A practical decision method for propositional dynamic logic (Preliminary Report)

Abstract

We give a new characterization of the set of satisfiable formulae of propositional dynamic logic (PDL) based on the method of tableaux. From it we derive a heuristically efficient goal-directed proof procedure and a complete axiom system for PDL. The proof procedure illustrates a striking connection between natural deduction and symbolic execution. The completeness proof for the axiom system incorporates a method for the automatic synthesis of invariants. We also augment DL with new modalities throughout, during, and preserves, supply a new semantic foundation for DL programs, and show how to extend the satisfiability characterizations for PDL to throughout.