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f40ba3e6db
yap-6.3/packages/sgml/RDF/rdf_write.pl
Vitor Santos Costa d6a06fe092 Experiment with porting SGML to YAP, and trying to preserve SWI code as much 
as possible.
2009-03-13 19:39:06 +00:00

636 lines
19 KiB
Prolog
Raw Blame History

/* $Id$
Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemak@uva.nl
WWW: http://www.swi-prolog.org
Copyright (C): 2004-2009, University of Amsterdam
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
As a special exception, if you link this library with other files,
compiled with a Free Software compiler, to produce an executable, this
library does not by itself cause the resulting executable to be covered
by the GNU General Public License. This exception does not however
invalidate any other reasons why the executable file might be covered by
the GNU General Public License.
*/
:- module(rdf_write,
[ rdf_write_xml/2 % +Stream, +Triples
]).
:- use_module(library('semweb/rdf_db')).
:- use_module(library(lists)).
:- use_module(library(sgml)).
:- use_module(library(sgml_write)).
:- use_module(library(assoc)).
:- use_module(library(pairs)).
:- use_module(library(debug)).
/** <module> Write RDF/XML from a list of triples
This module writes an RDF/XML document from a list of triples of the
format rdf(Subject, Predicate, Object). It is primarily intended for
communicating computed RDF model fragments to external programs using
RDF/XML.
When used from the HTTP library, use the following code:
==
reply_graph(RDF) :-
format('Content-type: application/rdf+xml; charset=UTF-8~n~n'),
rdf_write_xml(current_output, RDF).
==
@author Jan Wielemaker
@see library(semweb/rdf_db) offers saving a named graph directly from
the RDF database.
*/
/*******************************
* WRITE RDFXML *
*******************************/
%% rdf_write_xml(+Out:stream, +Triples:list(rdf(S,P,O))) is det.
%
% Write an RDF/XML serialization of Triples to Out.
rdf_write_xml(Out, Triples) :-
sort(Triples, Unique),
rdf_write_header(Out, Unique),
node_id_map(Unique, AnonIDs),
rdf_write_triples(Unique, AnonIDs, Out),
rdf_write_footer(Out).
/*******************************
* HEADER/FOOTER *
*******************************/
%% rdf_write_header(+Out, +Triples)
%
% Save XML document header, doctype and open the RDF environment.
% This predicate also sets up the namespace notation.
rdf_write_header(Out, Triples) :-
xml_encoding(Out, Enc, Encoding),
format(Out, '<?xml version=\'1.0\' encoding=\'~w\'?>~n', [Encoding]),
format(Out, '<!DOCTYPE rdf:RDF [', []),
used_namespaces(Triples, NSList),
( member(Id, NSList),
ns(Id, NS),
rdf_quote_uri(NS, QNS),
xml_quote_attribute(QNS, NSText0, Enc),
xml_escape_parameter_entity(NSText0, NSText),
format(Out, '~N <!ENTITY ~w \'~w\'>', [Id, NSText]),
fail
; true
),
format(Out, '~N]>~n~n', []),
format(Out, '<rdf:RDF', []),
( member(Id, NSList),
format(Out, '~N xmlns:~w="&~w;"~n', [Id, Id]),
fail
; true
),
format(Out, '>~n', []).
xml_encoding(Out, Enc, Encoding) :-
stream_property(Out, encoding(Enc)),
( xml_encoding_name(Enc, Encoding)
-> true
; throw(error(domain_error(rdf_encoding, Enc), _))
).
xml_encoding_name(ascii, 'US-ASCII').
xml_encoding_name(iso_latin_1, 'ISO-8859-1').
xml_encoding_name(utf8, 'UTF-8').
%% xml_escape_parameter_entity(+In, -Out) is det.
