REC-xml-19980210.xml
1 <?xml version='1.0' encoding='ISO-8859-1' standalone='no'?> 2 <!DOCTYPE spec SYSTEM "dtds/spec.dtd" [ 3 4 <!-- LAST TOUCHED BY: Tim Bray, 8 February 1997 --> 5 6 <!-- The words 'FINAL EDIT' in comments mark places where changes 7 need to be made after approval of the document by the ERB, before 8 publication. --> 9 10 <!ENTITY XML.version "1.0"> 11 <!ENTITY doc.date "10 February 1998"> 12 <!ENTITY iso6.doc.date "19980210"> 13 <!ENTITY w3c.doc.date "02-Feb-1998"> 14 <!ENTITY draft.day '10'> 15 <!ENTITY draft.month 'February'> 16 <!ENTITY draft.year '1998'> 17 18 <!ENTITY WebSGML 19 'WebSGML Adaptations Annex to ISO 8879'> 20 21 <!ENTITY lt "<"> 22 <!ENTITY gt ">"> 23 <!ENTITY xmlpio "'<?xml'"> 24 <!ENTITY pic "'?>'"> 25 <!ENTITY br "\n"> 26 <!ENTITY cellback '#c0d9c0'> 27 <!ENTITY mdash "--"> <!-- —, but nsgmls doesn't grok hex --> 28 <!ENTITY com "--"> 29 <!ENTITY como "--"> 30 <!ENTITY comc "--"> 31 <!ENTITY hcro "&#x"> 32 <!-- <!ENTITY nbsp "�"> --> 33 <!ENTITY nbsp " "> 34 <!ENTITY magicents "<code>amp</code>, 35 <code>lt</code>, 36 <code>gt</code>, 37 <code>apos</code>, 38 <code>quot</code>"> 39 40 <!-- audience and distribution status: for use at publication time --> 41 <!ENTITY doc.audience "public review and discussion"> 42 <!ENTITY doc.distribution "may be distributed freely, as long as 43 all text and legal notices remain intact"> 44 45 ]> 46 47 <!-- for Panorama *--> 48 <?VERBATIM "eg" ?> 49 50 <spec> 51 <header> 52 <title>Extensible Markup Language (XML) 1.0</title> 53 <version></version> 54 <w3c-designation>REC-xml-&iso6.doc.date;</w3c-designation> 55 <w3c-doctype>W3C Recommendation</w3c-doctype> 56 <pubdate><day>&draft.day;</day><month>&draft.month;</month><year>&draft.year;</year></pubdate> 57 58 <publoc> 59 <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;"> 60 http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;</loc> 61 <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.xml"> 62 http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.xml</loc> 63 <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.html"> 64 http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.html</loc> 65 <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.pdf"> 66 http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.pdf</loc> 67 <loc href="http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.ps"> 68 http://www.w3.org/TR/1998/REC-xml-&iso6.doc.date;.ps</loc> 69 </publoc> 70 <latestloc> 71 <loc href="http://www.w3.org/TR/REC-xml"> 72 http://www.w3.org/TR/REC-xml</loc> 73 </latestloc> 74 <prevlocs> 75 <loc href="http://www.w3.org/TR/PR-xml-971208"> 76 http://www.w3.org/TR/PR-xml-971208</loc> 77 <!-- 78 <loc href='http://www.w3.org/TR/WD-xml-961114'> 79 http://www.w3.org/TR/WD-xml-961114</loc> 80 <loc href='http://www.w3.org/TR/WD-xml-lang-970331'> 81 http://www.w3.org/TR/WD-xml-lang-970331</loc> 82 <loc href='http://www.w3.org/TR/WD-xml-lang-970630'> 83 http://www.w3.org/TR/WD-xml-lang-970630</loc> 84 <loc href='http://www.w3.org/TR/WD-xml-970807'> 85 http://www.w3.org/TR/WD-xml-970807</loc> 86 <loc href='http://www.w3.org/TR/WD-xml-971117'> 87 http://www.w3.org/TR/WD-xml-971117</loc>--> 88 </prevlocs> 89 <authlist> 90 <author><name>Tim Bray</name> 91 <affiliation>Textuality and Netscape</affiliation> 92 <email 93 href="mailto:tbray@textuality.com">tbray@textuality.com</email></author> 94 <author><name>Jean Paoli</name> 95 <affiliation>Microsoft</affiliation> 96 <email href="mailto:jeanpa@microsoft.com">jeanpa@microsoft.com</email></author> 97 <author><name>C. M. Sperberg-McQueen</name> 98 <affiliation>University of Illinois at Chicago</affiliation> 99 <email href="mailto:cmsmcq@uic.edu">cmsmcq@uic.edu</email></author> 100 </authlist> 101 <abstract> 102 <p>The Extensible Markup Language (XML) is a subset of 103 SGML that is completely described in this document. Its goal is to 104 enable generic SGML to be served, received, and processed on the Web 105 in the way that is now possible with HTML. XML has been designed for 106 ease of implementation and for interoperability with both SGML and 107 HTML.</p> 108 </abstract> 109 <status> 110 <p>This document has been reviewed by W3C Members and 111 other interested parties and has been endorsed by the 112 Director as a W3C Recommendation. It is a stable 113 document and may be used as reference material or cited 114 as a normative reference from another document. W3C's 115 role in making the Recommendation is to draw attention 116 to the specification and to promote its widespread 117 deployment. This enhances the functionality and 118 interoperability of the Web.</p> 119 <p> 120 This document specifies a syntax created by subsetting an existing, 121 widely used international text processing standard (Standard 122 Generalized Markup Language, ISO 8879:1986(E) as amended and 123 corrected) for use on the World Wide Web. It is a product of the W3C 124 XML Activity, details of which can be found at <loc 125 href='http://www.w3.org/XML'>http://www.w3.org/XML</loc>. A list of 126 current W3C Recommendations and other technical documents can be found 127 at <loc href='http://www.w3.org/TR'>http://www.w3.org/TR</loc>. 128 </p> 129 <p>This specification uses the term URI, which is defined by <bibref 130 ref="Berners-Lee"/>, a work in progress expected to update <bibref 131 ref="RFC1738"/> and <bibref ref="RFC1808"/>. 132 </p> 133 <p>The list of known errors in this specification is 134 available at 135 <loc href='http://www.w3.org/XML/xml-19980210-errata'>http://www.w3.org/XML/xml-19980210-errata</loc>.</p> 136 <p>Please report errors in this document to 137 <loc href='mailto:xml-editor@w3.org'>xml-editor@w3.org</loc>. 138 </p> 139 </status> 140 141 142 <pubstmt> 143 <p>Chicago, Vancouver, Mountain View, et al.: 144 World-Wide Web Consortium, XML Working Group, 1996, 1997.</p> 145 </pubstmt> 146 <sourcedesc> 147 <p>Created in electronic form.</p> 148 </sourcedesc> 149 <langusage> 150 <language id='EN'>English</language> 151 <language id='ebnf'>Extended Backus-Naur Form (formal grammar)</language> 152 </langusage> 153 <revisiondesc> 154 <slist> 155 <sitem>1997-12-03 : CMSMcQ : yet further changes</sitem> 156 <sitem>1997-12-02 : TB : further changes (see TB to XML WG, 157 2 December 1997)</sitem> 158 <sitem>1997-12-02 : CMSMcQ : deal with as many corrections and 159 comments from the proofreaders as possible: 160 entify hard-coded document date in pubdate element, 161 change expansion of entity WebSGML, 162 update status description as per Dan Connolly (am not sure 163 about refernece to Berners-Lee et al.), 164 add 'The' to abstract as per WG decision, 165 move Relationship to Existing Standards to back matter and 166 combine with References, 167 re-order back matter so normative appendices come first, 168 re-tag back matter so informative appendices are tagged informdiv1, 169 remove XXX XXX from list of 'normative' specs in prose, 170 move some references from Other References to Normative References, 171 add RFC 1738, 1808, and 2141 to Other References (they are not 172 normative since we do not require the processor to enforce any 173 rules based on them), 174 add reference to 'Fielding draft' (Berners-Lee et al.), 175 move notation section to end of body, 176 drop URIchar non-terminal and use SkipLit instead, 177 lose stray reference to defunct nonterminal 'markupdecls', 178 move reference to Aho et al. into appendix (Tim's right), 179 add prose note saying that hash marks and fragment identifiers are 180 NOT part of the URI formally speaking, and are NOT legal in 181 system identifiers (processor 'may' signal an error). 182 Work through: 183 Tim Bray reacting to James Clark, 184 Tim Bray on his own, 185 Eve Maler, 186 187 NOT DONE YET: 188 change binary / text to unparsed / parsed. 