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
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
|
<!DOCTYPE PUBLIC "-//W3C//DTD HTML 3.2//EN">
<html>
<head>
<title>SWI-Prolog SGML/XML parser</title>
</head>
<body>
<center>
<h1>SWI-Prolog SGML/XML parser<br>
<font size="+0"><em>Version 1.0.14, March 2001</em></font></h1>
<br>
<a href="mailto:jan@swi.psy.uva.nl"><em>Jan Wielemaker</em></a><br>
<em> SWI, <br>
University of Amsterdam <br>
The Netherlands
</em>
</center>
<blockquote>
<hr>
Markup languages are an increasingly important method for
data-representation and exchange. This article documents the package
<b>sgml2pl</b>, a foreign library for SWI-Prolog to parse SGML and XML
documents, returning information on both the document and the document's
DTD. The parser is designed to be small, fast and flexible.
<hr>
</blockquote>
<h1>Table of Content</h1>
<ul>
<li><a href="#sec:sec-1">Introduction</a>
<li><a href="#sec:sec-2">Bluffer's Guide</a>
<ul>
<li><a href="#sec:sec-2.1">`Goodies' Predicates</a>
</ul>
<li><a href="#sec:sec-3">Predicate Reference</a>
<ul>
<li><a href="#sec:sec-3.1">Loading Structured Documents</a>
<li><a href="#sec:space">Handling white-space</a>
<li><a href="#sec:xml">XML documents</a>
<ul>
<li><a href="#sec:xmlns">XML Namespaces</a>
</ul>
<li><a href="#sec:sec-3.4">DTD-Handling</a>
<ul>
<li><a href="#sec:sec-3.4.1">The DOCTYPE declaration</a>
</ul>
<li><a href="#sec:implicitdtd">Extracting a DTD</a>
<li><a href="#sec:sec-3.6">Parsing Primitives</a>
<ul>
<li><a href="#sec:sec-3.6.1">Partial Parsing</a>
</ul>
</ul>
<li><a href="#sec:indexaccess">Processing Indexed Files</a>
<li><a href="#sec:sec-5">External entities</a>
<li><a href="#sec:sec-6">Unsupported features</a>
<li><a href="#sec:sec-7">Installation</a>
<ul>
<li><a href="#sec:sec-7.1">Unix systems</a>
</ul>
<li><a href="#sec:sec-8">Acknowledgements</a>
</ul>
<p>
<h1><a name="sec:sec-1">Introduction</a></h1>
<p>
Markup languages have recently regained popularity for two reasons. One
is document exchange, which is largely based on HTML, an instance of
SGML, and the other is for data exchange between programs, which is often
based on XML, which can be considered a simplified and rationalised
version of SGML.
<p>
James Clark's SP parser is a flexible SGML and XML parser. Unfortunately
it has some drawbacks. It is very big, not very fast, cannot work under
event-driven input and is generally hard to program beyond the scope of
the well designed generic interface. The generic interface however does
not provide access to the DTD, does not allow for flexible handling of
input or parsing the DTD independently of a document instance.
<p>
The parser described in this document is small (less than 50 kbytes
executable on a Pentium or 80 kbytes on a SPARC), fast (between 2 and 5
times faster than SP), provides access to the DTD, and provides flexible
input handling.
<p>
The document output is equal to the output produced by <b><em>xml2pl</em></b>,
an SP interface to SWI-Prolog written by Anjo Anjewierden.
<p>
<h1><a name="sec:sec-2">Bluffer's Guide</a></h1>
<p>
This package allows you to parse SGML, XML and HTML data into a Prolog
data structure. The high-level interface defined in <b>sgml</b>
provides access at the file-level, while the low-level interface defined
in the foreign module works with Prolog streams. Please use the source
of <b>sgml.pl</b> as a starting point for dealing with data from
other sources than files, such as SWI-Prolog resources, network-sockets,
character strings, <em>etc.</em> The first example below loads an HTML file.
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<html>
<head>
<title>Demo</title>
</head>
<body>
<h1 align=center>This is a demo</title>
<p>Paragraphs in HTML need not be closed.
<p>This is called `omitted-tag' handling.
</body>
</html>
</pre>
</td></tr>
</table>
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
?- load_html_file('test.html', Term),
pretty_print(Term).
[ element(html,
[],
[ element(head,
[],
[ element(title,
[],
[ 'Demo'
])
]),
element(body,
[],
[ '\n',
element(h1,
[ align = center
],
[ 'This is a demo'
]),
'\n\n',
element(p,
[],
[ 'Paragraphs in HTML need not be closed.\n'
]),
element(p,
[],
[ 'This is called `omitted-tag\' handling.'
])
])
])
].
</pre>
</td></tr>
</table>
<p>
The document is represented as a list, each element being an atom to
represent <a name="const:CDATA"><b><tt>CDATA</tt></b></a> or a term <code>element(Name, Attributes, Content)</code>.
Entities (e.g. <code>&lt;</code>) are returned as part of <a name="const:CDATA%2"><b><tt>CDATA</tt></b></a>,
unless they cannot be represented. See <a href="#load_sgml_file/2"><b>load_sgml_file/2</b></a> for
details.
<p>
<h2><a name="sec:sec-2.1">`Goodies' Predicates</a></h2>
<p>
These predicates are for basic use of the library, converting entire and
self-contained files in SGML, HTML, or XML into a structured term. They
are based on <a href="#load_structure/3"><b>load_structure/3</b></a>.
<dl>
<dt> <br>
<b><a name="load_sgml_file/2">load_sgml_file(<var>+File, -ListOfContent</var>)</a></b><dd>
Same as <code>load_structure(File, ListOfContent, [dialect(sgml)])</code>.
<dt> <br>
<b><a name="load_xml_file/2">load_xml_file(<var>+File, -ListOfContent</var>)</a></b><dd>
Same as <code>load_structure(File, ListOfContent, [dialect(xml)])</code>.
<dt> <br>
<b><a name="load_html_file/2">load_html_file(<var>+File, -Content</var>)</a></b><dd>
Load <var>File</var> and parse as HTML. Implemented as:
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
load_html_file(File, Term) :-
dtd(html, DTD),
load_structure(File, Term,
[ dtd(DTD),
dialect(sgml)
]).
</pre>
</td></tr>
</table>
</dl>
<p>
<h1><a name="sec:sec-3">Predicate Reference</a></h1>
<p>
<h2><a name="sec:sec-3.1">Loading Structured Documents</a></h2>
<p>
SGML or XML files are loaded through the common predicate
<a href="#load_structure/3"><b>load_structure/3</b></a>. This is a predicate with many options. For
simplicity a number of commonly used shorthands are provided: <a href="#load_sgml_file/2"><b>load_sgml_file/2</b></a>, <a href="#load_xml_file/2"><b>load_xml_file/2</b></a>, and
<a href="#load_html_file/2"><b>load_html_file/2</b></a>.
<dl>
<dt> <br>
<b><a name="load_structure/3">load_structure(<var>+File, -ListOfContent, +Options</var>)</a></b><dd>
Load the XML file <var>File</var> and return the resulting structure in <var>ListOfContent</var>. <var>Options</var> is a list of options controlling the
conversion process.
<p>
A proper XML document contains only a single toplevel element whose name
matches the document type. Nevertheless, a list is returned for
consistency with the representation of element content. The <var>ListOfContent</var> consists of the following types:
<dl>
<dt> <br>
<b><var>Atom</var></b><dd>
Atoms are used to represent <a name="const:CDATA%3"><b><tt>CDATA</tt></b></a>. Note
this is possible in SWI-Prolog, as there is no length-limit on atoms and
atom garbage collection is provided.
<dt> <br>
<b>element(<var>Name, ListAttributes, ListOfContent</var>)</b><dd>
<var>Name</var> is the name of the element. Using SGML, which is
case-insensitive, all element names are returned as lowercase atoms.
<p>
<var>ListOfAttributes</var> is a list of <var>Name</var>=<var>Value</var> pairs for
attributes that appeared in the source. No information is returned on
other attributes, such as <a name="const:fixed"><b><tt>fixed</tt></b></a> or <a name="const:default"><b><tt>default</tt></b></a> attributes. See
<a href="#dtd_property/2"><b>dtd_property/2</b></a> for accessing the DTD for this information.
