csswg-drafts/css3-namespace/Overview.html at bc36ac98bdad4ce3b0e2f45d4333dd69769dbf3f · w3c/csswg-drafts · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">

<html lang=en>
 <head><meta content="text/html; charset=utf-8" http-equiv=Content-Type>

  <title>CSS Namespaces Module</title>
  <link href="../default.css" rel=stylesheet type="text/css">
  <link href="http://www.w3.org/StyleSheets/TR/W3C-ED" rel=stylesheet
  type="text/css">

 <body>
  <div class=head> <!--begin-logo-->
   <p><a href="http://www.w3.org/"><img alt=W3C height=48
    src="http://www.w3.org/Icons/w3c_home" width=72></a> <!--end-logo-->

   <h1>CSS Namespaces Module</h1>

   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 3 January 2012</h2>

   <dl>
    <dt>This version:</dt>
    <!--
    <dd><a href="http://www.w3.org/TR/2012/ED-css3-namespace-20120103/">http://www.w3.org/TR/2012/PR-css3-namespace-20120103/</a></dd>
    -->

    <dd><a
     href="http://dev.w3.org/csswg/css3-namespace/">http://dev.w3.org/csswg/css3-namespace/</a>


    <dt>Latest version:

    <dd><a
     href="http://www.w3.org/TR/css3-namespace/">http://www.w3.org/TR/css3-namespace/</a>

    <dt>Previous version:

     href="http://www.w3.org/TR/2008/CR-css3-namespace-20080523/">http://www.w3.org/TR/2008/CR-css3-namespace-20080523/</a>

    <dt>Editors:

    <dd><a href="http://fantasai.inkedblade.net/contact">Elika J. Etemad</a>

    <dd><a href="http://annevankesteren.nl/about">Anne van Kesteren</a>,
     Opera Software ASA

    <dt>Previous Editors:

    <dd>Peter Linss, Netscape Communications

    <dd>Chris Lilley, W3C
   </dl>
   <!--begin-copyright-->
   <p class=copyright><a
    href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
    rel=license>Copyright</a> &copy; 2012 <a
    href="http://www.w3.org/"><acronym
    title="World Wide Web Consortium">W3C</acronym></a><sup>&reg;</sup> (<a
    href="http://www.csail.mit.edu/"><acronym
    title="Massachusetts Institute of Technology">MIT</acronym></a>, <a
    href="http://www.ercim.eu/"><acronym
    title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></a>,
    <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a
    href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
    <a
    href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
    and <a
    href="http://www.w3.org/Consortium/Legal/copyright-documents">document
    use</a> rules apply.</p>
   <!--end-copyright-->
   <hr title="Separator for header">
  </div>

  <h2 class="no-num no-toc" id=abstract>Abstract</h2>

  <p>This CSS Namespaces module defines the syntax for using namespaces in
   CSS. It defines the <code>@namespace</code> rule for declaring the default
   namespace and binding namespaces to namespace prefixes, and it also
   defines a syntax that other specifications can adopt for using those
   prefixes in namespace-qualified names.

  <h2 class="no-num no-toc" id=status>Status of this document</h2>
  <!--begin-status-->

  <p>This is a public copy of the editors' draft. It is provided for
   discussion only and may change at any moment. Its publication here does
   not imply endorsement of its contents by W3C. Don't cite this document
   other than as work in progress.

  <p>The (<a
   href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public
   mailing list <a
   href="mailto:www-style@w3.org?Subject=%5Bcss3-namespace%5D%20PUT%20SUBJECT%20HERE">
   www-style@w3.org</a> (see <a
   href="http://www.w3.org/Mail/Request">instructions</a>) is preferred for
   discussion of this specification. When sending e-mail, please put the text
   &#8220;css3-namespace&#8221; in the subject, preferably like this:
   &#8220;[<!---->css3-namespace<!---->] <em>&hellip;summary of
   comment&hellip;</em>&#8221;

  <p>This document was produced by the <a href="/Style/CSS/members">CSS
   Working Group</a> (part of the <a href="/Style/">Style Activity</a>).

