1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2014-2015, VU University Amsterdam
    7    All rights reserved.
    8
    9    Redistribution and use in source and binary forms, with or without
   10    modification, are permitted provided that the following conditions
   11    are met:
   12
   13    1. Redistributions of source code must retain the above copyright
   14       notice, this list of conditions and the following disclaimer.
   15
   16    2. Redistributions in binary form must reproduce the above copyright
   17       notice, this list of conditions and the following disclaimer in
   18       the documentation and/or other materials provided with the
   19       distribution.
   20
   21    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   22    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   23    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   24    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   25    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   26    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   27    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   28    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   29    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   31    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   32    POSSIBILITY OF SUCH DAMAGE.
   33*/
   34
   35:- module(rdfa,
   36	  [ read_rdfa/3,                % +Input, -RDF, +Options
   37	    xml_rdfa/3                  % +XMLDom, -RDF, +Options
   38	  ]).   39:- use_module(library(semweb/rdf_db),
   40	    [ rdf_register_prefix/2,
   41	      rdf_meta/1,
   42	      rdf_global_id/2,
   43	      rdf_equal/2,
   44	      rdf_is_bnode/1,
   45	      rdf_global_term/2,
   46	      rdf_transaction/2,
   47	      rdf_assert/4,
   48	      rdf_set_graph/2,
   49	      op(_,_,_)
   50	    ]).   51:- use_module(library(xpath),[xpath/3, op(_,_,_)]).   52
   53:- autoload(library(apply),[maplist/3,maplist/2,exclude/3,include/3]).   54:- use_module(library(debug),[debugging/1,debug/3]).   55:- autoload(library(error),[instantiation_error/1,type_error/2]).   56:- if(exists_source(library(guitracer))).   57:- autoload(library(gui_tracer),[gtrace/0]).   58:- endif.   59:- autoload(library(lists),[append/2,reverse/2,member/2,append/3]).   60:- autoload(library(option),[merge_options/3,option/2,option/3]).   61:- autoload(library(prolog_stack),[backtrace/1]).   62:- autoload(library(sgml),
   63	    [ load_xml/3, load_html/3, xml_basechar/1, xml_ideographic/1,
   64	      xml_digit/1, xml_combining_char/1, xml_extender/1
   65	    ]).   66:- autoload(library(sgml_write),[xml_write/2]).   67:- autoload(library(uri),
   68	    [ uri_file_name/2, uri_components/2, uri_data/3, uri_data/4,
   69	      iri_normalized/3, iri_normalized/2, uri_normalized/3
   70	    ]).   71:- autoload(library(dcg/basics),[blanks/2,blank/2,alpha_to_lower/3]).   72:- autoload(library(http/http_open),[http_open/3]).

   86:- rdf_register_prefix(rdfa, 'http://www.w3.org/ns/rdfa#').   87
   88:- rdf_meta
   89    add_triple(+, r, r, o),
   90    add_incomplete_triple(+, t).   91
   92:- discontiguous
   93    term_expansion/2.   94
   95:- predicate_options(xml_rdfa/3, 3,
   96		     [ base(atom),
   97		       anon_prefix(any),
   98		       lang(atom),
   99		       vocab(atom),
  100		       markup(atom)
  101		     ]).  102:- predicate_options(read_dom/3, 3,
  103		     [ pass_to(sgml:load_html/3, 3),
  104		       pass_to(sgml:load_xml/3, 3)
  105		     ]).  106:- predicate_options(read_rdfa/3, 3,
  107		     [ pass_to(read_dom/3, 3),
  108		       pass_to(xml_rdfa/3, 3),
  109		       pass_to(system:open/4, 4),
  110		       pass_to(http_open:http_open/3, 3)
  111		     ]).  112
  113
  114		 /*******************************
  115		 *          STREAM READING      *
  116		 *******************************/

 read_rdfa(+Input, -Triples, +Options) is det

True when Triples is a list of rdf(S,P,O) triples extracted from Input. Input is either a stream, a file name, a URL referencing a file name or a URL that is valid for http_open/3. Options are passed to open/4, http_open/3 and xml_rdfa/3. If no base is provided in Options, a base is deduced from Input.

  126read_rdfa(Input, Triples, Options) :-
  127    setup_call_cleanup(
  128	open_input(Input, In, NewOptions, Close, Options),
  129	read_dom(In, DOM, Options),
  130	close_input(Close)),
  131    merge_options(Options, NewOptions, RDFaOptions),
  132    xml_rdfa(DOM, Triples, RDFaOptions).
  133
  134open_input(Input, In, NewOptions, Close, Options) :-
  135    open_input2(Input, In, NewOptions, Close0, Options),
  136    detect_bom(In, Close0, Close).
  137
  138open_input2(stream(In), In, Options, true, _) :-
  139    !,
  140    (   stream_property(In, file_name(Name)),
  141	to_uri(Name, URI)
  142    ->  Options = [base(URI)]
  143    ;   Options = []
  144    ).
  145open_input2(In, In, Options, true, _) :-
  146    is_stream(In),
  147    !,
  148    (   stream_property(In, file_name(Name)),
  149	to_uri(Name, URI)
  150    ->  Options = [base(URI)]
  151    ;   Options = []
  152    ).
  153open_input2(URL, In, [base(URL)], close(In), Options) :-
  154    atom(URL),
  155    uri_file_name(URL, File),
  156    !,
  157    open(File, read, In, Options).
  158open_input2(URL, In, [base(Base)], close(In), Options) :-
  159    atom(URL),
  160    to_uri2(URL, Base),
  161    !,
  162    http_open(URL, In, Options).
  163open_input2(File, In, [base(URI)], close(In), Options) :-
  164    absolute_file_name(File, Path, [access(read)]),
  165    uri_file_name(URI, Path),
  166    open(Path, read, In, Options).

 detect_bom(+In, +Close0, -Close) is det

We may be loading a binary stream. In that case we want to do BOM detection.

