Implementing Superposition in iProver (System Description)

Abstract

iProver is a saturation theorem prover for first-order logic with equality, which is originally based on an instantiation calculus Inst-Gen. In this paper we describe an extension of iProver with the superposition calculus. We have developed a flexible simplification setup that subsumes and generalises common architectures such as DISCOUNT or Otter. This also includes the concept of “immediate simplification”, wherein newly derived clauses are more aggressively simplified among themselves, and the concept of “light normalisation”, wherein ground unit equations are stored in an interreduced TRS which is then used to simplify new clauses. We have also added support for associative-commutative theories (AC), namely by deletion of AC-joinable clauses, semantic detection of AC axioms, and preprocessing normalisation.