  <p>This document was produced by a group operating under the <a
   href="/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent
   Policy</a>. W3C maintains a <a href="/2004/01/pp-impl/32061/status"
   rel=disclosure>public list of any patent disclosures</a> made in
   connection with the deliverables of the group; that page also includes
   instructions for disclosing a patent. An individual who has actual
   knowledge of a patent which the individual believes contains <a
   href="/Consortium/Patent-Policy-20040205/#def-essential">Essential
   Claim(s)</a> must disclose the information in accordance with <a
   href="/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the
   W3C Patent Policy</a>.</p>
  <!--end-status-->

  <p>A CSS Namespace <a href="http://www.w3.org/Style/CSS/Test/">Test
   Suite</a> has been developed during the Candidate Recommendation phase of
   this CSS Namespaces specification. An <a
   href="/Style/CSS/Test/CSS3/Namespace/20090210/reports/implement-report.html">implementation
   report</a> is also available.

  <p>This document is the same as the previous, Candidate Recommendation
   version, except for editorial changes.

  <p><em>W3C asks that members of the W3C Advisory Committee review this
   document and fill in the corresponding <a
   href="/2002/09/wbs/33280/PR-css3-namespace/">online form
   [member-only].</a> The review closes on 8 September 2011.</em>

  <h2 class="no-num no-toc" id=contents>Table of contents</h2>
  <!--begin-toc-->

  <ul class=toc>
   <li><a href="#intro"><span class=secno>1. </span>Introduction</a>

   <li><a href="#conformance"><span class=secno>2. </span>Conformance</a>
    <ul class=toc>
     <li><a href="#terminology"><span class=secno>2.1. </span>Terminology</a>

    </ul>

   <li><a href="#declaration"><span class=secno>3. </span>Declaring
    namespaces: the <code>@namespace</code> rule</a>
    <ul class=toc>
     <li><a href="#syntax"><span class=secno>3.1. </span>Syntax</a>

     <li><a href="#scope"><span class=secno>3.2. </span>Scope</a>

     <li><a href="#prefixes"><span class=secno>3.3. </span>Declaring
      Prefixes</a>
    </ul>

   <li><a href="#css-qnames"><span class=secno>4. </span>CSS Qualified
    Names</a>

   <li class=no-num><a href="#acknowledgments">Acknowledgments</a>

   <li class=no-num><a href="#references">References</a>
    <ul class=toc>
     <li class=no-num><a href="#normative-references">Normative
      references</a>

     <li class=no-num><a href="#informative-references">Informative
      references</a>
    </ul>
  </ul>
  <!--end-toc-->

  <div>
   <h2 id=intro><span class=secno>1. </span>Introduction</h2>

   <p><em>This section is non-normative.</em></p>

   <p>This CSS Namespaces module defines syntax for using namespaces in CSS.
    It defines the <code>@namespace</code> rule for declaring a default
    namespace and for binding namespaces to namespace prefixes. It also
    defines a syntax for using those prefixes to represent
    namespace-qualified names. It does not define where such names are valid
    or what they mean: that depends on their context and is defined by a host
    language, such as Selectors (<a href="#SELECT"
    rel=biblioentry>[SELECT]<!--{{SELECT}}--></a>), that references the
    syntax defined in the CSS Namespaces module.

   <p>Note that a CSS client that does not support this module will (if it
    properly conforms to <a
    href="http://www.w3.org/TR/CSS21/syndata.html#parsing-errors">CSS's
    forward-compatible parsing rules</a>) ignore all <code>@namespace</code>
    rules, as well as all style rules that make use of namespace qualified
    names. The syntax of delimiting namespace prefixes in CSS was
    deliberately chosen so that these CSS clients would ignore the style
    rules rather than possibly match them incorrectly.</p>
  </div>

  <div>
   <h2 id=conformance><span class=secno>2. </span>Conformance</h2>

   <p>A document or implementation cannot conform to CSS Namespaces alone,
    but can claim conformance to CSS Namespaces if it satisfies the
    conformance requirements in this specification when implementing CSS or
    another host language that normatively references this specification.</p>

   <p>Conformance to CSS Namespaces is defined for two classes:

   <dl>
    <dt><dfn id=style-sheet>style sheet</dfn>

    <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
     style sheet</a> (or a complete unit of another host language that
     normatively references CSS Namespaces).