189 handle James's suggestion about < in attriubte values 190 uppercase hex characters, 191 namechar list, 192 </sitem> 193 <sitem>1997-12-01 : JB : add some column-width parameters</sitem> 194 <sitem>1997-12-01 : CMSMcQ : begin round of changes to incorporate 195 recent WG decisions and other corrections: 196 binding sources of character encoding info (27 Aug / 3 Sept), 197 correct wording of Faust quotation (restore dropped line), 198 drop SDD from EncodingDecl, 199 change text at version number 1.0, 200 drop misleading (wrong!) sentence about ignorables and extenders, 201 modify definition of PCData to make bar on msc grammatical, 202 change grammar's handling of internal subset (drop non-terminal markupdecls), 203 change definition of includeSect to allow conditional sections, 204 add integral-declaration constraint on internal subset, 205 drop misleading / dangerous sentence about relationship of 206 entities with system storage objects, 207 change table body tag to htbody as per EM change to DTD, 208 add rule about space normalization in public identifiers, 209 add description of how to generate our name-space rules from 210 Unicode character database (needs further work!). 211 </sitem> 212 <sitem>1997-10-08 : TB : Removed %-constructs again, new rules 213 for PE appearance.</sitem> 214 <sitem>1997-10-01 : TB : Case-sensitive markup; cleaned up 215 element-type defs, lotsa little edits for style</sitem> 216 <sitem>1997-09-25 : TB : Change to elm's new DTD, with 217 substantial detail cleanup as a side-effect</sitem> 218 <sitem>1997-07-24 : CMSMcQ : correct error (lost *) in definition 219 of ignoreSectContents (thanks to Makoto Murata)</sitem> 220 <sitem>Allow all empty elements to have end-tags, consistent with 221 SGML TC (as per JJC).</sitem> 222 <sitem>1997-07-23 : CMSMcQ : pre-emptive strike on pending corrections: 223 introduce the term 'empty-element tag', note that all empty elements 224 may use it, and elements declared EMPTY must use it. 225 Add WFC requiring encoding decl to come first in an entity. 226 Redefine notations to point to PIs as well as binary entities. 227 Change autodetection table by removing bytes 3 and 4 from 228 examples with Byte Order Mark. 229 Add content model as a term and clarify that it applies to both 230 mixed and element content. 231 </sitem> 232 <sitem>1997-06-30 : CMSMcQ : change date, some cosmetic changes, 233 changes to productions for choice, seq, Mixed, NotationType, 234 Enumeration. Follow James Clark's suggestion and prohibit 235 conditional sections in internal subset. TO DO: simplify 236 production for ignored sections as a result, since we don't 237 need to worry about parsers which don't expand PErefs finding 238 a conditional section.</sitem> 239 <sitem>1997-06-29 : TB : various edits</sitem> 240 <sitem>1997-06-29 : CMSMcQ : further changes: 241 Suppress old FINAL EDIT comments and some dead material. 242 Revise occurrences of % in grammar to exploit Henry Thompson's pun, 243 especially markupdecl and attdef. 244 Remove RMD requirement relating to element content (?). 245 </sitem> 246 <sitem>1997-06-28 : CMSMcQ : Various changes for 1 July draft: 247 Add text for draconian error handling (introduce 248 the term Fatal Error). 249 RE deleta est (changing wording from 250 original announcement to restrict the requirement to validating 251 parsers). 252 Tag definition of validating processor and link to it. 253 Add colon as name character. 254 Change def of %operator. 255 Change standard definitions of lt, gt, amp. 256 Strip leading zeros from #x00nn forms.</sitem> 257 <sitem>1997-04-02 : CMSMcQ : final corrections of editorial errors 258 found in last night's proofreading. Reverse course once more on 259 well-formed: Webster's Second hyphenates it, and that's enough 260 for me.</sitem> 261 <sitem>1997-04-01 : CMSMcQ : corrections from JJC, EM, HT, and self</sitem> 262 <sitem>1997-03-31 : Tim Bray : many changes</sitem> 263 <sitem>1997-03-29 : CMSMcQ : some Henry Thompson (on entity handling), 264 some Charles Goldfarb, some ERB decisions (PE handling in miscellaneous 265 declarations. Changed Ident element to accept def attribute. 266 Allow normalization of Unicode characters. move def of systemliteral 267 into section on literals.</sitem> 268 <sitem>1997-03-28 : CMSMcQ : make as many corrections as possible, from 269 Terry Allen, Norbert Mikula, James Clark, Jon Bosak, Henry Thompson, 270 Paul Grosso, and self. Among other things: give in on "well formed" 271 (Terry is right), tentatively rename QuotedCData as AttValue 272 and Literal as EntityValue to be more informative, since attribute 273 values are the <emph>only</emph> place QuotedCData was used, and 274 vice versa for entity text and Literal. (I'd call it Entity Text, 275 but 8879 uses that name for both internal and external entities.)</sitem> 276 <sitem>1997-03-26 : CMSMcQ : resynch the two forks of this draft, reapply 277 my changes dated 03-20 and 03-21. Normalize old 'may not' to 'must not' 278 except in the one case where it meant 'may or may not'.</sitem> 279 <sitem>1997-03-21 : TB : massive changes on plane flight from Chicago 280 to Vancouver</sitem> 281 <sitem>1997-03-21 : CMSMcQ : correct as many reported errors as possible. 282 </sitem> 283 <sitem>1997-03-20 : CMSMcQ : correct typos listed in CMSMcQ hand copy of spec.</sitem> 284 <sitem>1997-03-20 : CMSMcQ : cosmetic changes preparatory to revision for 285 WWW conference April 1997: restore some of the internal entity 286 references (e.g. to docdate, etc.), change character xA0 to &nbsp; 287 and define nbsp as &#160;, and refill a lot of paragraphs for 288 legibility.</sitem> 289 <sitem>1996-11-12 : CMSMcQ : revise using Tim's edits: 290 Add list type of NUMBERED and change most lists either to 291 BULLETS or to NUMBERED. 292 Suppress QuotedNames, Names (not used). 293 Correct trivial-grammar doc type decl. 294 Rename 'marked section' as 'CDATA section' passim. 295 Also edits from James Clark: 296 Define the set of characters from which [^abc] subtracts. 297 Charref should use just [0-9] not Digit. 298 Location info needs cleaner treatment: remove? (ERB 299 question). 300 One example of a PI has wrong pic. 301 Clarify discussion of encoding names. 302 Encoding failure should lead to unspecified results; don't 303 prescribe error recovery. 304 Don't require exposure of entity boundaries. 305 Ignore white space in element content. 306 Reserve entity names of the form u-NNNN. 307 Clarify relative URLs. 308 And some of my own: 309 Correct productions for content model: model cannot 310 consist of a name, so "elements ::= cp" is no good. 311 </sitem> 312 <sitem>1996-11-11 : CMSMcQ : revise for style. 313 Add new rhs to entity declaration, for parameter entities.</sitem> 314 <sitem>1996-11-10 : CMSMcQ : revise for style. 315 Fix / complete section on names, characters. 316 Add sections on parameter entities, conditional sections. 317 Still to do: Add compatibility note on deterministic content models. 318 Finish stylistic revision.</sitem> 319 <sitem>1996-10-31 : TB : Add Entity Handling section</sitem> 320 <sitem>1996-10-30 : TB : Clean up term & termdef. Slip in 321 ERB decision re EMPTY.</sitem> 322 <sitem>1996-10-28 : TB : Change DTD. Implement some of Michael's 323 suggestions. Change comments back to //. Introduce language for 324 XML namespace reservation. Add section on white-space handling. 325 Lots more cleanup.</sitem> 326 <sitem>1996-10-24 : CMSMcQ : quick tweaks, implement some ERB 327 decisions. Characters are not integers. Comments are /* */ not //. 328 Add bibliographic refs to 10646, HyTime, Unicode. 329 Rename old Cdata as MsData since it's <emph>only</emph> seen 330 in marked sections. Call them attribute-value pairs not 331 name-value pairs, except once. Internal subset is optional, needs 332 '?'. Implied attributes should be signaled to the app, not 333 have values supplied by processor.</sitem> 334 <sitem>1996-10-16 : TB : track down & excise all DSD references; 335 introduce some EBNF for entity declarations.</sitem> 336 <sitem>1996-10-?? : TB : consistency check, fix up scraps so 337 they all parse, get formatter working, correct a few productions.