Fair enough, but to a database theoretician SQL means "non-recursive conjunctive queries". And I skimmed the tutorial and there is not a single example of using Logica to compute something recursively. Transitive closure is the canonical example for showing off Datalog.
SQL 99 only requires support for linear recursion, i.e. "each FROM has at most one reference to a recursively-defined relation". Datalog doesn't have such a restriction