%
% Escape % as &#37; for entity declarations.
xml_escape_parameter_entity(In, Out) :-
sub_atom(In, _, _, _, '%'), !,
atom_codes(In, Codes),
phrase(escape_parent(Codes), OutCodes),
atom_codes(Out, OutCodes).
xml_escape_parameter_entity(In, In).
escape_parent([]) --> [].
escape_parent([H|T]) -->
( { H == 37 }
-> "&#37;"
; [H]
),
escape_parent(T).
%% used_namespaces(+Triples:list(rdf(S,P,O)), -List:atom) is det.
%
% Return the list of namespace abbreviations used in a set of
% triples.
used_namespaces(Triples, NSList) :-
decl_used_predicate_ns(Triples),
resources(Triples, Resources),
empty_assoc(A0),
put_assoc(rdf, A0, *, A1), % needed for rdf:RDF
res_used_namespaces(Resources, _NoNS, A1, A),
assoc_to_keys(A, NSList).
res_used_namespaces([], [], A, A).
res_used_namespaces([Resource|T], NoNS, A0, A) :-
ns(NS, Full),
Full \== '',
atom_concat(Full, _Local, Resource), !,
put_assoc(NS, A0, *, A1),
res_used_namespaces(T, NoNS, A1, A).
res_used_namespaces([R|T0], [R|T], A0, A) :-
res_used_namespaces(T0, T, A0, A).
%% resources(+Triples:list(rdf(S,P,O)), -Resources:list(atom)) is det.
%
% Resources is the set of resources referenced in Triples.
resources(Triples, Resources) :-
phrase(resources(Triples), Raw),
sort(Raw, Resources).
resources([]) -->
[].
resources([rdf(S,P,O)|T]) -->
[S,P],
object_resources(O),
resources(T).
object_resources(Atom) -->
{ atom(Atom) }, !,
[ Atom ].
object_resources(literal(type(Type, _))) --> !,
[ Type ].
object_resources(_) -->
[].
%% decl_used_predicate_ns(+Triples:list(rdf(S,P,O)))
%
% For every URL used as a predicate we *MUST* define a namespace
% as we cannot use names holding /, :, etc. as XML identifiers.
:- thread_local
predicate_ns/2.
decl_used_predicate_ns(Triples) :-
retractall(predicate_ns(_,_)),
( member(rdf(_,P,_), Triples),
decl_predicate_ns(P),
fail
; true
).
decl_predicate_ns(Pred) :-
predicate_ns(Pred, _), !.
decl_predicate_ns(Pred) :-
rdf_global_id(NS:_Local, Pred),
assert(predicate_ns(Pred, NS)), !.
decl_predicate_ns(Pred) :-
is_bag_li_predicate(Pred), !.
decl_predicate_ns(Pred) :-
atom_codes(Pred, Codes),
append(NSCodes, LocalCodes, Codes),
xml_codes(LocalCodes), !,
( NSCodes \== []
-> atom_codes(NS, NSCodes),
( ns(Id, NS)
-> assert(predicate_ns(Pred, Id))
; between(1, infinite, N),
atom_concat(ns, N, Id),
\+ ns(Id, _)
-> rdf_register_ns(Id, NS),
print_message(informational,
rdf(using_namespace(Id, NS)))
),
assert(predicate_ns(Pred, Id))
; assert(predicate_ns(Pred, -)) % no namespace used
).
xml_codes([]).
xml_codes([H|T]) :-
xml_code(H),
xml_codes(T).
xml_code(X) :-
code_type(X, csym), !.
xml_code(0'-). % '
rdf_write_footer(Out) :-
format(Out, '</rdf:RDF>~n', []).
/*******************************
* ANONYMOUS IDS *
*******************************/
%% node_id_map(+Triples, -IdMap) is det.