</sitem> 338 <sitem>1996-10-10/11 : CMSMcQ : various maintenance, stylistic, and 339 organizational changes: 340 Replace a few literals with xmlpio and 341 pic entities, to make them consistent and ensure we can change pic 342 reliably when the ERB votes. 343 Drop paragraph on recognizers from notation section. 344 Add match, exact match to terminology. 345 Move old 2.2 XML Processors and Apps into intro. 346 Mention comments, PIs, and marked sections in discussion of 347 delimiter escaping. 348 Streamline discussion of doctype decl syntax. 349 Drop old section of 'PI syntax' for doctype decl, and add 350 section on partial-DTD summary PIs to end of Logical Structures 351 section. 352 Revise DSD syntax section to use Tim's subset-in-a-PI 353 mechanism.</sitem> 354 <sitem>1996-10-10 : TB : eliminate name recognizers (and more?)</sitem> 355 <sitem>1996-10-09 : CMSMcQ : revise for style, consistency through 2.3 356 (Characters)</sitem> 357 <sitem>1996-10-09 : CMSMcQ : re-unite everything for convenience, 358 at least temporarily, and revise quickly</sitem> 359 <sitem>1996-10-08 : TB : first major homogenization pass</sitem> 360 <sitem>1996-10-08 : TB : turn "current" attribute on div type into 361 CDATA</sitem> 362 <sitem>1996-10-02 : TB : remould into skeleton + entities</sitem> 363 <sitem>1996-09-30 : CMSMcQ : add a few more sections prior to exchange 364 with Tim.</sitem> 365 <sitem>1996-09-20 : CMSMcQ : finish transcribing notes.</sitem> 366 <sitem>1996-09-19 : CMSMcQ : begin transcribing notes for draft.</sitem> 367 <sitem>1996-09-13 : CMSMcQ : made outline from notes of 09-06, 368 do some housekeeping</sitem> 369 </slist> 370 </revisiondesc> 371 </header> 372 <body> 373 <div1 id='sec-intro'> 374 <head>Introduction</head> 375 <p>Extensible Markup Language, abbreviated XML, describes a class of 376 data objects called <termref def="dt-xml-doc">XML documents</termref> and 377 partially describes the behavior of 378 computer programs which process them. XML is an application profile or 379 restricted form of SGML, the Standard Generalized Markup 380 Language <bibref ref='ISO8879'/>. 381 By construction, XML documents 382 are conforming SGML documents. 383 </p> 384 <p>XML documents are made up of storage units called <termref 385 def="dt-entity">entities</termref>, which contain either parsed 386 or unparsed data. 387 Parsed data is made up of <termref def="dt-character">characters</termref>, 388 some 389 of which form <termref def="dt-chardata">character data</termref>, 390 and some of which form <termref def="dt-markup">markup</termref>. 391 Markup encodes a description of the document's storage layout and 392 logical structure. XML provides a mechanism to impose constraints on 393 the storage layout and logical structure.</p> 394 <p><termdef id="dt-xml-proc" term="XML Processor">A software module 395 called an <term>XML processor</term> is used to read XML documents 396 and provide access to their content and structure.</termdef> <termdef 397 id="dt-app" term="Application">It is assumed that an XML processor is 398 doing its work on behalf of another module, called the 399 <term>application</term>.</termdef> This specification describes the 400 required behavior of an XML processor in terms of how it must read XML 401 data and the information it must provide to the application.</p> 402 403 <div2 id='sec-origin-goals'> 404 <head>Origin and Goals</head> 405 <p>XML was developed by an XML Working Group (originally known as the 406 SGML Editorial Review Board) formed under the auspices of the World 407 Wide Web Consortium (W3C) in 1996. 408 It was chaired by Jon Bosak of Sun 409 Microsystems with the active participation of an XML Special 410 Interest Group (previously known as the SGML Working Group) also 411 organized by the W3C. The membership of the XML Working Group is given 412 in an appendix. Dan Connolly served as the WG's contact with the W3C. 413 </p> 414 <p>The design goals for XML are:<olist> 415 <item><p>XML shall be straightforwardly usable over the 416 Internet.</p></item> 417 <item><p>XML shall support a wide variety of applications.</p></item> 418 <item><p>XML shall be compatible with SGML.</p></item> 419 <item><p>It shall be easy to write programs which process XML 420 documents.</p></item> 421 <item><p>The number of optional features in XML is to be kept to the 422 absolute minimum, ideally zero.</p></item> 423 <item><p>XML documents should be human-legible and reasonably 424 clear.</p></item> 425 <item><p>The XML design should be prepared quickly.</p></item> 426 <item><p>The design of XML shall be formal and concise.</p></item> 427 <item><p>XML documents shall be easy to create.</p></item> 428 <item><p>Terseness in XML markup is of minimal importance.</p></item></olist> 429 </p> 430 <p>This specification, 431 together with associated standards 432 (Unicode and ISO/IEC 10646 for characters, 433 Internet RFC 1766 for language identification tags, 434 ISO 639 for language name codes, and 435 ISO 3166 for country name codes), 436 provides all the information necessary to understand 437 XML Version &XML.version; 438 and construct computer programs to process it.</p> 439 <p>This version of the XML specification 440 <!-- is for &doc.audience;.--> 441 &doc.distribution;.</p> 442 443 </div2> 444 445 446 447 448 <div2 id='sec-terminology'> 449 <head>Terminology</head> 450 451 <p>The terminology used to describe XML documents is defined in the body of 452 this specification. 453 The terms defined in the following list are used in building those 454 definitions and in describing the actions of an XML processor: 455 <glist> 456 <gitem> 457 <label>may</label> 458 <def><p><termdef id="dt-may" term="May">Conforming documents and XML 459 processors are permitted to but need not behave as 460 described.</termdef></p></def> 461 </gitem> 462 <gitem> 463 <label>must</label> 464 <def><p>Conforming documents and XML processors 465 are required to behave as described; otherwise they are in error. 466 <!-- do NOT change this! this is what defines a violation of 467 a 'must' clause as 'an error'. -MSM --> 468 </p></def> 469 </gitem> 470 <gitem> 471 <label>error</label> 472 <def><p><termdef id='dt-error' term='Error' 473 >A violation of the rules of this 474 specification; results are 475 undefined. Conforming software may detect and report an error and may 476 recover from it.</termdef></p></def> 477 </gitem> 478 <gitem> 479 <label>fatal error</label> 480 <def><p><termdef id="dt-fatal" term="Fatal Error">An error 481 which a conforming <termref def="dt-xml-proc">XML processor</termref> 482 must detect and report to the application. 483 After encountering a fatal error, the 484 processor may continue 485 processing the data to search for further errors and may report such 486 errors to the application. In order to support correction of errors, 487 the processor may make unprocessed data from the document (with 488 intermingled character data and markup) available to the application. 489 Once a fatal error is detected, however, the processor must not 490 continue normal processing (i.e., it must not 491 continue to pass character data and information about the document's 492 logical structure to the application in the normal way). 493 </termdef></p></def> 494 </gitem> 495 <gitem> 496 <label>at user option</label> 497 <def><p>Conforming software may or must (depending on the modal verb in the 498 sentence) behave as described; if it does, it must 499 provide users a means to enable or disable the behavior 500 described.</p></def> 501 </gitem> 502 <gitem> 503 <label>validity constraint</label> 504 <def><p>A rule which applies to all 505 <termref def="dt-valid">valid</termref> XML documents. 506 Violations of validity constraints are errors; they must, at user option, 507 be reported by 508 <termref def="dt-validating">validating XML processors</termref>.</p></def> 509 </gitem> 510 <gitem> 511 <label>well-formedness constraint</label> 512 <def><p>A rule which applies to all <termref 513 def="dt-wellformed">well-formed</termref> XML documents. 