Techiques in Symbolic Model Checking.

Ashutosh Trivedi

Model checking is a highly automatic verification technique for finite state concurrent systems. In this approach for verification, temporal specifications are exhaustively verified over the state-space of the concurrent system. The number of states grows exponentially with the concurrency of the system and that makes explicit state-space enumeration based techniques inefficient. This phenomenon is called state space explosion. One of the possible ways to overcome this limitation is to avoid explicit enumeration of the state space. These approaches, commonly known as Symbolic Model Checking, use Boolean formulas to represent set of states and transition relations. Traditionally, symbolic model checking has become identified with Binary Decision Diagrams (BDD), a canonical form of representing Boolean formulas. But recently, some other representations like Conjunctive Normal Form (CNF) using satisfiability solving (SAT) and polynomial algebra have been demonstrated to be quite powerful in practice. In this thesis, we propose an approach to symbolic model checking where model checking is performed by decomposing a finite state system into components. We first review the decomposition process by Chakraborty and Soni, and enhance it by guiding the process of decomposition. We observed that computing the components of the system is an expensive operation. Therefore our approach computes a new component only if the information in existing component is not sufficient to prove (falsify) the safety property. We call this approach Lazy decomposition. The ideas are evaluated on publicly available benchmarks from ISCAS-89 benchmark using BDD and SAT based implementations. We report the experimental results and compare it with earlier schemes.

MTech Thesis, Indian Institute of Technology Bombay. 2003.
PDF © 2003 Ashutosh Trivedi.