187: <scrap id="ext-Subset">
1188: <head>External Subset</head>
1189: <prodgroup pcw2="6" pcw4="17.5" pcw5="9">
1190: <prod id='NT-extSubset'><lhs>extSubset</lhs>
1191: <rhs><nt def='NT-TextDecl'>TextDecl</nt>?
1192: <nt def='NT-extSubsetDecl'>extSubsetDecl</nt></rhs></prod>
1193: <prod id='NT-extSubsetDecl'><lhs>extSubsetDecl</lhs>
1194: <rhs>(
1195: <nt def='NT-markupdecl'>markupdecl</nt>
1196: | <nt def='NT-conditionalSect'>conditionalSect</nt>
1197: | <nt def='NT-PEReference'>PEReference</nt>
1198: | <nt def='NT-S'>S</nt>
1199: )*</rhs>
1200: </prod>
1201: </prodgroup>
1202: </scrap></p>
1203: <p>The external subset and external parameter entities also differ
1204: from the internal subset in that in them,
1205: <termref def="dt-PERef">parameter-entity references</termref>
1206: are permitted <emph>within</emph> markup declarations,
1207: not only <emph>between</emph> markup declarations.</p>
1208: <p>An example of an XML document with a document type declaration:
1209: <eg><![CDATA[<?xml version="1.0"?>
1210: <!DOCTYPE greeting SYSTEM "hello.dtd">
1211: <greeting>Hello, world!</greeting>
1212: ]]></eg>
1213: The <termref def="dt-sysid">system identifier</termref>
1214: "<code>hello.dtd</code>" gives the URI of a DTD for the document.</p>
1215: <p>The declarations can also be given locally, as in this
1216: example:
1217: <eg><![CDATA[<?xml version="1.0" encoding="UTF-8" ?>
1218: <!DOCTYPE greeting [
1219: <!ELEMENT greeting (#PCDATA)>
1220: ]>
1221: <greeting>Hello, world!</greeting>
1222: ]]></eg>
1223: If both the external and internal subsets are used, the
1224: internal subset is considered to occur before the external subset.
1225: <!-- 'is considered to'? boo. whazzat mean? -->
1226: This has the effect that entity and attribute-list declarations in the
1227: internal subset take precedence over those in the external subset.
1228: </p>
1229: </div2>
1230:
1231: <div2 id='sec-rmd'>
1232: <head>Standalone Document Declaration</head>
1233: <p>Markup declarations can affect the content of the document,
1234: as passed from an <termref def="dt-xml-proc">XML processor</termref>
1235: to an application; examples are attribute defaults and entity
1236: declarations.
1237: The standalone document declaration,
1238: which may appear as a component of the XML declaration, signals
1239: whether or not there are such declarations which appear external to
1240: the <termref def='dt-docent'>document entity</termref>.
1241: <scrap lang="ebnf" id='fulldtd'>
1242: <head>Standalone Document Declaration</head>
1243: <prodgroup pcw2="4" pcw4="19.5" pcw5="9">
1244: <prod id='NT-SDDecl'><lhs>SDDecl</lhs>
1245: <rhs>
1246: <nt def="NT-S">S</nt>
1247: 'standalone' <nt def='NT-Eq'>Eq</nt>
1248: (("'" ('yes' | 'no') "'") | ('"' ('yes' | 'no') '"'))
1249: </rhs>
1250: <vc def='vc-check-rmd'/></prod>
1251: </prodgroup>
1252: </scrap></p>
1253: <p>
1254: In a standalone document declaration, the value "<code>yes</code>" indicates
1255: that there
1256: are no markup declarations external to the <termref def='dt-docent'>document
1257: entity</termref> (either in the DTD external subset, or in an
1258: external parameter entity referenced from the internal subset)
1259: which affect the information passed from the XML processor to
1260: the application.
1261: The value "<code>no</code>" indicates that there are or may be such
1262: external markup declarations.
1263: Note that the standalone document declaration only
1264: denotes the presence of external <emph>declarations</emph>; the presence, in a
1265: document, of
1266: references to external <emph>entities</emph>, when those entities are
1267: internally declared,
1268: does not change its standalone status.</p>
1269: <p>If there are no external markup declarations, the standalone document
1270: declaration has no meaning.
1271: If there are external markup declarations but there is no standalone
1272: document declaration, the value "<code>no</code>" is assumed.</p>
1273: <p>Any XML document for which <code>standalone="no"</code> holds can
1274: be converted algorithmically to a standalone document,
1275: which may be desirable for some network delivery applications.</p>
1276: <vcnote id='vc-check-rmd'>
1277: <head>Standalone Document Declaration</head>
1278: <p>The standalone document declaration must have
1279: the value "<code>no</code>" if any external markup declarations
1280: contain declarations of:</p><ulist>
1281: <item><p>attributes with <termref def="dt-default">default</termref> values, if
1282: elements to which
1283: these attributes apply appear in the document without
1284: specifications of values for these attributes, or</p></item>
1285: <item><p>entities (other than &magicents;),
1286: if <termref def="dt-entref">references</termref> to those
1287: entities appear in the document, or</p>
1288: </item>
1289: <item><p>attributes with values subject to
1290: <titleref href='AVNormalize'>normalization</titleref>, where the
1291: attribute appears in the document with a value which will
1292: change as a result of normalization, or</p>
1293: </item>
1294: <item>
1295: <p>element types with <termref def="dt-elemcontent">element content</termref>,
1296: if white space occurs
1297: directly within any instance of those types.
1298: </p></item>
1299: </ulist>
1300:
1301: </vcnote>
1302: <p>An example XML declaration with a standalone document declaration:<eg
1303: ><?xml version="&XML.version;" standalone='yes'?></eg></p>
1304: </div2>
1305: <div2 id='sec-white-space'>
1306: <head>White Space Handling</head>
1307:
1308: <p>In editing XML documents, it is often convenient to use "white space"
1309: (spaces, tabs, and blank lines, denoted by the nonterminal
1310: <nt def='NT-S'>S</nt> in this specification) to
1311: set apart the markup for greater readability. Such white space is typically
1312: not intended for inclusion in the delivered version of the document.
1313: On the other hand, "significant" white space that should be preserved in the
1314: delivered version is common, for example in poetry and
1315: source code.</p>
1316: <p>An <termref def='dt-xml-proc'>XML processor</termref>
1317: must always pass all characters in a document that are not
1318: markup through to the application. A <termref def='dt-validating'>
1319: validating XML processor</termref> must also inform the application
1320: which of these characters constitute white space appearing
1321: in <termref def="dt-elemcontent">element content</termref>.
1322: </p>
1323: <p>A special <termref def='dt-attr'>attribute</termref>
1324: named <kw>xml:space</kw> may be attached to an element
1325: to signal an intention that in that element,
1326: white space should be preserved by applications.
1327: In valid documents, this attribute, like any other, must be
1328: <termref def="dt-attdecl">declared</termref> if it is used.
1329: When declared, it must be given as an
1330: <termref def='dt-enumerated'>enumerated type</termref> whose only
1331: possible values are "<code>default</code>" and "<code>preserve</code>".
1332: For example:<eg><![CDATA[ <!ATTLIST poem xml:space (default|preserve) 'preserve'>]]></eg></p>
1333: <p>The value "<code>default</code>" signals that applications'
1334: default white-space processing modes are acceptable for this element; the
1335: value "<code>preserve</code>" indicates the intent that applications preserve
1336: all the white space.
1337: This declared intent is considered to apply to all elements within the content
1338: of the element where it is specified, unless overriden with another instance
1339: of the <kw>xml:space</kw> attribute.
1340: </p>
1341: <p>The <termref def='dt-root'>root element</termref> of any document
1342: is considered to have signaled no intentions as regards application space
1343: handling, unless it provides a value for
1344: this attribute or the attribute is declared with a default value.
1345: </p>
1346:
1347: </div2>
1348: <div2 id='sec-line-ends'>
1349: <head>End-of-Line Handling</head>
1350: <p>XML <termref def='dt-parsedent'>parsed entities</termref> are often stored in
1351: computer files which, for editing convenience, are organized into lines.
1352: These lines are typically separated by some combination of the characters
1353: carriage-return (#xD) and line-feed (#xA).</p>
1354: <p>To simplify the tasks of <termref def='dt-app'>applications</termref>,
1355: wherever an external parsed entity or the literal entity value
1356: of an internal parsed entity contains either the literal
1357: two-character sequence "#xD#xA" or a standalone literal
1358: #xD, an <termref def='dt-xml-proc'>XML processor</termref> must
1359: pass to the application the single character #xA.
1360: (This behavior can
1361: conveniently be produced by normalizing all
1362: line breaks to #xA on input, before parsing.)
1363: </p>
1364: </div2>
1365: <div2 id='sec-lang-tag'>
1366: <head>Language Identification</head>
1367: <p>In document processing, it is often useful to
1368: identify the natural or formal language
1369: in which the content is
1370: written.
1371: A special <termref def="dt-attr">attribute</termref> named
1372: <kw>xml:lang</kw> may be inserted in
1373: documents to specify the
1374: language used in the contents and attribute values
1375: of any element in an XML document.
1376: In valid documents, this attribute, like any other, must be
1377: <termref def="dt-attdecl">declared</termref> if it is used.
1378: The values of the attribute are language identifiers as defined
1379: by <bibref ref="RFC1766"/>, "Tags for the Identification of Languages":
1380: <scrap lang='ebnf'>
1381: <head>Language Identification</head>
1382: <prod id='NT-LanguageID'><lhs>LanguageID</lhs>
1383: <rhs><nt def='NT-Langcode'>Langcode</nt>
1384: ('-' <nt def='NT-Subcode'>Subcode</nt>)*</rhs></prod>
1385: <prod id='NT-Langcode'><lhs>Langcode</lhs>
1386: <rhs><nt def='NT-ISO639Code'>ISO639Code</nt> |
1387: <nt def='NT-IanaCode'>IanaCode</nt> |
1388: <nt def='NT-UserCode'>UserCode</nt></rhs>
1389: </prod>
1390: <prod id='NT-ISO639Code'><lhs>ISO639Code</lhs>
1391: <rhs>([a-z] | [A-Z]) ([a-z] | [A-Z])</rhs></prod>
1392: <prod id='NT-IanaCode'><lhs>IanaCode</lhs>
1393: <rhs>('i' | 'I') '-' ([a-z] | [A-Z])+</rhs></prod>
1394: <prod id='NT-UserCode'><lhs>UserCode</lhs>
1395: <rhs>('x' | 'X') '-' ([a-z] | [A-Z])+</rhs></prod>
1396: <prod id='NT-Subcode'><lhs>Subcode</lhs>
1397: <rhs>([a-z] | [A-Z])+</rhs></prod>
1398: </scrap>
1399: The <nt def='NT-Langcode'>Langcode</nt> may be any of the following:
1400: <ulist>
1401: <item><p>a two-letter language code as defined by
1402: <bibref ref="ISO639"/>, "Codes
1403: for the representation of names of languages"</p></item>
1404: <item><p>a language identifier registered with the Internet
1405: Assigned Numbers Authority <bibref ref='IANA'/>; these begin with the
1406: prefix "<code>i-</code>" (or "<code>I-</code>")</p></item>
1407: <item><p>a language identifier assigned by the user, or agreed on
1408: between parties in private use; these must begin with the
1409: prefix "<code>x-</code>" or "<code>X-</code>" in order to ensure that they do not conflict
1410: with names later standardized or registered with IANA</p></item>
1411: </ulist></p>
1412: <p>There may be any number of <nt def='NT-Subcode'>Subcode</nt> segments; if
1413: the first
1414: subcode segment exists and the Subcode consists of two
1415: letters, then it must be a country code from
1416: <bibref ref="ISO3166"/>, "Codes
1417: for the representation of names of countries."
1418: If the first
1419: subcode consists of more than two letters, it must be
1420: a subcode for the language in question registered with IANA,
1421: unless the <nt def='NT-Langcode'>Langcode</nt> begins with the prefix
1422: "<code>x-</code>" or
1423: "<code>X-</code>". </p>
1424: <p>It is customary to give the language code in lower case, and
1425: the country code (if any) in upper case.
1426: Note that these values, unlike other names in XML documents,
1427: are case insensitive.</p>
1428: <p>For example:
1429: <eg><![CDATA[<p xml:lang="en">The quick brown fox jumps over the lazy dog.</p>
1430: <p xml:lang="en-GB">What colour is it?</p>
1431: <p xml:lang="en-US">What color is it?</p>
1432: <sp who="Faust" desc='leise' xml:lang="de">
1433: <l>Habe nun, ach! Philosophie,</l>
1434: <l>Juristerei, und Medizin</l>
1435: <l>und leider auch Theologie</l>
1436: <l>durchaus studiert mit heißem Bemüh'n.</l>
1437: </sp>]]></eg></p>
1438: <!--<p>The xml:lang value is considered to apply both to the contents of an
1439: element and
1440: (unless otherwise via attribute default values) to the
1441: values of all of its attributes with free-text (CDATA) values. -->
1442: <p>The intent declared with <kw>xml:lang</kw> is considered to apply to
1443: all attributes and content of the element where it is specified,
1444: unless overridden with an instance of <kw>xml:lang</kw>
1445: on another element within that content.</p>
1446: <!--
1447: If no
1448: value is specified for xml:lang on an element, and no default value is
1449: defined for it in the DTD, then the xml:lang attribute of any element
1450: takes the same value it has in the parent element, if any. The two
1451: technical terms in the following example both have the same effective
1452: value for xml:lang:
1453:
1454: <p xml:lang="en">Here the keywords are
1455: <term xml:lang="en">shift</term> and
1456: <term>reduce</term>. ...</p>
1457:
1458: The application, not the XML processor, is responsible for this '
1459: inheritance' of attribute values.
1460: -->
1461: <p>A simple declaration for <kw>xml:lang</kw> might take
1462: the form
1463: <eg>xml:lang NMTOKEN #IMPLIED</eg>
1464: but specific default values may also be given, if appropriate. In a
1465: collection of French poems for English students, with glosses and
1466: notes in English, the xml:lang attribute might be declared this way:
1467: <eg><![CDATA[ <!ATTLIST poem xml:lang NMTOKEN 'fr'>
1468: <!ATTLIST gloss xml:lang NMTOKEN 'en'>
1469: <!ATTLIST note xml:lang NMTOKEN 'en'>]]></eg>
1470: </p>
1471:
1472: </div2>
1473: </div1>
1474: <!-- &Elements; -->
1475:
1476: <div1 id='sec-logical-struct'>
1477: <head>Logical Structures</head>
1478:
1479: <p><termdef id="dt-element" term="Element">Each <termref
1480: def="dt-xml-doc">XML document</termref> contains one or more
1481: <term>elements</term>, the boundaries of which are
1482: either delimited by <termref def="dt-stag">start-tags</termref>
1483: and <termref def="dt-etag">end-tags</termref>, or, for <termref
1484: def="dt-empty">empty</termref> elements, by an <termref
1485: def="dt-eetag">empty-element tag</termref>. Each element has a type,
1486: identified by name, sometimes called its "generic
1487: identifier" (GI), and may have a set of
1488: attribute specifications.</termdef> Each attribute specification
1489: has a <termref
1490: def="dt-attrname">name</termref> and a <termref
1491: def="dt-attrval">value</termref>.
1492: </p>
1493: <scrap lang='ebnf'><head>Element</head>
1494: <prod id='NT-element'><lhs>element</lhs>
1495: <rhs><nt def='NT-EmptyElemTag'>EmptyElemTag</nt></rhs>
1496: <rhs>| <nt def='NT-STag'>STag</nt> <nt def='NT-content'>content</nt>
1497: <nt def='NT-ETag'>ETag</nt></rhs>
1498: <wfc def='GIMatch'/>
1499: <vc def='elementvalid'/>
1500: </prod>
1501: </scrap>
1502: <p>This specification does not constrain the semantics, use, or (beyond
1503: syntax) names of the element types and attributes, except that names
1504: beginning with a match to <code>(('X'|'x')('M'|'m')('L'|'l'))</code>
1505: are reserved for standardization in this or future versions of this
1506: specification.
1507: </p>
1508: <wfcnote id='GIMatch'>
1509: <head>Element Type Match</head>
1510: <p>
1511: The <nt def='NT-Name'>Name</nt> in an element's end-tag must match
1512: the element type in
1513: the start-tag.
1514: </p>
1515: </wfcnote>
1516: <vcnote id='elementvalid'>
1517: <head>Element Valid</head>
1518: <p>An element is
1519: valid if
1520: there is a declaration matching
1521: <nt def='NT-elementdecl'>elementdecl</nt> where the
1522: <nt def='NT-Name'>Name</nt> matches the element type, and
1523: one of the following holds:</p>
1524: <olist>
1525: <item><p>The declaration matches <kw>EMPTY</kw> and the element has no
1526: <termref def='dt-content'>content</termref>.</p></item>
1527: <item><p>The declaration matches <nt def='NT-children'>children</nt> and
1528: the sequence of
1529: <termref def="dt-parentchild">child elements</termref>
1530: belongs to the language generated by the regular expression in
1531: the content model, with optional white space (characters
1532: matching the nonterminal <nt def='NT-S'>S</nt>) between each pair
1533: of child elements.</p></item>
1534: <item><p>The declaration matches <nt def='NT-Mixed'>Mixed</nt> and
1535: the content consists of <termref def='dt-chardata'>character
1536: data</termref> and <termref def='dt-parentchild'>child elements</termref>
1537: whose types match names in the content model.</p></item>
1538: <item><p>The declaration matches <kw>ANY</kw>, and the types
1539: of any <termref def='dt-parentchild'>child elements</termref> have
1540: been declared.</p></item>
1541: </olist>
1542: </vcnote>
1543:
1544: <div2 id='sec-starttags'>
1545: <head>Start-Tags, End-Tags, and Empty-Element Tags</head>
1546:
1547: <p><termdef id="dt-stag" term="Start-Tag">The beginning of every
1548: non-empty XML element is marked by a <term>start-tag</term>.
