The primary difference is that it has a strong static haskell-ish type system. Secondarily it is purely declarative (though so is datalog) and functional so no

The primary difference is that it has a strong static haskell-ish type system. Secondarily it is purely declarative (though so is datalog) and functional so no side effects and the clauses can be written/checked in any order (though it uses monads, like in Haskell to be do IO and force ordered evaluation when that's important)