General Clauses for SAT-Based Proof Search in Intuitionistic Propositional Logic

In recent years some papers have addressed the problem of the validity in Intuitionistic Propositional Logic (IPL) using the approach proposed by Claessen and Rosén based on reduction to Satisfiability Modulo Theories. This approach depends on an initial preprocessing phase that reduces the input formula in the intuitionistic language to an equivalent sequent in the language of clauses. In this paper we present general clauses, an extension of the clauses used by Claessen and Rosén, that allow us to define a natural relationship between the semantics of the extended clauses and Kripke semantics. We present a decision procedure for general clauses and we show how to encode intuitionistic formulas in the language of general clauses so to decide IPL. The experimental results show that our implementation in general outperforms the state-of-the-art provers for IPL. In principle general clauses can be used as a target language for other non-classical logics with Kripke semantics, so that our decision procedure can be used to decide them.