I believe it uses Prolog rather than Datalog (I'd be interested to learn more about how they differ).

Datalog is the positive, function-free fragment of Prolog, i.e., what Prolog offers over Datalog is negation and “value invention” through function terms. One consequence of that is that deciding whether a Prolog program entails a fact is undecidable (i.e., Prolog is Turing-complete), deciding whether a Datalog program entails a fact is can be done in polynomial time with respect to the size of the database.