%
% Create an assoc Resource -> NodeID for those anonymous resources
% in Triples that need a NodeID. This implies all anonymous
% resources that are used multiple times as object value.
node_id_map(Triples, IdMap) :-
anonymous_objects(Triples, Objs),
msort(Objs, Sorted),
empty_assoc(IdMap0),
nodeid_map(Sorted, 0, IdMap0, IdMap).
anonymous_objects([], []).
anonymous_objects([rdf(_,_,O)|T0], Anon) :-
rdf_is_bnode(O), !,
Anon = [O|T],
anonymous_objects(T0, T).
anonymous_objects([_|T0], T) :-
anonymous_objects(T0, T).
nodeid_map([], _, Map, Map).
nodeid_map([H,H|T0], Id, Map0, Map) :- !,
remove_leading(H, T0, T),
atom_concat(bn, Id, NodeId),
put_assoc(H, Map0, NodeId, Map1),
Id2 is Id + 1,
nodeid_map(T, Id2, Map1, Map).
nodeid_map([_|T], Id, Map0, Map) :-
nodeid_map(T, Id, Map0, Map).
remove_leading(H, [H|T0], T) :- !,
remove_leading(H, T0, T).
remove_leading(_, T, T).
/*******************************
* TRIPLES *
*******************************/
rdf_write_triples(Triples, NodeIDs, Out) :-
rdf_write_triples(Triples, NodeIDs, Out, [], Anon),
rdf_write_anon(Anon, NodeIDs, Out, Anon).
rdf_write_triples([], _, _, Anon, Anon).
rdf_write_triples([H|T0], NodeIDs, Out, Anon0, Anon) :-
arg(1, H, S),
subject_triples(S, [H|T0], T, OnSubject),
( rdf_is_bnode(S)
-> rdf_write_triples(T, NodeIDs, Out, [anon(S,_,OnSubject)|Anon0], Anon)
; rdf_write_subject(OnSubject, S, NodeIDs, Out, Anon0),
rdf_write_triples(T, NodeIDs, Out, Anon0, Anon)
).
subject_triples(S, [H|T0], T, [H|M]) :-
arg(1, H, S), !,
subject_triples(S, T0, T, M).
subject_triples(_, T, T, []).
rdf_write_anon([], _, _, _).
rdf_write_anon([anon(Subject, Done, Triples)|T], NodeIDs, Out, Anon) :-
Done \== true, !,
Done = true,
rdf_write_subject(Triples, Subject, NodeIDs, Out, Anon),
rdf_write_anon(T, NodeIDs, Out, Anon).
rdf_write_anon([_|T], NodeIDs, Out, Anon) :-
rdf_write_anon(T, NodeIDs, Out, Anon).
rdf_write_subject(Triples, Subject, NodeIDs, Out, Anon) :-
rdf_write_subject(Triples, Out, Subject, NodeIDs, -, 0, Anon), !,
format(Out, '~n', []).
rdf_write_subject(_, Subject, _, _, _) :-
throw(error(rdf_save_failed(Subject), 'Internal error')).
rdf_write_subject(Triples, Out, Subject, NodeIDs, DefNS, Indent, Anon) :-
rdf_equal(rdf:type, RdfType),
select(rdf(_, RdfType,Type), Triples, Triples1),
rdf_id(Type, DefNS, TypeId),
xml_is_name(TypeId), !,
format(Out, '~*|<', [Indent]),
rdf_write_id(Out, TypeId),
save_about(Out, Subject, NodeIDs),
save_attributes(Triples1, DefNS, Out, NodeIDs, TypeId, Indent, Anon).
rdf_write_subject(Triples, Out, Subject, NodeIDs, _DefNS, Indent, Anon) :-
format(Out, '~*|<rdf:Description', [Indent]),
save_about(Out, Subject, NodeIDs),
save_attributes(Triples, rdf, Out, NodeIDs, rdf:'Description', Indent, Anon).
xml_is_name(_NS:Atom) :- !,
xml_name(Atom).
xml_is_name(Atom) :-
xml_name(Atom).
save_about(Out, Subject, NodeIDs) :-
rdf_is_bnode(Subject), !,
( get_assoc(Subject, NodeIDs, NodeID)
-> format(Out,' rdf:nodeID="~w"', [NodeID])
; true
).
save_about(Out, Subject, _) :-
stream_property(Out, encoding(Encoding)),
rdf_value(Subject, QSubject, Encoding),
format(Out, ' rdf:about="~w"', [QSubject]), !.
save_about(_, _, _) :-
assertion(fail).