514 Violations of well-formedness constraints are 515 <termref def="dt-fatal">fatal errors</termref>.</p></def> 516 </gitem> 517 518 <gitem> 519 <label>match</label> 520 <def><p><termdef id="dt-match" term="match">(Of strings or names:) 521 Two strings or names being compared must be identical. 522 Characters with multiple possible representations in ISO/IEC 10646 (e.g. 523 characters with 524 both precomposed and base+diacritic forms) match only if they have the 525 same representation in both strings. 526 At user option, processors may normalize such characters to 527 some canonical form. 528 No case folding is performed. 529 (Of strings and rules in the grammar:) 530 A string matches a grammatical production if it belongs to the 531 language generated by that production. 532 (Of content and content models:) 533 An element matches its declaration when it conforms 534 in the fashion described in the constraint 535 <specref ref='elementvalid'/>. 536 </termdef> 537 </p></def> 538 </gitem> 539 <gitem> 540 <label>for compatibility</label> 541 <def><p><termdef id="dt-compat" term="For Compatibility">A feature of 542 XML included solely to ensure that XML remains compatible with SGML. 543 </termdef></p></def> 544 </gitem> 545 <gitem> 546 <label>for interoperability</label> 547 <def><p><termdef id="dt-interop" term="For interoperability">A 548 non-binding recommendation included to increase the chances that XML 549 documents can be processed by the existing installed base of SGML 550 processors which predate the 551 &WebSGML;.</termdef></p></def> 552 </gitem> 553 </glist> 554 </p> 555 </div2> 556 557 558 </div1> 559 <!-- &Docs; --> 560 561 <div1 id='sec-documents'> 562 <head>Documents</head> 563 564 <p><termdef id="dt-xml-doc" term="XML Document"> 565 A data object is an 566 <term>XML document</term> if it is 567 <termref def="dt-wellformed">well-formed</termref>, as 568 defined in this specification. 569 A well-formed XML document may in addition be 570 <termref def="dt-valid">valid</termref> if it meets certain further 571 constraints.</termdef></p> 572 573 <p>Each XML document has both a logical and a physical structure. 574 Physically, the document is composed of units called <termref 575 def="dt-entity">entities</termref>. An entity may <termref 576 def="dt-entref">refer</termref> to other entities to cause their 577 inclusion in the document. A document begins in a "root" or <termref 578 def="dt-docent">document entity</termref>. 579 Logically, the document is composed of declarations, elements, 580 comments, 581 character references, and 582 processing 583 instructions, all of which are indicated in the document by explicit 584 markup. 585 The logical and physical structures must nest properly, as described 586 in <specref ref='wf-entities'/>. 587 </p> 588 589 <div2 id='sec-well-formed'> 590 <head>Well-Formed XML Documents</head> 591 592 <p><termdef id="dt-wellformed" term="Well-Formed"> 593 A textual object is 594 a well-formed XML document if:</termdef> 595 <olist> 596 <item><p>Taken as a whole, it 597 matches the production labeled <nt def='NT-document'>document</nt>.</p></item> 598 <item><p>It 599 meets all the well-formedness constraints given in this specification.</p> 600 </item> 601 <item><p>Each of the <termref def='dt-parsedent'>parsed entities</termref> 602 which is referenced directly or indirectly within the document is 603 <titleref href='wf-entities'>well-formed</titleref>.</p></item> 604 </olist></p> 605 <p> 606 <scrap lang='ebnf' id='document'> 607 <head>Document</head> 608 <prod id='NT-document'><lhs>document</lhs> 609 <rhs><nt def='NT-prolog'>prolog</nt> 610 <nt def='NT-element'>element</nt> 611 <nt def='NT-Misc'>Misc</nt>*</rhs></prod> 612 </scrap> 613 </p> 614 <p>Matching the <nt def="NT-document">document</nt> production 615 implies that: 616 <olist> 617 <item><p>It contains one or more 618 <termref def="dt-element">elements</termref>.</p> 619 </item> 620 <!--* N.B. some readers (notably JC) find the following 621 paragraph awkward and redundant. I agree it's logically redundant: 622 it *says* it is summarizing the logical implications of 623 matching the grammar, and that means by definition it's 624 logically redundant. I don't think it's rhetorically 625 redundant or unnecessary, though, so I'm keeping it. It 626 could however use some recasting when the editors are feeling 627 stronger. -MSM *--> 628 <item><p><termdef id="dt-root" term="Root Element">There is exactly 629 one element, called the <term>root</term>, or document element, no 630 part of which appears in the <termref 631 def="dt-content">content</termref> of any other element.</termdef> 632 For all other elements, if the start-tag is in the content of another 633 element, the end-tag is in the content of the same element. More 634 simply stated, the elements, delimited by start- and end-tags, nest 635 properly within each other. 636 </p></item> 637 </olist> 638 </p> 639 <p><termdef id="dt-parentchild" term="Parent/Child">As a consequence 640 of this, 641 for each non-root element 642 <code>C</code> in the document, there is one other element <code>P</code> 643 in the document such that 644 <code>C</code> is in the content of <code>P</code>, but is not in 645 the content of any other element that is in the content of 646 <code>P</code>. 647 <code>P</code> is referred to as the 648 <term>parent</term> of <code>C</code>, and <code>C</code> as a 649 <term>child</term> of <code>P</code>.</termdef></p></div2> 650 651 <div2 id="charsets"> 652 <head>Characters</head> 653 654 <p><termdef id="dt-text" term="Text">A parsed entity contains 655 <term>text</term>, a sequence of 656 <termref def="dt-character">characters</termref>, 657 which may represent markup or character data.</termdef> 658 <termdef id="dt-character" term="Character">A <term>character</term> 659 is an atomic unit of text as specified by 660 ISO/IEC 10646 <bibref ref="ISO10646"/>. 661 Legal characters are tab, carriage return, line feed, and the legal 662 graphic characters of Unicode and ISO/IEC 10646. 663 The use of "compatibility characters", as defined in section 6.8 664 of <bibref ref='Unicode'/>, is discouraged. 665 </termdef> 666 <scrap lang="ebnf" id="char32"> 667 <head>Character Range</head> 668 <prodgroup pcw2="4" pcw4="17.5" pcw5="11"> 669 <prod id="NT-Char"><lhs>Char</lhs> 670 <rhs>#x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD] 671 | [#x10000-#x10FFFF]</rhs> 672 <com>any Unicode character, excluding the 673 surrogate blocks, FFFE, and FFFF.</com> </prod> 674 </prodgroup> 675 </scrap> 676 </p> 677 678 <p>The mechanism for encoding character code points into bit patterns may 679 vary from entity to entity. All XML processors must accept the UTF-8 680 and UTF-16 encodings of 10646; the mechanisms for signaling which of 681 the two is in use, or for bringing other encodings into play, are 682 discussed later, in <specref ref='charencoding'/>. 683 </p> 684 <!-- 685 <p>Regardless of the specific encoding used, any character in the ISO/IEC 686 10646 character set may be referred to by the decimal or hexadecimal 687 equivalent of its 688 UCS-4 code value. 689 </p>--> 690 </div2> 691 692 <div2 id='sec-common-syn'> 693 <head>Common Syntactic Constructs</head> 694 695 <p>This section defines some symbols used widely in the grammar.</p> 696 <p><nt def="NT-S">S</nt> (white space) consists of one or more space (#x20) 697 characters, carriage returns, line feeds, or tabs. 698 699 <scrap lang="ebnf" id='white'> 700 <head>White Space</head> 701 <prodgroup pcw2="4" pcw4="17.5" pcw5="11"> 702 <prod id='NT-S'><lhs>S</lhs> 703 <rhs>(#x20 | #x9 | #xD | #xA)+</rhs> 704 </prod> 705 </prodgroup> 706 </scrap></p> 707 <p>Characters are classified for convenience as letters, digits, or other 708 characters. Letters consist of an alphabetic or syllabic 709 base character possibly 710 followed by one or more combining characters, or of an ideographic 711 character. 