Chris@0: /*  $Id$
Chris@0: 
Chris@0:     Part of SWI-Prolog
Chris@0: 
Chris@0:     Author:        Jan Wielemaker
Chris@0:     E-mail:        wielemak@science.uva.nl
Chris@0:     WWW:           http://www.swi-prolog.org
Chris@0:     Copyright (C): 2004-2006, University of Amsterdam
Chris@0: 
Chris@0:     This program is free software; you can redistribute it and/or
Chris@0:     modify it under the terms of the GNU General Public License
Chris@0:     as published by the Free Software Foundation; either version 2
Chris@0:     of the License, or (at your option) any later version.
Chris@0: 
Chris@0:     This program is distributed in the hope that it will be useful,
Chris@0:     but WITHOUT ANY WARRANTY; without even the implied warranty of
Chris@0:     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
Chris@0:     GNU General Public License for more details.
Chris@0: 
Chris@0:     You should have received a copy of the GNU Lesser General Public
Chris@0:     License along with this library; if not, write to the Free Software
Chris@0:     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
Chris@0: 
Chris@0:     As a special exception, if you link this library with other files,
Chris@0:     compiled with a Free Software compiler, to produce an executable, this
Chris@0:     library does not by itself cause the resulting executable to be covered
Chris@0:     by the GNU General Public License. This exception does not however
Chris@0:     invalidate any other reasons why the executable file might be covered by
Chris@0:     the GNU General Public License.
Chris@0: */
Chris@0: 
Chris@0: :- module(sparql_client,
Chris@0: 	  [ sparql_query/3,		% +Query, -Row, +Options
Chris@0: 	    sparql_set_server/1		% +Options
Chris@0: 	  ]).
Chris@0: :- use_module(library('http/http_open')).
Chris@0: :- use_module(sparql_xml_result).
Chris@0: :- use_module(library(lists)).
Chris@0: :- use_module(library(rdf)).
Chris@0: 
Chris@0: 
Chris@0: %%	sparql_query(+Query, -Result, +Options) is nondet.
Chris@0: %
Chris@0: %	Execute a SPARQL query on an HTTP   SPARQL endpoint. Query is an
Chris@0: %	atom that denotes  the  query.  Result   is  unified  to  a term
Chris@0: %	rdf(S,P,O) for =construct= queries  and   row(...)  for =select=
Chris@0: %	queries.
Chris@0: 
Chris@0: sparql_query(Query, Row, Options) :-
Chris@0: 	sparql_param(host(Host), Options),
Chris@0: 	sparql_param(port(Port), Options),
Chris@0: 	sparql_param(path(Path), Options),
Chris@0: 	http_open([ protocol(http),
Chris@0: 		    host(Host),
Chris@0: 		    port(Port),
Chris@0: 		    path(Path),
Chris@0: 		    search([ query = Query
Chris@0: 			   ])
Chris@0: 		  ], In,
Chris@0: 		  [ header(content_type, ContentType)
Chris@0: 		  ]),
Chris@0: 	plain_content_type(ContentType, CleanType),
Chris@0: 	read_reply(CleanType, In, Row).
Chris@0: 
Chris@0: read_reply('application/rdf+xml', In, Row) :- !,
Chris@0: 	call_cleanup(load_rdf(stream(In), RDF), close(In)),
Chris@0: 	member(Row, RDF).
Chris@0: read_reply('application/sparql-result+xml', In, Row) :- !,
Chris@0: 	call_cleanup(sparql_read_xml_result(stream(In), Result),
Chris@0: 		     close(In)),
Chris@0: 	xml_result(Result, Row).
Chris@0: read_reply(Type, In, _) :-
Chris@0: 	close(In),
Chris@0: 	throw(error(domain_error(sparql_result_document, Type), _)).
Chris@0: 
Chris@0: plain_content_type(Type, Plain) :-
Chris@0: 	sub_atom(Type, B, _, _, (;)), !,
Chris@0: 	sub_string(Type, 0, B, _, Main),
Chris@0: 	normalize_space(atom(Plain), Main).
Chris@0: plain_content_type(Type, Type).
Chris@0: 
Chris@0: xml_result(ask(Bool), Result) :- !,
Chris@0: 	Result = Bool.
Chris@0: xml_result(select(_VarNames, Rows), Result) :-
Chris@0: 	member(Result, Rows).
Chris@0: 
Chris@0: 
Chris@0: 
Chris@0: 
Chris@0: 
Chris@0: 		 /*******************************
Chris@0: 		 *	      SETTINGS		*
Chris@0: 		 *******************************/
Chris@0: 
Chris@0: :- dynamic
Chris@0: 	sparql_setting/1.
Chris@0: 
Chris@0: sparql_param(Param, Options) :-
Chris@0: 	memberchk(Param, Options), !.
Chris@0: sparql_param(Param, _Options) :-
Chris@0: 	sparql_setting(Param), !.
Chris@0: sparql_param(Param, _Options) :-
Chris@0: 	functor(Param, Name, _),
Chris@0: 	throw(error(existence_error(option, Name), _)).
Chris@0: 
Chris@0: %%	sparql_set_server(+OptionOrList)
Chris@0: %	
Chris@0: %	Set sparql server default options.  Provided defaults are:
Chris@0: %	host, port and repository.  For example:
Chris@0: %	
Chris@0: %%		set_sparql_default([ host(localhost),
Chris@0: %%				     port(8080)
Chris@0: %%				     repository(world)
Chris@0: %				   ])
Chris@0: 
Chris@0: sparql_set_server([]) :- !.
Chris@0: sparql_set_server([H|T]) :- !,
Chris@0: 	sparql_set_server(H),
Chris@0: 	sparql_set_server(T).
Chris@0: sparql_set_server(Term) :-
Chris@0: 	functor(Term, Name, Arity),
Chris@0: 	functor(Unbound, Name, Arity),
Chris@0: 	retractall(sparql_setting(Unbound)),
Chris@0: 	assert(sparql_setting(Term)).