Abstract. Model checking is a formal technique for automatically verifying that a finite-state model satisfies a temporal property. In model checking, generally Binary Decision Diagrams (BDDs) are used to efficiently encode the transition relation of the finite-state model. Recently model checking algorithms based on Boolean satisfiability (SAT) procedures have been developed to complement the traditional BDD-based model checking. These algorithms can be broadly classified into three categories: (1) bounded model checking which is useful for finding failures (2) hybrid algorithms that combine SAT and BDD based methods for unbounded model checking, and (3) purely SAT-based unbounded model checking algorithms. The goal of this paper is to provide a uniform and comprehensive basis for evaluating these algorithms. The paper describes eight bounded and unbounded techniques, and analyzes the performance of these algorithms on a large and diverse set of hardware benchmarks.

The i-protocol, an optimized sliding-window protocol for GNU UUCP, came to our attention two years ago when we used the Concurrency Factory's local model checker to detect, locate, and correct a non-trivial livelock in version 1.04 of the protocol. Since then, we have repeated this verification effort with five widely used model checkers, namely, COSPAN, Murϕ, SMV, Spin, and XMC. It is our contention that the i-protocol makes for a particularly compelling case study in protocol verification and for a formidable benchmark of verification-tool performance, for the following reasons: 1) The i-protocol can be used to gauge a tool's ability to detect and diagnose livelock errors. 2) The size of the i-protocol's state space grows exponentially in the window size, and the entirety of this state space must be searched to verify that the protocol, with the livelock error eliminated, is deadlock-or livelock-free. 3) The i-protocol is an asynchronous, low-level software system equipped with a number of optimizations aimed at minimizing control-message and retransmission overhead. It lacks the regular structure that is often present in hardware designs. In this sense, it provides any verification tool with a vigorous test of its analysis capabilities.

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Abstract. We report on the current status of the LMC project, which seeks to deploy the latest developments in logic-programming technology to advance the state of the art of system speci cation and veri cation. In particular, the XMC model checker for value-passing CCS and the modal mu-calculus is discussed, as well as the XSB tabled logic programming system, on which XMC is based. Additionally, s e v eral ongoing e orts aimed at extending the LMC approach b e y ond traditional nite-state model checking are considered, including compositional model checking, the use of explicit induction techniques to model check parameterized systems, and the model checking of real-time systems. Finally, after a brief conclusion, future research directions are identi ed.

Abstract. We present GCCS, a graphical coordination language for hierarchical concurrent systems. GCCS, which is implemented in the Concurrency Factory design environment, represents a coordination model based on process algebra. Its coordination laws, given as a structural operational semantics, allow one to infer atomic system transitions on the basis of transitions taken by system components. We illustrate the language's utility by exhibiting a GCCS-coordinated specification of the Rether real-time ethernet protocol. The specification contains both graphical and textual components.

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