1549: <scrap lang='ebnf'>
1550: <head>Start-tag</head>
1551: <prodgroup pcw2="6" pcw4="15" pcw5="11.5">
1552: <prod id='NT-STag'><lhs>STag</lhs>
1553: <rhs>'<' <nt def='NT-Name'>Name</nt>
1554: (<nt def='NT-S'>S</nt> <nt def='NT-Attribute'>Attribute</nt>)*
1555: <nt def='NT-S'>S</nt>? '>'</rhs>
1556: <wfc def="uniqattspec"/>
1557: </prod>
1558: <prod id='NT-Attribute'><lhs>Attribute</lhs>
1559: <rhs><nt def='NT-Name'>Name</nt> <nt def='NT-Eq'>Eq</nt>
1560: <nt def='NT-AttValue'>AttValue</nt></rhs>
1561: <vc def='ValueType'/>
1562: <wfc def='NoExternalRefs'/>
1563: <wfc def='CleanAttrVals'/></prod>
1564: </prodgroup>
1565: </scrap>
1566: The <nt def='NT-Name'>Name</nt> in
1567: the start- and end-tags gives the
1568: element's <term>type</term>.</termdef>
1569: <termdef id="dt-attr" term="Attribute">
1570: The <nt def='NT-Name'>Name</nt>-<nt def='NT-AttValue'>AttValue</nt> pairs are
1571: referred to as
1572: the <term>attribute specifications</term> of the element</termdef>,
1573: <termdef id="dt-attrname" term="Attribute Name">with the
1574: <nt def='NT-Name'>Name</nt> in each pair
1575: referred to as the <term>attribute name</term></termdef> and
1576: <termdef id="dt-attrval" term="Attribute Value">the content of the
1577: <nt def='NT-AttValue'>AttValue</nt> (the text between the
1578: <code>'</code> or <code>"</code> delimiters)
1579: as the <term>attribute value</term>.</termdef>
1580: </p>
1581: <wfcnote id='uniqattspec'>
1582: <head>Unique Att Spec</head>
1583: <p>
1584: No attribute name may appear more than once in the same start-tag
1585: or empty-element tag.
1586: </p>
1587: </wfcnote>
1588: <vcnote id='ValueType'>
1589: <head>Attribute Value Type</head>
1590: <p>
1591: The attribute must have been declared; the value must be of the type
1592: declared for it.
1593: (For attribute types, see <specref ref='attdecls'/>.)
1594: </p>
1595: </vcnote>
1596: <wfcnote id='NoExternalRefs'>
1597: <head>No External Entity References</head>
1598: <p>
1599: Attribute values cannot contain direct or indirect entity references
1600: to external entities.
1601: </p>
1602: </wfcnote>
1603: <wfcnote id='CleanAttrVals'>
1604: <head>No <code><</code> in Attribute Values</head>
1605: <p>The <termref def='dt-repltext'>replacement text</termref> of any entity
1606: referred to directly or indirectly in an attribute
1607: value (other than "<code>&lt;</code>") must not contain
1608: a <code><</code>.
1609: </p></wfcnote>
1610: <p>An example of a start-tag:
1611: <eg><termdef id="dt-dog" term="dog"></eg></p>
1612: <p><termdef id="dt-etag" term="End Tag">The end of every element
1613: that begins with a start-tag must
1614: be marked by an <term>end-tag</term>
1615: containing a name that echoes the element's type as given in the
1616: start-tag:
1617: <scrap lang='ebnf'>
1618: <head>End-tag</head>
1619: <prodgroup pcw2="6" pcw4="15" pcw5="11.5">
1620: <prod id='NT-ETag'><lhs>ETag</lhs>
1621: <rhs>'</' <nt def='NT-Name'>Name</nt>
1622: <nt def='NT-S'>S</nt>? '>'</rhs></prod>
1623: </prodgroup>
1624: </scrap>
1625: </termdef></p>
1626: <p>An example of an end-tag:<eg></termdef></eg></p>
1627: <p><termdef id="dt-content" term="Content">The
1628: <termref def='dt-text'>text</termref> between the start-tag and
1629: end-tag is called the element's
1630: <term>content</term>:
1631: <scrap lang='ebnf'>
1632: <head>Content of Elements</head>
1633: <prodgroup pcw2="6" pcw4="15" pcw5="11.5">
1634: <prod id='NT-content'><lhs>content</lhs>
1635: <rhs>(<nt def='NT-element'>element</nt> | <nt def='NT-CharData'>CharData</nt>
1636: | <nt def='NT-Reference'>Reference</nt> | <nt def='NT-CDSect'>CDSect</nt>
1637: | <nt def='NT-PI'>PI</nt> | <nt def='NT-Comment'>Comment</nt>)*</rhs>
1638: </prod>
1639: </prodgroup>
1640: </scrap>
1641: </termdef></p>
1642: <p><termdef id="dt-empty" term="Empty">If an element is <term>empty</term>,
1643: it must be represented either by a start-tag immediately followed
1644: by an end-tag or by an empty-element tag.</termdef>
1645: <termdef id="dt-eetag" term="empty-element tag">An
1646: <term>empty-element tag</term> takes a special form:
1647: <scrap lang='ebnf'>
1648: <head>Tags for Empty Elements</head>
1649: <prodgroup pcw2="6" pcw4="15" pcw5="11.5">
1650: <prod id='NT-EmptyElemTag'><lhs>EmptyElemTag</lhs>
1651: <rhs>'<' <nt def='NT-Name'>Name</nt> (<nt def='NT-S'>S</nt>
1652: <nt def='NT-Attribute'>Attribute</nt>)* <nt def='NT-S'>S</nt>?
1653: '/>'</rhs>
1654: <wfc def="uniqattspec"/>
1655: </prod>
1656: </prodgroup>
1657: </scrap>
1658: </termdef></p>
1659: <p>Empty-element tags may be used for any element which has no
1660: content, whether or not it is declared using the keyword
1661: <kw>EMPTY</kw>.
1662: <termref def='dt-interop'>For interoperability</termref>, the empty-element
1663: tag must be used, and can only be used, for elements which are
1664: <termref def='dt-eldecl'>declared</termref> <kw>EMPTY</kw>.</p>
1665: <p>Examples of empty elements:
1666: <eg><IMG align="left"
1667: src="http://www.w3.org/Icons/WWW/w3c_home" />
1668: <br></br>
1669: <br/></eg></p>
1670: </div2>
1671:
1672: <div2 id='elemdecls'>
1673: <head>Element Type Declarations</head>
1674:
1675: <p>The <termref def="dt-element">element</termref> structure of an
1676: <termref def="dt-xml-doc">XML document</termref> may, for
1677: <termref def="dt-valid">validation</termref> purposes,
1678: be constrained
1679: using element type and attribute-list declarations.
1680: An element type declaration constrains the element's
1681: <termref def="dt-content">content</termref>.
1682: </p>
1683:
1684: <p>Element type declarations often constrain which element types can
1685: appear as <termref def="dt-parentchild">children</termref> of the element.
1686: At user option, an XML processor may issue a warning
1687: when a declaration mentions an element type for which no declaration
1688: is provided, but this is not an error.</p>
1689: <p><termdef id="dt-eldecl" term="Element Type declaration">An <term>element
1690: type declaration</term> takes the form:
1691: <scrap lang='ebnf'>
1692: <head>Element Type Declaration</head>
1693: <prodgroup pcw2="5.5" pcw4="18" pcw5="9">
1694: <prod id='NT-elementdecl'><lhs>elementdecl</lhs>
1695: <rhs>'<!ELEMENT' <nt def='NT-S'>S</nt>
1696: <nt def='NT-Name'>Name</nt>
1697: <nt def='NT-S'>S</nt>
1698: <nt def='NT-contentspec'>contentspec</nt>
1699: <nt def='NT-S'>S</nt>? '>'</rhs>
1700: <vc def='EDUnique'/></prod>
1701: <prod id='NT-contentspec'><lhs>contentspec</lhs>
1702: <rhs>'EMPTY'
1703: | 'ANY'
1704: | <nt def='NT-Mixed'>Mixed</nt>
1705: | <nt def='NT-children'>children</nt>
1706: </rhs>
1707: </prod>
1708: </prodgroup>
1709: </scrap>
1710: where the <nt def='NT-Name'>Name</nt> gives the element type
1711: being declared.</termdef>
1712: </p>
1713:
1714: <vcnote id='EDUnique'>
1715: <head>Unique Element Type Declaration</head>
1716: <p>
1717: No element type may be declared more than once.
1718: </p>
1719: </vcnote>
1720:
1721: <p>Examples of element type declarations:
1722: <eg><!ELEMENT br EMPTY>
1723: <!ELEMENT p (#PCDATA|emph)* >
1724: <!ELEMENT %name.para; %content.para; >
1725: <!ELEMENT container ANY></eg></p>
1726:
1727: <div3 id='sec-element-content'>
1728: <head>Element Content</head>
1729:
1730: <p><termdef id='dt-elemcontent' term='Element content'>An element <termref
1731: def="dt-stag">type</termref> has
1732: <term>element content</term> when elements of that
1733: type must contain only <termref def='dt-parentchild'>child</termref>
1734: elements (no character data), optionally separated by
1735: white space (characters matching the nonterminal
1736: <nt def='NT-S'>S</nt>).
1737: </termdef>
1738: In this case, the
1739: constraint includes a content model, a simple grammar governing
1740: the allowed types of the child
1741: elements and the order in which they are allowed to appear.
1742: The grammar is built on
1743: content particles (<nt def='NT-cp'>cp</nt>s), which consist of names,
1744: choice lists of content particles, or
1745: sequence lists of content particles:
1746: <scrap lang='ebnf'>
1747: <head>Element-content Models</head>
1748: <prodgroup pcw2="5.5" pcw4="16" pcw5="11">
1749: <prod id='NT-children'><lhs>children</lhs>
1750: <rhs>(<nt def='NT-choice'>choice</nt>
1751: | <nt def='NT-seq'>seq</nt>)
1752: ('?' | '*' | '+')?</rhs></prod>
1753: <prod id='NT-cp'><lhs>cp</lhs>
1754: <rhs>(<nt def='NT-Name'>Name</nt>
1755: | <nt def='NT-choice'>choice</nt>
1756: | <nt def='NT-seq'>seq</nt>)
1757: ('?' | '*' | '+')?</rhs></prod>
1758: <prod id='NT-choice'><lhs>choice</lhs>
1759: <rhs>'(' <nt def='NT-S'>S</nt>? cp
1760: ( <nt def='NT-S'>S</nt>? '|' <nt def='NT-S'>S</nt>? <nt def='NT-cp'>cp</nt> )*
1761: <nt def='NT-S'>S</nt>? ')'</rhs>
1762: <vc def='vc-PEinGroup'/></prod>
1763: <prod id='NT-seq'><lhs>seq</lhs>
1764: <rhs>'(' <nt def='NT-S'>S</nt>? cp
1765: ( <nt def='NT-S'>S</nt>? ',' <nt def='NT-S'>S</nt>? <nt def='NT-cp'>cp</nt> )*
1766: <nt def='NT-S'>S</nt>? ')'</rhs>
1767: <vc def='vc-PEinGroup'/></prod>
1768:
1769: </prodgroup>
1770: </scrap>
1771: where each <nt def='NT-Name'>Name</nt> is the type of an element which may
1772: appear as a <termref def="dt-parentchild">child</termref>.
1773: Any content
1774: particle in a choice list may appear in the <termref
1775: def="dt-elemcontent">element content</termref> at the location where
1776: the choice list appears in the grammar;
1777: content particles occurring in a sequence list must each
1778: appear in the <termref def="dt-elemcontent">element content</termref> in the
1779: order given in the list.
1780: The optional character following a name or list governs
1781: whether the element or the content particles in the list may occur one
1782: or more (<code>+</code>), zero or more (<code>*</code>), or zero or
1783: one times (<code>?</code>).
1784: The absence of such an operator means that the element or content particle
1785: must appear exactly once.
1786: This syntax
1787: and meaning are identical to those used in the productions in this
1788: specification.</p>
1789: <p>
1790: The content of an element matches a content model if and only if it is
1791: possible to trace out a path through the content model, obeying the
1792: sequence, choice, and repetition operators and matching each element in
1793: the content against an element type in the content model. <termref
1794: def='dt-compat'>For compatibility</termref>, it is an error
1795: if an element in the document can
1796: match more than one occurrence of an element type in the content model.
1797: For more information, see <specref ref="determinism"/>.
1798: <!-- appendix <specref ref="determinism"/>. -->
1799: <!-- appendix on deterministic content models. -->
1800: </p>
1801: <vcnote id='vc-PEinGroup'>
1802: <head>Proper Group/PE Nesting</head>
1803: <p>Parameter-entity
1804: <termref def='dt-repltext'>replacement text</termref> must be properly nested
1805: with parenthetized groups.
1806: That is to say, if either of the opening or closing parentheses
1807: in a <nt def='NT-choice'>choice</nt>, <nt def='NT-seq'>seq</nt>, or
1808: <nt def='NT-Mixed'>Mixed</nt> construct
1809: is contained in the replacement text for a
1810: <termref def='dt-PERef'>parameter entity</termref>,
1811: both must be contained in the same replacement text.</p>
1812: <p><termref def='dt-interop'>For interoperability</termref>,
1813: if a parameter-entity reference appears in a
1814: <nt def='NT-choice'>choice</nt>, <nt def='NT-seq'>seq</nt>, or
1815: <nt def='NT-Mixed'>Mixed</nt> construct, its replacement text
1816: should not be empty, and
1817: neither the first nor last non-blank
1818: character of the replacement text should be a connector
1819: (<code>|</code> or <code>,</code>).
1820: </p>
1821: </vcnote>
1822: <p>Examples of element-content models:
1823: <eg><!ELEMENT spec (front, body, back?)>
1824: <!ELEMENT div1 (head, (p | list | note)*, div2*)>
1825: <!ELEMENT dictionary-body (%div.mix; | %dict.mix;)*></eg></p>
1826: </div3>
1827:
1828: <div3 id='sec-mixed-content'>
1829: <head>Mixed Content</head>
1830:
1831: <p><termdef id='dt-mixed' term='Mixed Content'>An element
1832: <termref def='dt-stag'>type</termref> has
1833: <term>mixed content</term> when elements of that type may contain
1834: character data, optionally interspersed with
1835: <termref def="dt-parentchild">child</termref> elements.</termdef>
1836: In this case, the types of the child elements
1837: may be constrained, but not their order or their number of occurrences:
1838: <scrap lang='ebnf'>
1839: <head>Mixed-content Declaration</head>
1840: <prodgroup pcw2="5.5" pcw4="16" pcw5="11">
1841: <prod id='NT-Mixed'><lhs>Mixed</lhs>
1842: <rhs>'(' <nt def='NT-S'>S</nt>?
1843: '#PCDATA'
1844: (<nt def='NT-S'>S</nt>?
1845: '|'
1846: <nt def='NT-S'>S</nt>?
1847: <nt def='NT-Name'>Name</nt>)*
1848: <nt def='NT-S'>S</nt>?
1849: ')*' </rhs>
1850: <rhs>| '(' <nt def='NT-S'>S</nt>? '#PCDATA' <nt def='NT-S'>S</nt>? ')'
1851: </rhs><vc def='vc-PEinGroup'/>
1852: <vc def='vc-MixedChildrenUnique'/>
1853: </prod>
1854:
1855: </prodgroup>
1856: </scrap>
1857: where the <nt def='NT-Name'>Name</nt>s give the types of elements
1858: that may appear as children.
1859: </p>
1860: <vcnote id='vc-MixedChildrenUnique'>
1861: <head>No Duplicate Types</head>
1862: <p>The same name must not appear more than once in a single mixed-content
1863: declaration.
1864: </p></vcnote>
1865: <p>Examples of mixed content declarations:
1866: <eg><!ELEMENT p (#PCDATA|a|ul|b|i|em)*>
1867: <!ELEMENT p (#PCDATA | %font; | %phrase; | %special; | %form;)* >
1868: <!ELEMENT b (#PCDATA)></eg></p>
1869: </div3>
1870: </div2>
1871:
1872: <div2 id='attdecls'>
1873: <head>Attribute-List Declarations</head>
1874:
1875: <p><termref def="dt-attr">Attributes</termref> are used to associate
1876: name-value pairs with <termref def="dt-element">elements</termref>.
1877: Attribute specifications may appear only within <termref
1878: def="dt-stag">start-tags</termref>
1879: and <termref def="dt-eetag">empty-element tags</termref>;
1880: thus, the productions used to
1881: recognize them appear in <specref ref='sec-starttags'/>.