  173detect_bom(In, Close0, Close) :-
  174    stream_property(In, type(binary)),
  175    stream_property(In, encoding(Enc)),
  176    catch(set_stream(In, encoding(bom)),_,fail),
  177    !,
  178    merge_close(Close0, set_stream(In, encoding(Enc)), Close).
  179detect_bom(_, Close, Close).
  180
  181merge_close(true, Close, Close) :- !.
  182merge_close(Close, _, Close).
  183
  184to_uri(URI0, URI) :-
  185    to_uri2(URI0, URI),
  186    !.
  187to_uri(URI0, URI) :-
  188    absolute_file_name(URI0, Path),
  189    uri_file_name(URI, Path).
  190
  191to_uri2(URI0, Base) :-
  192    uri_components(URI0, Components),
  193    uri_data(scheme, Components, Scheme),
  194    ground(Scheme),
  195    http_scheme(Scheme),
  196    !,
  197    uri_data(fragment, Components, _, Components2),
  198    uri_components(Base, Components2).
  199
  200http_scheme(http).
  201http_scheme(https).
  202
  203close_input(true).
  204close_input(close(X)) :- close(X).
  205close_input(set_stream(In, encoding(Enc))) :- set_stream(In, encoding(Enc)).
  206
  207read_dom(In, DOM, Options) :-
  208    option(dialect(Dialect), Options),
  209    !,
  210    (   xml_dialect(Dialect)
  211    ->  load_xml(stream(In), DOM, Options)
  212    ;   load_html(stream(In), DOM, Options)
  213    ).
  214read_dom(In, DOM, Options) :-
  215    peek_string(In, 1000, Start),
  216    guess_dialect(Start, Dialect),
  217    read_dom(In, DOM, [dialect(Dialect)|Options]).
  218
  219xml_dialect(xml).
  220xml_dialect(xmlns).
  221xml_dialect(svg).
  222xml_dialect(xhtml).
  223xml_dialect(xhtml5).
  224
  225guess_dialect(Start, Dialect) :-
  226    sub_string(Start, _, _, _, "<?xml"),
  227    !,
  228    Dialect = xml.
  229guess_dialect(Start, Dialect) :-
  230    sub_string(Start, _, _, _, "<html"),
  231    !,
  232    (   sub_string(Start, _, _, _, "xmlns:")
  233    ->  Dialect = xhtml
  234    ;   string_codes(Start, Codes),
  235	phrase(html_doctype(DialectFound), Codes, _)
  236    ->  Dialect = DialectFound
  237    ;   Dialect = html
  238    ).
  239guess_dialect(Start, Dialect) :-
  240    sub_string(Start, _, _, _, "<svg"),
  241    !,
  242    Dialect = svg.
  243guess_dialect(_, xml).
  244
  245html_doctype(html5) -->
  246    blanks,
  247    "<!DOCTYPE", blank, blanks, "html", blanks, ">",
  248    !.
  249html_doctype(html4) -->
  250    blanks,
  251    "<!", icase_string(`doctype`), blank, blanks, icase_string(`html`),
  252    blank, blanks,
  253    icase_string(`public`),
  254    blank,
  255    !.
  256
  257icase_string([]) --> [].
  258icase_string([H|T]) --> alpha_to_lower(H), icase_string(T).
  259
  260
  261		 /*******************************
  262		 *        DOM PROCESSING        *
  263		 *******************************/

 xml_rdfa(+DOM, -RDF, +Options)

True when RDF is a list of rdf(S,P,O) terms extracted from DOM according to the RDFa specification. Options processed:

base(+BaseURI)

URI to use for ''. Normally set to the document URI.

anon_prefix(+AnnonPrefix)

Prefix for blank nodes.

lang(+Lang)

Default for lang

vocab(+Vocab)

Default for vocab

markup(+Markup)

Markup language processed (xhtml, xml, ...)

  281xml_rdfa(DOM, _, _) :-
  282    var(DOM),
  283    !,
  284    instantiation_error(DOM).
  285xml_rdfa(DOM, RDF, Options) :-
  286    is_list(DOM),
  287    !,
  288    maplist(xml_rdfa_aux(Options), DOM, RDFList),
  289    append(RDFList, RDF).
  290xml_rdfa(DOM, RDF, Options) :-
  291    DOM = element(_,_,_),
  292    !,
  293    rdfa_evaluation_context(DOM, EvalContext, Options),
  294    process_node(DOM, EvalContext),
  295    arg(1, EvalContext.triples, List),
  296    reverse(List, RDF0),
  297    apply_patterns(RDF0, RDF).
  298% XML Processing Instruction (PI).
  299xml_rdfa(DOM, [], _) :-
  300    DOM = pi(_),
  301    !.
  302xml_rdfa(DOM, _, _) :-
  303    type_error(xml_dom, DOM).
  304
  305xml_rdfa_aux(Options, DOM, RDF) :-
  306    xml_rdfa(DOM, RDF, Options).
  307
  308process_node(DOM, EvalContext) :-
  309    rdfa_local_context(EvalContext, LocalContext),  % 7.5.1
  310    update_vocab(DOM, LocalContext),                % 7.5.2
  311    update_prefixes(DOM, LocalContext),             % 7.5.3
  312    update_lang(DOM, LocalContext),                 % 7.5.4
  313    update_subject(DOM, LocalContext),              % 7.5.5, 7.5.6
  314    emit_typeof(DOM, LocalContext),                 % 7.5.7
  315    update_list_mapping(DOM, LocalContext),         % 7.5.8
  316    step_7_5_9(DOM, LocalContext),                  % 7.5.9
  317    step_7_5_10(DOM, LocalContext),                 % 7.5.10
  318    update_property_value(DOM, LocalContext),       % 7.5.11
  319    complete_triples(LocalContext),                 % 7.5.12
  320    descent(DOM, LocalContext),                     % 7.5.13
  321    complete_lists(LocalContext),
  322    !.                % 7.5.14
  323:- if(current_predicate(gtrace/0)).  324process_node(DOM, EvalContext) :-
  325    print_message(warning, rdfa(failed(DOM, EvalContext))),
  326    (   debugging(rdfa(test))
  327    ->  gtrace,
  328	process_node(DOM, EvalContext)
  329    ;   true
  330    ).
  331:- endif.

 rdfa_evaluation_context(+DOM, -Context, +Options)

7.5.0: Create the initial evaluation context

To be done

- : derive markup from DOM

  339rdfa_evaluation_context(DOM, Context, Options) :-
  340    Context = rdfa_eval{base:Base,                  % atom
  341			parent_subject:Base,        % atom
  342			parent_object:null,         % null or atom
  343			incomplete_triples:[],      % list
  344			list_mapping:ListMapping,   % IRI --> list(List)
  345			lang:Lang,                  % null or atom
  346			iri_mapping:IRIMappings,    % dict
  347			term_mapping:TermMappings,  % dict
  348			vocab:Vocab,                % null or atom
  349			bnode_id:bnode(1),          % integer
  350			markup:Markup,              % Processing profile
  351			anon_prefix:AnonPrefix,
  352			named_bnodes:r{v:_{}},
  353			root:DOM,                   % XML DOM
  354			triples:triples([])},       % list
  355    empty_list_mapping(ListMapping),
  356    option(markup(Markup), Options, xhtml),
  357    base(DOM, Options, Base),
  358    default_vocab(Markup, DefaultVocab),
  359    option(lang(Lang), Options, ''),
  360    option(vocab(Vocab), Options, DefaultVocab),
  361    (   option(anon_prefix(AnonPrefix), Options)
  362    ->  true
  363    ;   atom_concat('__', Base, AnonPrefix)
  364    ),
  365    default_prefixes(Markup, DefPrefixes),
  366    mapping(prefixes(IRIMappings0), Options),
  367    put_dict(DefPrefixes, IRIMappings0, IRIMappings),
  368    mapping(terms(TermMappings), Options).
  369
  370base(DOM, _Options, Base) :-
  371    xpath(DOM, //base(@href=Base), _),
  372    !.
  373base(_DOM, Options, Base) :-
  374    option(base(Base0), Options),
  375    rdf_global_id(Base0, Base),
  376    !.
  377base(_, _, 'http://www.example.org/').
  378
  379mapping(Term, Options) :-
  380    Term =.. [Name, Value],
  381    (   TermG =.. [Name, Var],
  382	option(TermG, Options)
  383    ->  dict_create(Value, Name, Var)
  384    ;   dict_create(Value, Name, [])
  385    ).

 default_prefixes(+Markup, -Dict)

Create a default prefix map. Which prefixes are supposed to be in this map?

  392default_prefixes(Markup, _{'':DefPrefix}) :-
  393    default_prefix_mapping(Markup, DefPrefix).

 rdfa_core_prefix(?Prefix, ?URI) is nondet

RDFa initial context prefix declarations.