Attributes of type <a name="const:CDATA%4"><b><tt>CDATA</tt></b></a> are returned literal. Multi-valued
attributes (<a name="const:NAMES"><b><tt>NAMES</tt></b></a>, <em>etc.</em>) are returned as a list of atoms.
Handling attributes of the types <a name="const:NUMBER"><b><tt>NUMBER</tt></b></a> and <a name="const:NUMBERS"><b><tt>NUMBERS</tt></b></a> depends on
the setting of the <code>number(+NumberMode)</code> attribute through
<a href="#set_sgml_parser/2"><b>set_sgml_parser/2</b></a> or <a href="#load_structure/3"><b>load_structure/3</b></a>. By
default they are returned as atoms, but automatic conversion to Prolog
integers is supported. <var>ListOfContent</var> defines the content for the
element.
<dt> <br>
<b>entity(<var>Code</var>)</b><dd>
If a character-entity (e.g. <code>&#913;</code>) is encoutered that
cannot be represented in the Prolog character set, this term is
returned, representing the referred character code.
<dt> <br>
<b>entity(<var>Name</var>)</b><dd>
If an entity refers to a character-entity holding a single character,
but this character cannot be represented in the Prolog character set,
this term is returned. For example, the HTML input text
<code>&Alpha; &lt; &Beta;</code>
is returned as below. Please note that entity names are case sensitive
in both SGML and XML.
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
[ entity('Alpha'), ' < ', entity('Beta') ]
</pre>
</td></tr>
</table>
<p>
This is a special case of <code>entity(Code)</code>, intended to handle
special symbols by their name rather than character code.
<dt> <br>
<b>sdata(<var>Text</var>)</b><dd>
If an entity with declared content-type <a name="const:SDATA"><b><tt>SDATA</tt></b></a> is encountered, this
term is returned holding the data in <var>Text</var>.
<dt> <br>
<b>ndata(<var>Text</var>)</b><dd>
If an entity with declared content-type <a name="const:NDATA"><b><tt>NDATA</tt></b></a> is encountered, this
term is returned holding the data in <var>Text</var>.
<dt> <br>
<b>pi(<var>Text</var>)</b><dd>
If a processing instruction is encountered (<code><?...?></code>), <var>Text</var> holds the text of the processing instruction. Please note that the
<code><?xml ...?></code> instruction is handled internally.
</dl>
<p>
The <var>Options</var> list controls the conversion process. Currently
defined options are:
<dl>
<dt> <br>
<b>dtd(<var>?DTD</var>)</b><dd>
Reference to a DTD object. If specified, the <code><!DOCTYPE ...></code>
declaration is ignored and the document is parsed and validated against
the provided DTD. If provided as a variable, the created DTD is
returned. See <a href="#sec:implicitdtd">implicitdtd</a>.
<dt> <br>
<b>dialect(<var>+Dialect</var>)</b><dd>
Specify the parsing dialect. Supported are <a name="const:sgml"><b><tt>sgml</tt></b></a> (default), <a name="const:xml"><b><tt>xml</tt></b></a>
and <a name="const:xmlns"><b><tt>xmlns</tt></b></a>. See <a href="#sec:xml">xml</a> for details on the differences.
<dt> <br>
<b>shorttag(<var>+Bool</var>)</b><dd>
Define whether SHORTTAG abbreviation is accepted. The default is true
for SGML mode and false for the XML modes. Without SHORTTAG, a <a name="const:/"><b><tt>/</tt></b></a>
is accepted with warning as part of an unquoted attribute-value, though
<a name="const:/>"><b><tt>/></tt></b></a> still closes the element-tag in XML mode. It may be set to
false for parsing HTML documents to allow for unquoted URLs containing
<a name="const:/%2"><b><tt>/</tt></b></a>.
<dt> <br>
<b>space(<var>+SpaceMode</var>)</b><dd>
Sets the `space-handling-mode' for the initial environment. This mode is
inherited by the other environments, which can override the inherited
value using the XML reserved attribute <b><tt>xml:space</tt></b>. See <a href="#sec:space">space</a>.
<dt> <br>
<b>number(<var>+NumberMode</var>)</b><dd>
Determines how attributes of type <a name="const:NUMBER%2"><b><tt>NUMBER</tt></b></a> and <a name="const:NUMBERS%2"><b><tt>NUMBERS</tt></b></a> are handled.
If <a name="const:token"><b><tt>token</tt></b></a> (default) they are passed as an atom. If <a name="const:integer"><b><tt>integer</tt></b></a> the
parser attempts to convert the value to an integer. If successful, the
attribute is passed as a Prolog integer. Otherwise it is still passed
as an atom. Note that SGML defines a numeric attribute to be a sequence
of digits. The <a name="const:-"><b><tt>-</tt></b></a> sign is not allowed and <code>1</code> is different from
<code>01</code>. For this reason the default is to handle numeric attributes as
tokens. If conversion to integer is enabled, negative values are silently
accepted.
<dt> <br>
<b>defaults(<var>+Bool</var>)</b><dd>
Determines how default and fixed values from the DTD are used. By
default, defaults are included in the output if they do not appear in
the source. If <a name="const:false"><b><tt>false</tt></b></a>, only the attributes occurring in the source
are emitted.
<dt> <br>
<b>file(<var>+Name</var>)</b><dd>
Sets the name of the file on which errors are reported. Sets the
linenumber to 1.
<dt> <br>
<b>line(<var>+Line</var>)</b><dd>
Sets the starting line-number for reporting errors.
<dt> <br>
<b>max_errors(<var>+Max</var>)</b><dd>
Sets the maximum number of errors. If this number is reached, an
exception of the format below is raised. The default is 50.
<blockquote>
<code>error(limit_exceeded(max_errors, Max), _)</code>
</blockquote>
</dl>
</dl>
<p>
<h2><a name="sec:space">Handling white-space</a></h2>
<p>
SGPL2PL has four modes for handling white-space. The initial mode can be
switched using the <code>space(SpaceMode)</code> option to
<a href="#load_structure/3"><b>load_structure/3</b></a> and <a href="#set_sgml_parser/2"><b>set_sgml_parser/2</b></a>. In XML
mode, the mode is further controlled by the <b><tt>xml:space</tt></b> attribute,
which may be specified both in the DTD and in the document. The defined
modes are:
<dl>
<dt> <br>
<b>space(<var>sgml</var>)</b><dd>
In SGML, newlines at the start and end of an element are removed.<a href="#fn-1" name="txt:fn-1"><sup>1</sup></a> This is the default mode for
the SGML dialect.
<dt> <br>
<b>space(<var>preserve</var>)</b><dd>
White space is passed literally to the application. This mode leaves all
white space handling to the application. This is the default mode for
the XML dialect.
<dt> <br>
<b>space(<var>default</var>)</b><dd>
In addition to <a name="const:sgml%2"><b><tt>sgml</tt></b></a> space-mode, all consequtive white-space is
reduced to a single space-character. This mode canonises all white
space.
<dt> <br>
<b>space(<var>remove</var>)</b><dd>
In addition to <a name="const:default%2"><b><tt>default</tt></b></a>, all leading and trailing white-space is
removed from <a name="const:CDATA%5"><b><tt>CDATA</tt></b></a> objects. If, as a result, the <a name="const:CDATA%6"><b><tt>CDATA</tt></b></a>
becomes empty, nothing is passed to the application. This mode is
especially handy for processing `data-oriented' documents, such as RDF.
It is not suitable for normal text documents. Consider the HTML
fragment below. When processed in this mode, the spaces between the
three modified words are lost. This mode is not part of any standard;
XML 1.0 allows only <a name="const:default%3"><b><tt>default</tt></b></a> and <a name="const:preserve"><b><tt>preserve</tt></b></a>.
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
Consider adjacent <b>bold</b> <ul>and</ul> <it>italic</it> words.
