Deriving Theory Superposition Calculi from Convergent Term Rewriting Systems

Colloque avec actes et comité de lecture. internationale.International audienceWe show how to derive refutationally complete ground superposition calculi systematically from convergent term rewriting systems for equational theories, in order to make automated theorem proving in these theories more effective. In particular we consider abelian groups and commutative rings. These are difficult for automated theorem provers, since their axioms of associativity, commutativity, distributivity and the inverse law can generate many variations of the same equation. For these theories ordering restrictions can be strengthened so that inferences apply only to maximal summands, and superpositions into the inverse law that move summands from one side of an equation to the other can be replaced by an isolation rule that isolates the maximal terms on one side. Additional inferences arise from superpositions of extended clauses, but we can show that most of these are redundant. In particular, none are needed in the case of abelian groups, and at most one for any pair of ground clauses in the case of commutative rings