See also

- http://www.w3.org/2011/rdfa-context/rdfa-1.1

  401rdfa_core_prefix(dcat,    'http://www.w3.org/ns/dcat#').
  402rdfa_core_prefix(qb,      'http://purl.org/linked-data/cube#').
  403rdfa_core_prefix(grddl,   'http://www.w3.org/2003/g/data-view#').
  404rdfa_core_prefix(ma,      'http://www.w3.org/ns/ma-ont#').
  405rdfa_core_prefix(org,     'http://www.w3.org/ns/org#').
  406rdfa_core_prefix(owl,     'http://www.w3.org/2002/07/owl#').
  407rdfa_core_prefix(prov,    'http://www.w3.org/ns/prov#').
  408rdfa_core_prefix(rdf,     'http://www.w3.org/1999/02/22-rdf-syntax-ns#').
  409rdfa_core_prefix(rdfa,    'http://www.w3.org/ns/rdfa#').
  410rdfa_core_prefix(rdfs,    'http://www.w3.org/2000/01/rdf-schema#').
  411rdfa_core_prefix(rif,     'http://www.w3.org/2007/rif#').
  412rdfa_core_prefix(rr,      'http://www.w3.org/ns/r2rml#').
  413rdfa_core_prefix(sd,      'http://www.w3.org/ns/sparql-service-description#').
  414rdfa_core_prefix(skos,    'http://www.w3.org/2004/02/skos/core#').
  415rdfa_core_prefix(skosxl,  'http://www.w3.org/2008/05/skos-xl#').
  416rdfa_core_prefix(wdr,     'http://www.w3.org/2007/05/powder#').
  417rdfa_core_prefix(void,    'http://rdfs.org/ns/void#').
  418rdfa_core_prefix(wdrs,    'http://www.w3.org/2007/05/powder-s#').
  419rdfa_core_prefix(xhv,     'http://www.w3.org/1999/xhtml/vocab#').
  420rdfa_core_prefix(xml,     'http://www.w3.org/XML/1998/namespace').
  421rdfa_core_prefix(xsd,     'http://www.w3.org/2001/XMLSchema#').
  422rdfa_core_prefix(cc,      'http://creativecommons.org/ns#').
  423rdfa_core_prefix(ctag,    'http://commontag.org/ns#').
  424rdfa_core_prefix(dc,      'http://purl.org/dc/terms/').
  425rdfa_core_prefix(dcterms, 'http://purl.org/dc/terms/').
  426rdfa_core_prefix(dc11,    'http://purl.org/dc/elements/1.1/').
  427rdfa_core_prefix(foaf,    'http://xmlns.com/foaf/0.1/').
  428rdfa_core_prefix(gr,      'http://purl.org/goodrelations/v1#').
  429rdfa_core_prefix(ical,    'http://www.w3.org/2002/12/cal/icaltzd#').
  430rdfa_core_prefix(og,      'http://ogp.me/ns#').
  431rdfa_core_prefix(rev,     'http://purl.org/stuff/rev#').
  432rdfa_core_prefix(sioc,    'http://rdfs.org/sioc/ns#').
  433rdfa_core_prefix(v,       'http://rdf.data-vocabulary.org/#').
  434rdfa_core_prefix(vcard,   'http://www.w3.org/2006/vcard/ns#').
  435rdfa_core_prefix(schema,  'http://schema.org/').
  436
  437default_prefix_mapping(xhtml, 'http://www.w3.org/1999/xhtml/vocab#') :- !.
  438default_prefix_mapping(_,     'http://www.example.org/').
  439
  440default_vocab(_, '').

 rdfa_local_context(EvalContext, LocalContext)

7.5.1: Create the local context

  446rdfa_local_context(EvalContext, LocalContext) :-
  447    LocalContext = rdfa_local{skip_element:false,
  448			      new_subject:null,
  449			      current_object_resource:null,
  450			      typed_resource:null,
  451			      iri_mapping:IRIMappings,
  452			      incomplete_triples:[],
  453			      list_mapping:ListMapping,
  454			      lang:Lang,
  455			      term_mapping:TermMapping,
  456			      vocab:Vocab,
  457			      eval_context:EvalContext
  458			     },
  459    _{ iri_mapping:IRIMappings,
  460       list_mapping:ListMapping,
  461       lang:Lang,
  462       term_mapping:TermMapping,
  463       vocab:Vocab
  464     } :< EvalContext.

 update_vocab(+DOM, +Context) is det

7.5.2. Handle @vocab

  471update_vocab(DOM, Context) :-
  472    xpath(DOM, /(*(@vocab=Vocab0)), _),
  473    !,
  474    (   Vocab0 == ''
  475    ->  Vocab = ''                  % Host Language defined default?
  476    ;   iri(Vocab0, Vocab, Context)
  477    ),
  478    nb_set_dict(vocab, Context, Vocab),
  479    add_triple(Context,
  480	       Context.eval_context.base,
  481	       rdfa:usesVocabulary,
  482	       Vocab).
  483update_vocab(_, _).

 update_prefixes(+DOM, +Context) is det

7.5.3: Update prefix map using @prefix and @xmlns. First processes xmlns:Prefix=IRI.

  490update_prefixes(DOM, Context) :-
  491    DOM=element(_,Attrs,_),
  492    xmlns_dict(Attrs, _{}, Dict0),
  493    (   xpath(DOM, /(*(@prefix=PrefixDecl)), _)
  494    ->  prefix_dict(PrefixDecl, Dict0, Dict)
  495    ;   Dict = Dict0
  496    ),
  497    Dict \= _{},
  498    !,
  499    put_dict(Dict, Context.iri_mapping, NewMapping),
  500    b_set_dict(iri_mapping, Context, NewMapping).
  501update_prefixes(_, _).
  502
  503xmlns_dict([], Dict, Dict).
  504xmlns_dict([Attr=IRI|T0], Dict0, Dict) :-
  505    (   Attr = xmlns:Name
  506    ;   atom_concat('xmlns:', Name, Attr)
  507    ),
  508    !,
  509    downcase_atom(Name, Prefix),
  510    put_dict(Prefix, Dict0, IRI, Dict1),
  511    xmlns_dict(T0, Dict1, Dict).
  512xmlns_dict([_|T0], Dict0, Dict) :-
  513    xmlns_dict(T0, Dict0, Dict).
  514
  515prefix_dict(Text, Dict0, Dict) :-
  516    atom_codes(Text, Codes),
  517    phrase(prefixes(Dict0, Dict), Codes).

 update_lang(+DOM, +Context) is det

7.5.4: Update lang

  523update_lang(DOM, Context) :-
  524    DOM=element(_,Attrs,_),
  525    (   (   memberchk(xml:lang=Lang, Attrs)         % XML with namespaces
  526	;   memberchk('xml:lang'=Lang, Attrs)       % XML without namespaces
  527	;   memberchk(lang=Lang, Attrs)             % HTML 5
  528	)
  529    ->  nb_set_dict(lang, Context, Lang)
  530    ;   true
  531    ),
  532    (   (   memberchk(xml:base=Base, Attrs)         % XML with namespaces
  533	;   memberchk('xml:base'=Base, Attrs)       % XML without namespaces
  534	)
  535    ->  nb_set_dict(base, Context.eval_context, Base)
  536    ;   true
  537    ).

