We demonstrate the feasibility of using the XSB tabled logic programming system as a programmable fixed-point engine for implementing efficient local model checkers. In particular, we present XMC, an XSBbased local model checker for a CCS-like value-passing language and the alternation-free fragment of the modal mu-calculus. XMC is written in under 200 lines of XSB code, which constitute a declarative specification of CCS and the modal mu-calculus at the level of semantic equations. In order to gauge the performance of XMC as an algorithmic model checker, we conducted a series of benchmarking experiments designed to compare the performance of XMC with the local model checkers implemented in C/C++ in the Concurrency Factory and SPIN specification and verification environments. After applying certain newly developed logic-programmingbased optimizations (along with some standard ones), XMC's performance became extremely competitive with that of the Factory and shows promise in its comparison with SPIN.

In this paper we suggest numerical decision diagrams, a BDD-based data-structure for representing certain subsets of the Euclidean space, namely those encountered in verification of timed automata. Unlike other representation schemes, NDD's are canonical and provide for all the necessary operations needed in the verification and synthesis of timed automata. We report some preliminary experimental results.

The use of an Ordered Binary Decision Diagram (OBDD) to store all visited states during on-thefly model checking (or reachability analysis) is investigated. To improve the time and space efficiency a state compression technique is introduced. This compression technique is safe, in the sense that no two unique states will have the same compressed representation. A number of examples are used to evaluate an experimental implementation of the OBDD state store within the SPIN validation tool. In all the examples a reduction in space is achieved when using the OBDD state store as opposed to the more traditional hash table state store. The memory and time usage when combining partial orders with the OBDD state store is also considered. 1 Introduction Temporal logics can express changes over time without introducing time explicitly and is therefore suitable for specifying many correctness properties of concurrent systems. Since many interesting programs can be modelled as finite-state system...

Temporal logic model checking is an automatic verification method for finite-state systems. An important feature of model checking is that a counterexample can be constructed when a temporal formula does not hold for the model. The very procedure of local model checking already constructs a witness for a formula in form of a tableau proof tree. However, local model checking has bad worst-case time and space complexities. For this and other reasons, global model checking has been applied much more often in practice. How to construct counterexamples in the case of global model checking is described in [CGMZ94] for the case that the temporal logic is restricted to fair CTL. This paper shows how counterexamples and witnesses for the whole modal -calculus can be constructed if the model checking procedure is global. The witness construction presented in this paper is polynomial in the size of the model and the length of the formula. 1 Introduction Complex finite state-transition...