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(serql_runtime,
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: :- use_module(library(xsdp_types)).
Chris@0: :- use_module(library(debug)).
Chris@0: :- use_module(library('semweb/rdf_db')).
Chris@0: 
Chris@0: 
Chris@0: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Chris@0: This module provides runtime support for running compiled SeRQL queries.
Chris@0: I.e. it defines special constructs that  may   be  emitted  by the SeRQL
Chris@0: compiler and optimizer. Predicates common to   all  query languages have
Chris@0: been moved to rdfql_runtime.pl
Chris@0: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
Chris@0: 
Chris@0: 
Chris@0: 		 /*******************************
Chris@0: 		 *	   RUNTIME TESTS	*
Chris@0: 		 *******************************/
Chris@0: 
Chris@0: %%	serql_compare(+Op, +Left, +Right)
Chris@0: %	
Chris@0: %	Handle numerical and textual comparison of literals.  Some work
Chris@0: %	must be done at compiletime.
Chris@0: 
Chris@0: serql_compare(Op, L, R) :-
Chris@0: 	serql_eval(L, VL),
Chris@0: 	serql_eval(R, VR), !,
Chris@0: 	do_compare(Op, VL, VR).
Chris@0: 
Chris@0: do_compare(like, literal(Value), Pattern) :- !,
Chris@0: 	to_string(Value, String),
Chris@0: 	rdf_match_label(like, Pattern, String).
Chris@0: do_compare(like, Resource, Pattern) :- !,
Chris@0: 	atom(Resource),
Chris@0: 	rdf_match_label(like, Pattern, Resource).
Chris@0: do_compare(=, X, X) :- !.
Chris@0: do_compare(=, literal(X), query(X)) :- !.
Chris@0: do_compare(=, X, query(X)) :- !.
Chris@0: do_compare(\=, X, Y) :- !,
Chris@0: 	\+ do_compare(=, X, Y).
Chris@0: do_compare(Op, literal(Data), query(Query)) :-
Chris@0: 	catch(to_number(Query, Right, TypeQ), _, fail), !,
Chris@0: 	(   nonvar(TypeQ), atom(Data)
Chris@0: 	->  catch(xsdp_convert(TypeQ, [Data], Left), _, fail)
Chris@0: 	;   catch(to_number(Data, Left, TypeD), _, fail),
Chris@0: 	    serql_subsumes(TypeQ, TypeD)
Chris@0: 	),
Chris@0: 	cmp_nums(Op, Left, Right).
Chris@0: do_compare(Op, literal(Data), query(Query)) :- !,
Chris@0: 	(   atom(Query)			% plain text
Chris@0: 	->  atom(Data),			% TBD: Lang and Type
Chris@0: 	    cmp_strings(Op, Data, Query)
Chris@0: 	).
Chris@0: do_compare(Op, query(Query), literal(Data)) :- !,
Chris@0: 	inverse_op(Op, Inverse),
Chris@0: 	do_compare(Inverse, literal(Data), query(Query)).
Chris@0: do_compare(Op, literal(Value), literal(Number)) :-
Chris@0: 	catch(to_number(Value, Left, TypeL), _, fail),
Chris@0: 	catch(to_number(Number, Right, TypeR), _, fail),
Chris@0: 	TypeL == TypeR,
Chris@0: 	cmp_nums(Op, Left, Right).
Chris@0: 
Chris@0: serql_eval(Var, X) :-
Chris@0: 	var(Var), !,
Chris@0: 	X = '$null$'.
Chris@0: serql_eval(lang(X), Lang) :- !,
Chris@0: 	lang(X, Lang).
Chris@0: serql_eval(datatype(X), Type) :- !,
Chris@0: 	datatype(X, Type).
Chris@0: serql_eval(label(X), Lang) :- !,
Chris@0: 	label(X, Lang).
Chris@0: serql_eval(X, X).
Chris@0: 
Chris@0: %%	lang(+Literal, -Lang) is det.
Chris@0: %%	datatype(+Literal, -DataType) is det.
