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): 1985-2005, 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(rdfql_runtime,
Chris@0: 	  [ rdfql_carthesian/1,		% +Bags
Chris@0: 	    rdfql_is_literal/1,		% +Node
Chris@0: 	    rdfql_is_resource/1,	% +Node
Chris@0: 
Chris@0: 	    rdfql_bind_null/1,		% +List
Chris@0: 	    rdfql_cond_bind_null/1,	% +List
Chris@0: 
Chris@0: 					% SeRQL support
Chris@0: 	    serql_compare/3,		% +Comparison, +Left, +Right
Chris@0: 	    serql_eval/2,		% +Term, -Evaluated
Chris@0: 	    serql_member_statement/2,	% -Triple, +List
Chris@0: 	    
Chris@0: 					% SPAQRL support
Chris@0: 	    sparql_true/1,		% +Term
Chris@0: 	    sparql_eval/2		% +Expression, -Result
Chris@0: 	  ]).
Chris@0: :- use_module(library(nb_set)).
Chris@0: :- use_module(library(debug)).
Chris@0: :- use_module(serql_runtime).
Chris@0: :- use_module(sparql_runtime).
Chris@0: 
Chris@0: :- meta_predicate
Chris@0: 	rdfql_carthesian(:),
Chris@0: 	solve_bags(:,+,-).
Chris@0: 
Chris@0: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Chris@0: This module provides runtime support for  running compiled queries. I.e.
Chris@0: it defines special constructs that may be   emitted  by the compiler and
Chris@0: optmizer that are common  to  all   query  languages.  Language specific
Chris@0: runtime support is in serql_runtime.pl and sparql_runtime.pl
Chris@0: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
Chris@0: 
Chris@0: 		 /*******************************
Chris@0: 		 *      CARTHESIAN PRODUCT	*
Chris@0: 		 *******************************/
Chris@0: 
Chris@0: rdfql_carthesian(Bags) :-
Chris@0: 	solve_bags(Bags, 1, Sets),
Chris@0: 	(   debugging(carthesian_size)
Chris@0: 	->  solution_set_size(Sets, Size),
Chris@0: 	    debug(carthesian_size, 'Total size = ~D; NO select', [Size])
Chris@0: 	;   true
Chris@0: 	),
Chris@0: 	(   debugging(carthesian_no_select)
Chris@0: 	->  true
Chris@0: 	;   carthesian_select(Sets)
Chris@0: 	).
Chris@0: 
Chris@0: solve_bags([], _, []).
Chris@0: solve_bags([bag(Vars, Goal)|T0], N, [set(Templ,Set,Size)|T]) :-
Chris@0: 	Templ =.. [v|Vars],
Chris@0: 	empty_nb_set(Set),
Chris@0: 	(   Goal,
Chris@0: 	    add_nb_set(Templ, Set),
Chris@0: 	    fail
Chris@0: 	;   true
Chris@0: 	),
Chris@0: 	size_nb_set(Set, Size),
Chris@0: 	debug(carthesian_bags, 'Bag ~d: solution size = ~D', [N, Size]),
Chris@0: 	Size > 0,
Chris@0: 	N2 is N + 1,
Chris@0: 	solve_bags(T0, N2, T).
Chris@0: 
Chris@0: carthesian_select([]).
Chris@0: carthesian_select([set(Templ,Set,_)|T]) :-
Chris@0: 	gen_nb_set(Set, Templ),
Chris@0: 	carthesian_select(T).
Chris@0: 
Chris@0: solution_set_size([], 0).
Chris@0: solution_set_size([set(_,_,Len)|T], Size) :-
Chris@0: 	(   T == []
Chris@0: 	->  Size = Len
Chris@0: 	;   solution_set_size(T, Size0),
Chris@0: 	    Size is Len * Size0
Chris@0: 	).
Chris@0: 
Chris@0: 
Chris@0: 		 /*******************************
Chris@0: 		 *	    NULL HANDLING	*
Chris@0: 		 *******************************/
Chris@0: 
Chris@0: rdfql_cond_bind_null([]).
Chris@0: rdfql_cond_bind_null([H|T]) :-
Chris@0: 	(   var(H)
Chris@0: 	->  H = '$null$'
Chris@0: 	;   true
Chris@0: 	),
Chris@0: 	rdfql_cond_bind_null(T).
Chris@0: 
Chris@0: 
Chris@0: rdfql_bind_null([]).
Chris@0: rdfql_bind_null(['$null$'|T]) :-
Chris@0: 	rdfql_bind_null(T).
Chris@0: 
Chris@0: 
Chris@0: rdfql_is_literal(literal(_)).
Chris@0: rdfql_is_resource(X) :-
Chris@0: 	atom(X).