</pre>
</td></tr>
</table>
</dl>
<p>
<h2><a name="sec:xml">XML documents</a></h2>
<p>
The parser can operate in two modes: <a name="const:sgml%3"><b><tt>sgml</tt></b></a> mode and <a name="const:xml%2"><b><tt>xml</tt></b></a> mode, as
defined by the <code>dialect(Dialect)</code> option. Regardless of this
option, if the first line of the document reads as below, the parser is
switched automatically into XML mode.
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
<?xml ... ?>
</pre>
</td></tr>
</table>
<p>
Currently switching to XML mode implies:
<ul>
<li><em>XML empty elements</em><br>
The construct <code><element [attribute...] /></code> is recognised as
an empty element.
<li><em>Predefined entities</em><br>
The following entitities are predefined: <a name="const:lt"><b><tt>lt</tt></b></a> (<code><</code>), <a name="const:gt"><b><tt>gt</tt></b></a>
(<code>></code>), <a name="const:amp"><b><tt>amp</tt></b></a> (<code>&</code>), <a name="const:apos"><b><tt>apos</tt></b></a> (<code>'</code>)
and <a name="const:quot"><b><tt>quot</tt></b></a> (<code>"</code>).
<li><em>Case sensitivity</em><br>
In XML mode, names are treated case-sensitive, except for the DTD
reserved names (i.e. <code>ELEMENT</code>, <em>etc.</em>).
<li><em>Character classes</em><br>
In XML mode, underscores (<code>_</code>) and colon (<code>:</code>) are
allowed in names.
<li><em>White-space handling</em><br>
White space mode is set to <a name="const:preserve%2"><b><tt>preserve</tt></b></a>. In addition to setting
white-space handling at the toplevel the XML reserved attribute
<b><tt>xml:space</tt></b> is honoured. It may appear both in the document and the
DTD. The <a name="const:remove"><b><tt>remove</tt></b></a> extension is honoured as <b><tt>xml:space</tt></b> value. For
example, the DTD statement below ensures that the <b><tt>pre</tt></b> element
preserves space, regardless of the default processing mode.
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
<!ATTLIST pre xml:space nmtoken #fixed preserve>
</pre>
</td></tr>
</table>
</ul>
<p>
<h3><a name="sec:xmlns">XML Namespaces</a></h3>
<p>
Using the <b><em>dialect</em></b> <a name="const:xmlns%2"><b><tt>xmlns</tt></b></a>, the parser will interpret XML
namespaces. In this case, the names of elements are returned as a term
of the format
<blockquote>
<var>URL</var><a name="const::"><b><tt>:</tt></b></a><var>LocalName</var>
</blockquote>
<p>
If an identifier has no namespace and there is no default namespace it
is returned as a simple atom. If an identifier has a namespace but this
namespace is undeclared, the namespace name rather than the related URL
is returned.
<p>
Attributes declaring namespaces (<code>xmlns:<var>ns</var>=<var>url</var></code>)
are reported as if <a name="const:xmlns%3"><b><tt>xmlns</tt></b></a> were not a defined resource.
<p>
In many cases, getting attribute-names as <code><var>url</var>:<var>name</var></code>
is not desirable. Such terms are hard to unify and sometimes multiple
URLs may be mapped to the same identifier. This may happen due to poor
version management, poor standardisation or because the the application
doesn't care too much about versions. This package defines two
call-backs that can be set using <a href="#set_sgml_parser/2"><b>set_sgml_parser/2</b></a> to deal
with this problem.
<p>
The call-back <a name="const:xmlns%4"><b><tt>xmlns</tt></b></a> is called as XML namespaces are noticed.
It can be used to extend a canonical mapping for later use
by the <a name="const:urlns"><b><tt>urlns</tt></b></a> call-back. The following illustrates this behaviour.
Any namespace containing <a name="const:rdf-syntax"><b><tt>rdf-syntax</tt></b></a> in its URL or that is used as
<a name="const:rdf"><b><tt>rdf</tt></b></a> namespace is canonised to <a name="const:rdf%2"><b><tt>rdf</tt></b></a>. This implies that any
attribute and element name from the RDF namespace appears as
<code>rdf:<var>name</var></code>.
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
:- dynamic
xmlns/3.
on_xmlns(rdf, URL, _Parser) :- !,
asserta(xmlns(URL, rdf, _)).
on_xmlns(_, URL, _Parser) :-
sub_atom(URL, _, _, _, 'rdf-syntax'), !,
asserta(xmlns(URL, rdf, _)).
load_rdf_xml(File, Term) :-
load_structure(File, Term,
[ dialect(xmlns),
call(xmlns, on_xmlns),
call(urlns, xmlns)
]).
</pre>
</td></tr>
</table>
<p>
<h2><a name="sec:sec-3.4">DTD-Handling</a></h2>
<p>
The DTD (<b>D</b>ocument <b>T</b>ype <b>D</b>efinition) is a separate
entity in sgml2pl, that can be created, freed, defined and inspected.
Like the parser itself, it is filled by opening it as a Prolog output
stream and sending data to it. This section summarises the predicates
for handling the DTD.
<dl>
<dt> <br>
<b><a name="new_dtd/2">new_dtd(<var>+DocType, -DTD</var>)</a></b><dd>
Creates an empty DTD for the named <var>DocType</var>. The returned
DTD-reference is an opaque term that can be used in the other predicates
of this package.
<dt> <br>
<b><a name="free_dtd/1">free_dtd(<var>+DTD</var>)</a></b><dd>
Deallocate all resources associated to the DTD. Further use of <var>DTD</var>
is invalid.
<dt> <br>
<b><a name="load_dtd/2">load_dtd(<var>+DTD, +File</var>)</a></b><dd>
Define the DTD by loading the SGML-DTD file <var>File</var>. This predicate
is defined using the low-level <a href="#open_dtd/3"><b>open_dtd/3</b></a> predicate:
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
load_dtd(DTD, DtdFile) :-
open_dtd(DTD, [], DtdOut),
open(DtdFile, read, DtdIn),
copy_stream_data(DtdIn, DtdOut),
close(DtdIn),
close(DtdOut).
</pre>
</td></tr>
</table>
<dt> <br>
<b><a name="open_dtd/3">open_dtd(<var>+DTD, +Options, -OutStream</var>)</a></b><dd>
Open a DTD as an output stream. The option-list is currently
empty. See <a href="#load_dtd/2"><b>load_dtd/2</b></a> for an example.
<dt> <br>
<b><a name="dtd/2">dtd(<var>+DocType, -DTD</var>)</a></b><dd>
Find the DTD representing the indicated <b><em>doctype</em></b>. This predicate
uses a cache of DTD objects. If a doctype has no associated dtd, it
searches for a file using the file search path <code>dtd</code> using the call:
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
...,
absolute_file_name(dtd(Type),
[ extensions([dtd]),
access(read)
], DtdFile),
...
</pre>
</td></tr>
</table>
<dt> <br>
<b><a name="dtd_property/2">dtd_property(<var>+DTD, ?Property</var>)</a></b><dd>
This predicate is used to examine the content of a DTD. Property is one
of:
<dl>
<dt> <br>
<b>doctype(<var>DocType</var>)</b><dd>
An atom representing the document-type defined by this DTD.
<dt> <br>
<b>elements(<var>ListOfElements</var>)</b><dd>
A list of atoms representing the names of the elements in this DTD.
<dt> <br>
<b>element(<var>Name, Omit, Content</var>)</b><dd>
The DTD contains an element with the given name. <var>Omit</var> is a term
of the format <code>omit(OmitOpen, OmitClose)</code>, where both
arguments are booleans (<a name="const:true"><b><tt>true</tt></b></a> or <a name="const:false%2"><b><tt>false</tt></b></a> representing whether the
open- or close-tag may be omitted. <var>Content</var> is the content-model
of the element represented as a Prolog term. This term takes the
following form:
<dl>
<dt> <br>
<b><a name="const:empty"><b><tt>empty</tt></b></a></b><dd>
The element has no content.
<dt> <br>
<b><a name="const:cdata"><b><tt>cdata</tt></b></a></b><dd>
The element contains non-parsed character data. All data up to the
matching end-tag is included in the data (<b><em>declared content</em></b>).