Chris@0: %%	label(+Literal, -Label) is det.
Chris@0: %	
Chris@0: %	Defined functions on literals.  
Chris@0: 
Chris@0: lang(literal(lang(Lang0, _)), Lang) :-
Chris@0:      nonvar(Lang0), !,
Chris@0:      Lang = literal(Lang0).
Chris@0: lang(_, '$null$').
Chris@0: 
Chris@0: datatype(literal(type(Type0, _)), Type) :-
Chris@0:      nonvar(Type0), !,
Chris@0:      Type = Type0.
Chris@0: datatype(_, '$null$').
Chris@0: 
Chris@0: label(literal(lang(_, Label0)), Label) :-
Chris@0:      nonvar(Label0), !,
Chris@0:      Label = literal(Label0).
Chris@0: label(literal(Label0), Label) :-
Chris@0:      nonvar(Label0), !,
Chris@0:      Label = literal(Label0).
Chris@0: label(_, '$null$').
Chris@0: 
Chris@0: 
Chris@0: cmp_nums(=, L, R)  :- L =:= R.
Chris@0: cmp_nums(=<, L, R) :- L =< R.
Chris@0: cmp_nums(<, L, R)  :- L < R.
Chris@0: cmp_nums(>, L, R)  :- L > R.
Chris@0: cmp_nums(>=, L, R) :- L >= R.
Chris@0: 
Chris@0: cmp_strings(Op, S1, S2) :-
Chris@0: 	atom(S1), atom(S2),
Chris@0: 	compare(Op, S1, S2).
Chris@0: 
Chris@0: inverse_op(=, =).
Chris@0: inverse_op(=<, >).
Chris@0: inverse_op(<, >=).
Chris@0: inverse_op(>, =<).
Chris@0: inverse_op(>=, <).
Chris@0: 
Chris@0: to_number(type(Type, String), Num, Type) :- !,	% TBD: Check type
Chris@0: 	atom_number(String, Num).
Chris@0: to_number(lang(_Lang, String), Num, _) :- !,
Chris@0: 	atom_number(String, Num).
Chris@0: to_number(String, Num, _) :-
Chris@0: 	assertion(atom(String)),
Chris@0: 	atom_number(String, Num).
Chris@0: 
Chris@0: %%	serql_subsumes(QueryType, DataType)
Chris@0: 
Chris@0: serql_subsumes(Q, Var) :-		% odd rule!
Chris@0: 	nonvar(Q),
Chris@0: 	var(Var), !.
Chris@0: serql_subsumes(_, Var) :-		% odd rule!
Chris@0: 	var(Var), !, fail.
Chris@0: serql_subsumes(Var, _) :-		% type is not specified in query
Chris@0: 	var(Var), !.
Chris@0: serql_subsumes(Query, Data) :-
Chris@0: 	xsdp_subtype_of(Data, Query).
Chris@0: 
Chris@0: to_string(lang(_, String), String) :- !.
Chris@0: to_string(type(_, String), String) :- !.
Chris@0: to_string(String, String) :-
Chris@0: 	atom(String).
Chris@0: 
Chris@0: %%	serql_member_statement(-Triple, +List)
Chris@0: %	
Chris@0: %	Get the individual triples from  the   original  reply. Used for
Chris@0: %	CONSTRUCT queries. As handling optional matches is different int
Chris@0: %	SeRQL compared to SPARQL, the selection  is in the SeRQL runtime
Chris@0: %	module.
Chris@0: 
Chris@0: serql_member_statement(RDF, [H|_]) :-
Chris@0: 	member_statement2(RDF, H).
Chris@0: serql_member_statement(RDF, [_|T]) :-
Chris@0: 	serql_member_statement(RDF, T).
Chris@0: 
Chris@0: member_statement2(RDF, optional(True, Statements)) :- !,
Chris@0: 	True = true,
Chris@0: 	serql_member_statement(RDF, Statements).
Chris@0: member_statement2(RDF, RDF).