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1	/* xml.pl : Contains parse/[2,3] a bi-directional XML parser written in
2	* Prolog.
3	*
4	* Copyright (C) 2001-2005 Binding Time Limited
5	* Copyright (C) 2005, 2006 John Fletcher
6	*
7	* Current Release: $Revision: 2.0 $
8	*
9	* TERMS AND CONDITIONS:
10	*
11	* This program is offered free of charge, as unsupported source code. You may
12	* use it, copy it, distribute it, modify it or sell it without restriction,
13	* but entirely at your own risk.
14	*
15	*/
16
17	:- object(xml).
18
19	:- info([
20	version is 2.0,
21	author is 'John Fletcher',
22	date is 2006/11/2,
23	copyright is 'Copyright (C) 2001-2005 Binding Time Limited, Copyright (C) 2005, 2006 John Fletcher',
24	license is 'The code has been placed into the public domain, to encourage the use of Prolog with XML. This program is offered free of charge, as unsupported source code. You may use it, copy it, distribute it, modify it or sell it without restriction, but entirely at your own risk.',
25	comment is 'Bi-directional XML parser.',
26	remarks is [
27	'On-line documentation:' - 'http://www.zen37763.zen.co.uk/xml.pl.html',
28	'Compliance:' - 'This XML parser supports a subset of XML suitable for XML Data and Worldwide Web applications. It is neither as strict nor as comprehensive as the XML 1.0 Specification mandates. It is not as strict, because, while the specification must eliminate ambiguities, not all errors need to be regarded as faults, and some reasonable examples of real XML usage would have to be rejected if they were. It is not as comprehensive, because, where the XML specification makes provision for more or less complete DTDs to be provided as part of a document, xml.pl actions the local definition of ENTITIES only. Other DTD extensions are treated as commentary.',
29	'Bi-directional conversions:' - 'The conversions are not completely symmetrical, in that weaker XML is accepted than can be generated. Specifically, in-bound (Chars -> Document) parsing does not require strictly well-formed XML. If Chars does not represent well-formed XML, Document is instantiated to the term malformed(<attributes>, <content>).'
30	]]).
31
32	:- public(parse/2).
33	:- mode(parse(+nonvar, ?nonvar), zero_or_one).
34	:- mode(parse(?nonvar, +nonvar), zero_or_one).
35	:- info(parse/2, [
36	comment is 'Parses Chars to/from a data structure of the form xml(<atts>, <content>).',
37	argnames is ['Chars', 'Document']]).
38
39	:- public(parse/3).
40	:- mode(parse(+nonvar, +nonvar, ?nonvar), zero_or_one).
41	:- mode(parse(+nonvar, ?nonvar, +nonvar), zero_or_one).
42	:- info(parse/3, [
43	comment is 'Parses Chars to/from a data structure of the form xml(<atts>, <content>).',
44	argnames is ['Controls', 'Chars', 'Document']]).
45
46	:- public(subterm/2).
47	:- mode(subterm(+nonvar, ?nonvar), zero_or_one).
48	:- info(subterm/2, [
49	comment is 'Unifies Subterm with a sub-term of XMLTerm. Note that XMLTerm is a sub-term of itself.',
50	argnames is ['XMLTerm', 'Subterm']]).
51
52	:- public(pp/1).
53	:- mode(pp(+nonvar), zero_or_one).
54	:- info(pp/1, [
55	comment is 'Pretty prints a XML document on the current output stream.',
56	argnames is ['XMLDocument']]).
57
58	:- uses(list, [append/3, member/2, select/3, valid/1::is_list/1]).
59	:- uses(term, [ground/1]).
60
61	/* parse( {+Controls}, +?Chars, ?+Document ) parses Chars to/from a data
62	* structure of the form xml(<atts>, <content>). <atts> is a list of
63	* <atom>=<string> attributes from the (possibly implicit) XML signature of the
64	* document. <content> is a (possibly empty) list comprising occurrences of :
65	*
66	* pcdata(<string>) : Text
67	* comment(<string>) : An xml comment;
68	* element(<tag>,<atts>,<content>) : <tag>..</tag> encloses <content>
69	* : <tag /> if empty
70	* instructions(<atom>, <string>) : Processing <? <atom> <params> ?>"
71	* cdata( <string> ) : <![CDATA[ <string> ]]>
72	* doctype(<atom>, <doctype id>) : DTD <!DOCTYPE .. >
73	*
74	* The conversions are not completely symmetrical, in that weaker XML is
75	* accepted than can be generated. Specifically, in-bound (Chars -> Document)
76	* does not require strictly well-formed XML. Document is instantiated to the
77	* term malformed(Attributes, Content) if Chars does not represent well-formed
78	* XML. The Content of a malformed/2 structure can contain:
79	*
80	* unparsed( <string> ) : Text which has not been parsed
81	* out_of_context( <tag> ) : <tag> is not closed
82	*
83	* in addition to the standard term types.
84	*
85	* Out-bound (Document -> Chars) parsing _does_ require that Document defines
86	* strictly well-formed XML. If an error is detected a 'domain' exception is
87	* raised.
88	*
89	* The domain exception will attempt to identify the particular sub-term in
90	* error and the message will show a list of its ancestor elements in the form
91	* <tag>{(id)}* where <id> is the value of any attribute _named_ id.
92	*
93	* At this release, the Controls applying to in-bound (Chars -> Document)
94	* parsing are:
95	*
96	* extended_characters(<bool>) : Use the extended character
97	* : entities for XHTML (default true)
98	*
99	* format(<bool>) : Strip layouts when no character data
100	* : appears between elements.
101	* : (default true)
102	*
103	* remove_attribute_prefixes(<bool>) : Remove namespace prefixes from
104	* : attributes when it's the same as the
105	* : prefix of the parent element
106	* : (default false).
107	*
108	* allow_ampersand(<bool>) : Allow unescaped ampersand
109	* : characters (&) to occur in PCDATA.
110	* : (default false).
111	*
112	* [<bool> is one of 'true' or 'false']
113	*
114	* For out-bound (Document -> Chars) parsing, the only available option is:
115	*
116	* format(<Bool>) : Indent the element content
117	* : (default true)
118	*
119	* Different DCGs for input and output are used because input parsing is
120	* more flexible than output parsing. Errors in input are recorded as part
121	* of the data structure. Output parsing throws an exception if the document
122	* is not well-formed, diagnosis tries to identify the specific culprit term.
123	*/
124	parse( Chars, Document ) :-
125	parse( [], Chars, Document ).