%% save_attributes(+List, +DefNS, +Out, +NodeIDs, Element, +Indent, +Anon)
%
% Save the attributes. Short literal attributes are saved in the
% tag. Others as the content of the description element. The
% begin tag has already been filled.
save_attributes(Triples, DefNS, Out, NodeIDs, Element, Indent, Anon) :-
split_attributes(Triples, InTag, InBody),
SubIndent is Indent + 2,
save_attributes2(InTag, DefNS, tag, Out, NodeIDs, SubIndent, Anon),
( InBody == []
-> format(Out, '/>~n', [])
; format(Out, '>~n', []),
save_attributes2(InBody, _, body, Out, NodeIDs, SubIndent, Anon),
format(Out, '~N~*|</~w>~n', [Indent, Element])
).
% split_attributes(+Triples, -HeadAttrs, -BodyAttr)
%
% Split attribute (Name=Value) list into attributes for the head
% and body. Attributes can only be in the head if they are literal
% and appear only one time in the attribute list.
split_attributes(Triples, HeadAttr, BodyAttr) :-
duplicate_attributes(Triples, Dupls, Singles),
simple_literal_attributes(Singles, HeadAttr, Rest),
append(Dupls, Rest, BodyAttr).
% duplicate_attributes(+Attrs, -Duplicates, -Singles)
%
% Extract attributes that appear more than onces as we cannot
% dublicate an attribute in the head according to the XML rules.
duplicate_attributes([], [], []).
duplicate_attributes([H|T], Dupls, Singles) :-
arg(2, H, Name),
named_attributes(Name, T, D, R),
D \== [],
append([H|D], Dupls2, Dupls), !,
duplicate_attributes(R, Dupls2, Singles).
duplicate_attributes([H|T], Dupls2, [H|Singles]) :-
duplicate_attributes(T, Dupls2, Singles).
named_attributes(_, [], [], []) :- !.
named_attributes(Name, [H|T], D, R) :-
( arg(2, H, Name)
-> D = [H|DT],
named_attributes(Name, T, DT, R)
; R = [H|RT],
named_attributes(Name, T, D, RT)
).
% simple_literal_attributes(+Attributes, -Inline, -Body)
%
% Split attributes for (literal) attributes to be used in the
% begin-tag and ones that have to go into the body of the description.
simple_literal_attributes([], [], []).
simple_literal_attributes([H|TA], [H|TI], B) :-
in_tag_attribute(H), !,
simple_literal_attributes(TA, TI, B).
simple_literal_attributes([H|TA], I, [H|TB]) :-
simple_literal_attributes(TA, I, TB).
in_tag_attribute(rdf(_,P,literal(Text))) :-
atom(Text), % may not have lang qualifier
atom_length(Text, Len),
Len < 60,
\+ is_bag_li_predicate(P).
% save_attributes(+List, +DefNS, +TagOrBody, +Out, +NodeIDs, +Indent, +Anon)
%
% Save a list of attributes.
save_attributes2([], _, _, _, _, _, _).
save_attributes2([H|T], DefNS, Where, Out, NodeIDs, Indent, Anon) :-
save_attribute(Where, H, DefNS, Out, NodeIDs, Indent, Anon),
save_attributes2(T, DefNS, Where, Out, NodeIDs, Indent, Anon).