1882: Attribute-list
1883: declarations may be used:
1884: <ulist>
1885: <item><p>To define the set of attributes pertaining to a given
1886: element type.</p></item>
1887: <item><p>To establish type constraints for these
1888: attributes.</p></item>
1889: <item><p>To provide <termref def="dt-default">default values</termref>
1890: for attributes.</p></item>
1891: </ulist>
1892: </p>
1893: <p><termdef id="dt-attdecl" term="Attribute-List Declaration">
1894: <term>Attribute-list declarations</term> specify the name, data type, and default
1895: value (if any) of each attribute associated with a given element type:
1896: <scrap lang='ebnf'>
1897: <head>Attribute-list Declaration</head>
1898: <prod id='NT-AttlistDecl'><lhs>AttlistDecl</lhs>
1899: <rhs>'<!ATTLIST' <nt def='NT-S'>S</nt>
1900: <nt def='NT-Name'>Name</nt>
1901: <nt def='NT-AttDef'>AttDef</nt>*
1902: <nt def='NT-S'>S</nt>? '>'</rhs>
1903: </prod>
1904: <prod id='NT-AttDef'><lhs>AttDef</lhs>
1905: <rhs><nt def='NT-S'>S</nt> <nt def='NT-Name'>Name</nt>
1906: <nt def='NT-S'>S</nt> <nt def='NT-AttType'>AttType</nt>
1907: <nt def='NT-S'>S</nt> <nt def='NT-DefaultDecl'>DefaultDecl</nt></rhs>
1908: </prod>
1909: </scrap>
1910: The <nt def="NT-Name">Name</nt> in the
1911: <nt def='NT-AttlistDecl'>AttlistDecl</nt> rule is the type of an element. At
1912: user option, an XML processor may issue a warning if attributes are
1913: declared for an element type not itself declared, but this is not an
1914: error. The <nt def='NT-Name'>Name</nt> in the
1915: <nt def='NT-AttDef'>AttDef</nt> rule is
1916: the name of the attribute.</termdef></p>
1917: <p>
1918: When more than one <nt def='NT-AttlistDecl'>AttlistDecl</nt> is provided for a
1919: given element type, the contents of all those provided are merged. When
1920: more than one definition is provided for the same attribute of a
1921: given element type, the first declaration is binding and later
1922: declarations are ignored.
1923: <termref def='dt-interop'>For interoperability,</termref> writers of DTDs
1924: may choose to provide at most one attribute-list declaration
1925: for a given element type, at most one attribute definition
1926: for a given attribute name, and at least one attribute definition
1927: in each attribute-list declaration.
1928: For interoperability, an XML processor may at user option
1929: issue a warning when more than one attribute-list declaration is
1930: provided for a given element type, or more than one attribute definition
1931: is provided
1932: for a given attribute, but this is not an error.
1933: </p>
1934:
1935: <div3 id='sec-attribute-types'>
1936: <head>Attribute Types</head>
1937:
1938: <p>XML attribute types are of three kinds: a string type, a
1939: set of tokenized types, and enumerated types. The string type may take
1940: any literal string as a value; the tokenized types have varying lexical
1941: and semantic constraints, as noted:
1942: <scrap lang='ebnf'>
1943: <head>Attribute Types</head>
1944: <prodgroup pcw4="14" pcw5="11.5">
1945: <prod id='NT-AttType'><lhs>AttType</lhs>
1946: <rhs><nt def='NT-StringType'>StringType</nt>
1947: | <nt def='NT-TokenizedType'>TokenizedType</nt>
1948: | <nt def='NT-EnumeratedType'>EnumeratedType</nt>
1949: </rhs>
1950: </prod>
1951: <prod id='NT-StringType'><lhs>StringType</lhs>
1952: <rhs>'CDATA'</rhs>
1953: </prod>
1954: <prod id='NT-TokenizedType'><lhs>TokenizedType</lhs>
1955: <rhs>'ID'</rhs>
1956: <vc def='id'/>
1957: <vc def='one-id-per-el'/>
1958: <vc def='id-default'/>
1959: <rhs>| 'IDREF'</rhs>
1960: <vc def='idref'/>
1961: <rhs>| 'IDREFS'</rhs>
1962: <vc def='idref'/>
1963: <rhs>| 'ENTITY'</rhs>
1964: <vc def='entname'/>
1965: <rhs>| 'ENTITIES'</rhs>
1966: <vc def='entname'/>
1967: <rhs>| 'NMTOKEN'</rhs>
1968: <vc def='nmtok'/>
1969: <rhs>| 'NMTOKENS'</rhs>
1970: <vc def='nmtok'/></prod>
1971: </prodgroup>
1972: </scrap>
1973: </p>
1974: <vcnote id='id' >
1975: <head>ID</head>
1976: <p>
1977: Values of type <kw>ID</kw> must match the
1978: <nt def='NT-Name'>Name</nt> production.
1979: A name must not appear more than once in
1980: an XML document as a value of this type; i.e., ID values must uniquely
1981: identify the elements which bear them.
1982: </p>
1983: </vcnote>
1984: <vcnote id='one-id-per-el'>
1985: <head>One ID per Element Type</head>
1986: <p>No element type may have more than one ID attribute specified.</p>
1987: </vcnote>
1988: <vcnote id='id-default'>
1989: <head>ID Attribute Default</head>
1990: <p>An ID attribute must have a declared default of <kw>#IMPLIED</kw> or
1991: <kw>#REQUIRED</kw>.</p>
1992: </vcnote>
1993: <vcnote id='idref'>
1994: <head>IDREF</head>
1995: <p>
1996: Values of type <kw>IDREF</kw> must match
1997: the <nt def="NT-Name">Name</nt> production, and
1998: values of type <kw>IDREFS</kw> must match
1999: <nt def="NT-Names">Names</nt>;
2000: each <nt def='NT-Name'>Name</nt> must match the value of an ID attribute on
2001: some element in the XML document; i.e. <kw>IDREF</kw> values must
2002: match the value of some ID attribute.
2003: </p>
2004: </vcnote>
2005: <vcnote id='entname'>
2006: <head>Entity Name</head>
2007: <p>
2008: Values of type <kw>ENTITY</kw>
2009: must match the <nt def="NT-Name">Name</nt> production,
2010: values of type <kw>ENTITIES</kw> must match
2011: <nt def="NT-Names">Names</nt>;
2012: each <nt def="NT-Name">Name</nt> must
2013: match the
2014: name of an <termref def="dt-unparsed">unparsed entity</termref> declared in the
2015: <termref def="dt-doctype">DTD</termref>.
2016: </p>
2017: </vcnote>
2018: <vcnote id='nmtok'>
2019: <head>Name Token</head>
2020: <p>
2021: Values of type <kw>NMTOKEN</kw> must match the
2022: <nt def="NT-Nmtoken">Nmtoken</nt> production;
2023: values of type <kw>NMTOKENS</kw> must
2024: match <termref def="NT-Nmtokens">Nmtokens</termref>.
2025: </p>
2026: </vcnote>
2027: <!-- why?
2028: <p>The XML processor must normalize attribute values before
2029: passing them to the application, as described in
2030: <specref ref="AVNormalize"/>.</p>-->
2031: <p><termdef id='dt-enumerated' term='Enumerated Attribute
2032: Values'><term>Enumerated attributes</term> can take one
2033: of a list of values provided in the declaration</termdef>. There are two
2034: kinds of enumerated types:
2035: <scrap lang='ebnf'>
2036: <head>Enumerated Attribute Types</head>
2037: <prod id='NT-EnumeratedType'><lhs>EnumeratedType</lhs>
2038: <rhs><nt def='NT-NotationType'>NotationType</nt>
2039: | <nt def='NT-Enumeration'>Enumeration</nt>
2040: </rhs></prod>
2041: <prod id='NT-NotationType'><lhs>NotationType</lhs>
2042: <rhs>'NOTATION'
2043: <nt def='NT-S'>S</nt>
2044: '('
2045: <nt def='NT-S'>S</nt>?
2046: <nt def='NT-Name'>Name</nt>
2047: (<nt def='NT-S'>S</nt>? '|' <nt def='NT-S'>S</nt>?
2048: <nt def='NT-Name'>Name</nt>)*
2049: <nt def='NT-S'>S</nt>? ')'
2050: </rhs>
2051: <vc def='notatn' /></prod>
2052: <prod id='NT-Enumeration'><lhs>Enumeration</lhs>
2053: <rhs>'(' <nt def='NT-S'>S</nt>?
2054: <nt def='NT-Nmtoken'>Nmtoken</nt>
2055: (<nt def='NT-S'>S</nt>? '|'
2056: <nt def='NT-S'>S</nt>?
2057: <nt def='NT-Nmtoken'>Nmtoken</nt>)*
2058: <nt def='NT-S'>S</nt>?
2059: ')'</rhs>
2060: <vc def='enum'/></prod>
2061: </scrap>
2062: A <kw>NOTATION</kw> attribute identifies a
2063: <termref def='dt-notation'>notation</termref>, declared in the
2064: DTD with associated system and/or public identifiers, to
2065: be used in interpreting the element to which the attribute
2066: is attached.
2067: </p>
2068:
2069: <vcnote id='notatn'>
2070: <head>Notation Attributes</head>
2071: <p>
2072: Values of this type must match
2073: one of the <titleref href='Notations'>notation</titleref> names included in
2074: the declaration; all notation names in the declaration must
2075: be declared.
2076: </p>
2077: </vcnote>
2078: <vcnote id='enum'>
2079: <head>Enumeration</head>
2080: <p>
2081: Values of this type
2082: must match one of the <nt def='NT-Nmtoken'>Nmtoken</nt> tokens in the
2083: declaration.
2084: </p>
2085: </vcnote>
2086: <p><termref def='dt-interop'>For interoperability,</termref> the same
2087: <nt def='NT-Nmtoken'>Nmtoken</nt> should not occur more than once in the
2088: enumerated attribute types of a single element type.
2089: </p>
2090: </div3>
2091:
2092: <div3 id='sec-attr-defaults'>
2093: <head>Attribute Defaults</head>
2094:
2095: <p>An <termref def="dt-attdecl">attribute declaration</termref> provides
2096: information on whether
2097: the attribute's presence is required, and if not, how an XML processor should
2098: react if a declared attribute is absent in a document.
2099: <scrap lang='ebnf'>
2100: <head>Attribute Defaults</head>
2101: <prodgroup pcw4="14" pcw5="11.5">
2102: <prod id='NT-DefaultDecl'><lhs>DefaultDecl</lhs>
2103: <rhs>'#REQUIRED'
2104: | '#IMPLIED' </rhs>
2105: <rhs>| (('#FIXED' S)? <nt def='NT-AttValue'>AttValue</nt>)</rhs>
2106: <vc def='RequiredAttr'/>
2107: <vc def='defattrvalid'/>
2108: <wfc def="CleanAttrVals"/>
2109: <vc def='FixedAttr'/>
2110: </prod>
2111: </prodgroup>
2112: </scrap>
2113:
2114: </p>
2115: <p>In an attribute declaration, <kw>#REQUIRED</kw> means that the
2116: attribute must always be provided, <kw>#IMPLIED</kw> that no default
2117: value is provided.
2118: <!-- not any more!!
2119: <kw>#IMPLIED</kw> means that if the attribute is omitted
2120: from an element of this type,
2121: the XML processor must inform the application
2122: that no value was specified; no constraint is placed on the behavior
2123: of the application. -->
2124: <termdef id="dt-default" term="Attribute Default">If the
2125: declaration
2126: is neither <kw>#REQUIRED</kw> nor <kw>#IMPLIED</kw>, then the
2127: <nt def='NT-AttValue'>AttValue</nt> value contains the declared
2128: <term>default</term> value; the <kw>#FIXED</kw> keyword states that
2129: the attribute must always have the default value.
2130: If a default value
2131: is declared, when an XML processor encounters an omitted attribute, it
2132: is to behave as though the attribute were present with
2133: the declared default value.</termdef></p>
2134: <vcnote id='RequiredAttr'>
2135: <head>Required Attribute</head>
2136: <p>If the default declaration is the keyword <kw>#REQUIRED</kw>, then
2137: the attribute must be specified for
2138: all elements of the type in the attribute-list declaration.
2139: </p></vcnote>
2140: <vcnote id='defattrvalid'>
2141: <head>Attribute Default Legal</head>
2142: <p>
2143: The declared
2144: default value must meet the lexical constraints of the declared attribute type.
2145: </p>
2146: </vcnote>
2147: <vcnote id='FixedAttr'>
2148: <head>Fixed Attribute Default</head>
2149: <p>If an attribute has a default value declared with the
2150: <kw>#FIXED</kw> keyword, instances of that attribute must
2151: match the default value.
2152: </p></vcnote>
2153:
2154: <p>Examples of attribute-list declarations:
2155: <eg><!ATTLIST termdef
2156: id ID #REQUIRED
2157: name CDATA #IMPLIED>
2158: <!ATTLIST list
2159: type (bullets|ordered|glossary) "ordered">
2160: <!ATTLIST form
2161: method CDATA #FIXED "POST"></eg></p>
2162: </div3>
2163: <div3 id='AVNormalize'>
2164: <head>Attribute-Value Normalization</head>
2165: <p>Before the value of an attribute is passed to the application
2166: or checked for validity, the
2167: XML processor must normalize it as follows:
2168: <ulist>
2169: <item><p>a character reference is processed by appending the referenced
2170: character to the attribute value</p></item>
2171: <item><p>an entity reference is processed by recursively processing the
2172: replacement text of the entity</p></item>
2173: <item><p>a whitespace character (#x20, #xD, #xA, #x9) is processed by
2174: appending #x20 to the normalized value, except that only a single #x20
2175: is appended for a "#xD#xA" sequence that is part of an external
2176: parsed entity or the literal entity value of an internal parsed
2177: entity</p></item>
2178: <item><p>other characters are processed by appending them to the normalized
2179: value</p>
2180: </item></ulist>
2181: </p>
2182: <p>If the declared value is not CDATA, then the XML processor must
2183: further process the normalized attribute value by discarding any
2184: leading and trailing space (#x20) characters, and by replacing
2185: sequences of space (#x20) characters by a single space (#x20)
2186: character.</p>
2187: <p>
2188: All attributes for which no declaration has been read should be treated
2189: by a non-validating parser as if declared
2190: <kw>CDATA</kw>.
2191: </p>
2192: </div3>
2193: </div2>
2194: <div2 id='sec-condition-sect'>
2195: <head>Conditional Sections</head>
2196: <p><termdef id='dt-cond-section' term='conditional section'>
2197: <term>Conditional sections</term> are portions of the
2198: <termref def='dt-doctype'>document type declaration external subset</termref>
2199: which are
2200: included in, or excluded from, the logical structure of the DTD based on
2201: the keyword which governs them.</termdef>
2202: <scrap lang='ebnf'>
2203: <head>Conditional Section</head>
2204: <prodgroup pcw2="9" pcw4="14.5">
2205: <prod id='NT-conditionalSect'><lhs>conditionalSect</lhs>
2206: <rhs><nt def='NT-includeSect'>includeSect</nt>
2207: | <nt def='NT-ignoreSect'>ignoreSect</nt>
2208: </rhs>
2209: </prod>
2210: <prod id='NT-includeSect'><lhs>includeSect</lhs>
2211: <rhs>'<![' S? 'INCLUDE' S? '['
2212:
2213: <nt def="NT-extSubsetDecl">extSubsetDecl</nt>
2214: ']]>'
2215: </rhs>
2216: </prod>
2217: <prod id='NT-ignoreSect'><lhs>ignoreSect</lhs>
2218: <rhs>'<![' S? 'IGNORE' S? '['
2219: <nt def="NT-ignoreSectContents">ignoreSectContents</nt>*
2220: ']]>'</rhs>
2221: </prod>
2222:
2223: <prod id='NT-ignoreSectContents'><lhs>ignoreSectContents</lhs>
2224: <rhs><nt def='NT-Ignore'>Ignore</nt>
2225: ('<![' <nt def='NT-ignoreSectContents'>ignoreSectContents</nt> ']]>'
2226: <nt def='NT-Ignore'>Ignore</nt>)*</rhs></prod>
2227: <prod id='NT-Ignore'><lhs>Ignore</lhs>
2228: <rhs><nt def='NT-Char'>Char</nt>* -
2229: (<nt def='NT-Char'>Char</nt>* ('<![' | ']]>')
2230: <nt def='NT-Char'>Char</nt>*)
2231: </rhs></prod>
2232:
2233: </prodgroup>
2234: </scrap>
2235: </p>
2236: <p>Like the internal and external DTD subsets, a conditional section
2237: may contain one or more complete declarations,
2238: comments, processing instructions,
2239: or nested conditional sections, intermingled with white space.
2240: </p>
2241: <p>If the keyword of the
2242: conditional section is <kw>INCLUDE</kw>, then the contents of the conditional
2243: section are part of the DTD.
2244: If the keyword of the conditional
2245: section is <kw>IGNORE</kw>, then the contents of the conditional section are
2246: not logically part of the DTD.
2247: Note that for reliable parsing, the contents of even ignored
2248: conditional sections must be read in order to
2249: detect nested conditional sections and ensure that the end of the
2250: outermost (ignored) conditional section is properly detected.
2251: If a conditional section with a
2252: keyword of <kw>INCLUDE</kw> occurs within a larger conditional
2253: section with a keyword of <kw>IGNORE</kw>, both the outer and the
2254: inner conditional sections are ignored.</p>
2255: <p>If the keyword of the conditional section is a
2256: parameter-entity reference, the parameter entity must be replaced by its
2257: content before the processor decides whether to
2258: include or ignore the conditional section.</p>
2259: <p>An example:
2260: <eg><!ENTITY % draft 'INCLUDE' >
2261: <!ENTITY % final 'IGNORE' >
2262:
2263: <![%draft;[
2264: <!ELEMENT book (comments*, title, body, supplements?)>
2265: ]]>
2266: <![%final;[
2267: <!ELEMENT book (title, body, supplements?)>
2268: ]]>
2269: </eg>
2270: </p>
2271: </div2>
2272:
2273:
2274: <!--
2275: <div2 id='sec-pass-to-app'>
2276: <head>XML Processor Treatment of Logical Structure</head>
2277: <p>When an XML processor encounters a start-tag, it must make
2278: at least the following information available to the application:
2279: <ulist>
2280: <item>
2281: <p>the element type's generic identifier</p>
2282: </item>
2283: <item>
2284: <p>the names of attributes known to apply to this element type
2285: (validating processors must make available names of all attributes
2286: declared for the element type; non-validating processors must
2287: make available at least the names of the attributes for which
2288: values are specified.