126
127	parse( Controls, Chars, Document ) :-
128	( ground( Chars ) ->
129	xml_to_document( Controls, Chars, Document )
130	; document_to_xml( Controls, Document, Chars )
131	).
132
133	document_to_xml( Controls, Document, Chars ) :-
134	( member( format(false), Controls ) ->
135	Format = false
136	; Format = true
137	),
138	( ground( Document ),
139	document_generation(Format, Document, Chars0, [] ) ->
140	Chars = Chars0
141	; fault( Document, [], Culprit, Path, Message ),
142	throw(
143	application_error('XML Parse: ~s in ~q~nCulprit: ~q~nPath: ~s',
144	[Message,Document,Culprit,Path] )
145	)
146	).
147
148	/* subterm( +XMLTerm, ?Subterm ) unifies Subterm with a sub-term of Term.
149	* Note that XMLTerm is a sub-term of itself.
150	*/
151	subterm( Term, Term ).
152	subterm( xml(_Attributes, Content), Term ) :-
153	subterm( Content, Term ).
154	subterm( [H\|T], Term ) :-
155	( subterm( H, Term )
156	; subterm( T, Term )
157	).
158	subterm( element(_Name,_Attributes,Content), Term ) :-
159	subterm( Content, Term ).
160	subterm( namespace(_URI,_Prefix,Content), Term ) :-
161	subterm( Content, Term ).
162
163
164	/* xml_to_document( +Controls, +XML, ?Document ) translates the list of
165	* character codes XML into the Prolog term Document. Controls is a list
166	* of terms controlling the treatment of layout characters and character
167	* entities.
168	*/
169
170	:- private(xml_to_document/3).
171	:- mode(xml_to_document(+nonvar, +nonvar, ?nonvar), zero_or_one).
172	:- info(xml_to_document/3, [
173	comment is 'Translates the list of character codes XML into the Prolog term Document. Controls is a list of terms controlling the treatment of layout characters and character entities.',
174	argnames is ['Controls', 'XML', 'Document']]).
175
176	xml_to_document( Controls, XML, Document ) :-
177	initial_context( Controls, Context ),
178	( xml_declaration( Attributes0, XML, XML1 ) ->
179	Attributes = Attributes0
180	; otherwise ->
181	XML1 = XML,
182	Attributes = []
183	),
184	xml_to_document( XML1, Context, Terms, [], WellFormed ),
185	xml_to_document1( WellFormed, Attributes, Terms, Document ).
186
187	xml_to_document1( true, Attributes, Terms, xml(Attributes, Terms) ).
188	xml_to_document1( false, Attributes, Terms, malformed(Attributes, Terms) ).
189
190	% unparsed( +Unparsed, +Context, ?Terms, ?Residue, ?WellFormed )
191	unparsed( Unparsed, _Context, [unparsed(Unparsed)], [], false ).
192
193	xml_declaration( Attributes ) -->
194	spaces,
195	"<?",
196	nmtoken( xml ),
197	xml_declaration_attributes( Attributes ),
198	spaces,
199	"?>".
200
201	xml_to_document( [], Context, Terms, [], WF ) :-
202	close_context( Context, Terms, WF ).
203	xml_to_document( [Char\|Chars], Context, Terms, Residue, WF ) :-
204	( Char =:= "<" ->
205	markup_structure( Chars, Context, Terms, Residue, WF )
206	; Char =:= "&" ->
207	entity_reference( Chars, Context, Terms, Residue, WF )
208	; Char =< " ",
209	\+ space_preserve( Context ) ->
210	layouts( Chars, Context, [Char\|T], T, Terms, Residue, WF )
211	; void_context( Context ) ->
212	unparsed( [Char\|Chars], Context, Terms, Residue, WF )
213	; otherwise ->
214	Terms = [pcdata([Char\|Chars1])\|Terms1],
215	acquire_pcdata( Chars, Context, Chars1, Terms1, Residue, WF )
216	).
217
218	layouts( [], Context, _Plus, _Minus, Terms, [], WF ) :-
219	close_context( Context, Terms, WF ).
220	layouts( [Char\|Chars], Context, Plus, Minus, Terms, Residue, WF ) :-
221	( Char =:= "<" ->
222	markup_structure( Chars, Context, Terms, Residue, WF )
223	; Char =:= "&" ->
224	reference_in_layout( Chars, Context, Plus, Minus, Terms, Residue, WF )
225	; Char =< " " ->
226	Minus = [Char\|Minus1],
227	layouts( Chars, Context, Plus, Minus1, Terms, Residue, WF )
228	; void_context( Context ) ->
229	unparsed( [Char\|Chars], Context, Terms, Residue, WF )
230	; otherwise ->
231	Terms = [pcdata(Plus)\|Terms1],
232	Minus = [Char\|Chars1],
233	context_update( space_preserve, Context, true, Context1 ),
234	acquire_pcdata( Chars, Context1, Chars1, Terms1, Residue, WF )
235	).
236
237	acquire_pcdata( [], Context, [], Terms, [], WF ) :-
238	close_context( Context, Terms, WF ).
239	acquire_pcdata( [Char\|Chars], Context, Chars1, Terms, Residue, WF ) :-
240	( Char =:= "<" ->
241	Chars1 = [],
242	markup_structure( Chars, Context, Terms, Residue, WF )
243	; Char =:= "&" ->
244	reference_in_pcdata( Chars, Context, Chars1, Terms, Residue, WF )
245	; otherwise ->
246	Chars1 = [Char\|Chars2],
247	acquire_pcdata( Chars, Context, Chars2, Terms, Residue, WF )
248	).
249
250	markup_structure( [], Context, Terms, Residue, WF ) :-
251	unparsed( "<", Context, Terms, Residue, WF ).
252	markup_structure( Chars, Context, Terms, Residue, WF ) :-
253	Chars = [Char\|Chars1],
254	( Char =:= "/" ->
255	closing_tag( Context, Chars1, Terms, Residue, WF )
256	; Char =:= "?" ->
257	pi_acquisition( Chars1, Context, Terms, Residue, WF )
258	; Char =:= "!" ->
259	declaration_acquisition( Chars1, Context, Terms, Residue, WF )
260	; open_tag(Tag,Context,Attributes,Type, Chars, Chars2 ) ->
261	push_tag( Tag, Chars2, Context, Attributes, Type, Terms, Residue, WF )
262	; otherwise ->
263	unparsed( [0'<\|Chars], Context, Terms, Residue, WF ) %'
264	).