 update_subject(+DOM, +Context) is det

7.5.5 and 7.5.6: establish a value for new subject

  544update_subject(DOM, Context) :-
  545    DOM=element(E,Attrs,_),
  546    \+ has_attribute(rel, Attrs, Context),
  547    \+ has_attribute(rev, Attrs, Context),    % Commit to rule-set 7.5.5
  548    !,
  549    (   memberchk(property=_, Attrs),
  550	\+ memberchk(content=_, Attrs),
  551	\+ memberchk(datatype=_, Attrs)
  552    ->  (   (   about(DOM, About, Context)  % 7.5.5.1
  553	    ;   About = Context.eval_context.parent_object
  554	    ),
  555	    About \== null
  556	->  nb_set_dict(new_subject, Context, About)
  557	;   true
  558	),
  559	(   memberchk(typeof=_, Attrs)
  560	->  (   (   iri_attr(about, Attrs, TypedIRI, Context),
  561		    TypedIRI \== null
  562		;   DOM == Context.eval_context.root
  563		->  iri('', TypedIRI, Context)
  564		;   (   iri_attr(resource, Attrs, TypedIRI, Context)
  565		    ;   iri_attr(href,     Attrs, TypedIRI, Context)
  566		    ;   iri_attr(src,      Attrs, TypedIRI, Context)
  567		    ;   new_bnode(TypedIRI, Context)
  568		    ),
  569		    TypedIRI \== null
  570		->  nb_set_dict(typed_resource, Context, TypedIRI),
  571		    nb_set_dict(current_object_resource, Context, TypedIRI)
  572		)
  573	    ->  nb_set_dict(typed_resource, Context, TypedIRI)
  574	    ;   true
  575	    )
  576	;   true
  577	)
  578    ;   (   new_subject_attr_2(SubjectAttr),        % 7.5.5.2
  579	    memberchk(SubjectAttr=About0, Attrs),
  580	    attr_convert(SubjectAttr, About0, About, Context),
  581	    About \== null
  582	->  true
  583	;   html_root(E, Context),
  584	    About = Context.eval_context.parent_object,
  585	    About \== null
  586	->  true
  587	;   DOM == Context.eval_context.root
  588	->  iri('', About, Context)
  589	;   memberchk(typeof=_, Attrs)
  590	->  new_bnode(About, Context)
  591	;   About = Context.eval_context.parent_object,
  592	    About \== null
  593	->  (   \+ memberchk(typeof=_, Attrs)
  594	    ->  nb_set_dict(skip_element, Context, true)
  595	    ;   true
  596	    )
  597	),
  598	debug(rdfa(new_subject), '~w: set new_subject to ~p', [E, About]),
  599	nb_set_dict(new_subject, Context, About),
  600	(   memberchk(typeof=_, Attrs)
  601	->  nb_set_dict(typed_resource, Context, About)
  602	;   true
  603	)
  604    ).
  605update_subject(DOM, Context) :-
  606    DOM=element(_,Attrs,_),                 % 7.5.6
  607    (   iri_attr(about, Attrs, NewSubject, Context)
  608    ->  nb_set_dict(new_subject, Context, NewSubject),
  609	(   memberchk(typeof=_, Attrs)
  610	->  nb_set_dict(typed_resource, Context, NewSubject)
  611	;   true
  612	)
  613    ;   true        % was \+ memberchk(resource=_, Attrs):
  614		    % If no resource is provided ...
  615    ->  (   DOM == Context.eval_context.root
  616	->  iri('', NewSubject, Context),
  617	    nb_set_dict(new_subject, Context, NewSubject),
  618	    (   memberchk(typeof=_, Attrs)
  619	    ->  nb_set_dict(typed_resource, Context, NewSubject)
  620	    ;   true
  621	    )
  622	;   NewSubject = Context.eval_context.parent_object,
  623	    NewSubject \== null
  624	->  nb_set_dict(new_subject, Context, NewSubject)
  625	;   true
  626	)
  627    ),
  628    (   (   iri_attr(resource, Attrs, CurrentObjectResource, Context)
  629	;   iri_attr(href,     Attrs, CurrentObjectResource, Context)
  630	;   iri_attr(src,      Attrs, CurrentObjectResource, Context)
  631	;   memberchk(typeof=_, Attrs),
  632	    \+ memberchk(about=_, Attrs),
  633	    new_bnode(CurrentObjectResource, Context)
  634	),
  635	CurrentObjectResource \== null
  636    ->  nb_set_dict(current_object_resource, Context, CurrentObjectResource)
  637    ;   true
  638    ),
  639    (   memberchk(typeof=_, Attrs),
  640	\+ memberchk(about=_, Attrs)
  641    ->  nb_set_dict(typed_resource, Context,
  642		    Context.current_object_resource)
  643    ;   true
  644    ).
  645
  646new_subject_attr_2(about).
  647new_subject_attr_2(resource).
  648new_subject_attr_2(href).
  649new_subject_attr_2(src).
  650
  651html_root(head, Context) :- html_markup(Context.eval_context.markup).
  652html_root(body, Context) :- html_markup(Context.eval_context.markup).
  653
  654html_markup(html).
  655html_markup(xhtml).

 emit_typeof(+DOM, +LocalContext) is det

7.5.7: emit triples for @typeof value.

  661emit_typeof(DOM, Context) :-
  662    DOM = element(_,Attrs,_),
  663    Subject = Context.typed_resource,
  664    Subject \== null,
  665    memberchk(typeof=TypeOf, Attrs),
  666    !,
  667    iri_list(TypeOf, IRIs, Context),
  668    maplist(type_triple(Context), IRIs).
  669emit_typeof(_, _).
  670
  671type_triple(Context, IRI) :-
  672    add_triple(Context, Context.typed_resource, rdf:type, IRI).

 update_list_mapping(+DOM, +Context) is det

7.5.8: Create a list mapping if appropriate

  678update_list_mapping(_DOM, Context) :-
  679    Context.new_subject \== null,
  680    Context.new_subject \== Context.eval_context.parent_object,
  681    !,
  682    empty_list_mapping(ListMapping),
  683    b_set_dict(list_mapping, Context, ListMapping).
  684update_list_mapping(_, _).

 empty_list_mapping(-Mapping) is det

empty_list_mapping(+Mapping) is semidet

 get_list_mapping(+IRI, +Mapping, -List) is semidet

 add_list_mapping(+IRI, !Mapping, +List) is det

Manage a list mapping. Note this needs to be wrapped in a term to be able to extend the mapping while keeping its identity.