    <dt><dfn id=interpreter>interpreter</dfn>

    <dd>Someone or something that interprets the semantics of a style sheet.
     (CSS <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">user
     agents</a> fall under this category.)
   </dl>

   <p>The conformance requirements are expressed with a combination of
    descriptive assertions and RFC 2119 terminology. The key words "MUST",
    "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
    "RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this
    document are to be interpreted as described in RFC 2119. However, for
    readability, these words do not appear in all uppercase letters in this
    specification. All of the text of this specification is normative except
    sections explicitly marked as non-normative, examples, and notes. <a
    href="#RFC2119" rel=biblioentry>[RFC2119]<!--{{!RFC2119}}--></a></p>

   <p>Examples in this specification are introduced with the words "for
    example" or are set apart from the normative text with
    <code>class="example"</code>, like this:

   <div class=example>
    <p>This is an example of an informative example.</p>
   </div>

   <p>Informative notes begin with the word "Note" and are set apart from the
    normative text with <code>class="note"</code>, like this:

   <p class=note>Note, this is an informative note.</p>

   <h3 id=terminology><span class=secno>2.1. </span>Terminology</h3>

   <p>Besides terms introduced by this specification, CSS Namespaces uses the
    terminology defined in Namespaces in XML 1.0. <a href="#XML-NAMES"
    rel=biblioentry>[XML-NAMES]<!--{{!XML-NAMES}}--></a> However, the syntax
    defined here is not restricted to representing XML element and attribute
    names and may represent other kinds of namespaces as defined by the host
    language.</p>

   <p>In CSS Namespaces a namespace name consisting of the empty string is
    taken to represent the null namespace or lack of a namespace.</p>

   <div class=example>
    <p>For example, given the namespace declarations:</p>

    <pre>@namespace empty "";
<!--  -->@namespace "";</pre>

    <p>The <a href="http://www.w3.org/TR/css3-selectors/#type-selectors">type
     selectors</a> <code>elem</code>, <code>|elem</code>, and
     <code>empty|elem</code> are equivalent.</p>
   </div>
  </div>

  <div>
   <h2 id=declaration><span class=secno>3. </span>Declaring namespaces: the
    <code>@namespace</code> rule</h2>

   <p>The <code>@namespace</code> <a
    href="http://www.w3.org/TR/CSS21/syndata.html#at-rules">at-rule</a>
    declares a namespace prefix and associates it with a given namespace name
    (a string). This namespace prefix can then be used in namespace-qualified
    names such as the <a href="#css-qnames">CSS qualified names</a> defined
    below.</p>

   <div class=example>
    <pre>@namespace "http://www.w3.org/1999/xhtml";
<!--  -->@namespace svg "http://www.w3.org/2000/svg";</pre>

    <p>The first rule declares a default namespace
     <code>http://www.w3.org/1999/xhtml</code> to be applied to names that
     have no explicit namespace component.</p>

    <p>The second rule declares a namespace prefix <code>svg</code> that is
     used to apply the namespace <code>http://www.w3.org/2000/svg</code>
     where the <code>svg</code> namespace prefix is used.</p>
   </div>

   <p id=expanded-name-match>In CSS Namespaces, as in Namespaces in XML 1.0,
    the prefix is merely a syntactic construct; it is the <em><dfn
    id=expanded-name>expanded name</dfn></em> (the tuple of local name and
    namespace name) that is significant. Thus the actual prefixes used in a
    CSS style sheet, and whether they are defaulted or not, are independent
    of the namespace prefixes used in the markup and whether these are
    defaulted or not.</p>

