Abstract

In this paper we show that it is possible to eliminate the converse operator from the propositional dynamic logic CPDL (Converse PDL), without compromising the soundness and completeness of inference for it. Specifically we present an encoding of CPDL formulae into PDL that eliminates the converse programs from a CPDL formula, but adds enough information so as not to destroy its original meaning with respect to satisfiability, validity, and logical implication. Notably, the resulting PDL formula is polynomially related to the original one. This fact allows one to build inference procedures for CPDL, by encoding CPDL formulae into PDL, and then running an inference procedure for PDL.