Chris@0: /*  $Id$
Chris@0: 
Chris@0:     Part of SWI-Prolog
Chris@0: 
Chris@0:     Author:        Jan Wielemaker
Chris@0:     E-mail:        jan@swi.psy.uva.nl
Chris@0:     WWW:           http://www.swi-prolog.org
Chris@0:     Copyright (C): 1985-2004, 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(rdf_io,
Chris@0: 	  [ write_table/2,	% +Row, +Options
Chris@0: 	    write_graph/2,	% +Triples, +Options
Chris@0: 	    load_triples/2,	% +Input, +Options
Chris@0: 	    get_triples/3	% +Input, -Triples, +Options
Chris@0: 	  ]).
Chris@0: :- use_module(library('semweb/rdf_db')).
Chris@0: :- use_module(library(rdf_write)).
Chris@0: :- use_module(library(rdf)).
Chris@0: :- use_module(library(lists)).
Chris@0: 
Chris@0: :- multifile
Chris@0: 	write_table/4,		% +Format, +Serialization, +Rows, +Options
Chris@0: 	write_graph/4,		% +Format, +Serialization, +Triples, +Options
Chris@0: 	load_triples/3,		% +Format, +Input, +Options
Chris@0: 	get_triples/4.		% +Format, +Input, -Triples, +Options
Chris@0: 
Chris@0: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Chris@0: This module acts as a dispatcher module,   allowing other modules to add
Chris@0: clauses  for  write_table/4  and  write_graph/4    and   thus  providing
Chris@0: additional output formats without modifications to the kernel source.
Chris@0: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
Chris@0: 
Chris@0: %%	write_table(+Rows, +Options)
Chris@0: %	
Chris@0: %	Write a result-table in the specified format.  Rows is a list of
Chris@0: %	terms row(C1, C2, ...).  Options specifies additional processing
Chris@0: %	options.  Defined options are:
Chris@0: %	
Chris@0: %		* variables(+Vars)
Chris@0: %		Specifies the names of the columns.  Vars is a term with
Chris@0: %		functor =vars= and atom-arguments describing the names
Chris@0: %		of each subsequent column.  For Example:
Chris@0: %		
Chris@0: %		==
Chris@0: %		variables(vars('Name', 'Address'))
Chris@0: %		==
Chris@0: 		
Chris@0: 
Chris@0: write_table(Rows, Options) :-
Chris@0: 	needed_option(result_format(Format), Options),
Chris@0: 	needed_option(serialization(Serialization), Options),
Chris@0: 	write_table(Format, Serialization, Rows, Options).
Chris@0: 
Chris@0: 
Chris@0: write_graph(Triples, Options) :-
Chris@0: 	needed_option(serialization(Serialization), Options),
Chris@0: 	(   Serialization == rdfxml
Chris@0: 	->  (   memberchk(result_format(Format), Options)
Chris@0: 	    ->	true
Chris@0: 	    ;	Format = xml
Chris@0: 	    )
Chris@0: 	;   needed_option(result_format(Format), Options)
Chris@0: 	),
Chris@0: 	write_graph(Format, Serialization, Triples, Options).
Chris@0: 
Chris@0: 
Chris@0: 		 /*******************************
Chris@0: 		 *	       READING		*
Chris@0: 		 *******************************/
Chris@0: 
Chris@0: load_triples(Input, Options0) :-
Chris@0: 	select(data_format(Format), Options0, Options),
Chris@0: 	load_triples(Format, Input, Options).
Chris@0: 
Chris@0: 
Chris@0: load_triples(rdfxml, Input, Options) :- !,
Chris@0: 	rdf_load(Input, Options).
Chris@0: 
Chris@0: get_triples(Input, Triples, Options0) :-
Chris@0: 	select(data_format(Format), Options0, Options),
Chris@0: 	get_triples(Format, Input, Triples, Options).
Chris@0: 
Chris@0: 
Chris@0: get_triples(rdfxml, Input, Triples, Options) :- !,
Chris@0: 	load_rdf(Input, Triples, Options).
Chris@0: 
Chris@0: 
Chris@0: 		 /*******************************
Chris@0: 		 *	       HOOK		*
Chris@0: 		 *******************************/
Chris@0: 
Chris@0: %%	write_graph(+ResultFormat, +Serialization, +Triples, +Options)
Chris@0: %	
Chris@0: %	Provide hook for rdf_io.pl plugin interface
Chris@0: 
Chris@0: write_graph(xml, rdfxml, Triples, _Options) :-
Chris@0: 	format('Content-type: application/rdf+xml~n~n'),
Chris@0: 	rdf_write_xml(current_output, Triples).
Chris@0: 
Chris@0: 		 /*******************************
Chris@0: 		 *		UTIL		*
Chris@0: 		 *******************************/
Chris@0: 
Chris@0: needed_option(Term, Options) :-
Chris@0: 	memberchk(Term, Options), !.
Chris@0: needed_option(Term, _) :-
Chris@0: 	functor(Term, Name, _),
Chris@0: 	throw(error(existence_error(option, Name), _)).