We present an automatic iterative abstraction-refinement methodology in which the initial abstract model is generated by an automatic analysis of the control structures in the program to be verified. Abstract models may admit erroneous (or "spurious") counterexamples. We devise new symbolic techniques which analyze such counterexamples and refine the abstract model correspondingly.

This paper describes the modeling language CHARON for modular design of interacting hybrid systems. The language allows specification of architectural as well as behavioral hierarchy, and discrete as well as continuous activities. The modular structure of the language is not merely syntactic, but is exploited by analysis tools, and is supported by a formal semantics with an accompanying compositional theory of refinement. We illustrate the benefits of CHARON in design of embedded control software using examples from automated highways concerning vehicle coordination.

The paper discusses an approach to construct discrete abstractions of hybrid systems by means of qualitative reasoning. The work is performed in the context of a modeling language for hybrid systems Charon.Weintroduce a qualitativeversion of the language and describe the abstraction technique using a motivational example. The resulting abstract model is conservative and can be used to analyze properties of the original hybrid system.

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Abstract. This paper investigates the use of tree automata with global equalities and disequalities (TAGED for short) in reachability analysis over term rewriting systems (TRSs). The reachability problem being in general undecidable on non terminating TRSs, we provide TAGEDbased construction, and then design approximation-based semi-decision procedures to model-check useful temporal patterns on in nite state rewriting graphs. To show that the above TAGED-based construction can be e ectively carried out, complexity analysis for rewriting TAGEDde nable languages is given. 1

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