712 Full definitions of the specific characters in each class 713 are given in <specref ref='CharClasses'/>.</p> 714 <p><termdef id="dt-name" term="Name">A <term>Name</term> is a token 715 beginning with a letter or one of a few punctuation characters, and continuing 716 with letters, digits, hyphens, underscores, colons, or full stops, together 717 known as name characters.</termdef> 718 Names beginning with the string "<code>xml</code>", or any string 719 which would match <code>(('X'|'x') ('M'|'m') ('L'|'l'))</code>, are 720 reserved for standardization in this or future versions of this 721 specification. 722 </p> 723 <note> 724 <p>The colon character within XML names is reserved for experimentation with 725 name spaces. 726 Its meaning is expected to be 727 standardized at some future point, at which point those documents 728 using the colon for experimental purposes may need to be updated. 729 (There is no guarantee that any name-space mechanism 730 adopted for XML will in fact use the colon as a name-space delimiter.) 731 In practice, this means that authors should not use the colon in XML 732 names except as part of name-space experiments, but that XML processors 733 should accept the colon as a name character.</p> 734 </note> 735 <p>An 736 <nt def='NT-Nmtoken'>Nmtoken</nt> (name token) is any mixture of 737 name characters. 738 <scrap lang='ebnf'> 739 <head>Names and Tokens</head> 740 <prod id='NT-NameChar'><lhs>NameChar</lhs> 741 <rhs><nt def="NT-Letter">Letter</nt> 742 | <nt def='NT-Digit'>Digit</nt> 743 | '.' | '-' | '_' | ':' 744 | <nt def='NT-CombiningChar'>CombiningChar</nt> 745 | <nt def='NT-Extender'>Extender</nt></rhs> 746 </prod> 747 <prod id='NT-Name'><lhs>Name</lhs> 748 <rhs>(<nt def='NT-Letter'>Letter</nt> | '_' | ':') 749 (<nt def='NT-NameChar'>NameChar</nt>)*</rhs></prod> 750 <prod id='NT-Names'><lhs>Names</lhs> 751 <rhs><nt def='NT-Name'>Name</nt> 752 (<nt def='NT-S'>S</nt> <nt def='NT-Name'>Name</nt>)*</rhs></prod> 753 <prod id='NT-Nmtoken'><lhs>Nmtoken</lhs> 754 <rhs>(<nt def='NT-NameChar'>NameChar</nt>)+</rhs></prod> 755 <prod id='NT-Nmtokens'><lhs>Nmtokens</lhs> 756 <rhs><nt def='NT-Nmtoken'>Nmtoken</nt> (<nt def='NT-S'>S</nt> <nt def='NT-Nmtoken'>Nmtoken</nt>)*</rhs></prod> 757 </scrap> 758 </p> 759 <p>Literal data is any quoted string not containing 760 the quotation mark used as a delimiter for that string. 761 Literals are used 762 for specifying the content of internal entities 763 (<nt def='NT-EntityValue'>EntityValue</nt>), 764 the values of attributes (<nt def='NT-AttValue'>AttValue</nt>), 765 and external identifiers 766 (<nt def="NT-SystemLiteral">SystemLiteral</nt>). 767 Note that a <nt def='NT-SystemLiteral'>SystemLiteral</nt> 768 can be parsed without scanning for markup. 769 <scrap lang='ebnf'> 770 <head>Literals</head> 771 <prod id='NT-EntityValue'><lhs>EntityValue</lhs> 772 <rhs>'"' 773 ([^%&"] 774 | <nt def='NT-PEReference'>PEReference</nt> 775 | <nt def='NT-Reference'>Reference</nt>)* 776 '"' 777 </rhs> 778 <rhs>| 779 "'" 780 ([^%&'] 781 | <nt def='NT-PEReference'>PEReference</nt> 782 | <nt def='NT-Reference'>Reference</nt>)* 783 "'"</rhs> 784 </prod> 785 <prod id='NT-AttValue'><lhs>AttValue</lhs> 786 <rhs>'"' 787 ([^<&"] 788 | <nt def='NT-Reference'>Reference</nt>)* 789 '"' 790 </rhs> 791 <rhs>| 792 "'" 793 ([^<&'] 794 | <nt def='NT-Reference'>Reference</nt>)* 795 "'"</rhs> 796 </prod> 797 <prod id="NT-SystemLiteral"><lhs>SystemLiteral</lhs> 798 <rhs>('"' [^"]* '"') | ("'" [^']* "'") 799 </rhs> 800 </prod> 801 <prod id="NT-PubidLiteral"><lhs>PubidLiteral</lhs> 802 <rhs>'"' <nt def='NT-PubidChar'>PubidChar</nt>* 803 '"' 804 | "'" (<nt def='NT-PubidChar'>PubidChar</nt> - "'")* "'"</rhs> 805 </prod> 806 <prod id="NT-PubidChar"><lhs>PubidChar</lhs> 807 <rhs>#x20 | #xD | #xA 808 | [a-zA-Z0-9] 809 | [-'()+,./:=?;!*#@$_%]</rhs> 810 </prod> 811 </scrap> 812 </p> 813 814 </div2> 815 816 <div2 id='syntax'> 817 <head>Character Data and Markup</head> 818 819 <p><termref def='dt-text'>Text</termref> consists of intermingled 820 <termref def="dt-chardata">character 821 data</termref> and markup. 822 <termdef id="dt-markup" term="Markup"><term>Markup</term> takes the form of 823 <termref def="dt-stag">start-tags</termref>, 824 <termref def="dt-etag">end-tags</termref>, 825 <termref def="dt-empty">empty-element tags</termref>, 826 <termref def="dt-entref">entity references</termref>, 827 <termref def="dt-charref">character references</termref>, 828 <termref def="dt-comment">comments</termref>, 829 <termref def="dt-cdsection">CDATA section</termref> delimiters, 830 <termref def="dt-doctype">document type declarations</termref>, and 831 <termref def="dt-pi">processing instructions</termref>. 832 </termdef> 833 </p> 834 <p><termdef id="dt-chardata" term="Character Data">All text that is not markup 835 constitutes the <term>character data</term> of 836 the document.</termdef></p> 837 <p>The ampersand character (&) and the left angle bracket (<) 838 may appear in their literal form <emph>only</emph> when used as markup 839 delimiters, or within a <termref def="dt-comment">comment</termref>, a 840 <termref def="dt-pi">processing instruction</termref>, 841 or a <termref def="dt-cdsection">CDATA section</termref>. 842 843 They are also legal within the <termref def='dt-litentval'>literal entity 844 value</termref> of an internal entity declaration; see 845 <specref ref='wf-entities'/>. 846 <!-- FINAL EDIT: restore internal entity decl or leave it out. --> 847 If they are needed elsewhere, 848 they must be <termref def="dt-escape">escaped</termref> 849 using either <termref def='dt-charref'>numeric character references</termref> 850 or the strings 851 "<code>&amp;</code>" and "<code>&lt;</code>" respectively. 852 The right angle 853 bracket (>) may be represented using the string 854 "<code>&gt;</code>", and must, <termref def='dt-compat'>for 855 compatibility</termref>, 856 be escaped using 857 "<code>&gt;</code>" or a character reference 858 when it appears in the string 859 "<code>]]></code>" 860 in content, 861 when that string is not marking the end of 862 a <termref def="dt-cdsection">CDATA section</termref>. 863 </p> 864 <p> 865 In the content of elements, character data 866 is any string of characters which does 867 not contain the start-delimiter of any markup. 868 In a CDATA section, character data 869 is any string of characters not including the CDATA-section-close 870 delimiter, "<code>]]></code>".</p> 871 <p> 872 To allow attribute values to contain both single and double quotes, the 873 apostrophe or single-quote character (') may be represented as 874 "<code>&apos;</code>", and the double-quote character (") as 875 "<code>&quot;</code>". 876 <scrap lang="ebnf"> 877 <head>Character Data</head> 878 <prod id='NT-CharData'> 879 <lhs>CharData</lhs> 880 <rhs>[^<&]* - ([^<&]* ']]>' [^<&]*)</rhs> 881 </prod> 882 </scrap> 883 </p> 884 </div2> 885 886 <div2 id='sec-comments'> 887 <head>Comments</head> 888 889 <p><termdef id="dt-comment" term="Comment"><term>Comments</term> may 890 appear anywhere in a document outside other 891 <termref def='dt-markup'>markup</termref>; in addition, 892 they may appear within the document type declaration 893 at places allowed by the grammar. 894 They are not part of the document's <termref def="dt-chardata">character 895 data</termref>; an XML 896 processor may, but need not, make it possible for an application to 897 retrieve the text of comments. 898 <termref def="dt-compat">For compatibility</termref>, the string 899 "<code>--</code>" (double-hyphen) must not occur within 900 comments. 901 <scrap lang="ebnf"> 902 <head>Comments</head> 903 <prod id='NT-Comment'><lhs>Comment</lhs> 904 <rhs>'<!--' 905 ((<nt def='NT-Char'>Char</nt> - '-') 906 | ('-' (<nt def='NT-Char'>Char</nt> - '-')))* 907 '-->'</rhs> 908 </prod> 909 </scrap> 910 </termdef></p> 911 <p>An example of a comment: 912 <eg><!