   <div class=example>
    <p>For example, given the following XML document:</p>

    <pre><!--
   -->&lt;qml:elem xmlns:qml="http://example.com/q-markup">&lt;/qml:elem><!--
 --></pre>

    <p>and the following <code>@namespace</code> declarations at the
     beginning of a CSS file:</p>

    <pre><!--
    -->@namespace Q "http://example.com/q-markup";
<!---->@namespace lq "http://example.com/q-markup";<!--
 --></pre>

    <p>The selectors <code>Q|elem</code> and <code>lq|elem</code> in that CSS
     file would both match the element <code>&lt;qml:elem&gt;</code>. (The
     selector <code>qml|elem</code> would be invalid.)</p>
   </div>

   <h3 id=syntax><span class=secno>3.1. </span>Syntax</h3>

   <p>The syntax for the <code>@namespace</code> rule is as follows (using
    the notation from the <a
    href="http://www.w3.org/TR/CSS21/grammar.html">Grammar appendix of CSS
    2.1</a> <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>):</p>

   <pre><!--
     -->namespace
<!-- -->  : NAMESPACE_SYM S* [namespace_prefix S*]? [STRING|URI] S* ';' S*
<!-- -->  ;
<!-- -->namespace_prefix
<!-- -->  : IDENT
<!-- -->  ;<!--
  --></pre>

   <p>with the new token:</p>

   <pre>@{N}{A}{M}{E}{S}{P}{A}{C}{E} {return NAMESPACE_SYM;}</pre>

   <p>Any <code>@namespace</code> rules must follow all @charset and @import
    rules and precede all other non-ignored at-rules and rule sets in a style
    sheet. For CSS syntax this adds <code>[ namespace [S|CDO|CDC]* ]*</code>
    immediately after <code>[ import [S|CDO|CDC]* ]*</code> in the
    <code>stylesheet</code> grammar.</p>

   <p>A syntactically invalid <code>@namespace</code> rule (whether malformed
    or misplaced) must be <a
    href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>. A CSS
    <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">style
    sheet</a> containing an invalid <code>@namespace</code> rule is not a <a
    href="http://www.w3.org/TR/CSS21/conform.html#valid-style-sheet">valid
    style sheet</a>.</p>

   <p>A URI string parsed from the <code>URI</code> syntax must be treated as
    a literal string: as with the <code>STRING</code> syntax, no URI-specific
    normalization is applied.</p>

   <p>All strings&#8212;including the empty string and strings representing
    invalid URIs&#8212;are valid namespace names in <code>@namespace</code>
    declarations.</p>

   <h3 id=scope><span class=secno>3.2. </span>Scope</h3>

   <p>The namespace prefix is declared only within the style sheet in which
    its <code>@namespace</code> rule appears. It is not declared in any style
    sheets importing or imported by that style sheet, nor in any other style
    sheets applying to the document.</p>

   <h3 id=prefixes><span class=secno>3.3. </span>Declaring Prefixes</h3>

   <p>A <dfn id=namespace-prefix>namespace prefix</dfn>, once declared,
    represents the namespace for which it was declared and can be used to
    indicate the namespace of a namespace-qualified name. Namespace prefixes
    are, <a href="http://www.w3.org/TR/CSS21/syndata.html#counter">like CSS
    counter names</a>, case-sensitive.</p>
   <!-- They do not, however, distinguish between equivalent
    canonical Unicode representations. Essentially, an <code>@namespace</code>
    declaration declares all prefixes that map to the same NFC representation as
    the given prefix to the same namespace name. (See [[!UNICODE]] for the definition
    of NFC normalization.) -->

