Modeling and Verification of Real-Time Systems with the Event Calculus and s(CASP)

Abstract

AbstractModeling a cyber-physical system’s requirement specifications makes it possible to verify its properties w.r.t. the expected behavior. Standard modeling approaches based on automata theory model these systems at the system architecture level, as they have to explicitly encode the notion of states and define explicit transitions between these states. Event Calculus encoding using Answer Set Programming (ASP) allows for elegant and succinct modeling of these dynamic systems at the requirements specification level, thanks to the near-zero semantics gap between the system’s requirement specifications and the Event Calculus encoding. In this work we propose a framework that uses the EARS notation to describe the system requirements, and an Event Calculus reasoner based on s(CASP), a goal-directed Constraint Answer Set Programming reasoner over the rationals/reals, to directly model these requirements. We evaluate our proposal by (i) modeling the well-known Train-Gate-Controller system, a railroad crossing problem, using the EARS notation and Event Calculus, (ii) translating the specifications into s(CASP), and (iii) checking safety and liveness of the system.