265
266	push_tag( Tag, Chars, Context, Attributes, Type, Terms, Residue, WF ) :-
267	new_element(Tag, Chars, Context, Attributes, Type, Term, Rest, WF0),
268	push_tag1( WF0, Context, Term, Rest, Terms, Residue, WF ).
269
270	push_tag1( true, Context, Term, Chars, [Term\|Terms], Residue, WF ) :-
271	xml_to_document( Chars, Context, Terms, Residue, WF ).
272	push_tag1( false, _Context, Term, Chars, [Term], Chars, false ).
273
274	new_element( TagChars, Chars, Context, Attributes0, Type, Term, Residue, WF ) :-
275	namespace_attributes( Attributes0, Context, Context1, Attributes1 ),
276	( append( NSChars, [0':\|TagChars1], TagChars ), %'
277	specific_namespace( NSChars, Context1, SpecificNamespace ) ->
278	Namespace0 = SpecificNamespace
279	; otherwise ->
280	NSChars = "",
281	TagChars1 = TagChars,
282	default_namespace( Context1, Namespace0 )
283	),
284	current_namespace( Context1, CurrentNamespace ),
285	( Namespace0 == CurrentNamespace ->
286	Term = element(Tag, Attributes, Contents),
287	Context2 = Context1
288	; otherwise ->
289	Term = namespace( Namespace0, NSChars,
290	element(Tag, Attributes, Contents)
291	),
292	context_update( current_namespace, Context1, Namespace0, Context2 )
293	),
294	input_attributes( Attributes1, Context2, Attributes ),
295	atom_codes( Tag, TagChars1 ),
296	close_tag( Type, Chars, Context2, Contents, Residue, WF ).
297
298	close_tag( empty, Residue, _Context, [], Residue, true ).
299	close_tag( push(Tag), Chars, Context0, Contents, Residue, WF ) :-
300	context_update( element, Context0, Tag, Context1 ),
301	xml_to_document( Chars, Context1, Contents, Residue, WF ).
302
303	pi_acquisition( Chars, Context, Terms, Residue, WellFormed ) :-
304	( inline_instruction(Target, Processing, Chars, Rest ),
305	Target \== xml ->
306	Terms = [instructions(Target, Processing)\|Terms1],
307	xml_to_document( Rest, Context, Terms1, Residue, WellFormed )
308	; otherwise ->
309	unparsed( [0'<,0'?\|Chars], Context, Terms, Residue, WellFormed )
310	).
311
312	declaration_acquisition( Chars, Context, Terms, Residue, WF ) :-
313	( declaration_type( Chars, Type, Chars1 ),
314	declaration_parse( Type, Context, Term, Context1, Chars1, Rest ) ->
315	Terms = [Term\|Terms1],
316	xml_to_document( Rest, Context1, Terms1, Residue, WF )
317	; otherwise ->
318	unparsed( [0'<,0'!\|Chars], Context, Terms, Residue, WF )
319	).
320
321	open_tag( Tag, Namespaces, Attributes, Termination ) -->
322	nmtoken_chars( Tag ),
323	attributes( Attributes, [], Namespaces ),
324	spaces,
325	open_tag_terminator( Tag, Termination ).
326
327	open_tag_terminator( Tag, push(Tag) ) -->
328	">".
329	open_tag_terminator( _Tag, empty ) -->
330	"/>".
331
332	declaration_parse( comment, Namespaces, comment(Comment), Namespaces ) -->
333	comment(Comment).
334	declaration_parse( cdata, Namespaces, cdata(CData), Namespaces ) -->
335	cdata( CData ).
336	declaration_parse( doctype, Namespaces0, doctype(Name, Names), Namespaces ) -->
337	doctype( Name, Names, Namespaces0, Namespaces ),
338	spaces,
339	">".
340
341	inline_instruction( Target, Processing, Plus, Minus ) :-
342	nmtoken(Target, Plus, Mid0 ),
343	spaces( Mid0, Mid1 ),
344	append( Processing, [0'?,0'>\|Minus], Mid1 ),
345	!.
346
347	entity_reference_name( Reference ) -->
348	nmtoken_chars( Reference ),
349	";".
350
351	declaration_type( [Char1,Char2\|Chars1], Class, Rest ) :-
352	Chars = [Char1,Char2\|Chars1],
353	( declaration_type1( Char1, Char2, Chars1, Class0, Residue ) ->
354	Class = Class0,
355	Rest = Residue
356	; otherwise ->
357	Class = generic,
358	Rest = Chars
359	).
360
361	declaration_type1( 0'-, 0'-, Chars, comment, Chars ).
362	declaration_type1( 0'[, 0'C, Chars, cdata, Residue ) :-
363	append( "DATA[", Residue, Chars ).
364	declaration_type1( 0'D, 0'O, Chars, doctype, Residue ) :-
365	append( "CTYPE", Residue, Chars ).
366
367	closing_tag( Context, Chars, Terms, Residue, WellFormed ) :-
368	( closing_tag_name( Tag, Chars, Rest ),
369	current_tag( Context, Tag ) ->
370	Terms = [],
371	Residue = Rest,
372	WellFormed = true
373	; otherwise ->
374	unparsed( [0'<,0'/\|Chars], Context, Terms, Residue, WellFormed )
375	).
376
377	closing_tag_name( Tag ) -->
378	nmtoken_chars( Tag ),
379	spaces,
380	">".
381
382	entity_reference( Chars, Context, Terms, Residue, WF ) :-
383	reference_in_layout( Chars, Context, L, L, Terms, Residue, WF ).
384
385	reference_in_layout( Chars, Context, Plus, Minus, Terms, Residue, WF ) :-
386	( standard_character_entity( Char, Chars, Rest ) ->
387	Minus = [Char\|Chars1],
388	Terms = [pcdata(Plus)\|Terms1],
389	acquire_pcdata( Rest, Context, Chars1, Terms1, Residue, WF )
390	; entity_reference_name( Reference, Chars, Rest ),
391	defined_entity( Reference, Context, String ) ->
392	append( String, Rest, Full ),
393	xml_to_document( Full, Context, Terms, Residue, WF )
394	; allow_ampersand( Context ) ->
395	Minus = [0'&\|Chars1], %'
396	Terms = [pcdata(Plus)\|Terms1],
397	acquire_pcdata( Chars, Context, Chars1, Terms1, Residue, WF )
398	; otherwise ->
399	unparsed( [0'&\|Chars], Context, Terms, Residue, WF ) %'
400	).