<dt> <br>
<b><a name="const:rcdata"><b><tt>rcdata</tt></b></a></b><dd>
As <a name="const:cdata%2"><b><tt>cdata</tt></b></a>, but entity-references are expanded.
<dt> <br>
<b><a name="const:any"><b><tt>any</tt></b></a></b><dd>
The element may contain any number of any element from the DTD in
any order.
<dt> <br>
<b><a name="const:#pcdata"><b><tt>#pcdata</tt></b></a></b><dd>
The element contains parsed character data .
<dt> <br>
<b><var>element</var></b><dd>
An element with this name.
<dt> <br>
<b>*(<var>SubModel</var>)</b><dd>
0 or more appearances.
<dt> <br>
<b>?(<var>SubModel</var>)</b><dd>
0 or one appearance.
<dt> <br>
<b>+(<var>SubModel</var>)</b><dd>
1 or more appearances.
<dt> <br>
<b>,(<var>SubModel1, SubModel2</var>)</b><dd>
<var>SubModel1</var> followed by <var>SubModel2</var>.
<dt> <br>
<b>&(<var>SubModel1, SubModel2</var>)</b><dd>
<var>SubModel1</var> and <var>SubModel2</var> in any order.
<dt> <br>
<b>|(<var>SubModel1, SubModel2</var>)</b><dd>
<var>SubModel1</var> or <var>SubModel2</var>.
</dl>
<dt> <br>
<b>attributes(<var>Element, ListOfAttributes</var>)</b><dd>
<var>ListOfAttributes</var> is a list of atoms representing the attributes
of the element <var>Element</var>.
<dt> <br>
<b>attribute(<var>Element, Attribute, Type, Default</var>)</b><dd>
Query an element. <var>Type</var> is one of <a name="const:cdata%3"><b><tt>cdata</tt></b></a>, <a name="const:entity"><b><tt>entity</tt></b></a>, <a name="const:id"><b><tt>id</tt></b></a>,
<a name="const:idref"><b><tt>idref</tt></b></a>, <a name="const:name"><b><tt>name</tt></b></a>, <a name="const:nmtoken"><b><tt>nmtoken</tt></b></a>, <a name="const:notation"><b><tt>notation</tt></b></a>, <a name="const:number"><b><tt>number</tt></b></a> or
<a name="const:nutoken"><b><tt>nutoken</tt></b></a>. For DTD types that allow for a list, the notation
<code>list(Type)</code> is used. Finally, the DTD construct
<code>(a|b|...)</code> is mapped to the term
<code>nameof(ListOfValues)</code>.
<p>
<var>Default</var> describes the sgml default. It is one <a name="const:required"><b><tt>required</tt></b></a>,
<a name="const:current"><b><tt>current</tt></b></a>, <a name="const:conref"><b><tt>conref</tt></b></a> or <a name="const:implied"><b><tt>implied</tt></b></a>. If a real default is present, it
is one of <code>default(Value)</code> or <code>fixed(Value)</code>.
<dt> <br>
<b>entities(<var>ListOfEntities</var>)</b><dd>
<var>ListOfEntities</var> is a list of atoms representing the names of the
defined entities.
<dt> <br>
<b>entity(<var>Name, Value</var>)</b><dd>
<var>Name</var> is the name of an entity with given value. Value is one of
<dl>
<dt> <br>
<b><var>Atom</var></b><dd>
If the value is atomic, it represents the
literal value of the entity.
<dt> <br>
<b>system(<var>Url</var>)</b><dd>
<var>Url</var> is the URL of the system external entity.
<dt> <br>
<b>public(<var>Id, Url</var>)</b><dd>
For external public entities, <var>Id</var> is the identifier. If an URL is
provided this is returned in <var>Url</var>. Otherwise this argument is
unbound.
</dl>
<dt> <br>
<b>notations(<var>ListOfNotations</var>)</b><dd>
Returns a list holding the names of all <a name="const:NOTATION"><b><tt>NOTATION</tt></b></a> declarations.
<dt> <br>
<b>notation(<var>Name, Decl</var>)</b><dd>
Unify <var>Decl</var> with a list if <code>system(+File)</code> and/or
<code>public(+PublicId)</code>.
</dl>
</dl>
<p>
<h3><a name="sec:sec-3.4.1">The DOCTYPE declaration</a></h3>
<p>
As this parser allows for processing partial documents and process the
DTD separately, the DOCTYPE declaration plays a special role.
<p>
If a document has no DOCTYPE declaraction, the parser returns a list
holding all elements and CDATA found. If the document has a DOCTYPE
declaraction, the parser will open the element defined in the DOCTYPE as
soon as the first real data is encountered.
<p>
<h2><a name="sec:implicitdtd">Extracting a DTD</a></h2>
<p>
Some documents have no DTD. One of the neat facilities of this library
is that it builds a DTD while parsing a document with an <b><em>implicit</em></b> DTD. The resulting DTD contains all elements encountered in
the document. For each element the content model is a disjunction of
elements and possibly <code>#PCDATA</code> that can be repeated. Thus,
if we found element <b><tt>y</tt></b> and CDATA in element <b><tt>x</tt></b>, the model
is:
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
<!ELEMENT x - - (y|#PCDATA)*>
</pre>
</td></tr>
</table>
<p>
Any encountered attribute is added to the attribute list with the type
<a name="const:CDATA%7"><b><tt>CDATA</tt></b></a> and default <a name="const:#IMPLIED"><b><tt>#IMPLIED</tt></b></a>.
<p>
The example below extracts the elements used in an unknown XML document.
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
elements_in_xml_document(File, Elements) :-
load_structure(File, _,
[ dialect(xml),
dtd(DTD)
]),
dtd_property(DTD, elements(Elements)),
free_dtd(DTD).
</pre>
</td></tr>
</table>
<p>
<h2><a name="sec:sec-3.6">Parsing Primitives</a></h2>
<dl>
<dt> <br>
<b><a name="new_sgml_parser/2">new_sgml_parser(<var>-Parser, +Options</var>)</a></b><dd>
Creates a new parser. A parser can be used one or multiple times for
parsing documents or parts thereof. It may be bound to a DTD or the DTD
may be left implicit, in which case it is created from the document
prologue or parsing is performed without a DTD. Options:
<dl>
<dt> <br>
<b>dtd(<var>?DTD</var>)</b><dd>
If specified with an initialised DTD, this DTD is used for parsing the
document, regardless of the document prologue. If specified using as a
variable, a reference to the created DTD is returned. This DTD may be
created from the document prologue or build implicitely from the
document's content.
</dl>
<dt> <br>
<b><a name="free_sgml_parser/1">free_sgml_parser(<var>+Parser</var>)</a></b><dd>
Destroy all resources related to the parser. This does not destroy the
DTD if the parser was created using the <code>dtd(DTD)</code> option.
<dt> <br>
<b><a name="set_sgml_parser/2">set_sgml_parser(<var>+Parser, +Option</var>)</a></b><dd>
Sets attributes to the parser. Currently defined attributes:
<dl>
<dt> <br>
<b>file(<var>File</var>)</b><dd>
Sets the file for reporting errors and warnings. Sets the line to 1.
<dt> <br>
<b>line(<var>Line</var>)</b><dd>
Sets the current line. Useful if the stream is not at the start of the
(file) object for generating proper line-numbers.
<dt> <br>
<b>charpos(<var>Offset</var>)</b><dd>
Sets the current character location. See also the <code>file(File)</code>
option.
<dt> <br>
<b>dialect(<var>Dialect</var>)</b><dd>
Set the markup dialect. Known dialects:
<dl>
<dt> <br>
<b><a name="const:sgml%4"><b><tt>sgml</tt></b></a></b><dd>
The default dialect is to process as SGML. This implies markup is
case-insensitive and standard SGML abbreviation is allowed (abreviated
attributes and omitted tags).
<dt> <br>
<b><a name="const:xml%3"><b><tt>xml</tt></b></a></b><dd>
This dialect is selected automatically if the processing instruction
<code><?xml ...></code> is encountered. See <a href="#sec:xml">xml</a> for details.
