Daniel Veillard | fb5476f | 2004-11-07 12:20:06 +0000 | [diff] [blame] | 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> |
Daniel Veillard | f6b71bd | 2005-01-04 17:50:14 +0000 | [diff] [blame] | 747 | <prod id='NT-Name'><lhs>Name</lhs> |
Daniel Veillard | fb5476f | 2004-11-07 12:20:06 +0000 | [diff] [blame] | 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 | --> |