401
402	reference_in_pcdata( Chars0, Context, Chars1, Terms, Residue, WF ) :-
403	( standard_character_entity( Char, Chars0, Rest ) ->
404	Chars1 = [Char\|Chars2],
405	acquire_pcdata( Rest, Context, Chars2, Terms, Residue, WF )
406	; entity_reference_name( Reference, Chars0, Rest ),
407	defined_entity( Reference, Context, String ) ->
408	append( String, Rest, Full ),
409	acquire_pcdata( Full, Context, Chars1, Terms, Residue, WF )
410	; allow_ampersand( Context ) ->
411	Chars1 = [0'&\|Chars2],
412	acquire_pcdata( Chars0, Context, Chars2, Terms, Residue, WF )
413	; otherwise ->
414	Chars1 = [],
415	unparsed( [0'&\|Chars0], Context, Terms, Residue, WF )
416	).
417
418	namespace_attributes( [], Context, Context, [] ).
419	namespace_attributes( Attributes0, Context0, Context, Attributes ) :-
420	Attributes0 = [_\|_],
421	append( "xmlns:", Unqualified, QualifiedNameChars ),
422	( select( "xmlns"=Value, Attributes0, Attributes1 ) ->
423	atom_codes( URI, Value ),
424	context_update( default_namespace, Context0, URI, Context1 ),
425	namespace_attributes( Attributes1, Context1, Context, Attributes )
426	; select( QualifiedNameChars=Value, Attributes0, Attributes1 ) ->
427	Attributes = [QualifiedNameChars=Value\|Attributes2],
428	atom_codes( URI, Value ),
429	context_update( ns_prefix(Unqualified), Context0, URI, Context1 ),
430	namespace_attributes( Attributes1, Context1, Context, Attributes2 )
431	; member( "xml:space"="preserve", Attributes0 ) ->
432	Attributes = Attributes0,
433	context_update( space_preserve, Context0, true, Context )
434	; otherwise ->
435	Context = Context0,
436	Attributes = Attributes0
437	).
438
439	input_attributes( [], _Context, [] ).
440	input_attributes( [NameChars=Value\|Attributes0], Context,
441	[Name=Value\|Attributes] ) :-
442	( remove_attribute_prefixes( Context ),
443	append( NSChars, [0':\|NameChars1], NameChars ), %'
444	NSChars \== "xmlns",
445	specific_namespace( NSChars, Context, Namespace ),
446	current_namespace( Context, Namespace ) ->
447	atom_codes( Name, NameChars1 )
448	; otherwise ->
449	atom_codes( Name, NameChars )
450	),
451	input_attributes( Attributes0, Context, Attributes ).
452
453	attributes( [Name=Value\|Attributes], Seen, Namespaces ) -->
454	spaces,
455	nmtoken_chars( Name ),
456	{\+ member(Name, Seen)},
457	spaces,
458	"=",
459	spaces,
460	attribute_value( Value, Namespaces ),
461	attributes( Attributes, [Name\|Seen], Namespaces ).
462	attributes( [], _Seen, _Namespaces ) --> "".
463
464	xml_declaration_attributes( [] ) --> "".
465	xml_declaration_attributes( [Name=Value\|Attributes] ) -->
466	spaces,
467	nmtoken( Name ),
468	spaces,
469	"=",
470	spaces,
471	xml_string( Value ),
472	{xml_declaration_attribute_valid(Name, Value)},
473	xml_declaration_attributes( Attributes ),
474	spaces.
475
476	doctype( Name, External, Namespaces0, Namespaces1 ) -->
477	spaces,
478	nmtoken( Name ),
479	spaces,
480	doctype_id( External0 ),
481	spaces,
482	doctype1( Namespaces0, Literals, Namespaces1 ),
483	{doctype_extension(Literals, External0, External)}.
484
485	doctype_extension( [], External, External ).
486	doctype_extension( [Literal\|Literals], External0, External ) :-
487	extended_doctype( External0, [Literal\|Literals], External ).
488
489	extended_doctype( system(URL), Literals, system(URL,Literals) ).
490	extended_doctype( public(URN,URL), Literals, public(URN,URL,Literals) ).
491	extended_doctype( local, Literals, local(Literals) ).
492
493	doctype1( Namespaces0, Literals, Namespaces1 ) -->
494	"[",
495	!,
496	dtd( Namespaces0, Literals, Namespaces1 ),
497	"]".
498	doctype1( Namespaces, [], Namespaces ) --> "".
499
500	doctype_id( system(URL) ) -->
501	"SYSTEM",
502	spaces,
503	uri( URL ).
504	doctype_id( public(URN,URL) ) -->
505	"PUBLIC",
506	spaces,
507	uri( URN ),
508	spaces,
509	uri( URL ).
510	doctype_id( local ) --> "".
511
512	dtd( Namespaces0, Literals, Namespaces1 ) -->
513	spaces,
514	"<!ENTITY",
515	!,
516	spaces,
517	nmtoken_chars( Name ),
518	spaces,
519	quote( Quote ),
520	entity_value( Quote, Namespaces0, String ),
521	spaces,
522	">",
523	{\+ character_entity( Name, _StandardChar ),
524	% Don't allow < &quote; etc. to be updated
525	context_update( entity(Name), Namespaces0, String, Namespaces2 )
526	},
527	dtd( Namespaces2, Literals, Namespaces1 ).
528	dtd( Namespaces0, Literals, Namespaces1 ) -->
529	spaces,
530	"<!--",
531	!,
532	dtd_comment,
533	">",
534	dtd( Namespaces0, Literals, Namespaces1 ).
535	dtd( Namespaces0, [dtd_literal(Literal)\|Literals], Namespaces1 ) -->
536	spaces,
537	"<!",
538	!,
539	dtd_literal( Literal ),
540	dtd( Namespaces0, Literals, Namespaces1 ).
541	dtd( Namespaces, [], Namespaces ) --> spaces.
542
543	dtd_literal( [] ) --> ">", !.
544	dtd_literal( Chars ) -->
545	"--",
546	!,
547	dtd_comment,
548	dtd_literal( Chars ).
549	dtd_literal( [Char\|Chars] ) -->
550	[Char],
551	dtd_literal( Chars ).
552
553	dtd_comment( Plus, Minus ) :-
554	append( _Chars, [0'-,0'-\|Minus], Plus ),
555	!.
556
557	nmtokens( [Name\|Names] ) -->
558	spaces,
559	nmtoken( Name ),
560	nmtokens( Names ).
