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)  2010-2013, University of 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(rdf_parser,
   36          [ xml_to_plrdf/3,             % +XMLTerm, -RDFTerm, +State
   37            element_to_plrdf/3,         % +ContentList, -RDFTerm, +State
   38            make_rdf_state/3,           % +Options, -State, -RestOptions
   39            rdf_modify_state/3,         % +XMLAttrs, +State0, -State
   40            rdf_name_space/1
   41          ]).   42:- use_module(library(record),[(record)/1, op(_,_,record)]).   43:- use_module(library(rewrite_term),
   44              [ rew_term_expansion/2,rew_goal_expansion/2,
   45                op(_,_,::=)
   46              ]).   47:- autoload(library(lists),[select/3,append/3,member/2]).   48:- autoload(library(occurs),[sub_term/2]).   49:- autoload(library(sgml),[xml_name/1]).   50:- autoload(library(uri),[iri_normalized/3]).   51
   52
   53% xml_name/1
   54:- op(500, fx, \?).                     % Optional (attrs)
   55
   56term_expansion(F, T) :- rew_term_expansion(F, T).
   57goal_expansion(F, T) :- rew_goal_expansion(F, T).
   58
   59goal_expansion(attrs(Attrs, List), Goal) :-
   60    translate_attrs(List, Attrs, Goal).
   61
   62translate_attrs(Var, Attrs, rewrite_term(Var, Attrs)) :-
   63    var(Var),
   64    !.
   65translate_attrs([], _, true) :- !.
   66translate_attrs([H], Attrs, Goal) :-
   67    !,
   68    (   var(H)
   69    ->  Goal = rewrite_term(H, Attrs)
   70    ;   H = \?Optional
   71    ->  Goal = (   member(A, Attrs),
   72                   OptRewrite
   73               ->  true
   74               ;   true
   75               ),
   76        expand_goal(rewrite_term(\Optional, A), OptRewrite)
   77    ;   Goal = (   member(A, Attrs),
   78                   Rewrite
   79               ->  true
   80               ),
   81        expand_goal(rewrite_term(H, A), Rewrite)
   82    ).
   83translate_attrs([H|T], Attrs0, (G0, G1)) :-
   84    !,
   85    (   var(H)
   86    ->  G0 = rewrite_term(H, Attrs0),
   87        Attrs1 = Attrs0
   88    ;   H = \?Optional
   89    ->  G0 = (   select(A, Attrs0, Attrs1),
   90                 OptRewrite
   91             ->  true
   92             ;   Attrs1 = Attrs0
   93             ),
   94        expand_goal(rewrite_term(\Optional, A), OptRewrite)
   95    ;   G0 = (   select(A, Attrs0, Attrs1),
   96                 Rewrite
   97             ),
   98        expand_goal(rewrite_term(H, A), Rewrite)
   99    ),
  100    translate_attrs(T, Attrs1, G1).
  101translate_attrs(Rule, Attrs, Goal) :-
  102    expand_goal(rewrite_term(Rule, Attrs), Goal).
  103
  104
  105:- multifile rdf_name_space/1.  106:- dynamic   rdf_name_space/1.  107
  108%!  rdf_name_space(?URL) is nondet.
  109%
  110%   True if URL must be handled  as rdf: Determines special handling
  111%   of rdf:about, rdf:resource, etc.
  112
  113
  114rdf_name_space('http://www.w3.org/1999/02/22-rdf-syntax-ns#').
  115rdf_name_space('http://www.w3.org/TR/REC-rdf-syntax').
  116
  117
  118:- record
  119    rdf_state(base_uri='',
  120              lang='',
  121              ignore_lang=false,
  122              convert_typed_literal).
  123
  124
  125%!  xml_to_plrdf(+RDFElementOrObject, -RDFTerm, +State)
  126%
  127%   Translate an XML (using namespaces)  term   into  an Prolog term
  128%   representing the RDF data.  This  term   can  then  be  fed into
  129%   rdf_triples/[2,3] to create a list of   RDF triples. State is an
  130%   instance of an rdf_state record.
  131
  132xml_to_plrdf(Element, RDF, State) :-
  133    (   is_list(Element)
  134    ->  rewrite_term(\xml_content_objects(RDF, State), Element)
  135    ;   rewrite_term(\xml_objects(RDF, State), Element)
  136    ).
  137
  138%!  element_to_plrdf(+DOM, -RDFTerm, +State)
  139%
  140%   Rewrite a single XML element.
  141
  142element_to_plrdf(Element, RDF, State) :-
  143    rewrite_term(\nodeElementList(RDF, State), [Element]).
