102 lines
3.3 KiB
Prolog
102 lines
3.3 KiB
Prolog
/* Part of SWI-Prolog
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Author: Jan Wielemaker
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E-mail: J.Wielemaker@uva.nl
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WWW: http://www.swi-prolog.org
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Copyright (C): 2009, University of Amsterdam
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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As a special exception, if you link this library with other files,
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compiled with a Free Software compiler, to produce an executable, this
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library does not by itself cause the resulting executable to be covered
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by the GNU General Public License. This exception does not however
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invalidate any other reasons why the executable file might be covered by
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the GNU General Public License.
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*/
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:- module(rdf_compare,
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[ rdf_equal_graphs/3 % +Graph1, +Graph2, -Substitutions
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]).
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:- use_module(library(semweb/rdf_db)).
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:- use_module(library(apply)).
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:- use_module(library(debug)).
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/** <module> Compare RDF graphs
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This library provides predicates that compare RDF graphs. The current
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version only provides one predicate: rdf_equal_graphs/3 verifies that
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two graphs are identical after proper labeling of the blank nodes.
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Future versions of this library may contain more advanced operations,
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such as diffing two graphs.
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*/
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%% rdf_equal_graphs(+GraphA, +GraphB, -Substition) is semidet.
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%
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% True if GraphA and GraphB are the same under Substition.
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% Substition is a list of BNodeA = BNodeB, where BNodeA is a blank
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% node that appears in GraphA and BNodeB is a blank node that
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% appears in GraphB.
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%
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% @param GraphA is a list of rdf(S,P,O) terms
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% @param GraphB is a list of rdf(S,P,O) terms
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% @param Substition is a list if NodeA = NodeB terms.
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% @tbd The current implementation is rather naive. After
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% dealing with the subgraphs that contain no bnodes,
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% it performs a fully non-deterministic substitution.
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rdf_equal_graphs(A, B, Substitutions) :-
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sort(A, SA),
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sort(B, SB),
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partition(contains_bnodes, SA, VA, GA),
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partition(contains_bnodes, SB, VB, GB),
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GA == GB,
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compare_list(VA, VB, [], Substitutions), !.
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contains_bnodes(rdf(S,P,O)) :-
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( node_id(S)
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; node_id(P)
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; node_id(O)
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), !.
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compare_list([], [], S, S).
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compare_list([H1|T1], In2, S0, S) :-
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select(H2, In2, T2),
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compare_triple(H1, H2, S0, S1),
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compare_list(T1, T2, S1, S).
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compare_triple(rdf(Subj1,P1,O1), rdf(Subj2, P2, O2), S0, S) :-
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compare_field(Subj1, Subj2, S0, S1),
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compare_field(P1, P2, S1, S2),
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compare_field(O1, O2, S2, S).
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compare_field(X, X, S, S) :- !.
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compare_field(literal(X), xml(X), S, S) :- !. % TBD
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compare_field(X, Id, S, S) :-
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memberchk(X=Id, S), !.
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compare_field(X, Y, S, [X=Y|S]) :-
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\+ memberchk(X=_, S),
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node_id(X),
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node_id(Y),
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debug(rdf_compare, 'Assume ~w = ~w~n', [X, Y]).
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node_id(node(_)) :- !.
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node_id(X) :-
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rdf_is_bnode(X).
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