  Answer-set programming (ASP) has emerged recently as a viable programming
paradigm. We describe here an ASP system, DATALOG with constraints or DC, based
on non-monotonic logic. Informally, DC theories consist of propositional
clauses (constraints) and of Horn rules. The semantics is a simple and natural
extension of the semantics of the propositional logic. However, thanks to the
presence of Horn rules in the system, modeling of transitive closure becomes
straightforward. We describe the syntax, use and implementation of DC and
provide experimental results.