561	nmtokens( [] ) --> [].
562
563	entity_value( Quote, Namespaces, String, [Char\|Plus], Minus ) :-
564	( Char == Quote ->
565	String = [],
566	Minus = Plus
567	; Char =:= "&" ->
568	reference_in_entity( Namespaces, Quote, String, Plus, Minus )
569	; otherwise ->
570	String = [Char\|String1],
571	entity_value( Quote, Namespaces, String1, Plus, Minus )
572	).
573
574	attribute_value( String, Namespaces ) -->
575	quote( Quote ),
576	attribute_leading_layouts( Quote, Namespaces, String ).
577
578	attribute_leading_layouts( _Quote, _Namespace, [], [], [] ).
579	attribute_leading_layouts( Quote, Namespaces, String, [Char\|Plus], Minus ) :-
580	( Char == Quote ->
581	String = [],
582	Minus = Plus
583	; Char =:= "&" ->
584	ref_in_attribute_layout( Namespaces, Quote, String, Plus, Minus )
585	; Char > 32, Char \== 160 ->
586	String = [Char\|String1],
587	attribute_layouts( Quote, Namespaces, false, String1, Plus, Minus )
588	; otherwise ->
589	attribute_leading_layouts( Quote, Namespaces, String, Plus, Minus )
590	).
591
592	attribute_layouts( _Quote, _Namespaces, _Layout, [], [], [] ).
593	attribute_layouts( Quote, Namespaces, Layout, String, [Char\|Plus], Minus ) :-
594	( Char == Quote ->
595	String = [],
596	Minus = Plus
597	; Char =:= "&" ->
598	reference_in_value( Namespaces, Quote, Layout, String, Plus, Minus )
599	; Char > 32, Char \== 160 ->
600	( Layout == true ->
601	String = [0' ,Char\|String1] %'
602	; otherwise ->
603	String = [Char\|String1]
604	),
605	attribute_layouts( Quote, Namespaces, false, String1, Plus, Minus )
606	; otherwise ->
607	attribute_layouts( Quote, Namespaces, true, String, Plus, Minus )
608	).
609
610	ref_in_attribute_layout( NS, Quote, String, Plus, Minus ) :-
611	( standard_character_entity( Char, Plus, Mid ) ->
612	String = [Char\|String1],
613	attribute_layouts( Quote, NS, false, String1, Mid, Minus )
614	; entity_reference_name( Name, Plus, Suffix ),
615	defined_entity( Name, NS, Text ) ->
616	append( Text, Suffix, Mid ),
617	attribute_leading_layouts( Quote, NS, String, Mid, Minus )
618	; otherwise -> % Just & is okay in a value
619	String = [0'&\|String1], %'
620	attribute_layouts( Quote, NS, false, String1, Plus, Minus )
621	).
622
623	reference_in_value( Namespaces, Quote, Layout, String, Plus, Minus ) :-
624	( standard_character_entity( Char, Plus, Mid ) ->
625	( Layout == true ->
626	String = [0' ,Char\|String1] %'
627	; otherwise ->
628	String = [Char\|String1]
629	),
630	Layout1 = false
631	; entity_reference_name( Name, Plus, Suffix ),
632	defined_entity( Name, Namespaces, Text ) ->
633	String = String1,
634	append( Text, Suffix, Mid ),
635	Layout1 = Layout
636	; otherwise -> % Just & is okay in a value
637	Mid = Plus,
638	String = [0'&\|String1], %'
639	Layout1 = false
640	),
641	attribute_layouts( Quote, Namespaces, Layout1, String1, Mid, Minus ).
642
643	/* References are resolved backwards in Entity defintions so that
644	* circularity is avoided.
645	*/
646	reference_in_entity( Namespaces, Quote, String, Plus, Minus ) :-
647	( standard_character_entity( _SomeChar, Plus, _Rest ) ->
648	String = [0'&\|String1], % ' Character entities are unparsed
649	Mid = Plus
650	; entity_reference_name( Name, Plus, Suffix ),
651	defined_entity( Name, Namespaces, Text ) ->
652	String = String1,
653	append( Text, Suffix, Mid )
654	),
655	entity_value( Quote, Namespaces, String1, Mid, Minus ).
656
657	standard_character_entity( Char ) -->
658	"#x", hex_character_reference( Char ), ";".
659	standard_character_entity( Char ) -->
660	"#", digit( Digit ), digits( Digits ), ";",
661	{number_chars( Char, [Digit\|Digits])}.
662	standard_character_entity( C ) -->
663	chars( String ),
664	";",
665	!,
666	{character_entity(String, C)}.
667
668	uri( URI ) -->
669	quote( Quote ),
670	uri1( Quote, URI ).
671
672	uri1( Quote, [] ) -->
673	quote( Quote ),
674	!.
675	uri1( Quote, [Char\|Chars] ) -->
676	[Char],
677	uri1( Quote, Chars ).
678
679	comment( Chars, Plus, Minus ) :-
680	append( Chars, [0'-,0'-,0'>\|Minus], Plus ), %'
681	!.
682
683	cdata( Chars, Plus, Minus ) :-
684	append( Chars, [0'],0'],0'>\|Minus], Plus ), %'
685	!.
686	% Syntax Components
687
688	hex_character_reference( Code ) -->
689	hex_character_reference1( 0, Code ).
690
691	hex_character_reference1( Current, Code ) -->
692	hex_digit_char( Value ),
693	!,
694	{New is (Current << 4) + Value},
695	hex_character_reference1( New, Code ).
696	hex_character_reference1( Code, Code ) --> "".
697
698	hex_digit_char( 0 ) --> "0".
699	hex_digit_char( 1 ) --> "1".
700	hex_digit_char( 2 ) --> "2".
701	hex_digit_char( 3 ) --> "3".
702	hex_digit_char( 4 ) --> "4".
703	hex_digit_char( 5 ) --> "5".
704	hex_digit_char( 6 ) --> "6".
705	hex_digit_char( 7 ) --> "7".
706	hex_digit_char( 8 ) --> "8".
707	hex_digit_char( 9 ) --> "9".
708	hex_digit_char( 10 ) --> "A".
709	hex_digit_char( 11 ) --> "B".
710	hex_digit_char( 12 ) --> "C".
711	hex_digit_char( 13 ) --> "D".
712	hex_digit_char( 14 ) --> "E".
713	hex_digit_char( 15 ) --> "F".
714	hex_digit_char( 10 ) --> "a".
715	hex_digit_char( 11 ) --> "b".