<dt> <br>
<b><a name="const:xmlns%5"><b><tt>xmlns</tt></b></a></b><dd>
Process file as XML file with namespace support. See <a href="#sec:xmlns">xmlns</a> for
details.
</dl>
<dt> <br>
<b>space(<var>SpaceMode</var>)</b><dd>
Define the initial handling of white-space in PCDATA. This attribute is
described in <a href="#sec:space">space</a>.
<dt> <br>
<b>number(<var>NumberMode</var>)</b><dd>
If <a name="const:token%2"><b><tt>token</tt></b></a> (default), attributes of type number are passed as a Prolog atom.
If <a name="const:integer%2"><b><tt>integer</tt></b></a>, such attributes are translated into Prolog integers. If
the conversion fails (e.g. due to overflow) a warning is issued and the
value is passed as an atom.
<dt> <br>
<b>doctype(<var>Element</var>)</b><dd>
Defines the toplevel element expected. If a <code><!DOCTYPE</code>
declaration has been parsed, the default is the defined doctype. The
parser can be instructed to accept the first element encountered as the
toplevel using <code>doctype(_)</code>. This feature is especially
useful when parsing part of a document (see the <a name="const:parse"><b><tt>parse</tt></b></a> option to
<a href="#sgml_parse/2"><b>sgml_parse/2</b></a>.
</dl>
<dt> <br>
<b><a name="get_sgml_parser/2">get_sgml_parser(<var>+Parser, -Option</var>)</a></b><dd>
Retrieve infomation on the current status of the parser. Notably useful
if the parser is used in the call-back mode. Currently defined options:
<dl>
<dt> <br>
<b>file(<var>-File</var>)</b><dd>
Current file-name. Note that this may be different from the provided
file if an external entity is being loaded.
<dt> <br>
<b>charpos(<var>-CharPos</var>)</b><dd>
Offset from where the parser started its processing in the file-object.
See <a href="#sec:indexaccess">indexaccess</a>.
<dt> <br>
<b>charpos(<var>-Start, -End</var>)</b><dd>
Character offsets of the start and end of the source processed causing the
current call-back. Used in <b>PceEmacs</b> to for colouring text in
SGML and XML modes.
<dt> <br>
<b>source(<var>-Stream</var>)</b><dd>
Prolog stream being processed. May be used in the <a name="const:on_begin"><b><tt>on_begin</tt></b></a>, <em>etc.</em>
callbacks from <a href="#sgml_parse/2"><b>sgml_parse/2</b></a>.
<dt> <br>
<b>dialect(<var>-Dialect</var>)</b><dd>
Return the current dialect used by the parser (<a name="const:sgml%5"><b><tt>sgml</tt></b></a>, <a name="const:xml%4"><b><tt>xml</tt></b></a> or <a name="const:xmlns%6"><b><tt>xmlns</tt></b></a>).
<dt> <br>
<b>event_class(<var>-Class</var>)</b><dd>
The <b><em>event class</em></b> can be requested in call-back events. It
denotes the cause of the event, providing useful information for syntax
highlighting. Defined values are:
<dl>
<dt> <br>
<b><a name="const:explicit"><b><tt>explicit</tt></b></a></b><dd>
The code generating this event is explicitely present in the
document.
<dt> <br>
<b><a name="const:omitted"><b><tt>omitted</tt></b></a></b><dd>
The current event is caused by the insertion of an omitted tag.
This may be a normal event in SGML mode or an error in XML mode.
<dt> <br>
<b><a name="const:shorttag"><b><tt>shorttag</tt></b></a></b><dd>
The current event (<a name="const:begin"><b><tt>begin</tt></b></a> or <a name="const:end"><b><tt>end</tt></b></a>) is caused by an
element written down using the <b><em>shorttag</em></b> notation
(<code><tag/value/></code>.
<dt> <br>
<b><a name="const:shortref"><b><tt>shortref</tt></b></a></b><dd>
The current event is caused by the expansion of a
<b><em>shortref</em></b>. This allows for highlighting shortref strings
in the source-text.
</dl>
<dt> <br>
<b>doctype(<var>-Element</var>)</b><dd>
Return the defined document-type (= toplevel element). See also
<a href="#set_sgml_parser/2"><b>set_sgml_parser/2</b></a>.
<dt> <br>
<b>dtd(<var>-DTD</var>)</b><dd>
Return the currently used DTD. See dtd_property/2 for obtaining information
on the DTD such as element and attribute properties.
<dt> <br>
<b>context(<var>-StackOfElements</var>)</b><dd>
Returns the stack of currently open elements as a list. The head of this
list is the current element. This can be used to determine the context
of, for example, CDATA events in call-back mode. The elements
are passed as atoms. Currently no access to the attributes is provided.
<dt> <br>
<b>allowed(<var>-Elements</var>)</b><dd>
Determines which elements may be inserted at the current location. This
information is returned as a list of element-names. If character data is
allowed in the current location, <a name="const:#pcdata%2"><b><tt>#pcdata</tt></b></a> is part of <var>Elements</var>.
If no element is open, the <b><em>doctype</em></b> is returned.
<p>
This option is intended to support syntax-sensitive editors. Such an
editor should load the DTD, find an appropriate starting point and then
feed all data between the starting point and the caret into the parser.
Next it can use this option to determine the elements allowed at this
point. Below is a code fragment illustrating this use given a parser
with loaded DTD, an input stream and a start-location.
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
...,
seek(In, Start, bof, _),
set_sgml_parser(Parser, charpos(Start)),
set_sgml_parser(Parser, doctype(_)),
Len is Caret - Start,
sgml_parse(Parser,
[ source(In),
content_length(Len),
parse(input) % do not complete document
]),
get_sgml_parser(Parser, allowed(Allowed)),
...
</pre>
</td></tr>
</table>
</dl>
<p>
<dt> <br>
<b><a name="sgml_parse/2">sgml_parse(<var>+Parser, +Options</var>)</a></b><dd>
Parse an XML file. The parser can operate in two input and two output
modes. Output is either a structured term as described with
<a href="#load_structure/2"><b>load_structure/2</b></a> or call-backs on predefined events. The
first is especially suitable for manipulating not-too-large documents,
while the latter provides a primitive means for handling very large
documents.
<p>
Input is a stream. A full description of the option-list is below.
<dl>
<dt> <br>
<b>document(<var>+Term</var>)</b><dd>
A variable that will be unified with a list describing the content of
the document (see <a href="#load_structure/2"><b>load_structure/2</b></a>).
<dt> <br>
<b>source(<var>+Stream</var>)</b><dd>
An input stream that is read. This option <em>must</em> be given.
<dt> <br>
<b>content_length(<var>+Characters</var>)</b><dd>
Stop parsing after <var>Characters</var>. This option is useful to parse
input embedded in <em>envelopes</em>, such as the HTTP protocol.
<dt> <br>
<b>parse(<var>Unit</var>)</b><dd>
Defines how much of the input is parsed. This option is used to parse
only parts of a file.
<dl>
<dt> <br>
<b><a name="const:file"><b><tt>file</tt></b></a></b><dd>
Default. Parse everything upto the end of the input.
<dt> <br>
<b><a name="const:element"><b><tt>element</tt></b></a></b><dd>
The parser stops after reading the first element. Using <code>source(Stream)</code>, this implies reading is stopped as soon as the
element is complete, and another call may be issued on the same stream
to read the next element.
<dt> <br>
<b><a name="const:content"><b><tt>content</tt></b></a></b><dd>
The value <a name="const:content%2"><b><tt>content</tt></b></a> is like <a name="const:element%2"><b><tt>element</tt></b></a> but assumes the element has
already been opened. It may be used in a call-back from
<code>call(<a name="const:on_begin%2"><b><tt>on_begin</tt></b></a>, Pred)</code> to parse individual elements after
validating their headers.
<dt> <br>
<b><a name="const:declaration"><b><tt>declaration</tt></b></a></b><dd>
This may be used to stop the parser after reading the first
declaration. This is especially useful to parse only the <code>doctype</code>
declaration.
