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Complexity of propositional projection temporal logic with star. (English) Zbl 1161.03008
Summary: This paper investigates the complexity of Propositional Projection Temporal Logic with Star (PPTL${}^{*}$). To this end, Propositional Projection Temporal Logic (PPTL) is first extended to include projection star. Then, by reducing the emptiness problem of star-free expressions to the problem of the satisfiability of PPTL${}^{*}$ formulas, the lower bound of the complexity for the satisfiability of PPTL${}^{*}$ formulas is proved to be non-elementary. Then, to prove the decidability of PPTL${}^{*}$, the normal form, normal form graph (NFG) and labelled normal form graph (LNFG) for PPTL${}^{*}$ are defined. Also, algorithms for transforming a formula to its normal form and LNFG are presented. Finally, a decision algorithm for checking the satisfiability of PPTL${}^{*}$ formulas is formalised using LNFGs.
MSC:
 03B44 Temporal logic 03B25 Decidability of theories; sets of sentences 68Q60 Specification and verification of programs