  144
  145xml_objects(Objects, Options0) ::=
  146        E0,
  147        { modify_state(E0, Options0, E, Options), !,
  148          rewrite_term(\xml_objects(Objects, Options), E)
  149        }.
  150xml_objects(Objects, Options) ::=
  151        element((\rdf('RDF'), !),
  152                _,
  153                \nodeElementList(Objects, Options)),
  154        !.
  155xml_objects(Objects, Options) ::=
  156        element(_, _, \xml_content_objects(Objects, Options)).
  157
  158xml_content_objects([], _) ::=
  159        [].
  160xml_content_objects([H|T], Options) ::=
  161        [ \xml_objects(H, Options)
  162        | \xml_content_objects(T, Options)
  163        ].
  164
  165
  166nodeElementList([], _Options) ::=
  167        [], !.
  168nodeElementList(L, Options) ::=
  169        [ (\ws, !)
  170        | \nodeElementList(L, Options)
  171        ].
  172nodeElementList([H|T], Options) ::=
  173        [ \nodeElementOrError(H, Options)
  174        | \nodeElementList(T, Options)
  175        ].
  176
  177nodeElementOrError(H, Options) ::=
  178        \nodeElement(H, Options), !.
  179nodeElementOrError(unparsed(Data), _Options) ::=
  180        Data.
  181
  182nodeElement(description(Type, About, Properties), Options) ::=
  183        \description(Type, About, Properties, Options).
  184
  185
  186                 /*******************************
  187                 *          DESCRIPTION         *
  188                 *******************************/
  189
  190description(Type, About, Properties, Options0) ::=
  191        E0,
  192        { modify_state(E0, Options0, E, Options), !,
  193          rewrite_term(\description(Type, About, Properties, Options), E)
  194        }.
  195description(description, About, Properties, Options) ::=
  196        element(\rdf('Description'),
  197                \attrs([ \?idAboutAttr(About, Options)
  198                       | \propAttrs(PropAttrs, Options)
  199                       ]),
  200                \propertyElts(PropElts, Options)),
  201        { !, append(PropAttrs, PropElts, Properties)
  202        }.
  203description(Type, About, Properties, Options) ::=
  204        element(\name_uri(Type, Options),
  205                \attrs([ \?idAboutAttr(About, Options)
  206                       | \propAttrs(PropAttrs, Options)
  207                       ]),
  208                \propertyElts(PropElts, Options)),
  209        { append(PropAttrs, PropElts, Properties)
  210        }.
  211
  212propAttrs([], _) ::=
  213        [], !.
  214propAttrs([H|T], Options) ::=
  215        [ \propAttr(H, Options)
  216        | \propAttrs(T, Options)
  217        ].
  218
  219propAttr(rdf:type = URI, Options) ::=
  220        \rdf_or_unqualified(type) = \value_uri(URI, Options), !.
  221propAttr(Name = Literal, Options) ::=
  222        Name = Value,
  223        { mkliteral(Value, Literal, Options)
  224        }.
  225
  226propertyElts([], _) ::=
  227        [], !.
  228propertyElts(Elts, Options) ::=
  229        [ (\ws, !)
  230        | \propertyElts(Elts, Options)
  231        ].
  232propertyElts([H|T], Options) ::=
  233        [ \propertyElt(H, Options)
  234        | \propertyElts(T, Options)
  235        ].
  236
  237propertyElt(E, Options) ::=
  238        \propertyElt(Id, Name, Value, Options),
  239        { mkprop(Name, Value, Prop),
  240          (   var(Id)
  241          ->  E = Prop
  242          ;   E = id(Id, Prop)
  243          )
  244        }.
  245
  246mkprop(NS:Local, Value, rdf:Local = Value) :-
  247    rdf_name_space(NS),
  248    !.
  249mkprop(Name, Value, Name = Value).
  250
  251
  252propertyElt(Id, Name, Value, Options0) ::=
  253        E0,
  254        { modify_state(E0, Options0, E, Options), !,
  255          rewrite_term(\propertyElt(Id, Name, Value, Options), E)
  256        }.
  257propertyElt(Id, Name, Value, Options) ::=
  258        \literalPropertyElt(Id, Name, Value, Options), !.
  259propertyElt(_, Name, Literal, Options) ::=
  260        element(Name,
  261                \attrs([ \parseLiteral
  262                       ]),
  263                Content),
  264        { !,
  265          literal_value(Content, Literal, Options)
  266        }.
  267propertyElt(Id, Name, collection(Elements), Options) ::=
  268        element(Name,
  269                \attrs([ \parseCollection,
  270                         \?idAttr(Id, Options)
  271                       ]),
  272                \nodeElementList(Elements, Options)).