716	hex_digit_char( 12 ) --> "c".
717	hex_digit_char( 13 ) --> "d".
718	hex_digit_char( 14 ) --> "e".
719	hex_digit_char( 15 ) --> "f".
720
721	quote( 0'" ) --> %'
722	"""".
723	quote( 0'' ) -->
724	"'".
725
726	spaces( [], [] ).
727	spaces( [Char\|Chars0], Chars1 ) :-
728	( Char =< 32 ->
729	spaces( Chars0, Chars1 )
730	; otherwise ->
731	Chars1 = [Char\|Chars0]
732	).
733
734	nmtoken( Name ) -->
735	nmtoken_chars( Chars ),
736	{atom_codes(Name, Chars)}.
737
738	nmtoken_chars( [Char\|Chars] ) -->
739	[Char],
740	{nmtoken_first( Char )},
741	nmtoken_chars_tail( Chars ).
742
743	nmtoken_chars_tail( [Char\|Chars] ) -->
744	[Char],
745	{nmtoken_char(Char)},
746	!,
747	nmtoken_chars_tail( Chars ).
748	nmtoken_chars_tail([]) --> "".
749
750	nmtoken_first( 0': ).
751	nmtoken_first( 0'_ ).
752	nmtoken_first( Char ) :-
753	alphabet( Char ).
754
755	nmtoken_char( 0'a ).
756	nmtoken_char( 0'b ).
757	nmtoken_char( 0'c ).
758	nmtoken_char( 0'd ).
759	nmtoken_char( 0'e ).
760	nmtoken_char( 0'f ).
761	nmtoken_char( 0'g ).
762	nmtoken_char( 0'h ).
763	nmtoken_char( 0'i ).
764	nmtoken_char( 0'j ).
765	nmtoken_char( 0'k ).
766	nmtoken_char( 0'l ).
767	nmtoken_char( 0'm ).
768	nmtoken_char( 0'n ).
769	nmtoken_char( 0'o ).
770	nmtoken_char( 0'p ).
771	nmtoken_char( 0'q ).
772	nmtoken_char( 0'r ).
773	nmtoken_char( 0's ).
774	nmtoken_char( 0't ).
775	nmtoken_char( 0'u ).
776	nmtoken_char( 0'v ).
777	nmtoken_char( 0'w ).
778	nmtoken_char( 0'x ).
779	nmtoken_char( 0'y ).
780	nmtoken_char( 0'z ).
781	nmtoken_char( 0'A ).
782	nmtoken_char( 0'B ).
783	nmtoken_char( 0'C ).
784	nmtoken_char( 0'D ).
785	nmtoken_char( 0'E ).
786	nmtoken_char( 0'F ).
787	nmtoken_char( 0'G ).
788	nmtoken_char( 0'H ).
789	nmtoken_char( 0'I ).
790	nmtoken_char( 0'J ).
791	nmtoken_char( 0'K ).
792	nmtoken_char( 0'L ).
793	nmtoken_char( 0'M ).
794	nmtoken_char( 0'N ).
795	nmtoken_char( 0'O ).
796	nmtoken_char( 0'P ).
797	nmtoken_char( 0'Q ).
798	nmtoken_char( 0'R ).
799	nmtoken_char( 0'S ).
800	nmtoken_char( 0'T ).
801	nmtoken_char( 0'U ).
802	nmtoken_char( 0'V ).
803	nmtoken_char( 0'W ).
804	nmtoken_char( 0'X ).
805	nmtoken_char( 0'Y ).
806	nmtoken_char( 0'Z ).
807	nmtoken_char( 0'0 ).
808	nmtoken_char( 0'1 ).
809	nmtoken_char( 0'2 ).
810	nmtoken_char( 0'3 ).
811	nmtoken_char( 0'4 ).
812	nmtoken_char( 0'5 ).
813	nmtoken_char( 0'6 ).
814	nmtoken_char( 0'7 ).
815	nmtoken_char( 0'8 ).
816	nmtoken_char( 0'9 ).
817	nmtoken_char( 0'. ).
818	nmtoken_char( 0'- ).
819	nmtoken_char( 0'_ ).
820	nmtoken_char( 0': ).
821
822	xml_string( String ) -->
823	quote( Quote ),
824	xml_string1( Quote, String ).
825
826	xml_string1( Quote, [] ) -->
827	quote( Quote ),
828	!.
829	xml_string1( Quote, [Char\|Chars] ) -->
830	[Char],
831	xml_string1( Quote, Chars ).
832
833	alphabet( 0'a ).
834	alphabet( 0'b ).
835	alphabet( 0'c ).
836	alphabet( 0'd ).
837	alphabet( 0'e ).
838	alphabet( 0'f ).
839	alphabet( 0'g ).
840	alphabet( 0'h ).
841	alphabet( 0'i ).
842	alphabet( 0'j ).
843	alphabet( 0'k ).
844	alphabet( 0'l ).
845	alphabet( 0'm ).
846	alphabet( 0'n ).
847	alphabet( 0'o ).
848	alphabet( 0'p ).
849	alphabet( 0'q ).
850	alphabet( 0'r ).
851	alphabet( 0's ).
852	alphabet( 0't ).
853	alphabet( 0'u ).
854	alphabet( 0'v ).
855	alphabet( 0'w ).
856	alphabet( 0'x ).
857	alphabet( 0'y ).
858	alphabet( 0'z ).
859	alphabet( 0'A ).
860	alphabet( 0'B ).
861	alphabet( 0'C ).
862	alphabet( 0'D ).
863	alphabet( 0'E ).
864	alphabet( 0'F ).
865	alphabet( 0'G ).
866	alphabet( 0'H ).
867	alphabet( 0'I ).
868	alphabet( 0'J ).
869	alphabet( 0'K ).
870	alphabet( 0'L ).
871	alphabet( 0'M ).
872	alphabet( 0'N ).
873	alphabet( 0'O ).
874	alphabet( 0'P ).
875	alphabet( 0'Q ).
876	alphabet( 0'R ).
877	alphabet( 0'S ).
878	alphabet( 0'T ).
879	alphabet( 0'U ).
880	alphabet( 0'V ).
881	alphabet( 0'W ).
882	alphabet( 0'X ).
883	alphabet( 0'Y ).
884	alphabet( 0'Z ).
885
886	digit( C ) --> [C], {digit_table( C )}.
887
888	digit_table( 0'0 ).
889	digit_table( 0'1 ).
890	digit_table( 0'2 ).
