/* Simple family relationships in SLEUTH */

/* Facts: parent relationships */
parent(tom, bob).
parent(tom, liz).
parent(bob, ann).
parent(bob, pat).
parent(pat, jim).

/* Rules */
grandparent(X, Z) :- parent(X, Y), parent(Y, Z).
ancestor(X, Y) :- parent(X, Y).
ancestor(X, Y) :- parent(X, Z), ancestor(Z, Y).

/* Queries would be like: ?- grandparent(tom, ann). */