The introduction of Past Operators enables to produce more natural formulation of a wide class of properties of reactive systems, compared to traditional pure future temporal logics. For this reason, past temporal logics are gaining increasing interest in several application areas, ranging from Requirement Engineering to Formal Verification and Model Checking. We show how SAT-based Bounded Model Checking techniques can be extended to deal with Linear Temporal Logics with Past Operators (PLTL). Though apparently simple, this task turns out to be absolutely non-trivial when tackled in its full generality. We discuss a bounded semantics for PLTL, we show that it is correct (and complete), and propose an encoding scheme able to cope with PLTL formulas. Finally, we implement the encoding in NuSMV, and present a first experimental evaluation of the approach.
['Marco Benedetti', 'Alessandro Cimatti']
Bounded model checking for past LTL