   <p>If in the namespace declaration the namespace prefix is omitted, then
    the namespace so declared is the default namespace. The <dfn
    id=default-namespace>default namespace</dfn> may apply to names that have
    no explicit namespace prefix: modules that employ namespace prefixes must
    define in which contexts the default namespace applies. For example,
    following <a href="#XML-NAMES"
    rel=biblioentry>[XML-NAMES]<!--{{!XML-NAMES}}--></a>, in Selectors <a
    href="#SELECT" rel=biblioentry>[SELECT]<!--{{SELECT}}--></a> the default
    namespace applies to type selectors&#8212;but it does not apply to
    attribute selectors. There is no default value for the default namespace:
    modules that assign unqualified names to the default namespace must
    define how those unqualified names are to be interpreted when no default
    namespace is declared.</p>

  
D54
 <p class=note>Note that using default namespaces in conjunction with type
    selectors can cause UAs that support default namespaces and UAs that
    don't support default namespaces to interpret selectors differently.</p>

   <p>If a namespace prefix or default namespace is declared more than once
    only the last declaration shall be used. Declaring a namespace prefix or
    default namespace more than once is nonconforming.</p>
  </div>

  <div>
   <h2 id=css-qnames><span class=secno>4. </span>CSS Qualified Names</h2>

   <p>A <dfn id=css-qualified-name>CSS qualified name</dfn> is a name
    explicitly located within (associated with) a namespace. To form a
    qualified name in CSS syntax, a namespace prefix that has been declared
    within scope is prepended to a local name (such as an element or
    attribute name), separated by a "vertical bar" (<code>|</code>, U+007C).
    The prefix, representing the namespace for which it has been declared,
    indicates the namespace of the local name. The prefix of a qualified name
    may be omitted to indicate that the name belongs to no namespace, i.e.
    that the namespace name part of the expanded name has no value. Some
    contexts (as defined by the host language) may allow the use of an
    asterisk (<code>*</code>, U+002A) as a wildcard prefix to indicate a name
    in any namespace, including no namespace.</p>

   <div class=example>
    <p>Given the namespace declarations:</p>

    <pre>@namespace toto "http://toto.example.org";
<!--  -->@namespace "http://example.com/foo";</pre>

    <p>In a context where the default namespace applies</p>

    <dl>
     <dt><code>toto|A</code>

     <dd>represents the name <code>A</code> in the
      <code>http://toto.example.org</code> namespace.

     <dt><code>|B</code>

     <dd>represents the name <code>B</code> that belongs to no namespace.

     <dt><code>*|C</code>

     <dd>represents the name <code>C</code> in any namespace, including no
      namespace.

     <dt><code>D</code>

     <dd>represents the name <code>D</code> in the
      <code>http://example.com/foo</code> namespace.
    </dl>
   </div>

   <p>The syntax for the portion of a CSS qualified name before the local
    name is given below, both for qualified names that allow wildcard
    prefixes (<code>wqname</code>) and for qualified names that disallow
    wildcard prefixes (<code>qname</code>). (The syntax uses notation from
    the <a href="http://www.w3.org/TR/CSS21/grammar.html">Grammar appendix of
    CSS 2.1</a>. <a href="#CSS21"
    rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> Note this means that
    comments, but not white space, are implicitly allowed between tokens.):</p>

   <pre><!--
     -->qname_prefix
<!-- -->  : namespace_prefix? '|'
<!-- -->  ;
<!-- -->wqname_prefix
<!-- -->  : [ namespace_prefix? | '*' ] '|'
<!-- -->  ;
<!-- -->qname
<!-- -->  : qname_prefix? ident
<!-- -->  ;
<!-- -->wqname
<!-- -->  : wqname_prefix? ident
<!-- -->  ;<!--
--></pre>

   <p>CSS qualified names can be used in (for example) selectors and property
    values as described in other modules. Those modules must define handling
    of namespace prefixes that have not been properly declared. Such handling
    should treat undeclared namespace prefixes as a parsing error that will
    cause the selector or declaration (etc.) to be considered invalid and, in
    CSS, <a
    href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.</p>

   <div class=example>
    <p>For example, the Selectors module <a href="#SELECT"
     rel=biblioentry>[SELECT]<!--{{SELECT}}--></a> defines a type selector
     with an undeclared namespace prefix to be an invalid selector, and CSS
     <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> requires
     rule sets with an invalid selector to be completely ignored.</p>
   </div>
  </div>