  694empty_list_mapping(list_mapping(_{})).
  695
  696get_list_mapping(IRI, list_mapping(Dict), Dict.get(IRI)).
  697
  698add_list_mapping(IRI, LM, List) :-
  699    LM = list_mapping(Dict),
  700    setarg(1, LM, Dict.put(IRI, List)).
  701
  702list_mapping_pairs(list_mapping(Dict), Pairs) :-
  703    dict_pairs(Dict, _, Pairs).

 step_7_5_9(+DOM, +Context)

  708step_7_5_9(_DOM, Context) :-
  709    Context.current_object_resource == null,
  710    !.
  711step_7_5_9(DOM, Context) :-
  712    DOM = element(_,Attrs,_),
  713    memberchk(inlist=_, Attrs),
  714    has_attribute(rel, Attrs, Rel, Context),
  715    !,
  716    iri_list(Rel, Preds, Context),
  717    CurrentObjectResource = Context.current_object_resource,
  718    maplist(add_property_list(Context, CurrentObjectResource),
  719	    Preds).
  720step_7_5_9(DOM, Context) :-
  721    DOM = element(_,Attrs,_),
  722    (   has_attribute(rel, Attrs, Rel, Context),
  723	\+ memberchk(inlist=_, Attrs)
  724    ->  iri_list(Rel, RelIRIs, Context),
  725	maplist(rel_triple(Context), RelIRIs)
  726    ;   true
  727    ),
  728    (   has_attribute(rev, Attrs, Rev, Context)
  729    ->  iri_list(Rev, RevIRIs, Context),
  730	maplist(rev_triple(Context), RevIRIs)
  731    ;   true
  732    ).
  733
  734rel_triple(Context, IRI) :-
  735    add_triple(Context,
  736	       Context.new_subject, IRI, Context.current_object_resource).
  737
  738rev_triple(Context, IRI) :-
  739    add_triple(Context,
  740	       Context.current_object_resource, IRI, Context.new_subject).

 step_7_5_10(+DOM, +Context)

Similar to step_7_5_9, but adding to incomplete triples.

  746step_7_5_10(_DOM, Context) :-
  747    Context.current_object_resource \== null,
  748    !.
  749step_7_5_10(DOM, Context) :-
  750    DOM = element(_,Attrs,_),
  751    memberchk(inlist=_, Attrs),
  752    has_attribute(rel, Attrs, Rel, Context),
  753    !,
  754    set_current_object_resource_to_bnode(Context),
  755    iri_list(Rel, IRIs, Context),
  756    maplist(incomplete_ll_triple(Context), IRIs).
  757step_7_5_10(DOM, Context) :-
  758    DOM = element(_,Attrs,_),
  759    (   has_attribute(rel, Attrs, Rel, Context),
  760	\+ memberchk(inlist=_, Attrs)
  761    ->  iri_list(Rel, RelIRIs, Context),
  762	set_current_object_resource_to_bnode(Context),
  763	maplist(incomplete_rel_triple(Context), RelIRIs)
  764    ;   true
  765    ),
  766    (   has_attribute(rev, Attrs, Rev, Context)
  767    ->  iri_list(Rev, RevIRIs, Context),
  768	set_current_object_resource_to_bnode(Context),
  769	maplist(incomplete_rev_triple(Context), RevIRIs)
  770    ;   true
  771    ).
  772
  773set_current_object_resource_to_bnode(Context) :-
  774    new_bnode(BNode, Context),
  775    b_set_dict(current_object_resource, Context, BNode).
  776
  777incomplete_ll_triple(Context, IRI) :-
  778    LM = Context.list_mapping,
  779    (   get_list_mapping(IRI, LM, LL)
  780    ->  true
  781    ;   LL = list([]),
  782	add_list_mapping(IRI, LM, LL)
  783    ),
  784    add_incomplete_triple(Context, _{list:LL, direction:none}).
  785
  786incomplete_rel_triple(Context, IRI) :-
  787    add_incomplete_triple(Context, _{predicate:IRI, direction:forward}).
  788
  789incomplete_rev_triple(Context, IRI) :-
  790    add_incomplete_triple(Context, _{predicate:IRI, direction:reverse}).

 update_property_value(+DOM, +Context) is det

7.5.11: establish current property value.

  797update_property_value(DOM, Context) :-
  798    DOM = element(Element,Attrs,Content),
  799    memberchk(property=PropSpec, Attrs),
  800    !,
  801    iri_list(PropSpec, Preds, Context),
  802    (   memberchk(datatype=DTSpec, Attrs)
  803    ->  (   DTSpec \== '',
  804	    term_or_curie_or_absiri(DTSpec, DataType, Context),
  805	    DataType \== null
  806	->  (   (   rdf_equal(rdf:'XMLLiteral', DataType)
  807		;   rdf_equal(rdf:'HTML', DataType)
  808		)
  809	    ->  content_xml(Content, Text)
  810	    ;   content_text(DOM, Text, Context)
  811	    ),
  812	    Obj0 = literal(type(DataType, Text))
  813	;   content_text(DOM, Text, Context),
  814	    Obj0 = literal(Text)
  815	)
  816    ;   memberchk(content=Text, Attrs)
  817    ->  Obj0 = literal(Text)
  818    ;   \+ has_attribute(rel, Attrs, Context),
  819	\+ has_attribute(rev, Attrs, Context),
  820	%\+ memberchk(content=_, Attrs),    % already guaranteed
  821	(   iri_attr(resource, Attrs, Obj0, Context)
  822	;   iri_attr(href,     Attrs, Obj0, Context)
  823	;   iri_attr(src,      Attrs, Obj0, Context)
  824	),
  825	Obj0 \== null
  826    ->  true
  827    ;   (   memberchk(datetime=DateTime, Attrs)
  828	;   Element == time,
  829	    Content = [DateTime]
  830	),
  831	html_markup(Context.eval_context.markup)
  832    ->  (   date_time_type(DateTime, DataType)
  833	->  Obj0 = literal(type(DataType, DateTime))
  834	;   Obj0 = literal(DateTime)
  835	)
  836    ;   memberchk(typeof=_, Attrs),
  837	\+ memberchk(about=_, Attrs)
  838    ->  Obj0 = Context.typed_resource
  839    ;   content_text(Content, Text, Context), % "as a plain literal"???
  840	Obj0 = literal(Text)
  841    ),
  842    (   Obj0 = literal(Text),
  843	atomic(Text),
  844	Context.lang \== ''
  845    ->  Obj = literal(lang(Context.lang, Text))
  846    ;   Obj = Obj0
  847    ),
  848    (   memberchk(inlist=_, Attrs)
  849    ->  maplist(add_property_list(Context, Obj), Preds)
  850    ;   NewSubject = Context.new_subject,
  851	maplist(add_property(Context, NewSubject, Obj), Preds)
  852    ).
  853update_property_value(_, _).
  854
  855add_property_list(Context, Obj, Pred) :-
  856    LM = Context.list_mapping,
  857    (   get_list_mapping(Pred, LM, LL)
  858    ->  LL = list(Old),
  859	setarg(1, LL, [Obj|Old])
  860    ;   add_list_mapping(Pred, LM, list([Obj]))
  861    ).
  862
  863add_property(Context, Subject, Object, Pred) :-
  864    add_triple(Context, Subject, Pred, Object).
  865
  866content_text(element(_,Attrs,_), Text, _Context) :-
  867    memberchk(content=Text, Attrs),
  868    !.
  869content_text(element(_,Attrs,_), Text, Context) :-
  870    memberchk(datetime=Text, Attrs),
  871    html_markup(Context.eval_context.markup),
  872    !.
  873content_text(element(_,_,Content), Text, _Context) :-
  874    !,
  875    phrase(text_nodes(Content), Texts),
  876    atomic_list_concat(Texts, Text).
  877content_text(Content, Text, _Context) :-
  878    !,
  879    phrase(text_nodes(Content), Texts),
  880    atomic_list_concat(Texts, Text).
  881
  882text_nodes([]) --> !.
  883text_nodes([H|T]) --> !, text_nodes(H), text_nodes(T).
  884text_nodes(element(_,_,Content)) --> !, text_nodes(Content).
  885text_nodes(CDATA) --> [CDATA].
  886
  887content_xml(DOM, Text) :-
  888    with_output_to(atom(Text), xml_write(DOM, [header(false)])).

 complete_triples(+Context)

