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%  Copyright 2018-2019 Paulo Moura
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:- set_logtalk_flag(hook, metagol).


:- object(kinship2,
	implements(metagol_example_protocol),
	extends(metagol)).

	%% tell metagol to use the BK
	body_pred(parent/2).

	%% metarules
	metarule([P,Q], [P,A,B], [[Q,A,B]]).
	metarule([P,Q], [P,A,B], [[Q,A,C],[P,C,B]]).

	%% background knowledge
	parent(queen_victoria,edward_seventh).
	parent(edward_seventh,george_fifth).
	parent(george_fifth,george_sixth).
	parent(george_sixth,elizabeth_second).
	parent(queen_mother,elizabeth_second).
	parent(elizabeth_second,prince_charles).
	parent(prince_philip,prince_charles).
	parent(prince_charles,prince_william).
	parent(prince_charles,prince_harry).
	parent(princess_diana,prince_william).
	parent(princess_diana,prince_harry).
	parent(prince_william,prince_george).

	learn(Clauses) :-
		Pos = [
			ancestor(elizabeth_second,prince_charles),
			ancestor(george_sixth,prince_harry),
			ancestor(queen_mother,prince_william)
		],
		^^learn(Pos, [], Prog),
		^^program_to_clauses(Prog, Clauses).

	learn :-
		learn(Clauses),
		^^pprint_clauses(Clauses).

:- end_object.