%% save_attribute(+Where, +Triple, +DefNS, +Out, +NodeIDs, +Indent, +Anon)
save_attribute(tag, rdf(_, Name, literal(Value)), DefNS, Out, _, Indent, _Anon) :-
AttIndent is Indent + 2,
rdf_att_id(Name, DefNS, NameText),
stream_property(Out, encoding(Encoding)),
xml_quote_attribute(Value, QVal, Encoding),
format(Out, '~N~*|', [AttIndent]),
rdf_write_id(Out, NameText),
format(Out, '="~w"', [QVal]).
save_attribute(body, rdf(_,Name,literal(Literal)), DefNS, Out, _, Indent, _) :- !,
rdf_p_id(Name, DefNS, NameText),
format(Out, '~N~*|<', [Indent]),
rdf_write_id(Out, NameText),
( Literal = lang(Lang, Value)
-> rdf_id(Lang, DefNS, LangText),
format(Out, ' xml:lang="~w">', [LangText])
; Literal = type(Type, Value)
-> ( rdf_equal(Type, rdf:'XMLLiteral')
-> write(Out, ' rdf:parseType="Literal">'),
Value = Literal
; stream_property(Out, encoding(Encoding)),
rdf_value(Type, QVal, Encoding),
format(Out, ' rdf:datatype="~w">', [QVal])
)
; atomic(Literal)
-> write(Out, '>'),
Value = Literal
; write(Out, ' rdf:parseType="Literal">'),
Value = Literal
),
save_attribute_value(Value, Out, Indent),
write(Out, '</'), rdf_write_id(Out, NameText), write(Out, '>').
save_attribute(body, rdf(_, Name, Value), DefNS, Out, NodeIDs, Indent, Anon) :-
rdf_is_bnode(Value),
memberchk(anon(Value, Done, ValueTriples), Anon), !,
rdf_p_id(Name, DefNS, NameText),
format(Out, '~N~*|<', [Indent]),
rdf_write_id(Out, NameText),
( var(Done)
-> Done = true,
SubIndent is Indent + 2,
( rdf_equal(RdfType, rdf:type),
rdf_equal(ListClass, rdf:'List'),
memberchk(rdf(_, RdfType, ListClass), ValueTriples)
-> format(Out, ' rdf:parseType="Collection">~n', []),
rdf_save_list(ValueTriples, Out, Value, NodeIDs, DefNS, SubIndent, Anon)
; format(Out, '>~n', []),
rdf_write_subject(ValueTriples, Out, Value, NodeIDs, DefNS, SubIndent, Anon)
),
format(Out, '~N~*|</', [Indent]),
rdf_write_id(Out, NameText),
format(Out, '>~n', [])
; get_assoc(Value, NodeIDs, NodeID)
-> format(Out, ' rdf:nodeID="~w"/>', [NodeID])
; assertion(fail)
).
save_attribute(body, rdf(_, Name, Value), DefNS, Out, _, Indent, _Anon) :-
stream_property(Out, encoding(Encoding)),
rdf_value(Value, QVal, Encoding),
rdf_p_id(Name, DefNS, NameText),
format(Out, '~N~*|<', [Indent]),
rdf_write_id(Out, NameText),
format(Out, ' rdf:resource="~w"/>', [QVal]).
save_attribute_value(Value, Out, _) :- % strings
atom(Value), !,
stream_property(Out, encoding(Encoding)),
xml_quote_cdata(Value, QVal, Encoding),
write(Out, QVal).
save_attribute_value(Value, Out, _) :- % numbers
number(Value), !,
writeq(Out, Value). % quoted: preserve floats
save_attribute_value(Value, Out, Indent) :-
xml_is_dom(Value), !,
XMLIndent is Indent+2,
xml_write(Out, Value,
[ header(false),
indent(XMLIndent)
]).
save_attribute_value(Value, _Out, _) :-
throw(error(save_attribute_value(Value), _)).
rdf_save_list(_, _, List, _, _, _, _) :-
rdf_equal(List, rdf:nil), !.
