/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: J.Wielemaker@vu.nl WWW: http://www.swi-prolog.org Copyright (c) 2010-2020, University of Amsterdam CWI, Amsterdam All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ :- module(rdf, [ load_rdf/2, % +File, -Triples load_rdf/3, % +File, -Triples, :Options xml_to_rdf/3, % +XML, -Triples, +Options process_rdf/3 % +File, :OnTriples, :Options ]). :- meta_predicate load_rdf(+, -, :), process_rdf(+, :, :). :- autoload(library(lists),[select/3,append/3]). :- autoload(library(option),[meta_options/3,option/3]). :- autoload(library(rdf_parser), [ make_rdf_state/3, xml_to_plrdf/3, rdf_name_space/1, rdf_modify_state/3, element_to_plrdf/3 ]). :- autoload(library(rdf_triple), [rdf_start_file/2,rdf_end_file/1,rdf_triples/2]). :- autoload(library(sgml), [ load_structure/3, new_sgml_parser/2, set_sgml_parser/2, open_dtd/3, xml_quote_attribute/2, sgml_parse/2, free_sgml_parser/1, get_sgml_parser/2 ]). /** RDF/XML parser This module parses RDF/XML documents. It defines two processing modes: load_rdf/2 and load_rdf/3 which process a document into a list of rdf(S,P,O) terms and process_rdf/3 which processes the input description-by-description and uses a callback to handle the triples. @tbd The predicate load_rdf/2,3 is too easily confused with the semweb library predicate rdf_load/2,3 which uses process_rdf/3 to store the triples in the triple DB. @tbd It would be better to use library(intercept) do distinguish to have one predicate that can operate in both collecting and streaming modes. */ %! load_rdf(+File, -Triples) is det. %! load_rdf(+File, -Triples, :Options) is det. % % Parse an XML file holding an RDF term into a list of RDF triples. % see rdf_triple.pl for a definition of the output format. Options: % % * base_uri(+URI) % URI to use as base % % * expand_foreach(+Bool) % Apply each(Container, Pred, Object) on the members of % Container % % * namespaces(-Namespaces:list(NS=URL)) % Return list of namespaces declared using xmlns:NS=URL in % the document. This can be used to update the namespace % list with rdf_register_ns/2. % % @see Use process_rdf/3 for processing large documents in % _|call-back|_ style. load_rdf(File, Triples) :- load_rdf(File, Triples, []). load_rdf(File, Triples, M:Options0) :- entity_options(Options0, EntOptions, Options1), meta_options(load_meta_option, M:Options1, Options), init_ns_collect(Options, NSList), load_structure(File, [ RDFElement ], [ dialect(xmlns), space(sgml), call(xmlns, rdf:on_xmlns) | EntOptions ]), rdf_start_file(Options, Cleanup), call_cleanup(xml_to_rdf(RDFElement, Triples0, Options), rdf_end_file(Cleanup)), exit_ns_collect(NSList), post_process(Options, Triples0, Triples). entity_options([], [], []). entity_options([H|T0], Entities, Rest) :- ( H = entity(_,_) -> Entities = [H|ET], entity_options(T0, ET, Rest) ; Rest = [H|RT], entity_options(T0, Entities, RT) ). load_meta_option(convert_typed_literal). %! xml_to_rdf(+XML, -Triples, +Options) xml_to_rdf(XML, Triples, Options) :- is_list(Options), !, make_rdf_state(Options, State, _), xml_to_plrdf(XML, RDF, State), rdf_triples(RDF, Triples). xml_to_rdf(XML, BaseURI, Triples) :- atom(BaseURI), !, xml_to_rdf(XML, Triples, [base_uri(BaseURI)]). /******************************* * POST-PROCESSING * *******************************/ post_process([], Triples, Triples). post_process([expand_foreach(true)|T], Triples0, Triples) :- !, expand_each(Triples0, Triples1), post_process(T, Triples1, Triples). post_process([_|T], Triples0, Triples) :- !, post_process(T, Triples0, Triples). /******************************* * EXPAND * *******************************/ expand_each(Triples0, Triples) :- select(rdf(each(Container), Pred, Object), Triples0, Triples1), !, each_triples(Triples1, Container, Pred, Object, Triples2), expand_each(Triples2, Triples). expand_each(Triples, Triples). each_triples([], _, _, _, []). each_triples([H0|T0], Container, P, O, [H0, rdf(S,P,O)|T]) :- H0 = rdf(Container, rdf:A, S), member_attribute(A), !, each_triples(T0, Container, P, O, T). each_triples([H|T0], Container, P, O, [H|T]) :- each_triples(T0, Container, P, O, T). member_attribute(A) :- sub_atom(A, 0, _, _, '_'). % must check number? /******************************* * BIG FILES * *******************************/ %! process_rdf(+Input, :OnObject, :Options) % % Process RDF from Input. Input is either an atom or a term of the % format stream(Handle). For each encountered description, call % OnObject(+Triples) to handle the triples resulting from the % description. Defined Options are: % % * base_uri(+URI) % Determines the reference URI. % % * db(DB) % When loading from a stream, the source is taken from % this option or -if non-existent- from base_uri. % % * lang(LanguageID) % Set initial language (as xml:lang) % % * convert_typed_literal(:Convertor) % Call Convertor(+Type, +Content, -RDFObject) to create % a triple rdf(S, P, RDFObject) instead of rdf(S, P, % literal(type(Type, Content)). % % * namespaces(-Namespaces:list(NS=URL)) % Return list of namespaces declared using xmlns:NS=URL in % the document. This can be used to update the namespace % list with rdf_register_ns/2. % % * entity(Name, Value) % Overrule entity values found in the file % % * embedded(Boolean) % If =true=, do not give warnings if rdf:RDF is embedded % in other XML data. process_rdf(File, OnObject, M:Options0) :- is_list(Options0), !, entity_options(Options0, EntOptions, Options1), meta_options(load_meta_option, M:Options1, Options2), option(base_uri(BaseURI), Options2, ''), rdf_start_file(Options2, Cleanup), strip_module(OnObject, Module, Pred), b_setval(rdf_object_handler, Module:Pred), nb_setval(rdf_options, Options2), nb_setval(rdf_state, -), init_ns_collect(Options2, NSList), ( File = stream(In) -> Source = BaseURI ; is_stream(File) -> In = File, option(graph(Source), Options2, BaseURI) ; open(File, read, In, [type(binary)]), Close = In, Source = File ), new_sgml_parser(Parser, [dtd(DTD)]), def_entities(EntOptions, DTD), ( Source \== [] -> set_sgml_parser(Parser, file(Source)) ; true ), set_sgml_parser(Parser, dialect(xmlns)), set_sgml_parser(Parser, space(sgml)), do_process_rdf(Parser, In, NSList, Close, Cleanup, Options2). process_rdf(File, BaseURI, OnObject) :- process_rdf(File, OnObject, [base_uri(BaseURI)]). def_entities([], _). def_entities([entity(Name, Value)|T], DTD) :- !, def_entity(DTD, Name, Value), def_entities(T, DTD). def_entities([_|T0], DTD) :- def_entities(T0, DTD). def_entity(DTD, Name, Value) :- open_dtd(DTD, [], Stream), xml_quote_attribute(Value, QValue), format(Stream, '~n', [Name, QValue]), close(Stream). do_process_rdf(Parser, In, NSList, Close, Cleanup, Options) :- call_cleanup(( sgml_parse(Parser, [ source(In), call(begin, on_begin), call(xmlns, on_xmlns) | Options ]), exit_ns_collect(NSList) ), cleanup_process(Close, Cleanup, Parser)). cleanup_process(In, Cleanup, Parser) :- ( var(In) -> true ; close(In) ), free_sgml_parser(Parser), nb_delete(rdf_options), nb_delete(rdf_object_handler), nb_delete(rdf_state), nb_delete(rdf_nslist), rdf_end_file(Cleanup). on_begin(NS:'RDF', Attr, _) :- rdf_name_space(NS), !, nb_getval(rdf_options, Options), make_rdf_state(Options, State0, _), rdf_modify_state(Attr, State0, State), nb_setval(rdf_state, State). on_begin(Tag, Attr, Parser) :- nb_getval(rdf_state, State), ( State == (-) -> nb_getval(rdf_options, RdfOptions), ( memberchk(embedded(true), RdfOptions) -> true ; print_message(warning, rdf(unexpected(Tag, Parser))) ) ; get_sgml_parser(Parser, line(Start)), get_sgml_parser(Parser, file(File)), sgml_parse(Parser, [ document(Content), parse(content) ]), b_getval(rdf_object_handler, OnTriples), element_to_plrdf(element(Tag, Attr, Content), Objects, State), rdf_triples(Objects, Triples), call(OnTriples, Triples, File:Start) ). %! on_xmlns(+NS, +URL, +Parser) % % Build up the list of encountered xmlns:NS=URL declarations. We % use destructive assignment here as an alternative to % assert/retract, ensuring thread-safety and better performance. on_xmlns(NS, URL, _Parser) :- ( nb_getval(rdf_nslist, List), List = list(L0) -> nb_linkarg(1, List, [NS=URL|L0]) ; true ). init_ns_collect(Options, NSList) :- ( option(namespaces(NSList), Options, -), NSList \== (-) -> nb_setval(rdf_nslist, list([])) ; nb_setval(rdf_nslist, -), NSList = (-) ). exit_ns_collect(NSList) :- ( NSList == (-) -> true ; nb_getval(rdf_nslist, list(NSList)) ). /******************************* * MESSAGES * *******************************/ :- multifile prolog:message/3. % Catch messages. sgml/4 is generated by the SGML2PL binding. prolog:message(rdf(unparsed(Data))) --> { phrase(unparse_xml(Data), XML) }, [ 'RDF: Failed to interpret "~s"'-[XML] ]. prolog:message(rdf(shared_blank_nodes(N))) --> [ 'RDF: Shared ~D blank nodes'-[N] ]. prolog:message(rdf(not_a_name(Name))) --> [ 'RDF: argument to rdf:ID is not an XML name: ~p'-[Name] ]. prolog:message(rdf(redefined_id(Id))) --> [ 'RDF: rdf:ID ~p: multiple definitions'-[Id] ]. prolog:message(rdf(unexpected(Tag, Parser))) --> { get_sgml_parser(Parser, file(File)), get_sgml_parser(Parser, line(Line)) }, [ 'RDF: ~w:~d: Unexpected element ~w'-[File, Line, Tag] ]. /******************************* * XML-TO-TEXT * *******************************/ unparse_xml([]) --> !, []. unparse_xml([H|T]) --> !, unparse_xml(H), unparse_xml(T). unparse_xml(Atom) --> { atom(Atom) }, !, atom(Atom). unparse_xml(element(Name, Attr, Content)) --> "<", identifier(Name), attributes(Attr), ( { Content == [] } -> "/>" ; ">", unparse_xml(Content) ). attributes([]) --> []. attributes([H|T]) --> attribute(H), attributes(T). attribute(Name=Value) --> " ", identifier(Name), "=", value(Value). identifier(NS:Local) --> !, "{", atom(NS), "}", atom(Local). identifier(Local) --> atom(Local). atom(Atom, Text, Rest) :- atom_codes(Atom, Chars), append(Chars, Rest, Text). value(Value) --> { atom_codes(Value, Chars) }, "\"", quoted(Chars), "\"". quoted([]) --> []. quoted([H|T]) --> quote(H), !, quoted(T). quote(0'<) --> "<". quote(0'>) --> ">". quote(0'") --> """. quote(0'&) --> "&". quote(X) --> [X]. /******************************* * XREF * *******************************/ :- multifile prolog:meta_goal/2. prolog:meta_goal(process_rdf(_,G,_), [G+2]).