Action Language verifier: an infinite-state model checker for reactive software specifications

Action Language is a specification language for reactive software systems. In this paper, we present the syntax and the semantics of the Action Language and we also present an infinite-state symbolic model checker called Action Language Verifier (ALV) that verifies (or falsifies) CTL properties of Action Language specifications. ALV is built on top of the Composite Symbolic Library, which is a symbolic manipulator that combines multiple symbolic representations. ALV is a polymorphic model checker that can use different combinations of the symbolic representations implemented in the Composite Symbolic Library. We describe the heuristics implemented in ALV for computing fixpoints using the composite symbolic representation. Since Action Language specifications allow declaration of unbounded integer variables and parameterized integer constants, verification of Action Language specifications is undecidable. ALV uses several heuristics to conservatively approximate the fixpoint computations. ALV also implements an automated abstraction technique that enables parameterized verification of a concurrent system with an arbitrary number of identical processes.