891	digit_table( 0'3 ).
892	digit_table( 0'4 ).
893	digit_table( 0'5 ).
894	digit_table( 0'6 ).
895	digit_table( 0'7 ).
896	digit_table( 0'8 ).
897	digit_table( 0'9 ).
898
899	digits( [Digit\|Digits] ) -->
900	digit( Digit ),
901	digits( Digits ).
902	digits( [] ) --> [].
903
904	character_entity( "quot", 0'" ). %'
905	character_entity( "amp", 0'& ). %'
906	character_entity( "lt", 0'< ). %'
907	character_entity( "gt", 0'> ). %'
908	character_entity( "apos", 0'' ).
909
910	/* pp( +XMLDocument ) "pretty prints" XMLDocument on the current
911	* output stream.
912	*/
913	pp( xml(Attributes, Document) ) :-
914	write( 'xml( ' ), pp_attributes( Attributes, 0 ), pp_comma, nl,
915	pp_list( Document, s(0) ),
916	write( ' ).' ), nl.
917	pp( malformed(Attributes, Document) ) :-
918	write( 'malformed( ' ), pp_attributes( Attributes, 0 ), pp_comma, nl,
919	pp_list( Document, s(0) ),
920	write( ' ).' ), nl.
921
922	pp_indented( [], Indent ) :-
923	pp_indent( Indent), write( '[]' ).
924	pp_indented( List, Indent ) :-
925	List = [_\|_],
926	pp_indent( Indent ),
927	pp_list( List, Indent ).
928	pp_indented( comment(Text), Indent ) :-
929	pp_indent( Indent ), write( 'comment(' ), pp_string(Text), write( ')' ).
930	pp_indented( namespace(URI,Prefix,Element), Indent ) :-
931	pp_indent( Indent ),
932	write( 'namespace( ' ), writeq( URI ), pp_comma_sp,
933	pp_string( Prefix ), pp_comma, nl,
934	pp_indented( Element, s(Indent) ), nl,
935	pp_indent( s(Indent) ), write( ')' ).
936	pp_indented( element(Tag,Attributes,Contents), Indent ) :-
937	pp_indent( Indent ), write( 'element( ' ), writeq( Tag ), pp_comma, nl,
938	pp_attributes( Attributes, s(Indent) ), pp_comma, nl,
939	pp_list( Contents, s(Indent) ), write( ' )' ).
940	pp_indented( instructions(Target, Processing), Indent ) :-
941	pp_indent( Indent ), write( 'instructions( ' ), writeq( Target ), pp_comma_sp,
942	pp_string(Processing), write( ')' ).
943	pp_indented( doctype(Name, DoctypeId), Indent ) :-
944	pp_indent( Indent ), write( 'doctype( ' ), writeq( Name ), pp_comma_sp,
945	pp_indented( DoctypeId, s(Indent) ), %'
946	write( ' )' ).
947	pp_indented( cdata(CData), Indent ) :-
948	pp_indent( Indent ), write( 'cdata(' ), pp_string(CData), write( ')' ).
949	pp_indented( pcdata(PCData), Indent ) :-
950	pp_indent( Indent ), write( 'pcdata(' ), pp_string(PCData), write( ')' ).
951	pp_indented( public(URN,URL), _Indent ) :-
952	write( 'public(' ), pp_string(URN), pp_comma_sp,
953	pp_string(URL), write( ')' ).
954	pp_indented( public(URN,URL,Literals), Indent ) :-
955	write( 'public(' ), pp_string(URN), pp_comma_sp,
956	pp_string(URL), pp_list( Literals, s(Indent) ), write( ')' ).
957	pp_indented( system(URL), _Indent ) :-
958	write( 'system(' ), pp_string(URL), write( ')' ).
959	pp_indented( system(URL,Literals), Indent ) :-
960	write( 'system(' ), pp_string(URL), pp_comma_sp,
961	pp_list( Literals, s(Indent) ), write( ')' ).
962	pp_indented( local, _Indent ) :-
963	write( local ).
964	pp_indented( local(Literals), Indent ) :-
965	write( 'local(' ), nl,
966	pp_list( Literals, s(Indent) ), write( ')' ).
967	pp_indented( dtd_literal(String), Indent ) :-
968	pp_indent( Indent ), write( 'dtd_literal(' ), pp_string(String), write( ')' ).
969	pp_indented( out_of_context(Tag), Indent ) :-
970	pp_indent( Indent ), write( '/* SYNTAX ERROR */ out_of_context( ' ),
971	writeq( Tag ), write( ' )' ).
972	pp_indented( unparsed(String), Indent ) :-
973	pp_indent( Indent ), write( '/* SYNTAX ERROR */ unparsed( ' ),
974	pp_string(String), write( ' )' ).
975
976	pp_list( [], Indent ) :-
977	pp_indent( Indent ), write( [] ).
978	pp_list( [H\|T], Indent ) :-
979	pp_indent( Indent ), write( '[' ), nl,
980	pp_indented( H, Indent ),
981	pp_list1( T, Indent ),
982	pp_indent( Indent ), write( ']' ).
983
984	pp_list1( [], _Indent ) :-
985	nl.
986	pp_list1( [H\|T], Indent ) :-
987	pp_comma, nl,
988	pp_indented( H, Indent ),
989	pp_list1( T, Indent ).
990
991	pp_attributes( [], Indent ) :-
992	pp_indent( Indent ), write( [] ).
993	pp_attributes( [Attribute\|Attributes], Indent ) :-
994	pp_indent( Indent ), write( '[' ),
995	pp_attributes1( Attributes, Attribute ),
996	write( ']' ).
997
998	pp_attributes1( [], Name=Value ) :-
999	pp_name( Name ), pp_string( Value ).
1000	pp_attributes1( [H\|T], Name=Value ) :-
1001	pp_name( Name ), pp_string( Value ), pp_comma_sp,
1002	pp_attributes1( T, H ).
1003
1004
1005	pp_name( Name ) :-
1006	( possible_operator( Name ) ->
1007	write( '(' ), write( Name ), write( ')=' )
1008	; otherwise ->
1009	writeq( Name ), write( '=' )
1010	).
1011
1012	possible_operator( (abolish) ).
1013	possible_operator( (attribute) ).
1014	possible_operator( (check_advice) ).
1015	possible_operator( (compile_command) ).
1016	possible_operator( (delay) ).
1017	possible_operator( (demon) ).
1018	possible_operator( (discontiguous) ).
1019	possible_operator( (div) ).
1020	possible_operator( (do) ).