2289: </p>
2290: </item>
2291: </ulist>
2292: </p>
2293: </div2>
2294: -->
2295:
2296: </div1>
2297: <!-- &Entities; -->
2298:
2299: <div1 id='sec-physical-struct'>
2300: <head>Physical Structures</head>
2301:
2302: <p><termdef id="dt-entity" term="Entity">An XML document may consist
2303: of one or many storage units. These are called
2304: <term>entities</term>; they all have <term>content</term> and are all
2305: (except for the document entity, see below, and
2306: the <termref def='dt-doctype'>external DTD subset</termref>)
2307: identified by <term>name</term>.
2308: </termdef>
2309: Each XML document has one entity
2310: called the <termref def="dt-docent">document entity</termref>, which serves
2311: as the starting point for the <termref def="dt-xml-proc">XML
2312: processor</termref> and may contain the whole document.</p>
2313: <p>Entities may be either parsed or unparsed.
2314: <termdef id="dt-parsedent" term="Text Entity">A <term>parsed entity's</term>
2315: contents are referred to as its
2316: <termref def='dt-repltext'>replacement text</termref>;
2317: this <termref def="dt-text">text</termref> is considered an
2318: integral part of the document.</termdef></p>
2319:
2320: <p><termdef id="dt-unparsed" term="Unparsed Entity">An
2321: <term>unparsed entity</term>
2322: is a resource whose contents may or may not be
2323: <termref def='dt-text'>text</termref>, and if text, may not be XML.
2324: Each unparsed entity
2325: has an associated <termref
2326: def="dt-notation">notation</termref>, identified by name.
2327: Beyond a requirement
2328: that an XML processor make the identifiers for the entity and
2329: notation available to the application,
2330: XML places no constraints on the contents of unparsed entities.</termdef>
2331: </p>
2332: <p>
2333: Parsed entities are invoked by name using entity references;
2334: unparsed entities by name, given in the value of <kw>ENTITY</kw>
2335: or <kw>ENTITIES</kw>
2336: attributes.</p>
2337: <p><termdef id='gen-entity' term='general entity'
2338: ><term>General entities</term>
2339: are entities for use within the document content.
2340: In this specification, general entities are sometimes referred
2341: to with the unqualified term <emph>entity</emph> when this leads
2342: to no ambiguity.</termdef>
2343: <termdef id='dt-PE' term='Parameter entity'>Parameter entities
2344: are parsed entities for use within the DTD.</termdef>
2345: These two types of entities use different forms of reference and
2346: are recognized in different contexts.
2347: Furthermore, they occupy different namespaces; a parameter entity and
2348: a general entity with the same name are two distinct entities.
2349: </p>
2350:
2351: <div2 id='sec-references'>
2352: <head>Character and Entity References</head>
2353: <p><termdef id="dt-charref" term="Character Reference">
2354: A <term>character reference</term> refers to a specific character in the
2355: ISO/IEC 10646 character set, for example one not directly accessible from
2356: available input devices.
2357: <scrap lang='ebnf'>
2358: <head>Character Reference</head>
2359: <prod id='NT-CharRef'><lhs>CharRef</lhs>
2360: <rhs>'&#' [0-9]+ ';' </rhs>
2361: <rhs>| '&hcro;' [0-9a-fA-F]+ ';'</rhs>
2362: <wfc def="wf-Legalchar"/>
2363: </prod>
2364: </scrap>
2365: <wfcnote id="wf-Legalchar">
2366: <head>Legal Character</head>
2367: <p>Characters referred to using character references must
2368: match the production for
2369: <termref def="NT-Char">Char</termref>.</p>
2370: </wfcnote>
2371: If the character reference begins with "<code>&#x</code>", the digits and
2372: letters up to the terminating <code>;</code> provide a hexadecimal
2373: representation of the character's code point in ISO/IEC 10646.
2374: If it begins just with "<code>&#</code>", the digits up to the terminating
2375: <code>;</code> provide a decimal representation of the character's
2376: code point.
2377: </termdef>
2378: </p>
2379: <p><termdef id="dt-entref" term="Entity Reference">An <term>entity
2380: reference</term> refers to the content of a named entity.</termdef>
2381: <termdef id='dt-GERef' term='General Entity Reference'>References to
2382: parsed general entities
2383: use ampersand (<code>&</code>) and semicolon (<code>;</code>) as
2384: delimiters.</termdef>
2385: <termdef id='dt-PERef' term='Parameter-entity reference'>
2386: <term>Parameter-entity references</term> use percent-sign (<code>%</code>) and
2387: semicolon
2388: (<code>;</code>) as delimiters.</termdef>
2389: </p>
2390: <scrap lang="ebnf">
2391: <head>Entity Reference</head>
2392: <prod id='NT-Reference'><lhs>Reference</lhs>
2393: <rhs><nt def='NT-EntityRef'>EntityRef</nt>
2394: | <nt def='NT-CharRef'>CharRef</nt></rhs></prod>
2395: <prod id='NT-EntityRef'><lhs>EntityRef</lhs>
2396: <rhs>'&' <nt def='NT-Name'>Name</nt> ';'</rhs>
2397: <wfc def='wf-entdeclared'/>
2398: <vc def='vc-entdeclared'/>
2399: <wfc def='textent'/>
2400: <wfc def='norecursion'/>
2401: </prod>
2402: <prod id='NT-PEReference'><lhs>PEReference</lhs>
2403: <rhs>'%' <nt def='NT-Name'>Name</nt> ';'</rhs>
2404: <vc def='vc-entdeclared'/>
2405: <wfc def='norecursion'/>
2406: <wfc def='indtd'/>
2407: </prod>
2408: </scrap>
2409:
2410: <wfcnote id='wf-entdeclared'>
2411: <head>Entity Declared</head>
2412: <p>In a document without any DTD, a document with only an internal
2413: DTD subset which contains no parameter entity references, or a document with
2414: "<code>standalone='yes'</code>",
2415: the <nt def='NT-Name'>Name</nt> given in the entity reference must
2416: <termref def="dt-match">match</termref> that in an
2417: <titleref href='sec-entity-decl'>entity declaration</titleref>, except that
2418: well-formed documents need not declare
2419: any of the following entities: &magicents;.
2420: The declaration of a parameter entity must precede any reference to it.
2421: Similarly, the declaration of a general entity must precede any
2422: reference to it which appears in a default value in an attribute-list
2423: declaration.</p>
2424: <p>Note that if entities are declared in the external subset or in
2425: external parameter entities, a non-validating processor is
2426: <titleref href='include-if-valid'>not obligated to</titleref> read
2427: and process their declarations; for such documents, the rule that
2428: an entity must be declared is a well-formedness constraint only
2429: if <titleref href='sec-rmd'>standalone='yes'</titleref>.</p>
2430: </wfcnote>
2431: <vcnote id="vc-entdeclared">
2432: <head>Entity Declared</head>
2433: <p>In a document with an external subset or external parameter
2434: entities with "<code>standalone='no'</code>",
2435: the <nt def='NT-Name'>Name</nt> given in the entity reference must <termref
2436: def="dt-match">match</termref> that in an
2437: <titleref href='sec-entity-decl'>entity declaration</titleref>.
2438: For interoperability, valid documents should declare the entities
2439: &magicents;, in the form
2440: specified in <specref ref="sec-predefined-ent"/>.
2441: The declaration of a parameter entity must precede any reference to it.
2442: Similarly, the declaration of a general entity must precede any
2443: reference to it which appears in a default value in an attribute-list
2444: declaration.</p>
2445: </vcnote>
2446: <!-- FINAL EDIT: is this duplication too clumsy? -->
2447: <wfcnote id='textent'>
2448: <head>Parsed Entity</head>
2449: <p>
2450: An entity reference must not contain the name of an <termref
2451: def="dt-unparsed">unparsed entity</termref>. Unparsed entities may be referred
2452: to only in <termref def="dt-attrval">attribute values</termref> declared to
2453: be of type <kw>ENTITY</kw> or <kw>ENTITIES</kw>.
2454: </p>
2455: </wfcnote>
2456: <wfcnote id='norecursion'>
2457: <head>No Recursion</head>
2458: <p>
2459: A parsed entity must not contain a recursive reference to itself,
2460: either directly or indirectly.
2461: </p>
2462: </wfcnote>
2463: <wfcnote id='indtd'>
2464: <head>In DTD</head>
2465: <p>
2466: Parameter-entity references may only appear in the
2467: <termref def='dt-doctype'>DTD</termref>.
2468: </p>
2469: </wfcnote>
2470: <p>Examples of character and entity references:
2471: <eg>Type <key>less-than</key> (&hcro;3C;) to save options.
2472: This document was prepared on &docdate; and
2473: is classified &security-level;.</eg></p>
2474: <p>Example of a parameter-entity reference:
2475: <eg><![CDATA[<!-- declare the parameter entity "ISOLat2"... -->
2476: <!ENTITY % ISOLat2
2477: SYSTEM "http://www.xml.com/iso/isolat2-xml.entities" >
2478: <!-- ... now reference it. -->
2479: %ISOLat2;]]></eg></p>
2480: </div2>
2481:
2482: <div2 id='sec-entity-decl'>
2483: <head>Entity Declarations</head>
2484:
2485: <p><termdef id="dt-entdecl" term="entity declaration">
2486: Entities are declared thus:
2487: <scrap lang='ebnf'>
2488: <head>Entity Declaration</head>
2489: <prodgroup pcw2="5" pcw4="18.5">
2490: <prod id='NT-EntityDecl'><lhs>EntityDecl</lhs>
2491: <rhs><nt def="NT-GEDecl">GEDecl</nt><!--</rhs><com>General entities</com>
2492: <rhs>--> | <nt def="NT-PEDecl">PEDecl</nt></rhs>
2493: <!--<com>Parameter entities</com>-->
2494: </prod>
2495: <prod id='NT-GEDecl'><lhs>GEDecl</lhs>
2496: <rhs>'<!ENTITY' <nt def='NT-S'>S</nt> <nt def='NT-Name'>Name</nt>
2497: <nt def='NT-S'>S</nt> <nt def='NT-EntityDef'>EntityDef</nt>
2498: <nt def='NT-S'>S</nt>? '>'</rhs>
2499: </prod>
2500: <prod id='NT-PEDecl'><lhs>PEDecl</lhs>
2501: <rhs>'<!ENTITY' <nt def='NT-S'>S</nt> '%' <nt def='NT-S'>S</nt>
2502: <nt def='NT-Name'>Name</nt> <nt def='NT-S'>S</nt>
2503: <nt def='NT-PEDef'>PEDef</nt> <nt def='NT-S'>S</nt>? '>'</rhs>
2504: <!--<com>Parameter entities</com>-->
2505: </prod>
2506: <prod id='NT-EntityDef'><lhs>EntityDef</lhs>
2507: <rhs><nt def='NT-EntityValue'>EntityValue</nt>
2508: <!--</rhs>
2509: <rhs>-->| (<nt def='NT-ExternalID'>ExternalID</nt>
2510: <nt def='NT-NDataDecl'>NDataDecl</nt>?)</rhs>
2511: <!-- <nt def='NT-ExternalDef'>ExternalDef</nt></rhs> -->
2512: </prod>
2513: <!-- FINAL EDIT: what happened to WFs here? -->
2514: <prod id='NT-PEDef'><lhs>PEDef</lhs>
2515: <rhs><nt def='NT-EntityValue'>EntityValue</nt>
2516: | <nt def='NT-ExternalID'>ExternalID</nt></rhs></prod>
2517: </prodgroup>
2518: </scrap>
2519: The <nt def='NT-Name'>Name</nt> identifies the entity in an
2520: <termref def="dt-entref">entity reference</termref> or, in the case of an
2521: unparsed entity, in the value of an <kw>ENTITY</kw> or <kw>ENTITIES</kw>
2522: attribute.
2523: If the same entity is declared more than once, the first declaration
2524: encountered is binding; at user option, an XML processor may issue a
2525: warning if entities are declared multiple times.</termdef>
2526: </p>
2527:
2528: <div3 id='sec-internal-ent'>
2529: <head>Internal Entities</head>
2530:
2531: <p><termdef id='dt-internent' term="Internal Entity Replacement Text">If
2532: the entity definition is an
2533: <nt def='NT-EntityValue'>EntityValue</nt>,
2534: the defined entity is called an <term>internal entity</term>.
2535: There is no separate physical
2536: storage object, and the content of the entity is given in the
2537: declaration. </termdef>
2538: Note that some processing of entity and character references in the
2539: <termref def='dt-litentval'>literal entity value</termref> may be required to
2540: produce the correct <termref def='dt-repltext'>replacement
2541: text</termref>: see <specref ref='intern-replacement'/>.
2542: </p>
2543: <p>An internal entity is a <termref def="dt-parsedent">parsed
2544: entity</termref>.</p>
2545: <p>Example of an internal entity declaration:
2546: <eg><!ENTITY Pub-Status "This is a pre-release of the
2547: specification."></eg></p>
2548: </div3>
2549:
2550: <div3 id='sec-external-ent'>
2551: <head>External Entities</head>
2552:
2553: <p><termdef id="dt-extent" term="External Entity">If the entity is not
2554: internal, it is an <term>external
2555: entity</term>, declared as follows:
2556: <scrap lang='ebnf'>
2557: <head>External Entity Declaration</head>
2558: <!--
2559: <prod id='NT-ExternalDef'><lhs>ExternalDef</lhs>
2560: <rhs></prod> -->
2561: <prod id='NT-ExternalID'><lhs>ExternalID</lhs>
2562: <rhs>'SYSTEM' <nt def='NT-S'>S</nt>
2563: <nt def='NT-SystemLiteral'>SystemLiteral</nt></rhs>
2564: <rhs>| 'PUBLIC' <nt def='NT-S'>S</nt>
2565: <nt def='NT-PubidLiteral'>PubidLiteral</nt>
2566: <nt def='NT-S'>S</nt>
2567: <nt def='NT-SystemLiteral'>SystemLiteral</nt>
2568: </rhs>
2569: </prod>
2570: <prod id='NT-NDataDecl'><lhs>NDataDecl</lhs>
2571: <rhs><nt def='NT-S'>S</nt> 'NDATA' <nt def='NT-S'>S</nt>
2572: <nt def='NT-Name'>Name</nt></rhs>
2573: <vc def='not-declared'/></prod>
2574: </scrap>
2575: If the <nt def='NT-NDataDecl'>NDataDecl</nt> is present, this is a
2576: general <termref def="dt-unparsed">unparsed
2577: entity</termref>; otherwise it is a parsed entity.</termdef></p>
2578: <vcnote id='not-declared'>
2579: <head>Notation Declared</head>
2580: <p>
2581: The <nt def='NT-Name'>Name</nt> must match the declared name of a
2582: <termref def="dt-notation">notation</termref>.
2583: </p>
2584: </vcnote>
2585: <p><termdef id="dt-sysid" term="System Identifier">The
2586: <nt def='NT-SystemLiteral'>SystemLiteral</nt>
2587: is called the entity's <term>system identifier</term>. It is a URI,
2588: which may be used to retrieve the entity.</termdef>
2589: Note that the hash mark (<code>#</code>) and fragment identifier
2590: frequently used with URIs are not, formally, part of the URI itself;
2591: an XML processor may signal an error if a fragment identifier is
2592: given as part of a system identifier.
2593: Unless otherwise provided by information outside the scope of this
2594: specification (e.g. a special XML element type defined by a particular
2595: DTD, or a processing instruction defined by a particular application
2596: specification), relative URIs are relative to the location of the
2597: resource within which the entity declaration occurs.
2598: A URI might thus be relative to the
2599: <termref def='dt-docent'>document entity</termref>, to the entity
2600: containing the <termref def='dt-doctype'>external DTD subset</termref>,
2601: or to some other <termref def='dt-extent'>external parameter entity</termref>.
2602: </p>
2603: <p>An XML processor should handle a non-ASCII character in a URI by
2604: representing the character in UTF-8 as one or more bytes, and then
2605: escaping these bytes with the URI escaping mechanism (i.e., by
2606: converting each byte to %HH, where HH is the hexadecimal notation of the
2607: byte value).</p>
2608: <p><termdef id="dt-pubid" term="Public identifier">
2609: In addition to a system identifier, an external identifier may
2610: include a <term>public identifier</term>.</termdef>
2611: An XML processor attempting to retrieve the entity's content may use the public
2612: identifier to try to generate an alternative URI. If the processor
2613: is unable to do so, it must use the URI specified in the system
2614: literal. Before a match is attempted, all strings
2615: of white space in the public identifier must be normalized to single space characters (#x20),
2616: and leading and trailing white space must be removed.</p>
2617: <p>Examples of external entity declarations:
2618: <eg><!ENTITY open-hatch
2619: SYSTEM "http://www.textuality.com/boilerplate/OpenHatch.xml">
2620: <!ENTITY open-hatch
2621: PUBLIC "-//Textuality//TEXT Standard open-hatch boilerplate//EN"
2622: "http://www.textuality.com/boilerplate/OpenHatch.xml">
2623: <!ENTITY hatch-pic
2624: SYSTEM "../grafix/OpenHatch.gif"
2625: NDATA gif ></eg></p>
2626: </div3>
2627:
2628: </div2>
2629:
2630: <div2 id='TextEntities'>
2631: <head>Parsed Entities</head>
2632: <div3 id='sec-TextDecl'>
2633: <head>The Text Declaration</head>
2634: <p>External parsed entities may each begin with a <term>text
2635: declaration</term>.
2636: <scrap lang='ebnf'>
2637: <head>Text Declaration</head>
2638: <prodgroup pcw4="12.5" pcw5="13">
2639: <prod id='NT-TextDecl'><lhs>TextDecl</lhs>
2640: <rhs>&xmlpio;
2641: <nt def='NT-VersionInfo'>VersionInfo</nt>?
