[seanmcdirmid]

Its also not that hard to build a backward (prolog) or forward (datalog) chaining predicate rule system in whatever your favorite language is; as a bonus, you'll get to learn the joys of unification, or go crazy with some higher order predicates.

Once you get bored with unification, then look at dealing with inequalities and learn some constraint solving. Prolog and datalog look quite simplistic compared to some of the more developed logics out there.