  273                                        % 5.14 emptyPropertyElt
  274propertyElt(Id, Name, Value, Options) ::=
  275        element(Name, A, \all_ws),
  276        { !,
  277          rewrite_term(\emptyPropertyElt(Id, Value, Options), A)
  278        }.
  279
  280propertyElt(_, Name, description(description, Id, Properties), Options) ::=
  281        element(Name,
  282                \attrs([ \parseResource,
  283                         \?idAboutAttr(Id, Options)
  284                       ]),
  285                \propertyElts(Properties, Options)),
  286        !.
  287propertyElt(Id, Name, Literal, Options) ::=
  288        element(Name,
  289                \attrs([ \?idAttr(Id, Options)
  290                       ]),
  291                [ Value ]),
  292        { atom(Value), !,
  293          mkliteral(Value, Literal, Options)
  294        }.
  295propertyElt(Id, Name, Value, Options) ::=
  296        element(Name,
  297                \attrs([ \?idAttr(Id, Options)
  298                       ]),
  299                \an_rdf_object(Value, Options)), !.
  300propertyElt(Id, Name, unparsed(Value), Options) ::=
  301        element(Name,
  302                \attrs([ \?idAttr(Id, Options)
  303                       ]),
  304                Value).
  305
  306literalPropertyElt(Id, Name, Literal, Options) ::=
  307        element(Name,
  308                \attrs([ \typeAttr(Type, Options),
  309                         \?idAttr(Id, Options)
  310                       ]),
  311                Content),
  312        { typed_literal(Type, Content, Literal, Options)
  313        }.
  314
  315emptyPropertyElt(Id, Literal, Options) ::=
  316        \attrs([ \?idAttr(Id, Options),
  317                 \?parseLiteral
  318               | \noMoreAttrs
  319               ]),
  320        { !,
  321          mkliteral('', Literal, Options)
  322        }.
  323emptyPropertyElt(Id,
  324                 description(description, About, Properties),
  325                 Options) ::=
  326        \attrs([ \?idAttr(Id, Options),
  327                 \?aboutResourceEmptyElt(About, Options),
  328                 \?parseResource
  329               | \propAttrs(Properties, Options)
  330               ]), !.
  331
  332aboutResourceEmptyElt(about(URI), Options) ::=
  333        \resourceAttr(URI, Options), !.
  334aboutResourceEmptyElt(node(URI), _Options) ::=
  335        \nodeIDAttr(URI).
  336
  337%!  literal_value(+In, -Value, +Options)
  338%
  339%   Create the literal value for rdf:parseType="Literal" attributes.
  340%   The content is the Prolog XML DOM tree for the literal.
  341%
  342%   @tbd    Note that the specs demand a canonical textual representation
  343%           of the XML data as a Unicode string.  For now the user can
  344%           achieve this using the convert_typed_literal hook.
  345
  346literal_value(Value, literal(type(rdf:'XMLLiteral', Value)), _).
  347
  348%!  mkliteral(+Atom, -Object, +Options)
  349%
  350%   Translate attribute value Atom into an RDF object using the
  351%   lang(Lang) option from Options.
  352
  353mkliteral(Text, literal(Val), Options) :-
  354    atom(Text),
  355    (   rdf_state_lang(Options, Lang),
  356        Lang \== ''
  357    ->  Val = lang(Lang, Text)
  358    ;   Val = Text
  359    ).
  360
  361%!  typed_literal(+Type, +Content, -Literal, +Options)
  362%
  363%   Handle a literal attribute with rdf:datatype=Type qualifier. NB:
  364%   possibly  it  is  faster  to  use  a  global  variable  for  the
  365%   conversion hook.
  366
  367typed_literal(Type, Content, literal(Object), Options) :-
  368    rdf_state_convert_typed_literal(Options, Convert),
  369    nonvar(Convert),
  370    !,
  371    (   catch(call(Convert, Type, Content, Object), E, true)
  372    ->  (   var(E)
  373        ->  true
  374        ;   Object = E
  375        )
  376    ;   Object = error(cannot_convert(Type, Content), _)
  377    ).
  378typed_literal(Type, [], literal(type(Type, '')), _Options) :- !.
  379typed_literal(Type, [Text], literal(type(Type, Text)), _Options) :- !.
  380typed_literal(Type, Content, literal(type(Type, Content)), _Options).
  381
  382
  383idAboutAttr(id(Id), Options) ::=
  384        \idAttr(Id, Options), !.
  385idAboutAttr(about(About), Options) ::=
  386        \aboutAttr(About, Options), !.