2642: <nt def='NT-EncodingDecl'>EncodingDecl</nt>
2643: <nt def='NT-S'>S</nt>? &pic;</rhs>
2644: </prod>
2645: </prodgroup>
2646: </scrap>
2647: </p>
2648: <p>The text declaration must be provided literally, not
2649: by reference to a parsed entity.
2650: No text declaration may appear at any position other than the beginning of
2651: an external parsed entity.</p>
2652: </div3>
2653: <div3 id='wf-entities'>
2654: <head>Well-Formed Parsed Entities</head>
2655: <p>The document entity is well-formed if it matches the production labeled
2656: <nt def='NT-document'>document</nt>.
2657: An external general
2658: parsed entity is well-formed if it matches the production labeled
2659: <nt def='NT-extParsedEnt'>extParsedEnt</nt>.
2660: An external parameter
2661: entity is well-formed if it matches the production labeled
2662: <nt def='NT-extPE'>extPE</nt>.
2663: <scrap lang='ebnf'>
2664: <head>Well-Formed External Parsed Entity</head>
2665: <prod id='NT-extParsedEnt'><lhs>extParsedEnt</lhs>
2666: <rhs><nt def='NT-TextDecl'>TextDecl</nt>?
2667: <nt def='NT-content'>content</nt></rhs>
2668: </prod>
2669: <prod id='NT-extPE'><lhs>extPE</lhs>
2670: <rhs><nt def='NT-TextDecl'>TextDecl</nt>?
2671: <nt def='NT-extSubsetDecl'>extSubsetDecl</nt></rhs>
2672: </prod>
2673: </scrap>
2674: An internal general parsed entity is well-formed if its replacement text
2675: matches the production labeled
2676: <nt def='NT-content'>content</nt>.
2677: All internal parameter entities are well-formed by definition.
2678: </p>
2679: <p>A consequence of well-formedness in entities is that the logical
2680: and physical structures in an XML document are properly nested; no
2681: <termref def='dt-stag'>start-tag</termref>,
2682: <termref def='dt-etag'>end-tag</termref>,
2683: <termref def="dt-empty">empty-element tag</termref>,
2684: <termref def='dt-element'>element</termref>,
2685: <termref def='dt-comment'>comment</termref>,
2686: <termref def='dt-pi'>processing instruction</termref>,
2687: <termref def='dt-charref'>character
2688: reference</termref>, or
2689: <termref def='dt-entref'>entity reference</termref>
2690: can begin in one entity and end in another.</p>
2691: </div3>
2692: <div3 id='charencoding'>
2693: <head>Character Encoding in Entities</head>
2694:
2695: <p>Each external parsed entity in an XML document may use a different
2696: encoding for its characters. All XML processors must be able to read
2697: entities in either UTF-8 or UTF-16.
2698:
2699: </p>
2700: <p>Entities encoded in UTF-16 must
2701: begin with the Byte Order Mark described by ISO/IEC 10646 Annex E and
2702: Unicode Appendix B (the ZERO WIDTH NO-BREAK SPACE character, #xFEFF).
2703: This is an encoding signature, not part of either the markup or the
2704: character data of the XML document.
2705: XML processors must be able to use this character to
2706: differentiate between UTF-8 and UTF-16 encoded documents.</p>
2707: <p>Although an XML processor is required to read only entities in
2708: the UTF-8 and UTF-16 encodings, it is recognized that other encodings are
2709: used around the world, and it may be desired for XML processors
2710: to read entities that use them.
2711: Parsed entities which are stored in an encoding other than
2712: UTF-8 or UTF-16 must begin with a <titleref href='TextDecl'>text
2713: declaration</titleref> containing an encoding declaration:
2714: <scrap lang='ebnf'>
2715: <head>Encoding Declaration</head>
2716: <prod id='NT-EncodingDecl'><lhs>EncodingDecl</lhs>
2717: <rhs><nt def="NT-S">S</nt>
2718: 'encoding' <nt def='NT-Eq'>Eq</nt>
2719: ('"' <nt def='NT-EncName'>EncName</nt> '"' |
2720: "'" <nt def='NT-EncName'>EncName</nt> "'" )
2721: </rhs>
2722: </prod>
2723: <prod id='NT-EncName'><lhs>EncName</lhs>
2724: <rhs>[A-Za-z] ([A-Za-z0-9._] | '-')*</rhs>
2725: <com>Encoding name contains only Latin characters</com>
2726: </prod>
2727: </scrap>
2728: In the <termref def='dt-docent'>document entity</termref>, the encoding
2729: declaration is part of the <termref def="dt-xmldecl">XML declaration</termref>.
2730: The <nt def="NT-EncName">EncName</nt> is the name of the encoding used.
2731: </p>
2732: <!-- FINAL EDIT: check name of IANA and charset names -->
2733: <p>In an encoding declaration, the values
2734: "<code>UTF-8</code>",
2735: "<code>UTF-16</code>",
2736: "<code>ISO-10646-UCS-2</code>", and
2737: "<code>ISO-10646-UCS-4</code>" should be
2738: used for the various encodings and transformations of Unicode /
2739: ISO/IEC 10646, the values
2740: "<code>ISO-8859-1</code>",
2741: "<code>ISO-8859-2</code>", ...
2742: "<code>ISO-8859-9</code>" should be used for the parts of ISO 8859, and
2743: the values
2744: "<code>ISO-2022-JP</code>",
2745: "<code>Shift_JIS</code>", and
2746: "<code>EUC-JP</code>"
2747: should be used for the various encoded forms of JIS X-0208-1997. XML
2748: processors may recognize other encodings; it is recommended that
2749: character encodings registered (as <emph>charset</emph>s)
2750: with the Internet Assigned Numbers
2751: Authority <bibref ref='IANA'/>, other than those just listed, should be
2752: referred to
2753: using their registered names.
2754: Note that these registered names are defined to be
2755: case-insensitive, so processors wishing to match against them
2756: should do so in a case-insensitive
2757: way.</p>
2758: <p>In the absence of information provided by an external
2759: transport protocol (e.g. HTTP or MIME),
2760: it is an <termref def="dt-error">error</termref> for an entity including
2761: an encoding declaration to be presented to the XML processor
2762: in an encoding other than that named in the declaration,
2763: for an encoding declaration to occur other than at the beginning
2764: of an external entity, or for
2765: an entity which begins with neither a Byte Order Mark nor an encoding
2766: declaration to use an encoding other than UTF-8.
2767: Note that since ASCII
2768: is a subset of UTF-8, ordinary ASCII entities do not strictly need
2769: an encoding declaration.</p>
2770:
2771: <p>It is a <termref def='dt-fatal'>fatal error</termref> when an XML processor
2772: encounters an entity with an encoding that it is unable to process.</p>
2773: <p>Examples of encoding declarations:
2774: <eg><?xml encoding='UTF-8'?>
2775: <?xml encoding='EUC-JP'?></eg></p>
2776: </div3>
2777: </div2>
2778: <div2 id='entproc'>
2779: <head>XML Processor Treatment of Entities and References</head>
2780: <p>The table below summarizes the contexts in which character references,
2781: entity references, and invocations of unparsed entities might appear and the
2782: required behavior of an <termref def='dt-xml-proc'>XML processor</termref> in
2783: each case.
2784: The labels in the leftmost column describe the recognition context:
2785: <glist>
2786: <gitem><label>Reference in Content</label>
2787: <def><p>as a reference
2788: anywhere after the <termref def='dt-stag'>start-tag</termref> and
2789: before the <termref def='dt-etag'>end-tag</termref> of an element; corresponds
2790: to the nonterminal <nt def='NT-content'>content</nt>.</p></def>
2791: </gitem>
2792: <gitem>
2793: <label>Reference in Attribute Value</label>
2794: <def><p>as a reference within either the value of an attribute in a
2795: <termref def='dt-stag'>start-tag</termref>, or a default
2796: value in an <termref def='dt-attdecl'>attribute declaration</termref>;
2797: corresponds to the nonterminal
2798: <nt def='NT-AttValue'>AttValue</nt>.</p></def></gitem>
2799: <gitem>
2800: <label>Occurs as Attribute Value</label>
2801: <def><p>as a <nt def='NT-Name'>Name</nt>, not a reference, appearing either as
2802: the value of an
2803: attribute which has been declared as type <kw>ENTITY</kw>, or as one of
2804: the space-separated tokens in the value of an attribute which has been
2805: declared as type <kw>ENTITIES</kw>.</p>
2806: </def></gitem>
2807: <gitem><label>Reference in Entity Value</label>
2808: <def><p>as a reference
2809: within a parameter or internal entity's
2810: <termref def='dt-litentval'>literal entity value</termref> in
2811: the entity's declaration; corresponds to the nonterminal
2812: <nt def='NT-EntityValue'>EntityValue</nt>.</p></def></gitem>
2813: <gitem><label>Reference in DTD</label>
2814: <def><p>as a reference within either the internal or external subsets of the
2815: <termref def='dt-doctype'>DTD</termref>, but outside
2816: of an <nt def='NT-EntityValue'>EntityValue</nt> or
2817: <nt def="NT-AttValue">AttValue</nt>.</p></def>
2818: </gitem>
2819: </glist></p>
2820: <htable border='1' cellpadding='7' align='center'>
2821: <htbody>
2822: <tr><td bgcolor='&cellback;' rowspan='2' colspan='1'></td>
2823: <td bgcolor='&cellback;' align='center' valign='bottom' colspan='4'>Entity Type</td>
2824: <td bgcolor='&cellback;' rowspan='2' align='center'>Character</td>
2825: </tr>
2826: <tr align='center' valign='bottom'>
2827: <td bgcolor='&cellback;'>Parameter</td>
2828: <td bgcolor='&cellback;'>Internal
2829: General</td>
2830: <td bgcolor='&cellback;'>External Parsed
2831: General</td>
2832: <td bgcolor='&cellback;'>Unparsed</td>
2833: </tr>
2834: <tr align='center' valign='middle'>
2835:
2836: <td bgcolor='&cellback;' align='right'>Reference
2837: in Content</td>
2838: <td bgcolor='&cellback;'><titleref href='not-recognized'>Not recognized</titleref></td>
2839: <td bgcolor='&cellback;'><titleref href='included'>Included</titleref></td>
2840: <td bgcolor='&cellback;'><titleref href='include-if-valid'>Included if validating</titleref></td>
2841: <td bgcolor='&cellback;'><titleref href='forbidden'>Forbidden</titleref></td>
2842: <td bgcolor='&cellback;'><titleref href='included'>Included</titleref></td>
2843: </tr>
2844: <tr align='center' valign='middle'>
2845: <td bgcolor='&cellback;' align='right'>Reference
2846: in Attribute Value</td>
2847: <td bgcolor='&cellback;'><titleref href='not-recognized'>Not recognized</titleref></td>
2848: <td bgcolor='&cellback;'><titleref href='inliteral'>Included in literal</titleref></td>
2849: <td bgcolor='&cellback;'><titleref href='forbidden'>Forbidden</titleref></td>
2850: <td bgcolor='&cellback;'><titleref href='forbidden'>Forbidden</titleref></td>
2851: <td bgcolor='&cellback;'><titleref href='included'>Included</titleref></td>
2852: </tr>
2853: <tr align='center' valign='middle'>
2854: <td bgcolor='&cellback;' align='right'>Occurs as
2855: Attribute Value</td>
2856: <td bgcolor='&cellback;'><titleref href='not-recognized'>Not recognized</titleref></td>
2857: <td bgcolor='&cellback;'><titleref href='not-recognized'>Forbidden</titleref></td>
2858: <td bgcolor='&cellback;'><titleref href='not-recognized'>Forbidden</titleref></td>
2859: <td bgcolor='&cellback;'><titleref href='notify'>Notify</titleref></td>
2860: <td bgcolor='&cellback;'><titleref href='not recognized'>Not recognized</titleref></td>
2861: </tr>
2862: <tr align='center' valign='middle'>
2863: <td bgcolor='&cellback;' align='right'>Reference
2864: in EntityValue</td>
2865: <td bgcolor='&cellback;'><titleref href='inliteral'>Included in literal</titleref></td>
2866: <td bgcolor='&cellback;'><titleref href='bypass'>Bypassed</titleref></td>
2867: <td bgcolor='&cellback;'><titleref href='bypass'>Bypassed</titleref></td>
2868: <td bgcolor='&cellback;'><titleref href='forbidden'>Forbidden</titleref></td>
2869: <td bgcolor='&cellback;'><titleref href='included'>Included</titleref></td>
2870: </tr>
2871: <tr align='center' valign='middle'>
2872: <td bgcolor='&cellback;' align='right'>Reference
2873: in DTD</td>
2874: <td bgcolor='&cellback;'><titleref href='as-PE'>Included as PE</titleref></td>
2875: <td bgcolor='&cellback;'><titleref href='forbidden'>Forbidden</titleref></td>
2876: <td bgcolor='&cellback;'><titleref href='forbidden'>Forbidden</titleref></td>
2877: <td bgcolor='&cellback;'><titleref href='forbidden'>Forbidden</titleref></td>
2878: <td bgcolor='&cellback;'><titleref href='forbidden'>Forbidden</titleref></td>
2879: </tr>
2880: </htbody>
2881: </htable>
2882: <div3 id='not-recognized'>
2883: <head>Not Recognized</head>
2884: <p>Outside the DTD, the <code>%</code> character has no
2885: special significance; thus, what would be parameter entity references in the
2886: DTD are not recognized as markup in <nt def='NT-content'>content</nt>.
2887: Similarly, the names of unparsed entities are not recognized except
2888: when they appear in the value of an appropriately declared attribute.
2889: </p>
2890: </div3>
2891: <div3 id='included'>
2892: <head>Included</head>
2893: <p><termdef id="dt-include" term="Include">An entity is
2894: <term>included</term> when its
2895: <termref def='dt-repltext'>replacement text</termref> is retrieved
2896: and processed, in place of the reference itself,
2897: as though it were part of the document at the location the
2898: reference was recognized.
2899: The replacement text may contain both
2900: <termref def='dt-chardata'>character data</termref>
2901: and (except for parameter entities) <termref def="dt-markup">markup</termref>,
2902: which must be recognized in
2903: the usual way, except that the replacement text of entities used to escape
2904: markup delimiters (the entities &magicents;) is always treated as
2905: data. (The string "<code>AT&amp;T;</code>" expands to
2906: "<code>AT&T;</code>" and the remaining ampersand is not recognized
2907: as an entity-reference delimiter.)
2908: A character reference is <term>included</term> when the indicated
2909: character is processed in place of the reference itself.
2910: </termdef></p>
2911: </div3>
2912: <div3 id='include-if-valid'>
2913: <head>Included If Validating</head>
2914: <p>When an XML processor recognizes a reference to a parsed entity, in order
2915: to <termref def="dt-valid">validate</termref>
2916: the document, the processor must
2917: <termref def="dt-include">include</termref> its
2918: replacement text.
2919: If the entity is external, and the processor is not
2920: attempting to validate the XML document, the
2921: processor <termref def="dt-may">may</termref>, but need not,
2922: include the entity's replacement text.
2923: If a non-validating parser does not include the replacement text,
2924: it must inform the application that it recognized, but did not
2925: read, the entity.</p>
2926: <p>This rule is based on the recognition that the automatic inclusion
2927: provided by the SGML and XML entity mechanism, primarily designed
2928: to support modularity in authoring, is not necessarily
2929: appropriate for other applications, in particular document browsing.
2930: Browsers, for example, when encountering an external parsed entity reference,
2931: might choose to provide a visual indication of the entity's
2932: presence and retrieve it for display only on demand.
2933: </p>
2934: </div3>
2935: <div3 id='forbidden'>
2936: <head>Forbidden</head>
2937: <p>The following are forbidden, and constitute
2938: <termref def='dt-fatal'>fatal</termref> errors:
2939: <ulist>
2940: <item><p>the appearance of a reference to an
2941: <termref def='dt-unparsed'>unparsed entity</termref>.
2942: </p></item>
2943: <item><p>the appearance of any character or general-entity reference in the
2944: DTD except within an <nt def='NT-EntityValue'>EntityValue</nt> or
2945: <nt def="NT-AttValue">AttValue</nt>.</p></item>
2946: <item><p>a reference to an external entity in an attribute value.</p>
2947: </item>
2948: </ulist>
2949: </p>
2950: </div3>
2951: <div3 id='inliteral'>
2952: <head>Included in Literal</head>
2953: <p>When an <termref def='dt-entref'>entity reference</termref> appears in an
2954: attribute value, or a parameter entity reference appears in a literal entity
2955: value, its <termref def='dt-repltext'>replacement text</termref> is
2956: processed in place of the reference itself as though it
2957: were part of the document at the location the reference was recognized,
2958: except that a single or double quote character in the replacement text
2959: is always treated as a normal data character and will not terminate the
2960: literal.
2961: For example, this is well-formed:
2962: <eg><![CDATA[<!ENTITY % YN '"Yes"' >
2963: <!ENTITY WhatHeSaid "He said &YN;" >]]></eg>
2964: while this is not:
2965: <eg><!ENTITY EndAttr "27'" >
2966: <element attribute='a-&EndAttr;></eg>
2967: </p></div3>
2968: <div3 id='notify'>
2969: <head>Notify</head>
2970: <p>When the name of an <termref def='dt-unparsed'>unparsed
2971: entity</termref> appears as a token in the
2972: value of an attribute of declared type <kw>ENTITY</kw> or <kw>ENTITIES</kw>,
2973: a validating processor must inform the
2974: application of the <termref def='dt-sysid'>system</termref>
2975: and <termref def='dt-pubid'>public</termref> (if any)
2976: identifiers for both the entity and its associated
2977: <termref def="dt-notation">notation</termref>.</p>
2978: </div3>
2979: <div3 id='bypass'>
2980: <head>Bypassed</head>
2981: <p>When a general entity reference appears in the
2982: <nt def='NT-EntityValue'>EntityValue</nt> in an entity declaration,
2983: it is bypassed and left as is.</p>
2984: </div3>
2985: <div3 id='as-PE'>
2986: <head>Included as PE</head>
2987: <p>Just as with external parsed entities, parameter entities
2988: need only be <titleref href='include-if-valid'>included if
2989: validating</titleref>.