<dt> <br>
<b><a name="const:input"><b><tt>input</tt></b></a></b><dd>
This option is intended to be used in conjunction with the
<code>allowed(Elements)</code> option of <a href="#get_sgml_parser/2"><b>get_sgml_parser/2</b></a>.
It disables the parser's default to complete the parse-tree by closing
all open elements.
</dl>
<dt> <br>
<b>max_errors(<var>+MaxErrors</var>)</b><dd>
Set the maximum number of errors. If this number is exceeded further
writes to the stream will yield an I/O error exception. Printing of
errors is suppressed after reaching this value. The default is 100.
<dt> <br>
<b>syntax_errors(<var>+ErrorMode</var>)</b><dd>
Defines how syntax errors are handled.
<dl>
<dt> <br>
<b>print</b><dd>
Default. Pass messages to <b>print_message/2</b>.
<dt> <br>
<b>quiet</b><dd>
Suppress all messages.
</dl>
<dt> <br>
<b>call(<var>+Event, :PredicateName</var>)</b><dd>
Issue call-backs on the specified events. <var>PredicateName</var> is the
name of the predicate to call on this event, possibly prefixed with a
module identifier. The defined events are:
<dl>
<dt> <br>
<b>begin</b><dd>
An open-tag has been parsed. The named handler is called with three
arguments: <code><var>Handler</var>(+Tag, +Attributes, +Parser)</code>.
<dt> <br>
<b>end</b><dd>
A close-tag has been parsed. The named handler is called with two
arguments: <code><var>Handler</var>(+Tag, +Parser)</code>.
<dt> <br>
<b>cdata</b><dd>
CDATA has been parsed. The named handler is called with two arguments: <code><var>Handler</var>(+CDATA, +Parser)</code>, where CDATA is an atom representing
the data.
<dt> <br>
<b>entity</b><dd>
An entity that cannot be represented as CDATA has been parsed. The named
handler is called with two arguments: <code><var>Handler</var>(+NameOrCode,
+Parser)</code>.
<dt> <br>
<b>pi</b><dd>
A processing instruction has been parsed. The named handler is called
with two arguments: <code><var>Handler</var>(+Text, +Parser)</code>, where
<var>Text</var> is the text of the processing instruction.
<dt> <br>
<b>decl</b><dd>
A declaration (<code><!...></code>) has been read. The named handler is
called with two arguments: <code><var>Handler</var>(+Text, +Parser)</code>,
where <var>Text</var> is the text of the declaration with comments removed.
<p>
This option is expecially useful for highlighting declarations and comments in
editor support, where the location of the declaration is extracted using
<a href="#get_sgml_parser/2"><b>get_sgml_parser/2</b></a>.
<dt> <br>
<b>error</b><dd>
An error has been encountered. the named handler is called with three
arguments: <code><var>Handler</var>(+Severity, +Message, +Parser)</code>, where
<var>Severity</var> is one of <a name="const:warning"><b><tt>warning</tt></b></a> or <a name="const:error"><b><tt>error</tt></b></a> and <var>Message</var> is
an atom representing the diagnostic message. The location of the error
can be determined using <a href="#get_sgml_parser/2"><b>get_sgml_parser/2</b></a>
<p>
If this option is present, errors and warnings are not reported using
<b>print_message/3</b>
<dt> <br>
<b>xmlns</b><dd>
When parsing an in <a name="const:xmlns%7"><b><tt>xmlns</tt></b></a> mode, a new namespace declaraction is
pushed on the environment. The named handler is called with three
arguments: <code><var>Handler</var>(+NameSpace, +URL, +Parser)</code>.
See <a href="#sec:xmlns">xmlns</a> for details.
<dt> <br>
<b>urlns</b><dd>
When parsing an in <a name="const:xmlns%8"><b><tt>xmlns</tt></b></a> mode, this predicate can be used to map a
url into either a canonical URL for this namespace or another internal
identifier. See <a href="#sec:xmlns">xmlns</a> for details.
</dl>
</dl>
</dl>
<p>
<h3><a name="sec:sec-3.6.1">Partial Parsing</a></h3>
<p>
In some cases, part of a document needs to be parsed. One option is to
use <a href="#load_structure/2"><b>load_structure/2</b></a> or one of its variations and extract
the desired elements from the returned structure. This is a clean
solution, especially on small and medium-sized documents. It however is
unsuitable for parsing really big documents. Such documents can only be
handled with the call-back output interface realised by the
<code>call(Event, Action)</code> option of <a href="#sgml_parse/2"><b>sgml_parse/2</b></a>.
Event-driven processing is not very natural in Prolog.
<p>
The SGML2PL library allows for a mixed approach. Consider the case where
we want to process all descriptions from RDF elements in a document. The
code below calls <code>process_rdf_description(Element)</code> on each element
that is directly inside an RDF element.
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
:- dynamic
in_rdf/0.
load_rdf(File) :-
retractall(in_rdf),
open(File, read, In),
new_sgml_parser(Parser, []),
set_sgml_parser(Parser, file(File)),
set_sgml_parser(Parser, dialect(xml)),
sgml_parse(Parser,
[ source(In),
call(begin, on_begin),
call(end, on_end)
]),
close(In).
on_end('RDF', _) :-
retractall(in_rdf).
on_begin('RDF', _, _) :-
assert(in_rdf).
on_begin(Tag, Attr, Parser) :-
in_rdf, !,
sgml_parse(Parser,
[ document(Content),
parse(content)
]),
process_rdf_description(element(Tag, Attr, Content)).
</pre>
</td></tr>
</table>
<p>
<h1><a name="sec:indexaccess">Processing Indexed Files</a></h1>
<p>
In some cases applications which to process small portions of large
SGML, XML or RDF files. For example, the <em>OpenDirectory</em> project
by Netscape has produced a 90MB RDF file representing the main index.
The parser described here can process this document as a unit, but
loading takes 85 seconds on a Pentium-II 450 and the resulting term
requires about 70MB global stack. One option is to process the entire
document and output it as a Prolog fact-base of RDF triplets, but in
many cases this is undesirable. Another example is a large SGML file
containing online documentation. The application normally wishes to
provide only small portions at a time to the user. Loading the entire
document into memory is then undesirable.
<p>
Using the <code>parse(element)</code> option, we open a file, seek
(using <b>seek/4</b>) to the position of the element and
read the desired element.
<p>
The index can be built using the call-back interface of
<a href="#sgml_parse/2"><b>sgml_parse/2</b></a>. For example, the following code makes an
index of the <b> structure.rdf</b> file of the OpenDirectory
project:
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
:- dynamic
location/3. % Id, File, Offset
rdf_index(File) :-
retractall(location(_,_)),
open(File, read, In, [type(binary)]),
new_sgml_parser(Parser, []),
set_sgml_parser(Parser, file(File)),
set_sgml_parser(Parser, dialect(xml)),
sgml_parse(Parser,
[ source(In),
call(begin, index_on_begin)
]),
close(In).
index_on_begin(_Element, Attributes, Parser) :-
memberchk('r:id'=Id, Attributes),
get_sgml_parser(Parser, charpos(Offset)),
get_sgml_parser(Parser, file(File)),
assert(location(Id, File, Offset)).
</pre>
</td></tr>
</table>
<p>
The following code extracts the RDF element with required id:
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
rdf_element(Id, Term) :-
location(Id, File, Offset),
load_structure(File, Term,
[ dialect(xml),
offset(Offset),
parse(element)
]).
</pre>
</td></tr>
</table>
<p>
<h1><a name="sec:sec-5">External entities</a></h1>
<p>
While processing an SGML document the document may refer to external
data. This occurs in three places: external parameter entities, normal
external entities and the <a name="const:DOCTYPE"><b><tt>DOCTYPE</tt></b></a> declaration. The current version
of this tool deals rather primitively with external data. External
entities can only be loaded from a file and the mapping between the
entity names and the file is done using a <b><em>catalog</em></b> file in a
format compatible with that used by James Clark's SP Parser,
based on the SGML Open (now OASIS) specification.
<p>
Catalog files can be specified using two primitives: the predicate
<a href="#sgml_register_catalog_file/2"><b>sgml_register_catalog_file/2</b></a> or the environment variable
<b>SGML_CATALOG_FILES</b> (compatible with the SP package).