7.5.12: Complete incomplete triples

  894complete_triples(Context) :-
  895    Context.skip_element == false,
  896    Context.new_subject \== null,
  897    Context.eval_context.incomplete_triples \== [],
  898    !,
  899    reverse(Context.eval_context.incomplete_triples, Incomplete),
  900    maplist(complete_triple(Context), Incomplete).
  901complete_triples(_).
  902
  903complete_triple(Context, Dict) :-
  904    complete_triple(Dict.direction, Dict, Context).
  905
  906complete_triple(none, Dict, Context) :-
  907    List = Dict.list,
  908    List = list(Old),
  909    setarg(1, List, [Context.new_subject|Old]).
  910complete_triple(forward, Dict, Context) :-
  911    add_triple(Context,
  912	       Context.eval_context.parent_subject,
  913	       Dict.predicate,
  914	       Context.new_subject).
  915complete_triple(reverse, Dict, Context) :-
  916    add_triple(Context,
  917	       Context.new_subject,
  918	       Dict.predicate,
  919	       Context.eval_context.parent_subject).

 descent(DOM, Context)

7.5.13: Descent into the children

  926descent(element(_,_,Content), Context) :-
  927    (   Context.skip_element == true
  928    ->  maplist(descent_skip(Context), Content)
  929    ;   maplist(descent_no_skip(Context), Content)
  930    ).
  931
  932descent_skip(Context, DOM) :-
  933    DOM = element(E,_,_),
  934    !,
  935    debug(rdfa(descent), 'skip: ~w: new_subject=~p',
  936	  [E, Context.new_subject]),
  937    process_node(DOM, Context.eval_context.put(
  938			  _{ lang:Context.lang,
  939			     vocab:Context.vocab,
  940			     iri_mapping:Context.iri_mapping
  941			   })).
  942descent_skip(_, _).
  943
  944descent_no_skip(Context, DOM) :-
  945    DOM = element(E,_,_),
  946    !,
  947    (   ParentSubject = Context.new_subject,
  948	ParentSubject \== null
  949    ->  true
  950    ;   ParentSubject = Context.eval_context.parent_subject
  951    ),
  952    (   ParentObject = Context.current_object_resource,
  953	ParentObject \== null
  954    ->  true
  955    ;   ParentObject = ParentSubject
  956    ),
  957    debug(rdfa(descent), 'no skip: ~w: parent subject = ~p, object = ~p',
  958	  [E, ParentSubject, ParentObject]),
  959    process_node(DOM, Context.eval_context.put(
  960			  _{ parent_subject:ParentSubject,
  961			     parent_object:ParentObject,
  962			     iri_mapping:Context.iri_mapping,
  963			     incomplete_triples:Context.incomplete_triples,
  964			     list_mapping:Context.list_mapping,
  965			     lang:Context.lang,
  966			     vocab:Context.vocab
  967			    })).
  968descent_no_skip(_, _).

 complete_lists(+Context) is det

7.5.14: Complete possibly pending lists

  974complete_lists(Context) :-
  975    empty_list_mapping(Context.list_mapping),
  976    !.
  977complete_lists(Context) :-
  978    (   CurrentSubject = Context.new_subject,
  979	CurrentSubject \== null
  980    ->  true
  981    ;   CurrentSubject = Context.eval_context.base
  982    ),
  983    list_mapping_pairs(Context.list_mapping, Pairs),
  984    maplist(complete_list(Context, CurrentSubject), Pairs).
  985
  986complete_list(Context, _, IRI-_) :-
  987    get_list_mapping(IRI, Context.eval_context.list_mapping, _),
  988    !.
  989complete_list(Context, CurrentSubject, IRI-list(List0)) :-
  990    reverse(List0, List),
  991    emit_list(List, ListURI, Context),
  992    add_triple(Context, CurrentSubject, IRI, ListURI).
  993
  994emit_list([], NIL, _) :-
  995    rdf_equal(NIL, rdf:nil).
  996emit_list([H|T], URI, Context) :-
  997    emit_list(T, TailURI, Context),
  998    new_bnode(URI, Context),
  999    add_triple(Context, URI, rdf:first, H),
 1000    add_triple(Context, URI, rdf:rest, TailURI).

 has_attribute(+Name, +Attrs, +Context) is semidet

 has_attribute(+Name, +Attrs, -Value, +Context) is semidet

True if Attrs contains Name. We sometimes need to ignore Attributes if their value is invalid.

See also

- HTML+RDFa, 3.1 Additional RDFa Processing Rules, point 7.

 1011has_attribute(Name, Attrs, Context) :-
 1012    has_attribute(Name, Attrs, _, Context).
 1013
 1014has_attribute(rel, Attrs, Rel, Context) :-
 1015    memberchk(rel=Rel, Attrs),
 1016    html_markup(Context.eval_context.markup),
 1017    memberchk(property=_, Attrs),
 1018    !,
 1019    html_non_empty_rel(Rel, Context).
 1020has_attribute(rev, Attrs, Rev, Context) :-
 1021    memberchk(rev=Rev, Attrs),
 1022    html_markup(Context.eval_context.markup),
 1023    memberchk(property=_, Attrs),
 1024    !,
 1025    html_non_empty_rel(Rev, Context).
 1026has_attribute(Name, Attrs, Value, _Context) :-
 1027    memberchk(Name=Value, Attrs).
 1028
 1029html_non_empty_rel(Spec, Context) :-
 1030    Sep = "\s\t\n\r",
 1031    split_string(Spec, Sep, Sep, SpecList),
 1032    member(Spec1, SpecList),
 1033    safe_curie_or_curie_or_absiri(Spec1, _, Context),
 1034    !.

 iri_attr(+AttName, +Attrs, -IRI, +Context) is semidet

 1039iri_attr(Name, Attrs, IRI, Context) :-
 1040    memberchk(Name=IRI0, Attrs),
 1041    attr_convert(Name, IRI0, IRI, Context).
 1042
 1043attr_convert(about, Spec, IRI, Context) :-
 1044    safe_curie_or_curie_or_iri(Spec, IRI, Context).
 1045attr_convert(href, Spec, IRI, Context) :-
 1046    iri(Spec, IRI, Context).
 1047attr_convert(src, Spec, IRI, Context) :-
 1048    iri(Spec, IRI, Context).
 1049attr_convert(resource, Spec, IRI, Context) :-
 1050    safe_curie_or_curie_or_iri(Spec, IRI, Context).
 1051attr_convert(vocab, Spec, IRI, Context) :-
 1052    iri(Spec, IRI, Context).
 1053attr_convert(datatype, Spec, IRI, Context) :-
 1054    term_or_curie_or_absiri(Spec, IRI, Context).
 1055
 1056
 1057about(DOM, About, Context) :-
 1058    DOM=element(_,Attrs,_),
 1059    (   memberchk(about=About0, Attrs)
 1060    ->  safe_curie_or_curie_or_iri(About0, About, Context)
 1061    ;   DOM == Context.eval_context.root
 1062    ->  iri('', About, Context)
 1063    ).

 new_bnode(-BNode, +Context) is det

Create a new blank node. Note that the current id is kept in a term to avoid copying the counter on the descent step.

