valuable(gold).
valuable(money).
king(john, france).
gives(john, book, mark).

mortal(X) :- man(X).  /* if X is a man, then X is mortal */
mortal(X) :- woman(X).

man(john).
woman(carol).

father(X,C) :- male(X), parent(X,C).
grandfather(G,C) :- father(G,X), parent(X,C).


male(joe).
male(jack).
female(jae).
female(boo).
parent(joe,boo).
parent(jae,boo).
parent(jack,joe).