We describe the translation of Esterel-like programs with delayed actions to equivalent transition relations and equation systems. Potential schizophrenia problems arising from local declarations are solved by (1) generating copies of the surface of the statement and (2) renaming the local variables in these copies to allow them to have different values at the same point of time. The translation runs in polynomial time and has been formally verified with the HOL theorem prover.

Synchronous programs are well-suited for the implementation of real-time embedded systems. However, their compilation is difficult due to the paradigm that microsteps are executed in zero time. This can yield cyclic dependencies that must be resolved to generate single-threaded code. State of the art techniques are based on a fixpoint computation at compile time that 'simulates' the microstep execution. However, existing procedures do not consider delayed actions that have been recently introduced in synchronous languages. In this paper, we show that the analysis of programs with delayed actions can be performed by two fixpoint computations, one for the initialization and one for the transitions of the system. Moreover, we discuss an implementation using BDDs that is based on dual rail encoding.

Abstract. Adaptation is important in dependable embedded systems to cope with changing environmental conditions. However, adaptation significantly complicates system design and poses new challenges to system correctness. We propose an integrated model-based development approach facilitating intuitive modelling as well as formal verification of dynamic adaptation behaviour. Our modelling concepts ease the specification of adaptation behaviour and improve the design of adaptive embedded systems by hiding the increased complexity from the developer. Based on a formal framework for representing adaptation behaviour, our approach allows to employ theorem proving, model checking as well as specialised verification techniques to prove properties characteristic for adaptive systems such as stability.

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Many complex embedded systems dynamically adapt their components, services, algorithms, and parameters to the environment. This leads to new classes of design errors, since adaptation has become an increasingly complex part of the systems' behavior. In particular, as adaptations often continuously trigger further adaptations in other components, inconsistent and unstable configurations may be reached. Formal verification, which is routinely applied in safety-critical applications, must therefore consider not only temporal and functional properties of a system, but also its ability to dynamically adapt itself according to external and internal stimuli.In this paper, we describe how the adaptation behavior of embedded systems can be modeled, specified, and verified at design time. The systems are thereby given at a high level of abstraction, where adaptation is triggered by the quality of data values. This allows to extract the relevant information in a form that can be directly used for verification. Moreover, we demonstrate how state-of-the-art model checkers can be used to formally reason about the resulting system description.

We present a new upproach to bounded nrodel checking that extends currenf nietlzods in two ways: First13 instead of a reduction to propositional logic, we choose a more POWerful, yet decidable target logic, naniely Presburger arithmetic. Secondly instead of unwinding tenrporal logic formulas, we i i~i w i~d corresponding w -automata. To this end, we eniplny a special technique for translaling safety and liveness properties to w-automata with corresponding acceptance conditions. T12i.s combination allows us to utilize bounded model cliecking rechniques for the eficient verificarion of infinite srare sysrems.

In principle, bounded model checking (BMC) leads to semidecision procedures that can be used to verify liveness properties and to falsify safety properties. If the procedures fail, there is usually no information about the validity of the considered specification. In this paper, we present a new approach to BMC based on three-valued logic that allows us in many cases to falsify liveness properties and to verify safety properties. Moreover, we employ both global and local model checking to take advantage of the different types of specifications that can be handled by these techniques.

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