2990: When a parameter-entity reference is recognized in the DTD
2991: and included, its
2992: <termref def='dt-repltext'>replacement
2993: text</termref> is enlarged by the attachment of one leading and one following
2994: space (#x20) character; the intent is to constrain the replacement
2995: text of parameter
2996: entities to contain an integral number of grammatical tokens in the DTD.
2997: </p>
2998: </div3>
2999:
3000: </div2>
3001: <div2 id='intern-replacement'>
3002: <head>Construction of Internal Entity Replacement Text</head>
3003: <p>In discussing the treatment
3004: of internal entities, it is
3005: useful to distinguish two forms of the entity's value.
3006: <termdef id="dt-litentval" term='Literal Entity Value'>The <term>literal
3007: entity value</term> is the quoted string actually
3008: present in the entity declaration, corresponding to the
3009: non-terminal <nt def='NT-EntityValue'>EntityValue</nt>.</termdef>
3010: <termdef id='dt-repltext' term='Replacement Text'>The <term>replacement
3011: text</term> is the content of the entity, after
3012: replacement of character references and parameter-entity
3013: references.
3014: </termdef></p>
3015:
3016: <p>The literal entity value
3017: as given in an internal entity declaration
3018: (<nt def='NT-EntityValue'>EntityValue</nt>) may contain character,
3019: parameter-entity, and general-entity references.
3020: Such references must be contained entirely within the
3021: literal entity value.
3022: The actual replacement text that is
3023: <termref def='dt-include'>included</termref> as described above
3024: must contain the <emph>replacement text</emph> of any
3025: parameter entities referred to, and must contain the character
3026: referred to, in place of any character references in the
3027: literal entity value; however,
3028: general-entity references must be left as-is, unexpanded.
3029: For example, given the following declarations:
3030:
3031: <eg><![CDATA[<!ENTITY % pub "Éditions Gallimard" >
3032: <!ENTITY rights "All rights reserved" >
3033: <!ENTITY book "La Peste: Albert Camus,
3034: © 1947 %pub;. &rights;" >]]></eg>
3035: then the replacement text for the entity "<code>book</code>" is:
3036: <eg>La Peste: Albert Camus,
3037: © 1947 Éditions Gallimard. &rights;</eg>
3038: The general-entity reference "<code>&rights;</code>" would be expanded
3039: should the reference "<code>&book;</code>" appear in the document's
3040: content or an attribute value.</p>
3041: <p>These simple rules may have complex interactions; for a detailed
3042: discussion of a difficult example, see
3043: <specref ref='sec-entexpand'/>.
3044: </p>
3045:
3046: </div2>
3047: <div2 id='sec-predefined-ent'>
3048: <head>Predefined Entities</head>
3049: <p><termdef id="dt-escape" term="escape">Entity and character
3050: references can both be used to <term>escape</term> the left angle bracket,
3051: ampersand, and other delimiters. A set of general entities
3052: (&magicents;) is specified for this purpose.
3053: Numeric character references may also be used; they are
3054: expanded immediately when recognized and must be treated as
3055: character data, so the numeric character references
3056: "<code>&#60;</code>" and "<code>&#38;</code>" may be used to
3057: escape <code><</code> and <code>&</code> when they occur
3058: in character data.</termdef></p>
3059: <p>All XML processors must recognize these entities whether they
3060: are declared or not.
3061: <termref def='dt-interop'>For interoperability</termref>,
3062: valid XML documents should declare these
3063: entities, like any others, before using them.
3064: If the entities in question are declared, they must be declared
3065: as internal entities whose replacement text is the single
3066: character being escaped or a character reference to
3067: that character, as shown below.
3068: <eg><![CDATA[<!ENTITY lt "&#60;">
3069: <!ENTITY gt ">">
3070: <!ENTITY amp "&#38;">
3071: <!ENTITY apos "'">
3072: <!ENTITY quot """>
3073: ]]></eg>
3074: Note that the <code><</code> and <code>&</code> characters
3075: in the declarations of "<code>lt</code>" and "<code>amp</code>"
3076: are doubly escaped to meet the requirement that entity replacement
3077: be well-formed.
3078: </p>
3079: </div2>
3080:
3081: <div2 id='Notations'>
3082: <head>Notation Declarations</head>
3083:
3084: <p><termdef id="dt-notation" term="Notation"><term>Notations</term> identify by
3085: name the format of <termref def="dt-extent">unparsed
3086: entities</termref>, the
3087: format of elements which bear a notation attribute,
3088: or the application to which
3089: a <termref def="dt-pi">processing instruction</termref> is
3090: addressed.</termdef></p>
3091: <p><termdef id="dt-notdecl" term="Notation Declaration">
3092: <term>Notation declarations</term>
3093: provide a name for the notation, for use in
3094: entity and attribute-list declarations and in attribute specifications,
3095: and an external identifier for the notation which may allow an XML
3096: processor or its client application to locate a helper application
3097: capable of processing data in the given notation.
3098: <scrap lang='ebnf'>
3099: <head>Notation Declarations</head>
3100: <prod id='NT-NotationDecl'><lhs>NotationDecl</lhs>
3101: <rhs>'<!NOTATION' <nt def='NT-S'>S</nt> <nt def='NT-Name'>Name</nt>
3102: <nt def='NT-S'>S</nt>
3103: (<nt def='NT-ExternalID'>ExternalID</nt> |
3104: <nt def='NT-PublicID'>PublicID</nt>)
3105: <nt def='NT-S'>S</nt>? '>'</rhs></prod>
3106: <prod id='NT-PublicID'><lhs>PublicID</lhs>
3107: <rhs>'PUBLIC' <nt def='NT-S'>S</nt>
3108: <nt def='NT-PubidLiteral'>PubidLiteral</nt>
3109: </rhs></prod>
3110: </scrap>
3111: </termdef></p>
3112: <p>XML processors must provide applications with the name and external
3113: identifier(s) of any notation declared and referred to in an attribute
3114: value, attribute definition, or entity declaration. They may
3115: additionally resolve the external identifier into the
3116: <termref def="dt-sysid">system identifier</termref>,
3117: file name, or other information needed to allow the
3118: application to call a processor for data in the notation described. (It
3119: is not an error, however, for XML documents to declare and refer to
3120: notations for which notation-specific applications are not available on
3121: the system where the XML processor or application is running.)</p>
3122: </div2>
3123:
3124:
3125: <div2 id='sec-doc-entity'>
3126: <head>Document Entity</head>
3127:
3128: <p><termdef id="dt-docent" term="Document Entity">The <term>document
3129: entity</term> serves as the root of the entity
3130: tree and a starting-point for an <termref def="dt-xml-proc">XML
3131: processor</termref>.</termdef>
3132: This specification does
3133: not specify how the document entity is to be located by an XML
3134: processor; unlike other entities, the document entity has no name and might
3135: well appear on a processor input stream
3136: without any identification at all.</p>
3137: </div2>
3138:
3139:
3140: </div1>
3141: <!-- &Conformance; -->
3142:
3143: <div1 id='sec-conformance'>
3144: <head>Conformance</head>
3145:
3146: <div2 id='proc-types'>
3147: <head>Validating and Non-Validating Processors</head>
3148: <p>Conforming <termref def="dt-xml-proc">XML processors</termref> fall into two
3149: classes: validating and non-validating.</p>
3150: <p>Validating and non-validating processors alike must report
3151: violations of this specification's well-formedness constraints
3152: in the content of the
3153: <termref def='dt-docent'>document entity</termref> and any
3154: other <termref def='dt-parsedent'>parsed entities</termref> that
3155: they read.</p>
3156: <p><termdef id="dt-validating" term="Validating Processor">
3157: <term>Validating processors</term> must report
3158: violations of the constraints expressed by the declarations in the
3159: <termref def="dt-doctype">DTD</termref>, and
3160: failures to fulfill the validity constraints given
3161: in this specification.
3162: </termdef>
3163: To accomplish this, validating XML processors must read and process the entire
3164: DTD and all external parsed entities referenced in the document.
3165: </p>
3166: <p>Non-validating processors are required to check only the
3167: <termref def='dt-docent'>document entity</termref>, including
3168: the entire internal DTD subset, for well-formedness.
3169: <termdef id='dt-use-mdecl' term='Process Declarations'>
3170: While they are not required to check the document for validity,
3171: they are required to
3172: <term>process</term> all the declarations they read in the
3173: internal DTD subset and in any parameter entity that they
3174: read, up to the first reference
3175: to a parameter entity that they do <emph>not</emph> read; that is to
3176: say, they must
3177: use the information in those declarations to
3178: <titleref href='AVNormalize'>normalize</titleref> attribute values,
3179: <titleref href='included'>include</titleref> the replacement text of
3180: internal entities, and supply
3181: <titleref href='sec-attr-defaults'>default attribute values</titleref>.
3182: </termdef>
3183: They must not <termref def='dt-use-mdecl'>process</termref>
3184: <termref def='dt-entdecl'>entity declarations</termref> or
3185: <termref def='dt-attdecl'>attribute-list declarations</termref>
3186: encountered after a reference to a parameter entity that is not
3187: read, since the entity may have contained overriding declarations.
3188: </p>
3189: </div2>
3190: <div2 id='safe-behavior'>
3191: <head>Using XML Processors</head>
3192: <p>The behavior of a validating XML processor is highly predictable; it
3193: must read every piece of a document and report all well-formedness and
3194: validity violations.
3195: Less is required of a non-validating processor; it need not read any
3196: part of the document other than the document entity.
3197: This has two effects that may be important to users of XML processors:
3198: <ulist>
3199: <item><p>Certain well-formedness errors, specifically those that require
3200: reading external entities, may not be detected by a non-validating processor.
3201: Examples include the constraints entitled
3202: <titleref href='wf-entdeclared'>Entity Declared</titleref>,
3203: <titleref href='wf-textent'>Parsed Entity</titleref>, and
3204: <titleref href='wf-norecursion'>No Recursion</titleref>, as well
3205: as some of the cases described as
3206: <titleref href='forbidden'>forbidden</titleref> in
3207: <specref ref='entproc'/>.</p></item>
3208: <item><p>The information passed from the processor to the application may
3209: vary, depending on whether the processor reads
3210: parameter and external entities.
3211: For example, a non-validating processor may not
3212: <titleref href='AVNormalize'>normalize</titleref> attribute values,
3213: <titleref href='included'>include</titleref> the replacement text of
3214: internal entities, or supply
3215: <titleref href='sec-attr-defaults'>default attribute values</titleref>,
3216: where doing so depends on having read declarations in
3217: external or parameter entities.</p></item>
3218: </ulist>
3219: </p>
3220: <p>For maximum reliability in interoperating between different XML
3221: processors, applications which use non-validating processors should not
3222: rely on any behaviors not required of such processors.
3223: Applications which require facilities such as the use of default
3224: attributes or internal entities which are declared in external
3225: entities should use validating XML processors.</p>
3226: </div2>
3227: </div1>
3228:
3229: <div1 id='sec-notation'>
3230: <head>Notation</head>
3231:
3232: <p>The formal grammar of XML is given in this specification using a simple
3233: Extended Backus-Naur Form (EBNF) notation. Each rule in the grammar defines
3234: one symbol, in the form
3235: <eg>symbol ::= expression</eg></p>
3236: <p>Symbols are written with an initial capital letter if they are
3237: defined by a regular expression, or with an initial lower case letter
3238: otherwise.
3239: Literal strings are quoted.
3240:
3241: </p>
3242:
3243: <p>Within the expression on the right-hand side of a rule, the following
3244: expressions are used to match strings of one or more characters:
3245: <glist>
3246: <gitem>
3247: <label><code>#xN</code></label>
3248: <def><p>where <code>N</code> is a hexadecimal integer, the
3249: expression matches the character in ISO/IEC 10646 whose canonical
3250: (UCS-4)
3251: code value, when interpreted as an unsigned binary number, has
3252: the value indicated. The number of leading zeros in the
3253: <code>#xN</code> form is insignificant; the number of leading
3254: zeros in the corresponding code value
3255: is governed by the character
3256: encoding in use and is not significant for XML.</p></def>
3257: </gitem>
3258: <gitem>
3259: <label><code>[a-zA-Z]</code>, <code>[#xN-#xN]</code></label>
3260: <def><p>matches any <termref def='dt-character'>character</termref>
3261: with a value in the range(s) indicated (inclusive).</p></def>
3262: </gitem>
3263: <gitem>
3264: <label><code>[^a-z]</code>, <code>[^#xN-#xN]</code></label>
3265: <def><p>matches any <termref def='dt-character'>character</termref>
3266: with a value <emph>outside</emph> the
3267: range indicated.</p></def>
3268: </gitem>
3269: <gitem>
3270: <label><code>[^abc]</code>, <code>[^#xN#xN#xN]</code></label>
3271: <def><p>matches any <termref def='dt-character'>character</termref>
3272: with a value not among the characters given.</p></def>
3273: </gitem>
3274: <gitem>
3275: <label><code>"string"</code></label>
3276: <def><p>matches a literal string <termref def="dt-match">matching</termref>
3277: that given inside the double quotes.</p></def>
3278: </gitem>
3279: <gitem>
3280: <label><code>'string'</code></label>
3281: <def><p>matches a literal string <termref def="dt-match">matching</termref>
3282: that given inside the single quotes.</p></def>
3283: </gitem>
3284: </glist>
3285: These symbols may be combined to match more complex patterns as follows,
3286: where <code>A</code> and <code>B</code> represent simple expressions:
3287: <glist>
3288: <gitem>
3289: <label>(<code>expression</code>)</label>
3290: <def><p><code>expression</code> is treated as a unit
3291: and may be combined as described in this list.</p></def>
3292: </gitem>
3293: <gitem>
3294: <label><code>A?</code></label>
3295: <def><p>matches <code>A</code> or nothing; optional <code>A</code>.</p></def>
3296: </gitem>
3297: <gitem>
3298: <label><code>A B</code></label>
3299: <def><p>matches <code>A</code> followed by <code>B</code>.</p></def>
3300: </gitem>
3301: <gitem>
3302: <label><code>A | B</code></label>
3303: <def><p>matches <code>A</code> or <code>B</code> but not both.</p></def>
3304: </gitem>
3305: <gitem>
3306: <label><code>A - B</code></label>
3307: <def><p>matches any string that matches <code>A</code> but does not match
3308: <code>B</code>.
3309: </p></def>
3310: </gitem>
3311: <gitem>
3312: <label><code>A+</code></label>
3313: <def><p>matches one or more occurrences of <code>A</code>.</p></def>
3314: </gitem>
3315: <gitem>
3316: <label><code>A*</code></label>
3317: <def><p>matches zero or more occurrences of <code>A</code>.</p></def>
3318: </gitem>
3319:
3320: </glist>
3321: Other notations used in the productions are:
3322: <glist>
3323: <gitem>
3324: <label><code>/* ... */</code></label>
3325: <def><p>comment.</p></def>
3326: </gitem>
3327: <gitem>
3328: <label><code>[ wfc: ... ]</code></label>
3329: <def><p>well-formedness constraint; this identifies by name a
3330: constraint on
3331: <termref def="dt-wellformed">well-formed</termref> documents
3332: associated with a production.</p></def>
3333: </gitem>
3334: <gitem>
3335: <label><code>[ vc: ... ]</code></label>
3336: <def><p>validity constraint; this identifies by name a constraint on
3337: <termref def="dt-valid">valid</termref> documents associated with
3338: a production.</p></def>
3339: </gitem>
3340: </glist>
3341: </p></div1>
3342:
3343: </body>
3344: <back>
3345: <!-- &SGML; -->
3346:
3347:
3348: <!-- &Biblio; -->
3349: <div1 id='sec-bibliography'>
3350:
3351: <head>References</head>
3352: <div2 id='sec-existing-stds'>
3353: <head>Normative References</head>
3354:
3355: <blist>
3356: <bibl id='IANA' key='IANA'>
3357: (Internet Assigned Numbers Authority) <emph>Official Names for
3358: Character Sets</emph>,
3359: ed. Keld Simonsen et al.
3360: See <loc href='ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets'>ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets</loc>.
3361: </bibl>
3362:
3363: <bibl id='RFC1766' key='IETF RFC 1766'>
3364: IETF (Internet Engineering Task Force).
3365: <emph>RFC 1766: Tags for the Identification of Languages</emph>,
3366: ed. H. Alvestrand.
3367: 1995.
3368: </bibl>
3369:
3370: <bibl id='ISO639' key='ISO 639'>
3371: (International Organization for Standardization).
3372: <emph>ISO 639:1988 (E).
3373: Code for the representation of names of languages.</emph>
3374: [Geneva]: International Organization for
3375: Standardization, 1988.</bibl>
3376:
3377: <bibl id='ISO3166' key='ISO 3166'>
3378: (International Organization for Standardization).
3379: <emph>ISO 3166-1:1997 (E).
3380: Codes for the representation of names of countries and their subdivisions
3381: — Part 1: Country codes</emph>
3382: [Geneva]: International Organization for
3383: Standardization, 1997.</bibl>
3384:
3385: <bibl id='ISO10646' key='ISO/IEC 10646'>ISO
3386: (International Organization for Standardization).