&como; declarations for <head> & <body> &comc;></eg> 913 </p> 914 </div2> 915 916 <div2 id='sec-pi'> 917 <head>Processing Instructions</head> 918 919 <p><termdef id="dt-pi" term="Processing instruction"><term>Processing 920 instructions</term> (PIs) allow documents to contain instructions 921 for applications. 922 923 <scrap lang="ebnf"> 924 <head>Processing Instructions</head> 925 <prod id='NT-PI'><lhs>PI</lhs> 926 <rhs>'<?' <nt def='NT-PITarget'>PITarget</nt> 927 (<nt def='NT-S'>S</nt> 928 (<nt def='NT-Char'>Char</nt>* - 929 (<nt def='NT-Char'>Char</nt>* &pic; <nt def='NT-Char'>Char</nt>*)))? 930 &pic;</rhs></prod> 931 <prod id='NT-PITarget'><lhs>PITarget</lhs> 932 <rhs><nt def='NT-Name'>Name</nt> - 933 (('X' | 'x') ('M' | 'm') ('L' | 'l'))</rhs> 934 </prod> 935 </scrap></termdef> 936 PIs are not part of the document's <termref def="dt-chardata">character 937 data</termref>, but must be passed through to the application. The 938 PI begins with a target (<nt def='NT-PITarget'>PITarget</nt>) used 939 to identify the application to which the instruction is directed. 940 The target names "<code>XML</code>", "<code>xml</code>", and so on are 941 reserved for standardization in this or future versions of this 942 specification. 943 The 944 XML <termref def='dt-notation'>Notation</termref> mechanism 945 may be used for 946 formal declaration of PI targets. 947 </p> 948 </div2> 949 950 <div2 id='sec-cdata-sect'> 951 <head>CDATA Sections</head> 952 953 <p><termdef id="dt-cdsection" term="CDATA Section"><term>CDATA sections</term> 954 may occur 955 anywhere character data may occur; they are 956 used to escape blocks of text containing characters which would 957 otherwise be recognized as markup. CDATA sections begin with the 958 string "<code><![CDATA[</code>" and end with the string 959 "<code>]]></code>": 960 <scrap lang="ebnf"> 961 <head>CDATA Sections</head> 962 <prod id='NT-CDSect'><lhs>CDSect</lhs> 963 <rhs><nt def='NT-CDStart'>CDStart</nt> 964 <nt def='NT-CData'>CData</nt> 965 <nt def='NT-CDEnd'>CDEnd</nt></rhs></prod> 966 <prod id='NT-CDStart'><lhs>CDStart</lhs> 967 <rhs>'<![CDATA['</rhs> 968 </prod> 969 <prod id='NT-CData'><lhs>CData</lhs> 970 <rhs>(<nt def='NT-Char'>Char</nt>* - 971 (<nt def='NT-Char'>Char</nt>* ']]>' <nt def='NT-Char'>Char</nt>*)) 972 </rhs> 973 </prod> 974 <prod id='NT-CDEnd'><lhs>CDEnd</lhs> 975 <rhs>']]>'</rhs> 976 </prod> 977 </scrap> 978 979 Within a CDATA section, only the <nt def='NT-CDEnd'>CDEnd</nt> string is 980 recognized as markup, so that left angle brackets and ampersands may occur in 981 their literal form; they need not (and cannot) be escaped using 982 "<code>&lt;</code>" and "<code>&amp;</code>". CDATA sections 983 cannot nest.</termdef> 984 </p> 985 986 <p>An example of a CDATA section, in which "<code><greeting></code>" and 987 "<code></greeting></code>" 988 are recognized as <termref def='dt-chardata'>character data</termref>, not 989 <termref def='dt-markup'>markup</termref>: 990 <eg><![CDATA[<greeting>Hello, world!</greeting>]]></eg> 991 </p> 992 </div2> 993 994 <div2 id='sec-prolog-dtd'> 995 <head>Prolog and Document Type Declaration</head> 996 997 <p><termdef id='dt-xmldecl' term='XML Declaration'>XML documents 998 may, and should, 999 begin with an <term>XML declaration</term> which specifies 1000 the version of 1001 XML being used.</termdef> 1002 For example, the following is a complete XML document, <termref 1003 def="dt-wellformed">well-formed</termref> but not 1004 <termref def="dt-valid">valid</termref>: 1005 <eg><![CDATA[<?xml version="1.0"?> 1006 <greeting>Hello, world!</greeting> 1007 ]]></eg> 1008 and so is this: 1009 <eg><![CDATA[<greeting>Hello, world!</greeting> 1010 ]]></eg> 1011 </p> 1012 1013 <p>The version number "<code>1.0</code>" should be used to indicate 1014 conformance to this version of this specification; it is an error 1015 for a document to use the value "<code>1.0</code>" 1016 if it does not conform to this version of this specification. 1017 It is the intent 1018 of the XML working group to give later versions of this specification 1019 numbers other than "<code>1.0</code>", but this intent does not 1020 indicate a 1021 commitment to produce any future versions of XML, nor if any are produced, to 1022 use any particular numbering scheme. 1023 Since future versions are not ruled out, this construct is provided 1024 as a means to allow the possibility of automatic version recognition, should 1025 it become necessary. 1026 Processors may signal an error if they receive documents labeled with 1027 versions they do not support. 1028 </p> 1029 <p>The function of the markup in an XML document is to describe its 1030 storage and logical structure and to associate attribute-value pairs 1031 with its logical structures. XML provides a mechanism, the <termref 1032 def="dt-doctype">document type declaration</termref>, to define 1033 constraints on the logical structure and to support the use of 1034 predefined storage units. 1035 1036 <termdef id="dt-valid" term="Validity">An XML document is 1037 <term>valid</term> if it has an associated document type 1038 declaration and if the document 1039 complies with the constraints expressed in it.</termdef></p> 1040 <p>The document type declaration must appear before 1041 the first <termref def="dt-element">element</termref> in the document. 1042 <scrap lang="ebnf" id='xmldoc'> 1043 <head>Prolog</head> 1044 <prodgroup pcw2="6" pcw4="17.5" pcw5="9"> 1045 <prod id='NT-prolog'><lhs>prolog</lhs> 1046 <rhs><nt def='NT-XMLDecl'>XMLDecl</nt>? 1047 <nt def='NT-Misc'>Misc</nt>* 1048 (<nt def='NT-doctypedecl'>doctypedecl</nt> 1049 <nt def='NT-Misc'>Misc</nt>*)?</rhs></prod> 1050 <prod id='NT-XMLDecl'><lhs>XMLDecl</lhs> 1051 <rhs>&xmlpio; 1052 <nt def='NT-VersionInfo'>VersionInfo</nt> 1053 <nt def='NT-EncodingDecl'>EncodingDecl</nt>? 1054 <nt def='NT-SDDecl'>SDDecl</nt>? 1055 <nt def="NT-S">S</nt>? 1056 &pic;</rhs> 1057 </prod> 1058 <prod id='NT-VersionInfo'><lhs>VersionInfo</lhs> 1059 <rhs><nt def="NT-S">S</nt> 'version' <nt def='NT-Eq'>Eq</nt> 1060 (' <nt def="NT-VersionNum">VersionNum</nt> ' 1061 | " <nt def="NT-VersionNum">VersionNum</nt> ")</rhs> 1062 </prod> 1063 <prod id='NT-Eq'><lhs>Eq</lhs> 1064 <rhs><nt def='NT-S'>S</nt>? '=' <nt def='NT-S'>S</nt>?</rhs></prod> 1065 <prod id="NT-VersionNum"> 1066 <lhs>VersionNum</lhs> 1067 <rhs>([a-zA-Z0-9_.:] | '-')+</rhs> 1068 </prod> 1069 <prod id='NT-Misc'><lhs>Misc</lhs> 1070 <rhs><nt def='NT-Comment'>Comment</nt> | <nt def='NT-PI'>PI</nt> | 1071 <nt def='NT-S'>S</nt></rhs></prod> 1072 </prodgroup> 1073 </scrap></p> 1074 1075 <p><termdef id="dt-doctype" term="Document Type Declaration">The XML 1076 <term>document type declaration</term> 1077 contains or points to 1078 <termref def='dt-markupdecl'>markup declarations</termref> 1079 that provide a grammar for a 1080 class of documents. 1081 This grammar is known as a document type definition, 1082 or <term>DTD</term>. 1083 The document type declaration can point to an external subset (a 1084 special kind of 1085 <termref def='dt-extent'>external entity</termref>) containing markup 1086 declarations, or can 1087 contain the markup declarations directly in an internal subset, or can do 1088 both. 1089 The DTD for a document consists of both subsets taken 1090 together.</termdef> 1091 </p> 1092 <p><termdef id="dt-markupdecl" term="markup declaration"> 1093 A <term>markup declaration</term> is 1094 an <termref def="dt-eldecl">element type declaration</termref>, 1095 an <termref def="dt-attdecl">attribute-list declaration</termref>, 1096 an <termref def="dt-entdecl">entity declaration</termref>, or 1097 a <termref def="dt-notdecl">notation declaration</termref>. 1098 </termdef> 1099 These declarations may be contained in whole or in part 1100 within <termref def='dt-PE'>parameter entities</termref>, 1101 as described in the well-formedness and validity constraints below. 1102 For fuller information, see 1103 <specref ref="sec-physical-struct"/>.