Thanks, I hadn't heard of that one!
Another very interesting language in the Prolog family is Mercury (http://www.mercurylang.org/), which has a more functional and static flavour than Prolog, and has a suite of compilers that can produce quite efficient code.
It's a lot like Prolog, but it's based in answer set programming, which gives you nice guarantees like "doesn't matter what order you write the rules in" and "always terminates".