 1070new_bnode(BNode, Context) :-
 1071    EvalCtx = Context.eval_context,
 1072    Node = EvalCtx.bnode_id,
 1073    arg(1, Node, Id),
 1074    succ(Id, Id1),
 1075    nb_setarg(1, Node, Id1),
 1076    Prefix = EvalCtx.anon_prefix,
 1077    (   atom(Prefix)
 1078    ->  atom_concat(Prefix, Id, BNode)
 1079    ;   BNode = bnode(Id)
 1080    ).

 iri_list(+Spec, -IRIs, +Context) is det

True when IRIs is a list of fulfy qualified IRIs from Spec

 1086iri_list(Spec, IRIs, Context) :-
 1087    Sep = "\s\t\n\r",
 1088    split_string(Spec, Sep, Sep, SpecList),
 1089    (   SpecList == [""]
 1090    ->  IRIs = []
 1091    ;   maplist(ctx_to_iri(Context), SpecList, IRIs0),
 1092	exclude(==(null), IRIs0, IRIs)
 1093    ).
 1094
 1095ctx_to_iri(Context, Spec, IRI) :-
 1096    term_or_curie_or_absiri(Spec, IRI, Context).

 iri(+Spec, -IRI, +Context)

Used for @href and @src attributes

 1102iri(Spec, IRI, Context) :-
 1103    iri_normalized(Spec, Context.eval_context.base, IRI).
 1104
 1105abs_iri(Spec, IRI) :-
 1106    uri_components(Spec, Components),
 1107    uri_data(authority, Components, Authority), nonvar(Authority),
 1108    uri_data(scheme,    Components, Scheme),    nonvar(Scheme),
 1109    !,
 1110    iri_normalized(Spec, IRI).

 safe_curie_or_curie_or_iri(+Spec, -IRI, +Context) is det

Implement section 7.4, CURIE and IRI Processing. Used for @about and @resource

 1118safe_curie_or_curie_or_iri(Spec, IRI, Context) :-
 1119    safe_curie_or_curie_or_absiri(Spec, IRI, Context),
 1120    !.
 1121safe_curie_or_curie_or_iri(Spec, IRI, Context) :-
 1122    uri_normalized(Spec, Context.eval_context.base, IRI).
 1123
 1124safe_curie_or_curie_or_absiri(Spec, IRI, _Context) :-
 1125    abs_iri(Spec, IRI0),
 1126    !,
 1127    IRI = IRI0.
 1128safe_curie_or_curie_or_absiri(Spec, IRI, Context) :-
 1129    atom_codes(Spec, Codes),
 1130    (   safe_curie(Codes, Curie)
 1131    ->  (   phrase(curie(IRI, Context), Curie)
 1132	->  true
 1133	;   IRI = null
 1134	)
 1135    ;   phrase(curie(IRI, Context), Codes)
 1136    ).
 1137
 1138safe_curie(Codes, Curie) :-
 1139    append([0'[|Curie], `]`, Codes).
 1140
 1141curie(IRI, Context) -->
 1142    "_:", !, reference_or_empty(Reference),
 1143    {   IRI = Context.eval_context.named_bnodes.v.get(Reference)
 1144    ->  true
 1145    ;   new_bnode(IRI, Context),
 1146	b_set_dict(v, Context.eval_context.named_bnodes,
 1147		   Context.eval_context.named_bnodes.v.put(Reference, IRI))
 1148    }.
 1149curie(IRI, Context) -->
 1150    ":", !, reference_or_empty(Reference),
 1151    { atom_concat(Context.iri_mapping.get(''), Reference, IRI) }.
 1152curie(IRI, Context) -->
 1153    nc_name(Prefix), ":", !, reference_or_empty(Reference),
 1154    {   atom_concat(Context.iri_mapping.get(Prefix), Reference, IRI0)
 1155    ->  IRI = IRI0
 1156    ;   rdfa_core_prefix(Prefix, URIPrefix)
 1157    ->  atom_concat(URIPrefix, Reference, IRI)
 1158    }.

 term_or_curie_or_absiri(+Spec, -IRI, +Context) is det

Used for @datatype and @property, @typeof, @rel and @rev

 1164term_or_curie_or_absiri(Spec, IRI, _Context) :-
 1165    abs_iri(Spec, IRI0),
 1166    !,
 1167    IRI = IRI0.
 1168term_or_curie_or_absiri(Spec, IRI, Context) :-
 1169    atom_codes(Spec, Codes),
 1170    (   phrase(term(Term), Codes),
 1171	downcase_atom(Term, LwrCase)
 1172    ->  (   Vocab = Context.vocab,
 1173	    Vocab \== ''
 1174	->  atom_concat(Vocab, Term, IRI)
 1175	;   term_iri(LwrCase, Context.eval_context.markup, IRI0)
 1176	->  IRI = IRI0
 1177	;   IRI = Context.term_mapping.get(Term)
 1178	->  true
 1179	;   dict_pairs(Context.term_mapping, _Tag, Pairs),
 1180	    member(TermCaps-IRI, Pairs),
 1181	    downcase_atom(TermCaps, LwrCase)
 1182	->  true
 1183	;   IRI = null
 1184	)
 1185    ;   phrase(curie(IRI, Context), Codes)
 1186    ->  true
 1187    ;   uri_normalized(Spec, Context.eval_context.base, IRI)
 1188    ).

 term_iri(?Term, ?Markup, ?IRI)

See also

- http://www.w3.org/2011/rdfa-context/xhtml-rdfa-1.1

 1194term_expansion(term_iri(Term, Markup), term_iri(Term, Markup, URI)) :-
 1195    default_prefix_mapping(Markup, Prefix),
 1196    atom_concat(Prefix, Term, URI).
 1197
 1198term_iri(alternate,  xhtml).
 1199term_iri(appendix,   xhtml).
 1200term_iri(cite,       xhtml).
 1201term_iri(bookmark,   xhtml).
 1202term_iri(contents,   xhtml).
 1203term_iri(chapter,    xhtml).
 1204term_iri(copyright,  xhtml).
 1205term_iri(first,      xhtml).
 1206term_iri(glossary,   xhtml).
 1207term_iri(help,       xhtml).
 1208term_iri(icon,       xhtml).
 1209term_iri(index,      xhtml).
 1210term_iri(last,       xhtml).
 1211term_iri(meta,       xhtml).
 1212term_iri(next,       xhtml).
 1213term_iri(prev,       xhtml).
 1214term_iri(previous,   xhtml).
 1215term_iri(section,    xhtml).
 1216term_iri(start,      xhtml).
 1217term_iri(stylesheet, xhtml).
 1218term_iri(subsection, xhtml).
 1219term_iri(top,        xhtml).
 1220term_iri(up,         xhtml).
 1221term_iri(p3pv1,      xhtml).
 1222
 1223term_iri(describedby, _, 'http://www.w3.org/2007/05/powder-s#describedby').
 1224term_iri(license,     _, 'http://www.w3.org/1999/xhtml/vocab#license').
 1225term_iri(role,        _, 'http://www.w3.org/1999/xhtml/vocab#role').
 1226
 1227		 /*******************************
 1228		 *           GRAMMARS           *
 1229		 *******************************/
 1230
 1231prefixes(Dict0, Dict) -->
 1232    ws, nc_name(Name), ws, ":", ws, reference(IRI), !, ws,
 1233    prefixes(Dict0.put(Name,IRI), Dict).
 1234prefixes(Dict, Dict) --> [].
 1235
 1236ws --> ws1, !, ws.
 1237ws --> [].
 1238
 1239ws1 --> " ".
 1240ws1 --> "\t".
 1241ws1 --> "\r".
 1242ws1 --> "\n".
 1243
 1244nc_name(Name) -->
 1245    [H], {nc_name_start_code(H)},
 1246    nc_name_codes(Codes),
 1247    { atom_codes(Name0, [H|Codes]),
 1248      downcase_atom(Name0, Name)
 1249    }.