3387: <emph>ISO/IEC 10646-1993 (E). Information technology — Universal
3388: Multiple-Octet Coded Character Set (UCS) — Part 1:
3389: Architecture and Basic Multilingual Plane.</emph>
3390: [Geneva]: International Organization for
3391: Standardization, 1993 (plus amendments AM 1 through AM 7).
3392: </bibl>
3393:
3394: <bibl id='Unicode' key='Unicode'>The Unicode Consortium.
3395: <emph>The Unicode Standard, Version 2.0.</emph>
3396: Reading, Mass.: Addison-Wesley Developers Press, 1996.</bibl>
3397:
3398: </blist>
3399:
3400: </div2>
3401:
3402: <div2><head>Other References</head>
3403:
3404: <blist>
3405:
3406: <bibl id='Aho' key='Aho/Ullman'>Aho, Alfred V.,
3407: Ravi Sethi, and Jeffrey D. Ullman.
3408: <emph>Compilers: Principles, Techniques, and Tools</emph>.
3409: Reading: Addison-Wesley, 1986, rpt. corr. 1988.</bibl>
3410:
3411: <bibl id="Berners-Lee" xml-link="simple" key="Berners-Lee et al.">
3412: Berners-Lee, T., R. Fielding, and L. Masinter.
3413: <emph>Uniform Resource Identifiers (URI): Generic Syntax and
3414: Semantics</emph>.
3415: 1997.
3416: (Work in progress; see updates to RFC1738.)</bibl>
3417:
3418: <bibl id='ABK' key='Brüggemann-Klein'>Brüggemann-Klein, Anne.
3419: <emph>Regular Expressions into Finite Automata</emph>.
3420: Extended abstract in I. Simon, Hrsg., LATIN 1992,
3421: S. 97-98. Springer-Verlag, Berlin 1992.
3422: Full Version in Theoretical Computer Science 120: 197-213, 1993.
3423:
3424: </bibl>
3425:
3426: <bibl id='ABKDW' key='Brüggemann-Klein and Wood'>Brüggemann-Klein, Anne,
3427: and Derick Wood.
3428: <emph>Deterministic Regular Languages</emph>.
3429: Universität Freiburg, Institut für Informatik,
3430: Bericht 38, Oktober 1991.
3431: </bibl>
3432:
3433: <bibl id='Clark' key='Clark'>James Clark.
3434: Comparison of SGML and XML. See
3435: <loc href='http://www.w3.org/TR/NOTE-sgml-xml-971215'>http://www.w3.org/TR/NOTE-sgml-xml-971215</loc>.
3436: </bibl>
3437: <bibl id="RFC1738" xml-link="simple" key="IETF RFC1738">
3438: IETF (Internet Engineering Task Force).
3439: <emph>RFC 1738: Uniform Resource Locators (URL)</emph>,
3440: ed. T. Berners-Lee, L. Masinter, M. McCahill.
3441: 1994.
3442: </bibl>
3443:
3444: <bibl id="RFC1808" xml-link="simple" key="IETF RFC1808">
3445: IETF (Internet Engineering Task Force).
3446: <emph>RFC 1808: Relative Uniform Resource Locators</emph>,
3447: ed. R. Fielding.
3448: 1995.
3449: </bibl>
3450:
3451: <bibl id="RFC2141" xml-link="simple" key="IETF RFC2141">
3452: IETF (Internet Engineering Task Force).
3453: <emph>RFC 2141: URN Syntax</emph>,
3454: ed. R. Moats.
3455: 1997.
3456: </bibl>
3457:
3458: <bibl id='ISO8879' key='ISO 8879'>ISO
3459: (International Organization for Standardization).
3460: <emph>ISO 8879:1986(E). Information processing — Text and Office
3461: Systems — Standard Generalized Markup Language (SGML).</emph> First
3462: edition — 1986-10-15. [Geneva]: International Organization for
3463: Standardization, 1986.
3464: </bibl>
3465:
3466:
3467: <bibl id='ISO10744' key='ISO/IEC 10744'>ISO
3468: (International Organization for Standardization).
3469: <emph>ISO/IEC 10744-1992 (E). Information technology —
3470: Hypermedia/Time-based Structuring Language (HyTime).
3471: </emph>
3472: [Geneva]: International Organization for
3473: Standardization, 1992.
3474: <emph>Extended Facilities Annexe.</emph>
3475: [Geneva]: International Organization for
3476: Standardization, 1996.
3477: </bibl>
3478:
3479:
3480:
3481: </blist>
3482: </div2>
3483: </div1>
3484: <div1 id='CharClasses'>
3485: <head>Character Classes</head>
3486: <p>Following the characteristics defined in the Unicode standard,
3487: characters are classed as base characters (among others, these
3488: contain the alphabetic characters of the Latin alphabet, without
3489: diacritics), ideographic characters, and combining characters (among
3490: others, this class contains most diacritics); these classes combine
3491: to form the class of letters. Digits and extenders are
3492: also distinguished.
3493: <scrap lang="ebnf" id="CHARACTERS">
3494: <head>Characters</head>
3495: <prodgroup pcw3="3" pcw4="15">
3496: <prod id="NT-Letter"><lhs>Letter</lhs>
3497: <rhs><nt def="NT-BaseChar">BaseChar</nt>
3498: | <nt def="NT-Ideographic">Ideographic</nt></rhs> </prod>
3499: <prod id='NT-BaseChar'><lhs>BaseChar</lhs>
3500: <rhs>[#x0041-#x005A]
3501: | [#x0061-#x007A]
3502: | [#x00C0-#x00D6]
3503: | [#x00D8-#x00F6]
3504: | [#x00F8-#x00FF]
3505: | [#x0100-#x0131]
3506: | [#x0134-#x013E]
3507: | [#x0141-#x0148]
3508: | [#x014A-#x017E]
3509: | [#x0180-#x01C3]
3510: | [#x01CD-#x01F0]
3511: | [#x01F4-#x01F5]
3512: | [#x01FA-#x0217]
3513: | [#x0250-#x02A8]
3514: | [#x02BB-#x02C1]
3515: | #x0386
3516: | [#x0388-#x038A]
3517: | #x038C
3518: | [#x038E-#x03A1]
3519: | [#x03A3-#x03CE]
3520: | [#x03D0-#x03D6]
3521: | #x03DA
3522: | #x03DC
3523: | #x03DE
3524: | #x03E0
3525: | [#x03E2-#x03F3]
3526: | [#x0401-#x040C]
3527: | [#x040E-#x044F]
3528: | [#x0451-#x045C]
3529: | [#x045E-#x0481]
3530: | [#x0490-#x04C4]
3531: | [#x04C7-#x04C8]
3532: | [#x04CB-#x04CC]
3533: | [#x04D0-#x04EB]
3534: | [#x04EE-#x04F5]
3535: | [#x04F8-#x04F9]
3536: | [#x0531-#x0556]
3537: | #x0559
3538: | [#x0561-#x0586]
3539: | [#x05D0-#x05EA]
3540: | [#x05F0-#x05F2]
3541: | [#x0621-#x063A]
3542: | [#x0641-#x064A]
3543: | [#x0671-#x06B7]
3544: | [#x06BA-#x06BE]
3545: | [#x06C0-#x06CE]
3546: | [#x06D0-#x06D3]
3547: | #x06D5
3548: | [#x06E5-#x06E6]
3549: | [#x0905-#x0939]
3550: | #x093D
3551: | [#x0958-#x0961]
3552: | [#x0985-#x098C]
3553: | [#x098F-#x0990]
3554: | [#x0993-#x09A8]
3555: | [#x09AA-#x09B0]
3556: | #x09B2
3557: | [#x09B6-#x09B9]
3558: | [#x09DC-#x09DD]
3559: | [#x09DF-#x09E1]
3560: | [#x09F0-#x09F1]
3561: | [#x0A05-#x0A0A]
3562: | [#x0A0F-#x0A10]
3563: | [#x0A13-#x0A28]
3564: | [#x0A2A-#x0A30]
3565: | [#x0A32-#x0A33]
3566: | [#x0A35-#x0A36]
3567: | [#x0A38-#x0A39]
3568: | [#x0A59-#x0A5C]
3569: | #x0A5E
3570: | [#x0A72-#x0A74]
3571: | [#x0A85-#x0A8B]
3572: | #x0A8D
3573: | [#x0A8F-#x0A91]
3574: | [#x0A93-#x0AA8]
3575: | [#x0AAA-#x0AB0]
3576: | [#x0AB2-#x0AB3]
3577: | [#x0AB5-#x0AB9]
3578: | #x0ABD
3579: | #x0AE0
3580: | [#x0B05-#x0B0C]
3581: | [#x0B0F-#x0B10]
3582: | [#x0B13-#x0B28]
3583: | [#x0B2A-#x0B30]
3584: | [#x0B32-#x0B33]
3585: | [#x0B36-#x0B39]
3586: | #x0B3D
3587: | [#x0B5C-#x0B5D]
3588: | [#x0B5F-#x0B61]
3589: | [#x0B85-#x0B8A]
3590: | [#x0B8E-#x0B90]
3591: | [#x0B92-#x0B95]
3592: | [#x0B99-#x0B9A]
3593: | #x0B9C
3594: | [#x0B9E-#x0B9F]
3595: | [#x0BA3-#x0BA4]
3596: | [#x0BA8-#x0BAA]
3597: | [#x0BAE-#x0BB5]
3598: | [#x0BB7-#x0BB9]
3599: | [#x0C05-#x0C0C]
3600: | [#x0C0E-#x0C10]
3601: | [#x0C12-#x0C28]
3602: | [#x0C2A-#x0C33]
3603: | [#x0C35-#x0C39]
3604: | [#x0C60-#x0C61]
3605: | [#x0C85-#x0C8C]
3606: | [#x0C8E-#x0C90]
3607: | [#x0C92-#x0CA8]
3608: | [#x0CAA-#x0CB3]
3609: | [#x0CB5-#x0CB9]
3610: | #x0CDE
3611: | [#x0CE0-#x0CE1]
3612: | [#x0D05-#x0D0C]
3613: | [#x0D0E-#x0D10]
3614: | [#x0D12-#x0D28]
3615: | [#x0D2A-#x0D39]
3616: | [#x0D60-#x0D61]
3617: | [#x0E01-#x0E2E]
3618: | #x0E30
3619: | [#x0E32-#x0E33]
3620: | [#x0E40-#x0E45]
3621: | [#x0E81-#x0E82]
3622: | #x0E84
3623: | [#x0E87-#x0E88]
3624: | #x0E8A
3625: | #x0E8D
3626: | [#x0E94-#x0E97]
3627: | [#x0E99-#x0E9F]
3628: | [#x0EA1-#x0EA3]
3629: | #x0EA5
3630: | #x0EA7
3631: | [#x0EAA-#x0EAB]
3632: | [#x0EAD-#x0EAE]
3633: | #x0EB0
3634: | [#x0EB2-#x0EB3]
3635: | #x0EBD
3636: | [#x0EC0-#x0EC4]
3637: | [#x0F40-#x0F47]
3638: | [#x0F49-#x0F69]
3639: | [#x10A0-#x10C5]
3640: | [#x10D0-#x10F6]
3641: | #x1100
3642: | [#x1102-#x1103]
3643: | [#x1105-#x1107]
3644: | #x1109
3645: | [#x110B-#x110C]
3646: | [#x110E-#x1112]
3647: | #x113C
3648: | #x113E
3649: | #x1140
3650: | #x114C
3651: | #x114E
3652: | #x1150
3653: | [#x1154-#x1155]
3654: | #x1159
3655: | [#x115F-#x1161]
3656: | #x1163
3657: | #x1165
3658: | #x1167
3659: | #x1169
3660: | [#x116D-#x116E]
3661: | [#x1172-#x1173]
3662: | #x1175
3663: | #x119E
3664: | #x11A8
3665: | #x11AB
3666: | [#x11AE-#x11AF]
3667: | [#x11B7-#x11B8]
3668: | #x11BA
3669: | [#x11BC-#x11C2]
3670: | #x11EB
3671: | #x11F0
3672: | #x11F9
3673: | [#x1E00-#x1E9B]
3674: | [#x1EA0-#x1EF9]
3675: | [#x1F00-#x1F15]
3676: | [#x1F18-#x1F1D]
3677: | [#x1F20-#x1F45]
3678: | [#x1F48-#x1F4D]
3679: | [#x1F50-#x1F57]
3680: | #x1F59
3681: | #x1F5B
3682: | #x1F5D
3683: | [#x1F5F-#x1F7D]
3684: | [#x1F80-#x1FB4]
3685: | [#x1FB6-#x1FBC]
3686: | #x1FBE
3687: | [#x1FC2-#x1FC4]
3688: | [#x1FC6-#x1FCC]
3689: | [#x1FD0-#x1FD3]
3690: | [#x1FD6-#x1FDB]
3691: | [#x1FE0-#x1FEC]
3692: | [#x1FF2-#x1FF4]
3693: | [#x1FF6-#x1FFC]
3694: | #x2126
3695: | [#x212A-#x212B]
3696: | #x212E
3697: | [#x2180-#x2182]
3698: | [#x3041-#x3094]
3699: | [#x30A1-#x30FA]
3700: | [#x3105-#x312C]
3701: | [#xAC00-#xD7A3]
3702: </rhs></prod>
3703: <prod id='NT-Ideographic'><lhs>Ideographic</lhs>
3704: <rhs>[#x4E00-#x9FA5]
3705: | #x3007
3706: | [#x3021-#x3029]
3707: </rhs></prod>
3708: <prod id='NT-CombiningChar'><lhs>CombiningChar</lhs>
3709: <rhs>[#x0300-#x0345]
3710: | [#x0360-#x0361]
3711: | [#x0483-#x0486]
3712: | [#x0591-#x05A1]
3713: | [#x05A3-#x05B9]
3714: | [#x05BB-#x05BD]
3715: | #x05BF
3716: | [#x05C1-#x05C2]
3717: | #x05C4
3718: | [#x064B-#x0652]
3719: | #x0670
3720: | [#x06D6-#x06DC]
3721: | [#x06DD-#x06DF]
3722: | [#x06E0-#x06E4]
3723: | [#x06E7-#x06E8]
3724: | [#x06EA-#x06ED]
3725: | [#x0901-#x0903]
3726: | #x093C
3727: | [#x093E-#x094C]
3728: | #x094D
3729: | [#x0951-#x0954]
3730: | [#x0962-#x0963]
3731: | [#x0981-#x0983]
3732: | #x09BC
3733: | #x09BE
3734: | #x09BF
3735: | [#x09C0-#x09C4]
3736: | [#x09C7-#x09C8]
3737: | [#x09CB-#x09CD]
3738: | #x09D7
3739: | [#x09E2-#x09E3]
3740: | #x0A02
3741: | #x0A3C
3742: | #x0A3E
3743: | #x0A3F
3744: | [#x0A40-#x0A42]
3745: | [#x0A47-#x0A48]
3746: | [#x0A4B-#x0A4D]
3747: | [#x0A70-#x0A71]
3748: | [#x0A81-#x0A83]
3749: | #x0ABC
3750: | [#x0ABE-#x0AC5]
3751: | [#x0AC7-#x0AC9]
3752: | [#x0ACB-#x0ACD]
3753: | [#x0B01-#x0B03]
3754: | #x0B3C
3755: | [#x0B3E-#x0B43]
3756: | [#x0B47-#x0B48]
3757: | [#x0B4B-#x0B4D]
3758: | [#x0B56-#x0B57]
3759: | [#x0B82-#x0B83]
3760: | [#x0BBE-#x0BC2]
3761: | [#x0BC6-#x0BC8]
3762: | [#x0BCA-#x0BCD]
3763: | #x0BD7
3764: | [#x0C01-#x0C03]
3765: | [#x0C3E-#x0C44]
3766: | [#x0C46-#x0C48]
3767: | [#x0C4A-#x0C4D]
3768: | [#x0C55-#x0C56]
3769: | [#x0C82-#x0C83]
3770: | [#x0CBE-#x0CC4]
3771: | [#x0CC6-#x0CC8]
3772: | [#x0CCA-#x0CCD]
3773: | [#x0CD5-#x0CD6]
3774: | [#x0D02-#x0D03]
3775: | [#x0D3E-#x0D43]
3776: | [#x0D46-#x0D48]
3777: | [#x0D4A-#x0D4D]
3778: | #x0D57
3779: | #x0E31
3780: | [#x0E34-#x0E3A]
3781: | [#x0E47-#x0E4E]
3782: | #x0EB1
3783: | [#x0EB4-#x0EB9]
3784: | [#x0EBB-#x0EBC]
3785: | [#x0EC8-#x0ECD]
3786: | [#x0F18-#x0F19]
3787: | #x0F35
3788: | #x0F37
3789: | #x0F39
3790: | #x0F3E
3791: | #x0F3F
3792: | [#x0F71-#x0F84]
3793: | [#x0F86-#x0F8B]
3794: | [#x0F90-#x0F95]
3795: | #x0F97
3796: | [#x0F99-#x0FAD]
3797: | [#x0FB1-#x0FB7]
3798: | #x0FB9
3799: | [#x20D0-#x20DC]
3800: | #x20E1
3801: | [#x302A-#x302F]
3802: | #x3099
3803: | #x309A
3804: </rhs></prod>
3805: <prod id='NT-Digit'><lhs>Digit</lhs>
3806: <rhs>[#x0030-#x0039]
3807: | [#x0660-#x0669]
3808: | [#x06F0-#x06F9]
3809: | [#x0966-#x096F]
3810: | [#x09E6-#x09EF]
3811: | [#x0A66-#x0A6F]
3812: | [#x0AE6-#x0AEF]
3813: | [#x0B66-#x0B6F]
3814: | [#x0BE7-#x0BEF]
3815: | [#x0C66-#x0C6F]
3816: | [#x0CE6-#x0CEF]
3817: | [#x0D66-#x0D6F]
3818: | [#x0E50-#x0E59]
3819: | [#x0ED0-#x0ED9]
3820: | [#x0F20-#x0F29]
3821: </rhs></prod>
3822: <prod id='NT-Extender'><lhs>Extender</lhs>
3823: <rhs>#x00B7
3824: | #x02D0
3825: | #x02D1
3826: | #x0387
3827: | #x0640
3828: | #x0E46
3829: | #x0EC6
3830: | #x3005
3831: | [#x3031-#x3035]
3832: | [#x309D-#x309E]
3833: | [#x30FC-#x30FE]
3834: </rhs></prod>
3835:
3836: </prodgroup>
3837: </scrap>
3838: </p>
3839: <p>The character classes defined here can be derived from the
3840: Unicode character database as follows:
3841: <ulist>
3842: <item>
3843: <p>Name start characters must have one of the categories Ll, Lu,
3844: Lo, Lt, Nl.</p>
3845: </item>
3846: <item>
3847: <p>Name characters other than Name-start characters
3848: must have one of the categories Mc, Me, Mn, Lm, or Nd.</p>
3849: </item>
3850: <item>
3851: <p>Characters in the compatibility area (i.e. with character code
3852: greater than #xF900 and less than #xFFFE) are not allowed in XML
3853: names.</p>
3854: </item>
3855: <item>
3856: <p>Characters which have a font or compatibility decomposition (i.e. those
3857: with a "compatibility formatting tag" in field 5 of the database --
3858: marked by field 5 beginning with a "<") are not allowed.</p>
3859: </item>
3860: <item>
3861: <p>The following characters are treated as name-start characters
3862: rather than name characters, because the property file classifies
3863: them as Alphabetic: [#x02BB-#x02C1], #x0559, #x06E5, #x06E6.</p>
3864: </item>
3865: <item>
3866: <p>Characters #x20DD-#x20E0 are excluded (in accordance with
3867: Unicode, section 5.14).</p>
3868: </item>
3869: <item>
3870: <p>Character #x00B7 is classified as an extender, because the
3871: property list so identifies it.</p>
3872: </item>
3873: <item>
3874: <p>Character #x0387 is added as a name character, because #x00B7
3875: is its canonical equivalent.</p>
3876: </item>
3877: <item>
3878: <p>Characters ':' and '_' are allowed as name-start characters.</p>
3879: </item>
3880: <item>
3881: <p>Characters '-' and '.' are allowed as name characters.</p>
3882: </item>
3883: </ulist>
3884: </p>
3885: </div1>
3886: <inform-div1 id="sec-xml-and-sgml">
3887: <head>XML and SGML</head>
3888:
3889: <p>XML is designed to be a subset of SGML, in that every
3890: <termref def="dt-valid">valid</termref> XML document should also be a
3891: conformant SGML document.