</p> 1104 <scrap lang="ebnf" id='dtd'> 1105 <head>Document Type Definition</head> 1106 <prodgroup pcw2="6" pcw4="17.5" pcw5="9"> 1107 <prod id='NT-doctypedecl'><lhs>doctypedecl</lhs> 1108 <rhs>'<!DOCTYPE' <nt def='NT-S'>S</nt> 1109 <nt def='NT-Name'>Name</nt> (<nt def='NT-S'>S</nt> 1110 <nt def='NT-ExternalID'>ExternalID</nt>)? 1111 <nt def='NT-S'>S</nt>? ('[' 1112 (<nt def='NT-markupdecl'>markupdecl</nt> 1113 | <nt def='NT-PEReference'>PEReference</nt> 1114 | <nt def='NT-S'>S</nt>)* 1115 ']' 1116 <nt def='NT-S'>S</nt>?)? '>'</rhs> 1117 <vc def="vc-roottype"/> 1118 </prod> 1119 <prod id='NT-markupdecl'><lhs>markupdecl</lhs> 1120 <rhs><nt def='NT-elementdecl'>elementdecl</nt> 1121 | <nt def='NT-AttlistDecl'>AttlistDecl</nt> 1122 | <nt def='NT-EntityDecl'>EntityDecl</nt> 1123 | <nt def='NT-NotationDecl'>NotationDecl</nt> 1124 | <nt def='NT-PI'>PI</nt> 1125 | <nt def='NT-Comment'>Comment</nt> 1126 </rhs> 1127 <vc def='vc-PEinMarkupDecl'/> 1128 <wfc def="wfc-PEinInternalSubset"/> 1129 </prod> 1130 1131 </prodgroup> 1132 </scrap> 1133 1134 <p>The markup declarations may be made up in whole or in part of 1135 the <termref def='dt-repltext'>replacement text</termref> of 1136 <termref def='dt-PE'>parameter entities</termref>. 1137 The productions later in this specification for 1138 individual nonterminals (<nt def='NT-elementdecl'>elementdecl</nt>, 1139 <nt def='NT-AttlistDecl'>AttlistDecl</nt>, and so on) describe 1140 the declarations <emph>after</emph> all the parameter entities have been 1141 <termref def='dt-include'>included</termref>.</p> 1142 1143 <vcnote id="vc-roottype"> 1144 <head>Root Element Type</head> 1145 <p> 1146 The <nt def='NT-Name'>Name</nt> in the document type declaration must 1147 match the element type of the <termref def='dt-root'>root element</termref>. 1148 </p> 1149 </vcnote> 1150 1151 <vcnote id='vc-PEinMarkupDecl'> 1152 <head>Proper Declaration/PE Nesting</head> 1153 <p>Parameter-entity 1154 <termref def='dt-repltext'>replacement text</termref> must be properly nested 1155 with markup declarations. 1156 That is to say, if either the first character 1157 or the last character of a markup 1158 declaration (<nt def='NT-markupdecl'>markupdecl</nt> above) 1159 is contained in the replacement text for a 1160 <termref def='dt-PERef'>parameter-entity reference</termref>, 1161 both must be contained in the same replacement text.</p> 1162 </vcnote> 1163 <wfcnote id="wfc-PEinInternalSubset"> 1164 <head>PEs in Internal Subset</head> 1165 <p>In the internal DTD subset, 1166 <termref def='dt-PERef'>parameter-entity references</termref> 1167 can occur only where markup declarations can occur, not 1168 within markup declarations. (This does not apply to 1169 references that occur in 1170 external parameter entities or to the external subset.) 1171 </p> 1172 </wfcnote> 1173 <p> 1174 Like the internal subset, the external subset and 1175 any external parameter entities referred to in the DTD 1176 must consist of a series of complete markup declarations of the types 1177 allowed by the non-terminal symbol 1178 <nt def="NT-markupdecl">markupdecl</nt>, interspersed with white space 1179 or <termref def="dt-PERef">parameter-entity references</termref>. 1180 However, portions of the contents 1181 of the 1182 external subset or of external parameter entities may conditionally be ignored 1183 by using 1184 the <termref def="dt-cond-section">conditional section</termref> 1185 construct; this is not allowed in the internal subset. 1186 1187 <scrap id="ext-Subset"> 1188 <head>External Subset</head> 1189 <prodgroup pcw2="6" pcw4="17.5" pcw5="9"> 1190 <prod id='NT-extSubset'><lhs>extSubset</lhs> 1191 <rhs><nt def='NT-TextDecl'>TextDecl</nt>? 1192 <nt def='NT-extSubsetDecl'>extSubsetDecl</nt></rhs></prod> 1193 <prod id='NT-extSubsetDecl'><lhs>extSubsetDecl</lhs> 1194 <rhs>( 1195 <nt def='NT-markupdecl'>markupdecl</nt> 1196 | <nt def='NT-conditionalSect'>conditionalSect</nt> 1197 | <nt def='NT-PEReference'>PEReference</nt> 1198 | <nt def='NT-S'>S</nt> 1199 )*</rhs> 1200 </prod> 1201 </prodgroup> 1202 </scrap></p> 1203 <p>The external subset and external parameter entities also differ 1204 from the internal subset in that in them, 1205 <termref def="dt-PERef">parameter-entity references</termref> 1206 are permitted <emph>within</emph> markup declarations, 1207 not only <emph>between</emph> markup declarations.</p> 1208 <p>An example of an XML document with a document type declaration: 1209 <eg><![CDATA[<?xml version="1.0"?> 1210 <!DOCTYPE greeting SYSTEM "hello.dtd"> 1211 <greeting>Hello, world!</greeting> 1212 ]]></eg> 1213 The <termref def="dt-sysid">system identifier</termref> 1214 "<code>hello.dtd</code>" gives the URI of a DTD for the document.</p> 1215 <p>The declarations can also be given locally, as in this 1216 example: 1217 <eg><![CDATA[<?xml version="1.0" encoding="UTF-8" ?> 1218 <!DOCTYPE greeting [ 1219 <!ELEMENT greeting (#PCDATA)> 1220 ]> 1221 <greeting>Hello, world!</greeting> 1222 ]]></eg> 1223 If both the external and internal subsets are used, the 1224 internal subset is considered to occur before the external subset. 1225 <!-- 'is considered to'? boo. whazzat mean? --> 1226 This has the effect that entity and attribute-list declarations in the 1227 internal subset take precedence over those in the external subset. 1228 </p> 1229 </div2> 1230 1231 <div2 id='sec-rmd'> 1232 <head>Standalone Document Declaration</head> 1233 <p>Markup declarations can affect the content of the document, 1234 as passed from an <termref def="dt-xml-proc">XML processor</termref> 1235 to an application; examples are attribute defaults and entity 1236 declarations. 1237 The standalone document declaration, 1238 which may appear as a component of the XML declaration, signals 1239 whether or not there are such declarations which appear external to 1240 the <termref def='dt-docent'>document entity</termref>. 1241 <scrap lang="ebnf" id='fulldtd'> 1242 <head>Standalone Document Declaration</head> 1243 <prodgroup pcw2="4" pcw4="19.5" pcw5="9"> 1244 <prod id='NT-SDDecl'><lhs>SDDecl</lhs> 1245 <rhs> 1246 <nt def="NT-S">S</nt> 1247 'standalone' <nt def='NT-Eq'>Eq</nt> 1248 (("'" ('yes' | 'no') "'") | ('"' ('yes' | 'no') '"')) 1249 </rhs> 1250 <vc def='vc-check-rmd'/></prod> 1251 </prodgroup> 1252 </scrap></p> 1253 <p> 1254 In a standalone document declaration, the value "<code>yes</code>" indicates 1255 that there 1256 are no markup declarations external to the <termref def='dt-docent'>document 1257 entity</termref> (either in the DTD external subset, or in an 1258 external parameter entity referenced from the internal subset) 1259 which affect the information passed from the XML processor to 1260 the application. 1261 The value "<code>no</code>" indicates that there are or may be such 1262 external markup declarations. 1263 Note that the standalone document declaration only 1264 denotes the presence of external <emph>declarations</emph>; the presence, in a 1265 document, of 1266 references to external <emph>entities</emph>, when those entities are 1267 internally declared, 1268 does not change its standalone status.</p> 1269 <p>If there are no external markup declarations, the standalone document 1270 declaration has no meaning. 1271 If there are external markup declarations but there is no standalone 1272 document declaration, the value "<code>no</code>" is assumed.</p> 1273 <p>Any XML document for which <code>standalone="no"</code> holds can 1274 be converted algorithmically to a standalone document, 1275 which may be desirable for some network delivery applications.