1021	possible_operator( (document_export) ).
1022	possible_operator( (document_import) ).
1023	possible_operator( (dy) ).
1024	possible_operator( (dynamic) ).
1025	possible_operator( (edb) ).
1026	possible_operator( (eexport) ).
1027	possible_operator( (else) ).
1028	possible_operator( (except) ).
1029	possible_operator( (export) ).
1030	possible_operator( (foreign_pred) ).
1031	possible_operator( (from) ).
1032	possible_operator( (from_chars) ).
1033	possible_operator( (from_file) ).
1034	possible_operator( (from_stream) ).
1035	possible_operator( (global) ).
1036	possible_operator( (help) ).
1037	possible_operator( (hilog) ).
1038	possible_operator( (if) ).
1039	possible_operator( (import) ).
1040	possible_operator( (index) ).
1041	possible_operator( (initialization) ).
1042	possible_operator( (is) ).
1043	possible_operator( (listing) ).
1044	possible_operator( (local) ).
1045	possible_operator( (locked) ).
1046	possible_operator( (meta_predicate) ).
1047	possible_operator( (mod) ).
1048	possible_operator( (mode) ).
1049	possible_operator( (module_transparent) ).
1050	possible_operator( (multifile) ).
1051	possible_operator( (namic) ).
1052	possible_operator( (nocheck_advice) ).
1053	possible_operator( (nospy) ).
1054	possible_operator( (not) ).
1055	possible_operator( (of) ).
1056	possible_operator( (once) ).
1057	possible_operator( (onto_chars) ).
1058	possible_operator( (onto_file) ).
1059	possible_operator( (onto_stream) ).
1060	possible_operator( (parallel) ).
1061	possible_operator( (public) ).
1062	possible_operator( (r) ).
1063	possible_operator( (rem) ).
1064	possible_operator( (skipped) ).
1065	possible_operator( (spy) ).
1066	possible_operator( (table) ).
1067	possible_operator( (then) ).
1068	possible_operator( (thread_local) ).
1069	possible_operator( (ti) ).
1070	possible_operator( (ti_off) ).
1071	possible_operator( (traceable) ).
1072	possible_operator( (unskipped) ).
1073	possible_operator( (untraceable) ).
1074	possible_operator( (use_subsumptive_tabling) ).
1075	possible_operator( (use_variant_tabling) ).
1076	possible_operator( (volatile) ).
1077	possible_operator( (with) ).
1078	possible_operator( (with_input_from_chars) ).
1079	possible_operator( (with_output_to_chars) ).
1080	possible_operator( (xor) ).
1081
1082	pp_indent( 0 ).
1083	pp_indent( s(N) ) :-
1084	write( ' ' ),
1085	pp_indent( N ).
1086
1087	pp_comma :-
1088	write( ',' ).
1089
1090	pp_comma_sp :-
1091	write( ', ' ).
1092
1093
1094	% Entity and Namespace map operations: these maps are usually quite small, so
1095	% a linear list lookup is okay. They could be substituted by a logarithmic
1096	% data structure - in extremis.
1097
1098
1099	/* empty_map( ?Map ) is true if Map is a null map.
1100	*/
1101	:- private(empty_map/1).
1102	:- mode(empty_map(?nonvar), zero_or_one).
1103	:- info(empty_map/1, [
1104	comment is 'True if Map is a null map.',
1105	argnames is ['Map']]).
1106
1107	empty_map( [] ).
1108
1109	/* map_member( +Key, +Map, ?Data ) is true if Map is a ordered map structure
1110	* which records the pair Key-Data. Key must be ground.
1111	*/
1112	:- private(map_member/3).
1113	:- mode(map_member(+nonvar, +nonvar, ?nonvar), zero_or_one).
1114	:- info(map_member/3, [
1115	comment is 'True if Map is a ordered map structure which records the pair Key-Data. Key must be ground.',
1116	argnames is ['Key', 'Map', 'Data']]).
1117
1118	map_member( Key0, [Key1-Data1\|Rest], Data0 ) :-
1119	( Key0 == Key1 ->
1120	Data0 = Data1
1121	; Key0 @> Key1 ->
1122	map_member( Key0, Rest, Data0 )
1123	).
1124
1125	/* map_store( +Map0, +Key, +Data, ?Map1 ) is true if Map0 is an ordered map
1126	* structure, Key must be ground, and Map1 is identical to Map0 except that
1127	* the pair Key-Data is recorded by Map1.
1128	*/
1129	:- private(map_store/4).
1130	:- mode(map_store(+nonvar, +nonvar, +nonvar, ?nonvar), zero_or_one).
1131	:- info(map_store/4, [
1132	comment is 'True if Map0 is an ordered map structure, Key must be ground, and Map1 is identical to Map0 except that the pair Key-Data is recorded by Map1.',
1133	argnames is ['Map0', 'Key', 'Data', 'Map1']]).
1134
1135	map_store( [], Key, Data, [Key-Data] ).
1136	map_store( [Key0-Data0\|Map0], Key, Data, Map ) :-
1137	( Key == Key0 ->
1138	Map = [Key-Data\|Map0]
1139	; Key @< Key0 ->
1140	Map = [Key-Data,Key0-Data0\|Map0]
1141	; otherwise -> % >
1142	Map = [Key0-Data0\|Map1],
1143	map_store( Map0, Key, Data, Map1 )
1144	).
1145
1146	/* context(?Element, ?PreserveSpace, ?CurrentNS, ?DefaultNS, ?Entities, ?Namespaces )
1147	* is an ADT hiding the "state" arguments for XML Acquisition
1148	*/
1149	initial_context(
1150	Controls,
1151	context(void,PreserveSpace,'','',Entities,Empty,
1152	RemoveAttributePrefixes,AllowAmpersand)
1153	) :-
1154	empty_map( Empty ),
1155	( member( extended_characters(false), Controls ) ->
1156	Entities = Empty
1157	; otherwise ->
1158	extended_character_entities(Entities)
1159	),
1160	( member( format(false), Controls ) ->
1161	PreserveSpace = true
1162	; otherwise ->
1163	PreserveSpace = false
1164	),
1165	( member( remove_attribute_prefixes(true), Controls ) ->
1166	RemoveAttributePrefixes = true
1167	; otherwise ->
1168	RemoveAttributePrefixes = false
1169	),
1170	( member( allow_ampersand(true), Controls ) ->
1171	AllowAmpersand = true
1172	; otherwise ->
1173	AllowAmpersand = false
1174