 term(-Term)//

7.4.3

 1255term(Term) -->
 1256    [H], {nc_name_start_code(H)},
 1257    term_codes(Codes),
 1258    { atom_codes(Term, [H|Codes])
 1259    }.
 1260
 1261
 1262nc_name_codes([H|T]) --> nc_name_code(H), !, nc_name_codes(T).
 1263nc_name_codes([]) --> [].
 1264
 1265nc_name_code(H) --> [H], {nc_name_code(H)}.
 1266
 1267term_codes([H|T]) --> term_code(H), !, term_codes(T).
 1268term_codes([]) --> [].
 1269
 1270term_code(H) --> [H], {term_code(H)}.
 1271
 1272nc_name_start_code(0':) :- !, fail.
 1273nc_name_start_code(C) :- xml_basechar(C), !.
 1274nc_name_start_code(C) :- xml_ideographic(C).
 1275
 1276nc_name_code(0':) :- !, fail.
 1277nc_name_code(C) :- xml_basechar(C), !.
 1278nc_name_code(C) :- xml_digit(C), !.
 1279nc_name_code(C) :- xml_ideographic(C), !.
 1280nc_name_code(C) :- xml_combining_char(C), !.
 1281nc_name_code(C) :- xml_extender(C), !.
 1282
 1283term_code(0'/) :- !.
 1284term_code(C) :- nc_name_code(C).
 1285
 1286reference(IRI) -->
 1287    [H],
 1288    reference_codes(T),
 1289    { atom_codes(IRI, [H|T]) }.
 1290
 1291reference_codes([])    --> ws1, !.
 1292reference_codes([H|T]) --> [H], !, reference_codes(T).
 1293reference_codes([]) --> [].
 1294
 1295reference_or_empty(IRI) -->
 1296    reference_codes(Codes),
 1297    { atom_codes(IRI, Codes) }.

 date_time_type(+DateTime, -DataType) is semidet

True when DataType is the xsd type that matches the lexical representation of DateTime

 1305date_time_type(DateTime, DataType) :-
 1306    atom_codes(DateTime, Codes),
 1307    phrase(date_time_type(DataType), Codes).
 1308
 1309date_time_type(DT) --> duration,   !, { rdf_equal(DT, xsd:duration) }.
 1310date_time_type(DT) --> date_time,  !, { rdf_equal(DT, xsd:dateTime) }.
 1311date_time_type(DT) --> date,       !, { rdf_equal(DT, xsd:date) }.
 1312date_time_type(DT) --> time,       !, { rdf_equal(DT, xsd:time) }.
 1313date_time_type(DT) --> gyearmonth, !, { rdf_equal(DT, xsd:gYearMonth) }.
 1314date_time_type(DT) --> gyear,      !, { rdf_equal(DT, xsd:gYear) }.
 1315
 1316duration   --> opt_minus, "P",
 1317    opt_dy, opt_dm, opt_dd,
 1318    (   "T"
 1319    ->  opt_dh, opt_dm, opt_ds
 1320    ;   ""
 1321    ).
 1322
 1323date_time  --> opt_minus, yyyy, "-", !, mM, "-", dd,
 1324    "T", hh, ":", mm, ":", ss, opt_fraction, opt_zzzzzz.
 1325date       --> opt_minus, yyyy, "-", !, mM, "-", dd.
 1326time       --> hh, ":", mm, ":", ss, opt_fraction.
 1327gyearmonth --> opt_minus, yyyy, "-", !, mM.
 1328gyear      --> opt_minus, yyyy.
 1329
 1330opt_minus --> "-", !.
 1331opt_minus --> "".
 1332
 1333yyyy --> dnzs, d, d, d, d.
 1334
 1335dnzs --> "".
 1336dnzs --> dnz, dnzs.
 1337
 1338opt_fraction --> ".", !, ds.
 1339opt_fraction --> "".
 1340
 1341mM --> d(V1), d(V2), { M is V1*10+V2, M >= 1, M =< 12 }.
 1342dd --> d(V1), d(V2), { M is V1*10+V2, M >= 1, M =< 31 }.
 1343hh --> d(V1), d(V2), { M is V1*10+V2, M =< 23 }.
 1344mm --> d(V1), d(V2), { M is V1*10+V2, M =< 59 }.
 1345ss --> d(V1), d(V2), { M is V1*10+V2, M =< 59 }.
 1346
 1347d(V) --> [D], { between(0'0, 0'9, D), V is D-0'0 }.
 1348d    --> [D], { between(0'0, 0'9, D) }.
 1349dnz  --> [D], { between(0'1, 0'9, D) }.
 1350
 1351ds --> d, !, ds.
 1352ds --> "".
 1353
 1354opt_zzzzzz --> sign, hh, ":", mm.
 1355opt_zzzzzz --> "Z".
 1356opt_zzzzzz --> "".
 1357
 1358sign --> "+".
 1359sign --> "-".
 1360
 1361opt_dy --> ( int, "Y" | "" ).
 1362opt_dm --> ( int, "M" | "" ).
 1363opt_dd --> ( int, "D" | "" ).
 1364opt_dh --> ( int, "H" | "" ).
 1365opt_ds --> ( int, ("." -> int ; ""), "S" | "" ).
 1366
 1367int --> d, ds.
 1368
 1369		 /*******************************
 1370		 *           TRIPLES            *
 1371		 *******************************/

 add_triple(+Context, +S, +P, +O) is det

Add a triple to the global evaluation context. Triples are embedded in a term, so we can use setarg/3 on the list, while the evaluation context is copied for descending the node hierarchy.

 1380add_triple(Context, S, P, O) :-
 1381    (   debugging(rdfa(triple))
 1382    ->  debug(rdfa(triple), 'Added { ~p ~p ~p }', [S,P,O]),
 1383	backtrace(4)
 1384    ;   true
 1385    ),
 1386    valid_subject(S),
 1387    valid_predicate(P),
 1388    valid_object(O),
 1389    !,
 1390    Triples = Context.eval_context.triples,
 1391    arg(1, Triples, Old),
 1392    setarg(1, Triples, [rdf(S,P,O)|Old]).
 1393add_triple(_, _, _, _).                 % ignored invalid triple.
 1394
 1395valid_subject(S)   :- S \== null.
 1396valid_predicate(P) :- P \== null, \+ rdf_is_bnode(P).
 1397valid_object(O)    :- O \== null, ( atom(O) -> true ; valid_literal(O) ).
 1398
 1399valid_literal(literal(Plain)) :-
 1400    atom(Plain),
 1401    !.
 1402valid_literal(literal(type(T, _))) :-
 1403    !,
 1404    T \== null.
 1405valid_literal(literal(lang(_,_))).
 1406
 1407add_incomplete_triple(Context, Dict) :-
 1408    debug(rdfa(incomplete), 'Incomplete: ~p', [Dict]),
 1409    b_set_dict(incomplete_triples, Context,
 1410	       [ Dict
 1411	       | Context.incomplete_triples
 1412	       ]).
 1413
 1414
 1415		 /*******************************
 1416		 *            PATTERNS          *
 1417		 *******************************/