  387idAboutAttr(node(About), _Options) ::=
  388        \nodeIDAttr(About), !.
  389
  390%!  an_rdf_object(-Object, +OptionsURI)
  391%
  392%   Deals with an object, but there may be spaces around.  I'm still
  393%   not sure where to deal with these.  Best is to ask the XML parser
  394%   to get rid of them, So most likely this code will change if this
  395%   happens.
  396
  397an_rdf_object(Object, Options) ::=
  398        [ \nodeElement(Object, Options)
  399        ], !.
  400an_rdf_object(Object, Options) ::=
  401        [ (\ws, !)
  402        | \an_rdf_object(Object, Options)
  403        ].
  404an_rdf_object(Object, Options) ::=
  405        [ \nodeElement(Object, Options),
  406          \ws
  407        ], !.
  408
  409ws ::=
  410        A,
  411        { atom(A),
  412          atom_chars(A, Chars),
  413          all_blank(Chars), !
  414        }.
  415ws ::=
  416        pi(_).
  417
  418all_ws ::=
  419        [], !.
  420all_ws ::=
  421        [\ws | \all_ws].
  422
  423all_blank([]).
  424all_blank([H|T]) :-
  425    char_type(H, space),            % SWI-Prolog specific
  426    all_blank(T).
  427
  428
  429                 /*******************************
  430                 *         RDF ATTRIBUTES       *
  431                 *******************************/
  432
  433idAttr(Id, Options) ::=
  434        \rdf_or_unqualified('ID') = \uniqueid(Id, Options).
  435
  436aboutAttr(About, Options) ::=
  437        \rdf_or_unqualified(about) = \value_uri(About, Options).
  438
  439nodeIDAttr(About) ::=
  440        \rdf_or_unqualified(nodeID) = About.
  441
  442resourceAttr(URI, Options) ::=
  443        \rdf_or_unqualified(resource) = \value_uri(URI, Options).
  444
  445typeAttr(Type, Options) ::=
  446        \rdf_or_unqualified(datatype) = \value_uri(Type, Options).
  447
  448name_uri(URI, Options) ::=
  449        NS:Local,
  450        {   !, atom_concat(NS, Local, A),
  451            rewrite_term(\value_uri(URI, Options), A)
  452        }.
  453name_uri(URI, Options) ::=
  454        \value_uri(URI, Options).
  455
  456value_uri(URI, Options) ::=
  457        A,
  458        {   rdf_state_base_uri(Options, Base),
  459            (   Base \== []
  460            ->  iri_normalized(A, Base, URI)
  461            ;   URI = A
  462            )
  463        }.
  464
  465uniqueid(Id, Options) ::=
  466        A,
  467        {   unique_xml_name(A, HashID),
  468            make_globalid(HashID, Options, Id)
  469        }.
  470
  471unique_xml_name(Name, HashID) :-
  472    atom_concat(#, Name, HashID),
  473    (   xml_name(Name)
  474    ->  true
  475    ;   print_message(warning, rdf(not_a_name(Name)))
  476    ).
  477
  478make_globalid(In, Options, Id) :-
  479    rdf_state_base_uri(Options, Base),
  480    iri_normalized(In, Base, Id).
  481
  482parseLiteral    ::= \rdf_or_unqualified(parseType) = 'Literal'.
  483parseResource   ::= \rdf_or_unqualified(parseType) = 'Resource'.
  484parseCollection ::= \rdf_or_unqualified(parseType) = 'Collection'.
  485
  486
  487                 /*******************************
  488                 *           PRIMITIVES         *
  489                 *******************************/
  490
  491rdf(Tag) ::=
  492        NS:Tag,
  493        { rdf_name_space(NS), !
  494        }.
  495
  496rdf_or_unqualified(Tag) ::=
  497        Tag.
  498rdf_or_unqualified(Tag) ::=
  499        NS:Tag,
  500        { rdf_name_space(NS), !
  501        }.
  502
  503
  504                 /*******************************
  505                 *             BASICS           *
  506                 *******************************/
  507
  508/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  509This code is translated by the  goal_expansion/2   rule  at the start of
  510this file. We leave the original code for reference.
  511
  512attrs(Bag) ::=
  513        L0,
  514        { do_attrs(Bag, L0)
  515        }.
  516
  517do_attrs([], _) :- !.
  518do_attrs([\?H|T], L0) :- !,             % optional
  519        (   select(X, L0, L),
  520            rewrite_term(\H, X)
  521        ->  true
  522        ;   L = L0
  523        ),
  524        do_attrs(T, L).
  525do_attrs([H|T], L0) :-
  526        select(X, L0, L),
  527        rewrite_term(H, X), !,
  528        do_attrs(T, L).
