Joseph Sifakis

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We present a general framework for the formal specification and algorithmic analysis of hybrid systems. A hybrid system consists of a discrete program with an analog environment. We model hybrid systems as finite automata equipped with variables that evolve continuously with time according to dynamical laws. For verification purposes, we restrict ourselves(More)
We describe nite-state programs over real-numbered time in a guardedcommand language with real-valued clocks or, equivalently, as nite automata with real-valued clocks. Model checking answers the question which states of a real-time program satisfy a branching-time speci cation (given in an extension of CTL with clock variables). We develop an algorithm(More)
We present a methodology for modeling heterogeneous real-time components. Components are obtained as the superposition of three layers: behavior, specified as a set of transitions; Interactions between transitions of the behavior; Priorities, used to choose amongst possible interactions. A parameterized binary composition operator is used to compose(More)
This paper presents algorithms for the automatic synthesis of real time controllers by nding a winning strategy for certain games de ned by the timed automata of Alur and Dill In such games the outcome depends on the players actions as well as on their timing We believe that these results will pave the way for the application of program synthesis techniques(More)
We study a process algebra ATP for the description and analysis of systems of timed processes. An important feature of the algebra is that its vocabulary of actions contains a distinguished element . An occurrence of is a time event representing progress of time. The algebra has, apart from standard operators of process algebras like CCS or ACP, a primitive(More)
We study property preserving transformations for reactive systems The main idea is the use of simulationsparameterizedbyGalois connections relating the lattices of properties of two systems We propose and study a notion of preservation of properties expressed by formulas of a logic by a function mapping sets of states of a system S into sets of states of a(More)
We summarize some current trends in embedded systems design and point out some of their characteristics, such as the chasm between analytical and computational models, and the gap between safetycritical and best-effort engineering practices. We call for a coherent scientific foundation for embedded systems design, and we discuss a few key demands on such a(More)