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/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 2009-2013, University of Amsterdam
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/
:- module(rdf_compare,
[ rdf_equal_graphs/3 % +Graph1, +Graph2, -Substitutions
]).
:- use_module(library(semweb/rdf_db)).
:- use_module(library(apply)).
:- use_module(library(debug)).
/** <module> Compare RDF graphs
This library provides predicates that compare RDF graphs. The current
version only provides one predicate: rdf_equal_graphs/3 verifies that
two graphs are identical after proper labeling of the blank nodes.
Future versions of this library may contain more advanced operations,
such as diffing two graphs.
*/
%! rdf_equal_graphs(+GraphA, +GraphB, -Substition) is semidet.
%
% True if GraphA and GraphB are the same under Substition.
% Substition is a list of BNodeA = BNodeB, where BNodeA is a blank
% node that appears in GraphA and BNodeB is a blank node that
% appears in GraphB.
%
% @param GraphA is a list of rdf(S,P,O) terms
% @param GraphB is a list of rdf(S,P,O) terms
% @param Substition is a list if NodeA = NodeB terms.
% @tbd The current implementation is rather naive. After
% dealing with the subgraphs that contain no bnodes,
% it performs a fully non-deterministic substitution.
rdf_equal_graphs(A, B, Substitutions) :-
sort(A, SA),
sort(B, SB),
partition(contains_bnodes, SA, VA, GA),
partition(contains_bnodes, SB, VB, GB),
( GA == GB
-> true
; maplist(compare_triple, GA, GB)
),
compare_list(VA, VB, [], Substitutions),
!.
contains_bnodes(rdf(S,P,O)) :-
( node_id(S)
; node_id(P)
; node_id(O)
),
!.
compare_list([], [], S, S).
compare_list([H1|T1], In2, S0, S) :-
select(H2, In2, T2),
compare_triple(H1, H2, S0, S1),
compare_list(T1, T2, S1, S).
compare_triple(T1, T2) :-
compare_triple(T1,T2,[],[]).
compare_triple(rdf(Subj1,P1,O1), rdf(Subj2, P2, O2), S0, S) :-
compare_field(Subj1, Subj2, S0, S1),
compare_field(P1, P2, S1, S2),
compare_field(O1, O2, S2, S).
compare_field(X, X, S, S) :- !.
compare_field(literal(X), xml(X), S, S) :- !. % TBD
compare_field(literal(lang(L1,X)), literal(lang(L2,X)), S, S) :-
!,
lang_equal(L1, L2).
compare_field(X, Id, S, S) :-
memberchk(X=Id, S),
!.
compare_field(X, Y, S, [X=Y|S]) :-
\+ memberchk(X=_, S),
node_id(X),
node_id(Y),
debug(rdf_compare, 'Assume ~w = ~w~n', [X, Y]).
node_id(node(_)) :- !.
node_id(X) :-
rdf_is_bnode(X).
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