</p> 1276 <vcnote id='vc-check-rmd'> 1277 <head>Standalone Document Declaration</head> 1278 <p>The standalone document declaration must have 1279 the value "<code>no</code>" if any external markup declarations 1280 contain declarations of:</p><ulist> 1281 <item><p>attributes with <termref def="dt-default">default</termref> values, if 1282 elements to which 1283 these attributes apply appear in the document without 1284 specifications of values for these attributes, or</p></item> 1285 <item><p>entities (other than &magicents;), 1286 if <termref def="dt-entref">references</termref> to those 1287 entities appear in the document, or</p> 1288 </item> 1289 <item><p>attributes with values subject to 1290 <titleref href='AVNormalize'>normalization</titleref>, where the 1291 attribute appears in the document with a value which will 1292 change as a result of normalization, or</p> 1293 </item> 1294 <item> 1295 <p>element types with <termref def="dt-elemcontent">element content</termref>, 1296 if white space occurs 1297 directly within any instance of those types. 1298 </p></item> 1299 </ulist> 1300 1301 </vcnote> 1302 <p>An example XML declaration with a standalone document declaration:<eg 1303 ><?xml version="&XML.version;" standalone='yes'?></eg></p> 1304 </div2> 1305 <div2 id='sec-white-space'> 1306 <head>White Space Handling</head> 1307 1308 <p>In editing XML documents, it is often convenient to use "white space" 1309 (spaces, tabs, and blank lines, denoted by the nonterminal 1310 <nt def='NT-S'>S</nt> in this specification) to 1311 set apart the markup for greater readability. Such white space is typically 1312 not intended for inclusion in the delivered version of the document. 1313 On the other hand, "significant" white space that should be preserved in the 1314 delivered version is common, for example in poetry and 1315 source code.</p> 1316 <p>An <termref def='dt-xml-proc'>XML processor</termref> 1317 must always pass all characters in a document that are not 1318 markup through to the application. A <termref def='dt-validating'> 1319 validating XML processor</termref> must also inform the application 1320 which of these characters constitute white space appearing 1321 in <termref def="dt-elemcontent">element content</termref>. 1322 </p> 1323 <p>A special <termref def='dt-attr'>attribute</termref> 1324 named <kw>xml:space</kw> may be attached to an element 1325 to signal an intention that in that element, 1326 white space should be preserved by applications. 1327 In valid documents, this attribute, like any other, must be 1328 <termref def="dt-attdecl">declared</termref> if it is used. 1329 When declared, it must be given as an 1330 <termref def='dt-enumerated'>enumerated type</termref> whose only 1331 possible values are "<code>default</code>" and "<code>preserve</code>". 1332 For example:<eg><![CDATA[ <!ATTLIST poem xml:space (default|preserve) 'preserve'>]]></eg></p> 1333 <p>The value "<code>default</code>" signals that applications' 1334 default white-space processing modes are acceptable for this element; the 1335 value "<code>preserve</code>" indicates the intent that applications preserve 1336 all the white space. 1337 This declared intent is considered to apply to all elements within the content 1338 of the element where it is specified, unless overriden with another instance 1339 of the <kw>xml:space</kw> attribute. 1340 </p> 1341 <p>The <termref def='dt-root'>root element</termref> of any document 1342 is considered to have signaled no intentions as regards application space 1343 handling, unless it provides a value for 1344 this attribute or the attribute is declared with a default value. 1345 </p> 1346 1347 </div2> 1348 <div2 id='sec-line-ends'> 1349 <head>End-of-Line Handling</head> 1350 <p>XML <termref def='dt-parsedent'>parsed entities</termref> are often stored in 1351 computer files which, for editing convenience, are organized into lines. 1352 These lines are typically separated by some combination of the characters 1353 carriage-return (#xD) and line-feed (#xA).</p> 1354 <p>To simplify the tasks of <termref def='dt-app'>applications</termref>, 1355 wherever an external parsed entity or the literal entity value 1356 of an internal parsed entity contains either the literal 1357 two-character sequence "#xD#xA" or a standalone literal 1358 #xD, an <termref def='dt-xml-proc'>XML processor</termref> must 1359 pass to the application the single character #xA. 1360 (This behavior can 1361 conveniently be produced by normalizing all 1362 line breaks to #xA on input, before parsing.) 1363 </p> 1364 </div2> 1365 <div2 id='sec-lang-tag'> 1366 <head>Language Identification</head> 1367 <p>In document processing, it is often useful to 1368 identify the natural or formal language 1369 in which the content is 1370 written. 1371 A special <termref def="dt-attr">attribute</termref> named 1372 <kw>xml:lang</kw> may be inserted in 1373 documents to specify the 1374 language used in the contents and attribute values 1375 of any element in an XML document. 1376 In valid documents, this attribute, like any other, must be 1377 <termref def="dt-attdecl">declared</termref> if it is used. 1378 The values of the attribute are language identifiers as defined 1379 by <bibref ref="RFC1766"/>, "Tags for the Identification of Languages": 1380 <scrap lang='ebnf'> 1381 <head>Language Identification</head> 1382 <prod id='NT-LanguageID'><lhs>LanguageID</lhs> 1383 <rhs><nt def='NT-Langcode'>Langcode</nt> 1384 ('-' <nt def='NT-Subcode'>Subcode</nt>)*</rhs></prod> 1385 <prod id='NT-Langcode'><lhs>Langcode</lhs> 1386 <rhs><nt def='NT-ISO639Code'>ISO639Code</nt> | 1387 <nt def='NT-IanaCode'>IanaCode</nt> | 1388 <nt def='NT-UserCode'>UserCode</nt></rhs> 1389 </prod> 1390 <prod id='NT-ISO639Code'><lhs>ISO639Code</lhs> 1391 <rhs>([a-z] | [A-Z]) ([a-z] | [A-Z])</rhs></prod> 1392 <prod id='NT-IanaCode'><lhs>IanaCode</lhs> 1393 <rhs>('i' | 'I') '-' ([a-z] | [A-Z])+</rhs></prod> 1394 <prod id='NT-UserCode'><lhs>UserCode</lhs> 1395 <rhs>('x' | 'X') '-' ([a-z] | [A-Z])+</rhs></prod> 1396 <prod id='NT-Subcode'><lhs>Subcode</lhs> 1397 <rhs>([a-z] | [A-Z])+</rhs></prod> 1398 </scrap> 1399 The <nt def='NT-Langcode'>Langcode</nt> may be any of the following: 1400 <ulist> 1401 <item><p>a two-letter language code as defined by 1402 <bibref ref="ISO639"/>, "Codes 1403 for the representation of names of languages"</p></item> 1404 <item><p>a language identifier registered with the Internet 1405 Assigned Numbers Authority <bibref ref='IANA'/>; these begin with the 1406 prefix "<code>i-</code>" (or "<code>I-</code>")</p></item> 1407 <item><p>a language identifier assigned by the user, or agreed on 1408 between parties in private use; these must begin with the 1409 prefix "<code>x-</code>" or "<code>X-</code>" in order to ensure that they do not conflict 1410 with names later standardized or registered with IANA</p></item> 1411 </ulist></p> 1412 <p>There may be any number of <nt def='NT-Subcode'>Subcode</nt> segments; if 1413 the first 1414 subcode segment exists and the Subcode consists of two 1415 letters, then it must be a country code from 1416 <bibref ref="ISO3166"/>, "Codes 1417 for the representation of names of countries." 1418 If the first 1419 subcode consists of more than two letters, it must be 1420 a subcode for the language in question registered with IANA, 1421 unless the <nt def='NT-Langcode'>Langcode</nt> begins with the prefix 1422 "<code>x-</code>" or 1423 "<code>X-</code>". </p> 1424 <p>It is customary to give the language code in lower case, and 1425 the country code (if any) in upper case. 1426 Note that these values, unlike other names in XML documents, 1427 are case insensitive.</p> 1428 <p>For example: 1429 <eg><![CDATA[<p xml:lang="en">The quick brown fox jumps over the lazy dog.</p> 1430 <p xml:lang="en-GB">What colour is it?</p> 1431 <p xml:lang="en-US">What color is it?</p> 1432 <sp who="Faust" desc='leise' xml:lang="de"> 1433 <l>Habe nun, ach! Philosophie,</l> 1434 <l>Juristerei, und Medizin</l> 1435 <l>und leider auch Theologie</l> 1436 <l>durchaus studiert mit hei�em Bem�h'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='Br�ggemann-Klein'>Br�ggemann-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='Br�ggemann-Klein and Wood'>Br�ggemann-Klein, Anne, 3427 and Derick Wood. 3428 <emph>Deterministic Regular Languages</emph>. 3429 Universit�t Freiburg, Institut f�r 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 Br�ggemann-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 -->