I've toyed with this problem for years. I should really give up now.
steals(PERP, STUFF) :-
thief(PERP),
valuable(STUFF),
owns(VICTIM,STUFF),
not(knows(PERP,VICTIM)).
thief(badguy).
valuable(gold).
valuable(rubies).
owns(merlyn,gold).
owns(ovid,rubies).
knows(badguy,merlyn).