rdf_save_list(ListTriples, Out, List, NodeIDs, DefNS, Indent, Anon) :-
rdf_equal(RdfFirst, rdf:first),
memberchk(rdf(List, RdfFirst, First), ListTriples),
( rdf_is_bnode(First),
memberchk(anon(First, true, FirstTriples), Anon)
-> nl(Out),
rdf_write_subject(FirstTriples, Out, First, NodeIDs, DefNS, Indent, Anon)
; stream_property(Out, encoding(Encoding)),
rdf_value(First, QVal, Encoding),
format(Out, '~N~*|<rdf:Description about="~w"/>',
[Indent, QVal])
),
( rdf_equal(RdfRest, rdf:rest),
memberchk(rdf(List, RdfRest, List2), ListTriples),
\+ rdf_equal(List2, rdf:nil),
memberchk(anon(List2, true, List2Triples), Anon)
-> rdf_save_list(List2Triples, Out, List2, NodeIDs, DefNS, Indent, Anon)
; true
).
%% rdf_p_id(+Resource, +DefNS, -NSLocal)
%
% As rdf_id/3 for predicate names. Maps _:<N> to rdf:li.
%
% @tbd Ensure we are talking about an rdf:Bag
rdf_p_id(LI, _, 'rdf:li') :-
is_bag_li_predicate(LI), !.
rdf_p_id(Resource, DefNS, NSLocal) :-
rdf_id(Resource, DefNS, NSLocal).
%% is_bag_li_predicate(+Pred) is semidet.
%
% True if Pred is _:N, as used for members of an rdf:Bag, rdf:Seq
% or rdf:Alt.
is_bag_li_predicate(Pred) :-
atom_concat('_:', AN, Pred),
catch(atom_number(AN, N), _, true), integer(N), N >= 0, !.
%% rdf_id(+Resource, +DefNS, -NSLocal)
%
% Generate a NS:Local name for Resource given the indicated
% default namespace. This call is used for elements.
rdf_id(Id, NS, NS:Local) :-
ns(NS, Full),
Full \== '',
atom_concat(Full, Local, Id), !.
rdf_id(Id, _, NS:Local) :-
ns(NS, Full),
Full \== '',
atom_concat(Full, Local, Id), !.
rdf_id(Id, _, Id).
%% rdf_write_id(+Out, +NSLocal) is det.
%
% Write an identifier. We cannot use native write on it as both NS
% and Local can be operators.
rdf_write_id(Out, NS:Local) :- !,
format(Out, '~w:~w', [NS, Local]).
rdf_write_id(Out, Atom) :-
write(Out, Atom).
rdf_att_id(Id, _, NS:Local) :-
ns(NS, Full),
Full \== '',
atom_concat(Full, Local, Id), !.
rdf_att_id(Id, _, Id).
%% rdf_value(+Resource, -Text, +Encoding)
%
% According to "6.4 RDF URI References" of the RDF Syntax
% specification, a URI reference is UNICODE string not containing
% control sequences, represented as UTF-8 and then as escaped
% US-ASCII.
%
% NOTE: the to_be_described/1 trick ensures entity rewrite in
% resources that start with 'http://t-d-b.org?'. This is a of a
% hack to save the artchive data in the MultimediaN project. We
% should use a more general mechanism.
rdf_value(V, Text, Encoding) :-
to_be_described(Prefix),
atom_concat(Prefix, V1, V),
ns(NS, Full),
atom_concat(Full, Local, V1), !,
rdf_quote_uri(Local, QLocal0),
xml_quote_attribute(QLocal0, QLocal, Encoding),
concat_atom([Prefix, '&', NS, (';'), QLocal], Text).
rdf_value(V, Text, Encoding) :-
ns(NS, Full),
atom_concat(Full, Local, V), !,
rdf_quote_uri(Local, QLocal0),
xml_quote_attribute(QLocal0, QLocal, Encoding),
concat_atom(['&', NS, (';'), QLocal], Text).
rdf_value(V, Q, Encoding) :-
rdf_quote_uri(V, Q0),
xml_quote_attribute(Q0, Q, Encoding).
to_be_described('http://t-d-b.org?').
/*******************************
* UTIL *
*******************************/
ns(Id, Full) :-
rdf_db:ns(Id, Full).
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