<dl>
<dt> <br>
<b><a name="sgml_register_catalog_file/2">sgml_register_catalog_file(<var>+File, +Location</var>)</a></b><dd>
Register the indicated <var>File</var> as a catalog file. <var>Location</var> is
either <a name="const:start"><b><tt>start</tt></b></a> or <a name="const:end%2"><b><tt>end</tt></b></a> and defines whether the catalog is
considered first or last. This predicate has no effect if <var>File</var> is
already part of the catalog.
<p>
If no files are registered using this predicate, the first query on the
catalog examines <b>SGML_CATALOG_FILES</b> and fills the catalog with
all files in this path.
</dl>
<p>
Two types of lines are used by this package.
<p>
<pre>
<a name="const:DOCTYPE%2"><b><tt>DOCTYPE</tt></b></a> <var>doctype</var> <var>file</var>
<a name="const:PUBLIC"><b><tt>PUBLIC</tt></b></a> <code>"</code><var>Id</var><code>"</code> <var>file</var>
</pre>
<p>
The specified <var>file</var> path is taken relative to the location of the
catolog file. For the <a name="const:DOCTYPE%3"><b><tt>DOCTYPE</tt></b></a> declaraction, <b>sgml2pl</b> first makes
an attempt to resolve the <a name="const:SYSTEM"><b><tt>SYSTEM</tt></b></a> or <a name="const:PUBLIC%2"><b><tt>PUBLIC</tt></b></a> identifier. If this
fails it tries to resolve the <var>doctype</var> using the provided catalog
files.
<p>
Strictly speaking, <b>sgml2pl</b> breaks the rules for XML, where
system identifiers must be Universal Resource Indicators, not local file
names. Simple uses of relative URIs will work correctly under UNIX
and Windows.
<p>
In the future we will design a call-back mechanism for locating and
processing external entities, so Prolog-based file-location and Prolog
resources can be used to store external entities.
<p>
<h1><a name="sec:sec-6">Unsupported features</a></h1>
<p>
The current parser is rather limited. While it is able to deal with many
serious documents, it omits several less-used features of SGML and XML.
Known missing SGML features include
<ul>
<li><em>NOTATION on entities</em><br>
Though notation is parsed, notation attributes on external entity
declarations are not handed to the user.
<li><em>NOTATION attributes</em><br>
SGML notations may have attributes, declared using
<code><!ATTLIST #NOTATION name attributes></code>. Those data attributes
are provided when you declare an external CDATA, NDATA, or SDATA entity.
<p>
XML does not include external CDATA, NDATA, or SDATA entities,
nor any of the other uses to which data attributes are put in SGML,
so it doesn't include data attributes for notations either.
<p>
Sgml2pl does not support this feature and is unlikely to;
you should be aware that SGML documents using this feature cannot
be converted faithfully to XML.
<li><em>SHORTTAG</em><br>
The SGML SHORTTAG syntax is only partially implemented. Currently,
<code><tag/content/</code> is a valid abbreviation for
<code><tag>content</tag></code>, which can also be written as
<code><tag>content</></code>.
Empty start tags (<code><></code>), unclosed start tags
(<code><a<b</code>) and unclosed end tags (<code></a<b</code>) are not
supported.
<li><em>SGML declaration</em><br>
The `SGML declaration' is fixed, though most of the parameters are
handled through indirections in the implementation.
<li><em>The DATATAG feature</em><br>
It is regarded as superseeded by SHORTREF, which is supported.
(SP does not support it either.)
<li><em>The RANK feature</em><br>
It is regarded as obsolete.
<li><em>The LINK feature</em><br>
It is regarded as too complicated.
<li><em>The CONCUR feature</em><br>
Concurrent markup allows a document to be tagged according to more than
one DTD at the same time. It is not supported.
</ul>
<p>
In XML mode the parser recognises SGML constructs that are not allowed
in XML. Also various extensions of XML over SGML are not yet realised.
In particular, XInclude is not implemented because the designers of
XInclude can't make up their minds whether to base it on elements or
attributes yet, let alone details.
<p>
<h1><a name="sec:sec-7">Installation</a></h1>
<p>
<h2><a name="sec:sec-7.1">Unix systems</a></h2>
<p>
Installation on Unix system uses the commonly found <code>configure</code>,
<code>make</code> and <code>make install</code> sequence. SWI-Prolog should be
installed before building this package. If SWI-Prolog is not installed
as <b>pl</b>, the environment variable <b>PL</b> must be set to
the name of the SWI-Prolog executable. Installation is now accomplished
using:
<p>
<table width="90%" align="center" border="2" bgcolor="#f0f0f0">
<tr><td>
<pre>
% ./configure
% make
% make install
</pre>
</td></tr>
</table>
<p>
This installs the foreign libraries in <b>$PLBASE/lib/$PLARCH</b> and
the Prolog library files in <b>$PLBASE/library</b>, where
<b>$PLBASE</b> refers to the SWI-Prolog `home-directory'.
<p>
<h1><a name="sec:sec-8">Acknowledgements</a></h1>
<p>
The Prolog representation for parsed documents is based on the
SWI-Prolog interface to SP by Anjo Anjewierden.
<p>
Richard O'Keefe has put a lot of effort testing and providing bug
reports consisting of an illustrative example and explanation of the
standard. He also made many suggestions for improving this document.
<h1><a name="Summary">Summary of Predicates</a></h1>
<table border="2">
<tr><td><a href="#dtd/2"><b>dtd/2</b></a></td><td>Find or build a DTD for a document type</td></tr>
<tr><td><a href="#dtd_property/2"><b>dtd_property/2</b></a></td><td>Query elements, entities and attributes in a DTD</td></tr>
<tr><td><a href="#free_dtd/1"><b>free_dtd/1</b></a></td><td>Free a DTD object</td></tr>
<tr><td><a href="#free_sgml_parser/1"><b>free_sgml_parser/1</b></a></td><td>Destroy a parser</td></tr>
<tr><td><a href="#get_sgml_parser/2"><b>get_sgml_parser/2</b></a></td><td>Get parser options</td></tr>
<tr><td><a href="#load_dtd/2"><b>load_dtd/2</b></a></td><td>Read DTD information from a file</td></tr>
<tr><td><a href="#load_html_file/2"><b>load_html_file/2</b></a></td><td>Parse HTML file into Prolog term</td></tr>
<tr><td><a href="#load_sgml_file/2"><b>load_sgml_file/2</b></a></td><td>Parse SGML file into Prolog term </td></tr>
<tr><td><a href="#load_structure/3"><b>load_structure/3</b></a></td><td>Parse XML/SGML/HTML file into Prolog term</td></tr>
<tr><td><a href="#load_xml_file/2"><b>load_xml_file/2</b></a></td><td>Parse XML file into Prolog term</td></tr>
<tr><td><a href="#new_dtd/2"><b>new_dtd/2</b></a></td><td>Create a DTD object</td></tr>
<tr><td><a href="#new_sgml_parser/2"><b>new_sgml_parser/2</b></a></td><td>Create a new parser</td></tr>
<tr><td><a href="#open_dtd/3"><b>open_dtd/3</b></a></td><td>Open a DTD object as an output stream</td></tr>
<tr><td><a href="#set_sgml_parser/2"><b>set_sgml_parser/2</b></a></td><td>Set parser options (dialect, source, <em>etc.</em>)</td></tr>
<tr><td><a href="#sgml_parse/2"><b>sgml_parse/2</b></a></td><td>Parse the input</td></tr>
<tr><td><a href="#sgml_register_catalog_file/2"><b>sgml_register_catalog_file/2</b></a></td><td>Register a catalog file</td></tr>
</table>
<h1>Footnotes</h1>
<dl>
<dt><a href="#txt:fn-1" name="fn-1">1</a><dd>
In
addition, newlines at the end of lines containing only markup should be
deleted. This is not yet implemented.