  529do_attrs(C, L) :-
  530        rewrite_term(C, L).
  531- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  532
  533%       \noMoreAttrs
  534%
  535%       Check attribute-list is empty.  Reserved xml: attributes are
  536%       excluded from this test.
  537
  538noMoreAttrs ::=
  539        [], !.
  540noMoreAttrs ::=
  541        [ xml:_=_
  542        | \noMoreAttrs
  543        ].
  544
  545%!  modify_state(+Element0, +Options0, -Element, -Options) is semidet.
  546%
  547%   If Element0 contains xml:base = Base, strip it from the
  548%   attributes list and update base_uri(_) in the Options
  549%
  550%   It Element0 contains xml:lang = Lang, strip it from the
  551%   attributes list and update lang(_) in the Options
  552%
  553%   Remove all xmlns=_, xmlns:_=_ and xml:_=_.  Only succeed
  554%   if something changed.
  555
  556modify_state(element(Name, Attrs0, Content), Options0,
  557             element(Name, Attrs,  Content), Options) :-
  558    modify_a_state(Attrs0, Options0, Attrs, Options),
  559    Attrs0 \== Attrs.
  560
  561rdf_modify_state(Attributes, State0, State) :-
  562    modify_a_state(Attributes, State0, _, State).
  563
  564
  565modify_a_state([], Options, [], Options).
  566modify_a_state([Name=Value|T0], Options0, T, Options) :-
  567    modify_a(Name, Value, Options0, Options1),
  568    !,
  569    modify_a_state(T0, Options1, T, Options).
  570modify_a_state([H|T0], Options0, [H|T], Options) :-
  571    modify_a_state(T0, Options0, T, Options).
  572
  573
  574modify_a(xml:base, Base1, Options0, Options) :-
  575    !,
  576    rdf_state_base_uri(Options0, Base0),
  577    remove_fragment(Base1, Base2),
  578    iri_normalized(Base2, Base0, Base),
  579    set_base_uri_of_rdf_state(Base, Options0, Options).
  580modify_a(xml:lang, Lang, Options0, Options) :-
  581    !,
  582    rdf_state_ignore_lang(Options0, false),
  583    !,
  584    set_lang_of_rdf_state(Lang, Options0, Options).
  585modify_a(xmlns, _, Options, Options).
  586modify_a(xmlns:_, _, Options, Options).
  587modify_a(xml:_, _, Options, Options).
  588
  589
  590%!  remove_fragment(+URI, -WithoutFragment)
  591%
  592%   When handling xml:base, we must delete the possible fragment.
  593
  594remove_fragment(URI, Plain) :-
  595    sub_atom(URI, B, _, _, #),
  596    !,
  597    sub_atom(URI, 0, B, _, Plain).
  598remove_fragment(URI, URI).
  599
  600
  601                 /*******************************
  602                 *     HELP PCE-EMACS A BIT     *
  603                 *******************************/
  604
  605:- multifile
  606    emacs_prolog_colours:term_colours/2,
  607    emacs_prolog_colours:goal_classification/2.  608
  609expand(c(X), _, X) :- !.
  610expand(In,   Pattern, Colours) :-
  611    compound(In),
  612    !,
  613    In =.. [F|Args],
  614    expand_list(Args, PatternArgs, ColourArgs),
  615    Pattern =.. [F|PatternArgs],
  616    Colours = functor(F) - ColourArgs.
  617expand(X, X, classify).
  618
  619expand_list([], [], []).
  620expand_list([H|T], [PH|PT], [CH|CT]) :-
  621    expand(H, PH, CH),
  622    expand_list(T, PT, CT).
  623
  624:- discontiguous
  625    term_expansion/2.  626
  627term_expansion(term_colours(C),
  628               emacs_prolog_colours:term_colours(Pattern, Colours)) :-
  629    expand(C, Pattern, Colours).
  630
  631term_colours((c(head(+(1))) ::= c(match), {c(body)})).
  632term_colours((c(head(+(1))) ::= c(match))).
  633
  634emacs_prolog_colours:goal_classification(\_, expanded).
  635
  636:- dynamic
  637    prolog:meta_goal/2.  638:- multifile
  639    prolog:meta_goal/2,
  640    prolog:called_by/2.  641
  642prolog:meta_goal(rewrite_term(A, _), [A]).
  643prolog:meta_goal(\A,            [A+1]).
  644
  645prolog:called_by(attrs(Attrs, _Term), Called) :-
  646    findall(G+1, sub_term(\?G, Attrs), Called, Tail),
  647    findall(G+1, sub_term(\G, Attrs), Tail)