  <h2 class=no-num id=acknowledgments>Acknowledgments</h2>

  <p>This draft borrows heavily from earlier drafts on CSS namespace support
   by Chris Lilley and by Peter Linss and early (unpublished) drafts on CSS
   and XML by H&aring;kon Lie and Bert Bos, and XML Namespaces and CSS by
   Bert Bos and Steven Pemberton. Many current and former members of the CSS
   Working Group have contributed to this document. Discussions on
   www-style@w3.org and in other places have also contributed ideas to this
   specification. Special thanks goes to L. David Baron, Karl Dubost, Ian
   Hickson, Bj&ouml;ern H&ouml;hrmann, and Lachlan Hunt for their comments.

  <h2 class=no-num id=references>References</h2>

  <h3 class=no-num id=normative-references>Normative references</h3>
  <!--begin-normative-->
  <!-- Sorted by label -->

  <dl class=bibliography>
   <dt style="display: none"><!-- keeps the doc valid if the DL is empty -->
    <!---->

   <dt id=CSS21>[CSS21]

   <dd>Bert Bos; et al. <a
    href="http://www.w3.org/TR/2011/REC-CSS2-20110607"><cite>Cascading Style
    Sheets Level 2 Revision 1 (CSS&#160;2.1) Specification.</cite></a> 7 June
    2011. W3C Recommendation. URL: <a
    href="http://www.w3.org/TR/2011/REC-CSS2-20110607">http://www.w3.org/TR/2011/REC-CSS2-20110607</a>
    </dd>
   <!---->

   <dt id=RFC2119>[RFC2119]

   <dd>S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key
    words for use in RFCs to Indicate Requirement Levels.</cite></a> Internet
    RFC 2119. URL: <a
    href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a>
    </dd>
   <!---->

   <dt id=XML-NAMES>[XML-NAMES]

   <dd>Tim Bray; et al. <a
    href="http://www.w3.org/TR/2009/REC-xml-names-20091208/"><cite>Namespaces
    in XML 1.0 (Third Edition).</cite></a> 8 December 2009. W3C
    Recommendation. URL: <a
    href="http://www.w3.org/TR/2009/REC-xml-names-20091208/">http://www.w3.org/TR/2009/REC-xml-names-20091208/</a>
    </dd>
   <!---->
  </dl>
  <!--end-normative-->

  <h3 class=no-num id=informative-references>Informative references</h3>
  <!--begin-informative-->
  <!-- Sorted by label -->

  <dl class=bibliography>
   <dt style="display: none"><!-- keeps the doc valid if the DL is empty -->
    <!---->

   <dt id=SELECT>[SELECT]

   <dd>Tantek &#199;elik; et al. <a
    href="http://www.w3.org/TR/2011/REC-css3-selectors-20110929/"><cite>Selectors
    Level 3.</cite></a> 29 September 2011. W3C Recommendation. URL: <a
    href="http://www.w3.org/TR/2011/REC-css3-selectors-20110929/">http://www.w3.org/TR/2011/REC-css3-selectors-20110929/</a>
    </dd>
   <!---->
  </dl>
  <!--end-informative-->
</html>
<!-- Keep this comment at the end of the file
Local variables:
mode: sgml
sgml-declaration:"~/SGML/HTML4.decl"
sgml-default-doctype-name:"html"
sgml-minimize-attributes:t
sgml-nofill-elements:("pre" "style" "br")
sgml-live-element-indicator:t
sgml-omittag:nil
sgml-shorttag:nil
sgml-namecase-general:t
sgml-general-insert-case:lower
sgml-always-quote-attributes:t
sgml-indent-step:nil
sgml-indent-data:t
sgml-parent-document:nil
sgml-exposed-tags:nil
sgml-local-catalogs:nil
sgml-local-ecat-files:nil
End:
-->