</dl>
<h1>Index</h1>
<ul>
<li><a href="#const:#IMPLIED"><b><tt>#IMPLIED</tt></b></a>
<li><a href="#const:#pcdata"><b><tt>#pcdata</tt></b></a> [ <a href="#const:#pcdata%2">2</a>]
<li><a href="#const:-"><b><tt>-</tt></b></a>
<li><a href="#const:/"><b><tt>/</tt></b></a> [ <a href="#const:/%2">2</a>]
<li><a href="#const:/>"><b><tt>/></tt></b></a>
<li><a href="#const::"><b><tt>:</tt></b></a>
<li><a href="#const:CDATA"><b><tt>CDATA</tt></b></a> [ <a href="#const:CDATA%2">2</a> <a href="#const:CDATA%3">3</a> <a href="#const:CDATA%4">4</a> <a href="#const:CDATA%5">5</a> <a href="#const:CDATA%6">6</a> <a href="#const:CDATA%7">7</a>]
<li><a href="#const:DOCTYPE"><b><tt>DOCTYPE</tt></b></a> [ <a href="#const:DOCTYPE%2">2</a> <a href="#const:DOCTYPE%3">3</a>]
<li><a href="#const:NAMES"><b><tt>NAMES</tt></b></a>
<li><a href="#const:NDATA"><b><tt>NDATA</tt></b></a>
<li><a href="#const:NOTATION"><b><tt>NOTATION</tt></b></a>
<li><a href="#const:NUMBER"><b><tt>NUMBER</tt></b></a> [ <a href="#const:NUMBER%2">2</a>]
<li><a href="#const:NUMBERS"><b><tt>NUMBERS</tt></b></a> [ <a href="#const:NUMBERS%2">2</a>]
<li><a href="#const:PUBLIC"><b><tt>PUBLIC</tt></b></a> [ <a href="#const:PUBLIC%2">2</a>]
<li><a href="#const:SDATA"><b><tt>SDATA</tt></b></a>
<li><a href="#const:SYSTEM"><b><tt>SYSTEM</tt></b></a>
<li><a href="#const:amp"><b><tt>amp</tt></b></a>
<li><a href="#const:any"><b><tt>any</tt></b></a>
<li><a href="#const:apos"><b><tt>apos</tt></b></a>
<li><a href="#const:begin"><b><tt>begin</tt></b></a>
<li><a href="#const:cdata"><b><tt>cdata</tt></b></a> [ <a href="#const:cdata%2">2</a> <a href="#const:cdata%3">3</a>]
<li><a href="#const:conref"><b><tt>conref</tt></b></a>
<li><a href="#const:content"><b><tt>content</tt></b></a> [ <a href="#const:content%2">2</a>]
<li><a href="#const:current"><b><tt>current</tt></b></a>
<li><a href="#const:declaration"><b><tt>declaration</tt></b></a>
<li><a href="#const:default"><b><tt>default</tt></b></a> [ <a href="#const:default%2">2</a> <a href="#const:default%3">3</a>]
<li><a href="#dtd/2"><b>dtd/2</b></a>
<li><a href="#dtd_property/2"><b>dtd_property/2</b></a>
<li><a href="#const:element"><b><tt>element</tt></b></a> [ <a href="#const:element%2">2</a>]
<li><a href="#const:empty"><b><tt>empty</tt></b></a>
<li><a href="#const:end"><b><tt>end</tt></b></a> [ <a href="#const:end%2">2</a>]
<li><a href="#const:entity"><b><tt>entity</tt></b></a>
<li><a href="#const:error"><b><tt>error</tt></b></a>
<li><a href="#const:explicit"><b><tt>explicit</tt></b></a>
<li><a href="#const:false"><b><tt>false</tt></b></a> [ <a href="#const:false%2">2</a>]
<li><a href="#const:file"><b><tt>file</tt></b></a>
<li><a href="#const:fixed"><b><tt>fixed</tt></b></a>
<li><a href="#free_dtd/1"><b>free_dtd/1</b></a>
<li><a href="#free_sgml_parser/1"><b>free_sgml_parser/1</b></a>
<li><a href="#get_sgml_parser/2"><b>get_sgml_parser/2</b></a>
<li><a href="#const:gt"><b><tt>gt</tt></b></a>
<li><a href="#const:id"><b><tt>id</tt></b></a>
<li><a href="#const:idref"><b><tt>idref</tt></b></a>
<li><a href="#const:implied"><b><tt>implied</tt></b></a>
<li><a href="#const:input"><b><tt>input</tt></b></a>
<li><a href="#const:integer"><b><tt>integer</tt></b></a> [ <a href="#const:integer%2">2</a>]
<li><a href="#load_dtd/2"><b>load_dtd/2</b></a>
<li><a href="#load_html_file/2"><b>load_html_file/2</b></a>
<li><a href="#load_sgml_file/2"><b>load_sgml_file/2</b></a>
<li><a href="#load_structure/3"><b>load_structure/3</b></a>
<li><a href="#load_xml_file/2"><b>load_xml_file/2</b></a>
<li><a href="#const:lt"><b><tt>lt</tt></b></a>
<li><a href="#const:name"><b><tt>name</tt></b></a>
<li><a href="#new_dtd/2"><b>new_dtd/2</b></a>
<li><a href="#new_sgml_parser/2"><b>new_sgml_parser/2</b></a>
<li><a href="#const:nmtoken"><b><tt>nmtoken</tt></b></a>
<li><a href="#const:notation"><b><tt>notation</tt></b></a>
<li><a href="#const:number"><b><tt>number</tt></b></a>
<li><a href="#const:nutoken"><b><tt>nutoken</tt></b></a>
<li><a href="#const:omitted"><b><tt>omitted</tt></b></a>
<li><a href="#const:on_begin"><b><tt>on_begin</tt></b></a> [ <a href="#const:on_begin%2">2</a>]
<li><a href="#open_dtd/3"><b>open_dtd/3</b></a>
<li><a href="#const:parse"><b><tt>parse</tt></b></a>
<li><a href="#const:preserve"><b><tt>preserve</tt></b></a> [ <a href="#const:preserve%2">2</a>]
<li><a href="#const:quot"><b><tt>quot</tt></b></a>
<li><a href="#const:rcdata"><b><tt>rcdata</tt></b></a>
<li><a href="#const:rdf"><b><tt>rdf</tt></b></a> [ <a href="#const:rdf%2">2</a>]
<li><a href="#const:rdf-syntax"><b><tt>rdf-syntax</tt></b></a>
<li><a href="#const:remove"><b><tt>remove</tt></b></a>
<li><a href="#const:required"><b><tt>required</tt></b></a>
<li><a href="#set_sgml_parser/2"><b>set_sgml_parser/2</b></a>
<li><a href="#const:sgml"><b><tt>sgml</tt></b></a> [ <a href="#const:sgml%2">2</a> <a href="#const:sgml%3">3</a> <a href="#const:sgml%4">4</a> <a href="#const:sgml%5">5</a>]
<li><a href="#sgml_parse/2"><b>sgml_parse/2</b></a>
<li><a href="#sgml_register_catalog_file/2"><b>sgml_register_catalog_file/2</b></a>
<li><a href="#const:shortref"><b><tt>shortref</tt></b></a>
<li><a href="#const:shorttag"><b><tt>shorttag</tt></b></a>
<li><a href="#const:start"><b><tt>start</tt></b></a>
<li><a href="#const:token"><b><tt>token</tt></b></a> [ <a href="#const:token%2">2</a>]
<li><a href="#const:true"><b><tt>true</tt></b></a>
<li><a href="#const:urlns"><b><tt>urlns</tt></b></a>
<li><a href="#const:warning"><b><tt>warning</tt></b></a>
<li><a href="#const:xml"><b><tt>xml</tt></b></a> [ <a href="#const:xml%2">2</a> <a href="#const:xml%3">3</a> <a href="#const:xml%4">4</a>]
<li><a href="#const:xmlns"><b><tt>xmlns</tt></b></a> [ <a href="#const:xmlns%2">2</a> <a href="#const:xmlns%3">3</a> <a href="#const:xmlns%4">4</a> <a href="#const:xmlns%5">5</a> <a href="#const:xmlns%6">6</a> <a href="#const:xmlns%7">7</a> <a href="#const:xmlns%8">8</a>]
</ul>
</body>
</html>
|
