Action Language Verifier, Extended

Action Language Verifier (ALV) is an infinite state model checker which specializes on systems specified with linear arithmetic constraints on integer variables. An Action Language specification consists of integer, boolean and enumerated variables, parameterized integer constants and a set of modules and actions which are composed using synchronous and asynchronous composition operators [3, 7]. ALV uses symbolic model checking techniques to verify or falsify CTL properties of the input specifications. Since Action Language allows specifications with unbounded integer variables, fixpoint computations are not guaranteed to converge. ALV uses conservative approximation techniques, reachability and acceleration heuristics to achieve convergence. Originally, ALV was developed using a Polyhedral representation for linear arithmetic constraints [4]. In the last couple of years we extended ALV by adding an automata representation for linear arithmetic constraints [2]. ALV also uses BDDs to encode boolean and enumerated variables. These symbolic representations can be used in different combinations. For example, polyhedral and automata representations can be combined with BDDs using a disjunctive representation. ALV also supports efficient representation of bounded arithmetic constraints using BDDs [2]. Other extensions to ALV include several techniques to improve the efficiency of fixpoint computations such as marking heuristic and dependency analysis, and automated counting abstraction for verification of arbitrary number of finite state processes [7].