Model-Theoretic Semantics and Tractable Algorithm for CNF-BCP

CNF-BCP is a well-known propositional reasoner that extends clausal Boolean Constraint Propagation (BCP) to non-clausal theories. Although BCP has efficient linear-time implementations, CNF-BCP requires clausal form transformation that sometimes leads to an exponential increase in the size of a theory. We present a new quadratic-time reasoner, RFP, that infers exactly the same literals as CNF-BCP. Although CNF-BCP has been specified only syntactically, we present a simple model-theoretic semantics for RFP. We also present a convergent term-rewriting system for RFP that is suitable for reasoning with knowledge bases that are built incrementally. Potential applications of RFP include logical truth-maintenance systems and general-purpose knowledge representation systems. Introduction Given a propositional theory, it is important in many AI systems to be able to determine the formulae that it logically entails. Since this reasoning problem is intractable, many systems settle for sound, in..