3892: For a detailed comparison of the additional restrictions that XML places on
3893: documents beyond those of SGML, see <bibref ref='Clark'/>.
3894: </p>
3895: </inform-div1>
3896: <inform-div1 id="sec-entexpand">
3897: <head>Expansion of Entity and Character References</head>
3898: <p>This appendix contains some examples illustrating the
3899: sequence of entity- and character-reference recognition and
3900: expansion, as specified in <specref ref='entproc'/>.</p>
3901: <p>
3902: If the DTD contains the declaration
3903: <eg><![CDATA[<!ENTITY example "<p>An ampersand (&#38;) may be escaped
3904: numerically (&#38;#38;) or with a general entity
3905: (&amp;).</p>" >
3906: ]]></eg>
3907: then the XML processor will recognize the character references
3908: when it parses the entity declaration, and resolve them before
3909: storing the following string as the
3910: value of the entity "<code>example</code>":
3911: <eg><![CDATA[<p>An ampersand (&) may be escaped
3912: numerically (&#38;) or with a general entity
3913: (&amp;).</p>
3914: ]]></eg>
3915: A reference in the document to "<code>&example;</code>"
3916: will cause the text to be reparsed, at which time the
3917: start- and end-tags of the "<code>p</code>" element will be recognized
3918: and the three references will be recognized and expanded,
3919: resulting in a "<code>p</code>" element with the following content
3920: (all data, no delimiters or markup):
3921: <eg><![CDATA[An ampersand (&) may be escaped
3922: numerically (&) or with a general entity
3923: (&).
3924: ]]></eg>
3925: </p>
3926: <p>A more complex example will illustrate the rules and their
3927: effects fully. In the following example, the line numbers are
3928: solely for reference.
3929: <eg><![CDATA[1 <?xml version='1.0'?>
3930: 2 <!DOCTYPE test [
3931: 3 <!ELEMENT test (#PCDATA) >
3932: 4 <!ENTITY % xx '%zz;'>
3933: 5 <!ENTITY % zz '<!ENTITY tricky "error-prone" >' >
3934: 6 %xx;
3935: 7 ]>
3936: 8 <test>This sample shows a &tricky; method.</test>
3937: ]]></eg>
3938: This produces the following:
3939: <ulist spacing="compact">
3940: <item><p>in line 4, the reference to character 37 is expanded immediately,
3941: and the parameter entity "<code>xx</code>" is stored in the symbol
3942: table with the value "<code>%zz;</code>". Since the replacement text
3943: is not rescanned, the reference to parameter entity "<code>zz</code>"
3944: is not recognized. (And it would be an error if it were, since
3945: "<code>zz</code>" is not yet declared.)</p></item>
3946: <item><p>in line 5, the character reference "<code>&#60;</code>" is
3947: expanded immediately and the parameter entity "<code>zz</code>" is
3948: stored with the replacement text
3949: "<code><!ENTITY tricky "error-prone" ></code>",
3950: which is a well-formed entity declaration.</p></item>
3951: <item><p>in line 6, the reference to "<code>xx</code>" is recognized,
3952: and the replacement text of "<code>xx</code>" (namely
3953: "<code>%zz;</code>") is parsed. The reference to "<code>zz</code>"
3954: is recognized in its turn, and its replacement text
3955: ("<code><!ENTITY tricky "error-prone" ></code>") is parsed.
3956: The general entity "<code>tricky</code>" has now been
3957: declared, with the replacement text "<code>error-prone</code>".</p></item>
3958: <item><p>
3959: in line 8, the reference to the general entity "<code>tricky</code>" is
3960: recognized, and it is expanded, so the full content of the
3961: "<code>test</code>" element is the self-describing (and ungrammatical) string
3962: <emph>This sample shows a error-prone method.</emph>
3963: </p></item>
3964: </ulist>
3965: </p>
3966: </inform-div1>
3967: <inform-div1 id="determinism">
3968: <head>Deterministic Content Models</head>
3969: <p><termref def='dt-compat'>For compatibility</termref>, it is
3970: required
3971: that content models in element type declarations be deterministic.
3972: </p>
3973: <!-- FINAL EDIT: WebSGML allows ambiguity? -->
3974: <p>SGML
3975: requires deterministic content models (it calls them
3976: "unambiguous"); XML processors built using SGML systems may
3977: flag non-deterministic content models as errors.</p>
3978: <p>For example, the content model <code>((b, c) | (b, d))</code> is
3979: non-deterministic, because given an initial <code>b</code> the parser
3980: cannot know which <code>b</code> in the model is being matched without
3981: looking ahead to see which element follows the <code>b</code>.
3982: In this case, the two references to
3983: <code>b</code> can be collapsed
3984: into a single reference, making the model read
3985: <code>(b, (c | d))</code>. An initial <code>b</code> now clearly
3986: matches only a single name in the content model. The parser doesn't
3987: need to look ahead to see what follows; either <code>c</code> or
3988: <code>d</code> would be accepted.</p>
3989: <p>More formally: a finite state automaton may be constructed from the
3990: content model using the standard algorithms, e.g. algorithm 3.5
3991: in section 3.9
3992: of Aho, Sethi, and Ullman <bibref ref='Aho'/>.
3993: In many such algorithms, a follow set is constructed for each
3994: position in the regular expression (i.e., each leaf
3995: node in the
3996: syntax tree for the regular expression);
3997: if any position has a follow set in which
3998: more than one following position is
3999: labeled with the same element type name,
4000: then the content model is in error
4001: and may be reported as an error.
4002: </p>
4003: <p>Algorithms exist which allow many but not all non-deterministic
4004: content models to be reduced automatically to equivalent deterministic
4005: models; see Brüggemann-Klein 1991 <bibref ref='ABK'/>.</p>
4006: </inform-div1>
4007: <inform-div1 id="sec-guessing">
4008: <head>Autodetection of Character Encodings</head>
4009: <p>The XML encoding declaration functions as an internal label on each
4010: entity, indicating which character encoding is in use. Before an XML
4011: processor can read the internal label, however, it apparently has to
4012: know what character encoding is in use—which is what the internal label
4013: is trying to indicate. In the general case, this is a hopeless
4014: situation. It is not entirely hopeless in XML, however, because XML
4015: limits the general case in two ways: each implementation is assumed
4016: to support only a finite set of character encodings, and the XML
4017: encoding declaration is restricted in position and content in order to
4018: make it feasible to autodetect the character encoding in use in each
4019: entity in normal cases. Also, in many cases other sources of information
4020: are available in addition to the XML data stream itself.
4021: Two cases may be distinguished,
4022: depending on whether the XML entity is presented to the
4023: processor without, or with, any accompanying
4024: (external) information. We consider the first case first.
4025: </p>
4026: <p>
4027: Because each XML entity not in UTF-8 or UTF-16 format <emph>must</emph>
4028: begin with an XML encoding declaration, in which the first characters
4029: must be '<code><?xml</code>', any conforming processor can detect,
4030: after two to four octets of input, which of the following cases apply.
4031: In reading this list, it may help to know that in UCS-4, '<' is
4032: "<code>#x0000003C</code>" and '?' is "<code>#x0000003F</code>", and the Byte
4033: Order Mark required of UTF-16 data streams is "<code>#xFEFF</code>".</p>
4034: <p>
4035: <ulist>
4036: <item>
4037: <p><code>00 00 00 3C</code>: UCS-4, big-endian machine (1234 order)</p>
4038: </item>
4039: <item>
4040: <p><code>3C 00 00 00</code>: UCS-4, little-endian machine (4321 order)</p>
4041: </item>
4042: <item>
4043: <p><code>00 00 3C 00</code>: UCS-4, unusual octet order (2143)</p>
4044: </item>
4045: <item>
4046: <p><code>00 3C 00 00</code>: UCS-4, unusual octet order (3412)</p>
4047: </item>
4048: <item>
4049: <p><code>FE FF</code>: UTF-16, big-endian</p>
4050: </item>
4051: <item>
4052: <p><code>FF FE</code>: UTF-16, little-endian</p>
4053: </item>
4054: <item>
4055: <p><code>00 3C 00 3F</code>: UTF-16, big-endian, no Byte Order Mark
4056: (and thus, strictly speaking, in error)</p>
4057: </item>
4058: <item>
4059: <p><code>3C 00 3F 00</code>: UTF-16, little-endian, no Byte Order Mark
4060: (and thus, strictly speaking, in error)</p>
4061: </item>
4062: <item>
4063: <p><code>3C 3F 78 6D</code>: UTF-8, ISO 646, ASCII, some part of ISO 8859,
4064: Shift-JIS, EUC, or any other 7-bit, 8-bit, or mixed-width encoding
4065: which ensures that the characters of ASCII have their normal positions,
4066: width,
4067: and values; the actual encoding declaration must be read to
4068: detect which of these applies, but since all of these encodings
4069: use the same bit patterns for the ASCII characters, the encoding
4070: declaration itself may be read reliably
4071: </p>
4072: </item>
4073: <item>
4074: <p><code>4C 6F A7 94</code>: EBCDIC (in some flavor; the full
4075: encoding declaration must be read to tell which code page is in
4076: use)</p>
4077: </item>
4078: <item>
4079: <p>other: UTF-8 without an encoding declaration, or else
4080: the data stream is corrupt, fragmentary, or enclosed in
4081: a wrapper of some kind</p>
4082: </item>
4083: </ulist>
4084: </p>
4085: <p>
4086: This level of autodetection is enough to read the XML encoding
4087: declaration and parse the character-encoding identifier, which is
4088: still necessary to distinguish the individual members of each family
4089: of encodings (e.g. to tell UTF-8 from 8859, and the parts of 8859
4090: from each other, or to distinguish the specific EBCDIC code page in
4091: use, and so on).
4092: </p>
4093: <p>
4094: Because the contents of the encoding declaration are restricted to
4095: ASCII characters, a processor can reliably read the entire encoding
4096: declaration as soon as it has detected which family of encodings is in
4097: use. Since in practice, all widely used character encodings fall into
4098: one of the categories above, the XML encoding declaration allows
4099: reasonably reliable in-band labeling of character encodings, even when
4100: external sources of information at the operating-system or
4101: transport-protocol level are unreliable.
4102: </p>
4103: <p>
4104: Once the processor has detected the character encoding in use, it can
4105: act appropriately, whether by invoking a separate input routine for
4106: each case, or by calling the proper conversion function on each
4107: character of input.
4108: </p>
4109: <p>
4110: Like any self-labeling system, the XML encoding declaration will not
4111: work if any software changes the entity's character set or encoding
4112: without updating the encoding declaration. Implementors of
4113: character-encoding routines should be careful to ensure the accuracy
4114: of the internal and external information used to label the entity.
4115: </p>
4116: <p>The second possible case occurs when the XML entity is accompanied
4117: by encoding information, as in some file systems and some network
4118: protocols.
4119: When multiple sources of information are available,
4120:
4121: their relative
4122: priority and the preferred method of handling conflict should be
4123: specified as part of the higher-level protocol used to deliver XML.
4124: Rules for the relative priority of the internal label and the
4125: MIME-type label in an external header, for example, should be part of the
4126: RFC document defining the text/xml and application/xml MIME types. In
4127: the interests of interoperability, however, the following rules
4128: are recommended.
4129: <ulist>
4130: <item><p>If an XML entity is in a file, the Byte-Order Mark
4131: and encoding-declaration PI are used (if present) to determine the
4132: character encoding. All other heuristics and sources of information
4133: are solely for error recovery.
4134: </p></item>
4135: <item><p>If an XML entity is delivered with a
4136: MIME type of text/xml, then the <code>charset</code> parameter
4137: on the MIME type determines the
4138: character encoding method; all other heuristics and sources of
4139: information are solely for error recovery.
4140: </p></item>
4141: <item><p>If an XML entity is delivered
4142: with a
4143: MIME type of application/xml, then the Byte-Order Mark and
4144: encoding-declaration PI are used (if present) to determine the
4145: character encoding. All other heuristics and sources of
4146: information are solely for error recovery.
4147: </p></item>
4148: </ulist>
4149: These rules apply only in the absence of protocol-level documentation;
4150: in particular, when the MIME types text/xml and application/xml are
4151: defined, the recommendations of the relevant RFC will supersede
4152: these rules.
4153: </p>
4154:
4155: </inform-div1>
4156:
4157: <inform-div1 id="sec-xml-wg">
4158: <head>W3C XML Working Group</head>
4159:
4160: <p>This specification was prepared and approved for publication by the
4161: W3C XML Working Group (WG). WG approval of this specification does
4162: not necessarily imply that all WG members voted for its approval.
4163: The current and former members of the XML WG are:</p>
4164:
4165: <orglist>
4166: <member><name>Jon Bosak, Sun</name><role>Chair</role></member>
4167: <member><name>James Clark</name><role>Technical Lead</role></member>
4168: <member><name>Tim Bray, Textuality and Netscape</name><role>XML Co-editor</role></member>
4169: <member><name>Jean Paoli, Microsoft</name><role>XML Co-editor</role></member>
4170: <member><name>C. M. Sperberg-McQueen, U. of Ill.</name><role>XML
4171: Co-editor</role></member>
4172: <member><name>Dan Connolly, W3C</name><role>W3C Liaison</role></member>
4173: <member><name>Paula Angerstein, Texcel</name></member>
4174: <member><name>Steve DeRose, INSO</name></member>
4175: <member><name>Dave Hollander, HP</name></member>
4176: <member><name>Eliot Kimber, ISOGEN</name></member>
4177: <member><name>Eve Maler, ArborText</name></member>
4178: <member><name>Tom Magliery, NCSA</name></member>
4179: <member><name>Murray Maloney, Muzmo and Grif</name></member>
4180: <member><name>Makoto Murata, Fuji Xerox Information Systems</name></member>
4181: <member><name>Joel Nava, Adobe</name></member>
4182: <member><name>Conleth O'Connell, Vignette</name></member>
4183: <member><name>Peter Sharpe, SoftQuad</name></member>
4184: <member><name>John Tigue, DataChannel</name></member>
4185: </orglist>
4186:
4187: </inform-div1>
4188: </back>
4189: </spec>
4190: <!-- Keep this comment at the end of the file
4191: Local variables:
4192: mode: sgml
4193: sgml-default-dtd-file:"~/sgml/spec.ced"
4194: sgml-omittag:t
4195: sgml-shorttag:t
4196: End:
4197: -->
FreeBSD-CVSweb <freebsd-cvsweb@FreeBSD.org>
![[BACK]](/icons/cvsweb/back.gif){kind=icon}
Return to REC-xml-19980210.xml CVS log ![[TXT]](/icons/cvsweb/text.gif){kind=icon}
![[DIR]](/icons/cvsweb/dir.gif){kind=icon}
Up to [ELWIX - Embedded LightWeight unIX -] / embedaddon / libxml2 / test / valid