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A sister of a parent is an aunt of the child.
A brother of a parent is an uncle.
A wife of an uncle is an aunt and
a husband of an aunt is an uncle:
parents(william, diana, charles).
parents(henry, diana, charles).
parents(charles, elizabeth, philip).
parents(diana, frances, edward).
parents(anne, elizabeth, philip).
parents(andrew, elizabeth, philip).
parents(edwardW, elizabeth, philip).
married(diana, charles).
married(elizabeth, philip).
married(frances, edward).
married(anne, mark).
parent(C,M) <= parents(C,M,D).
parent(C,D) <= parents(C,M,D).
sibling(X,Y) <= parents(X,M,D)
and parents(Y,M,D). {NB. sibling(X, X)}
aORuDirect(C, A) <= parent(C,P) and sibling(P,A).
aORuMarr(C, A) <= aORuDirect(C,X) and married(X,A).
aORuMarr(C, A) <= aORuDirect(C,X) and married(A,X).
aORu(C,A) <= aORuDirect(C,A).
aORu(C,A) <= aORuMarr(C,A).
? aORu(william, A).
{ The Aunt/Uncle Relation. }
Unfortunately these rules, while finding correct aunts and uncles,
return parents as aunts or uncles,
and also give repeated solutions.
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The cure is to insist that siblings,
while sharing the same parents,
must be different individuals:
parents(william, diana, charles).
parents(henry, diana, charles).
parents(charles, elizabeth, philip).
parents(diana, frances, edward).
parents(anne, elizabeth, philip).
parents(andrew, elizabeth, philip).
parents(edwardW, elizabeth, philip).
married(diana, charles).
married(elizabeth, philip).
married(frances, edward).
married(anne, mark).
parent(C,M) <= parents(C,M,D).
parent(C,D) <= parents(C,M,D).
equal(X, X).
sibling(X,Y) <= parents(X,M,D)
and parents(Y,M,D) and not equal(X,Y).
aORuDirect(C, A) <= parent(C,P) and sibling(P,A).
aORuMarr(C, A) <= aORuDirect(C,X) and married(X,A).
aORuMarr(C, A) <= aORuDirect(C,X) and married(A,X).
aORu(C,A) <= aORuDirect(C,A).
aORu(C,A) <= aORuMarr(C,A).
? aORu(william, A).
{ The Aunt/Uncle Relation. }
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