Abstract
Esterel is a process-algebra-like language for real-time systems. One of its main characteristics is the combination of perfect synchrony with powerful constructs for preemption, suspension and trap handling. It is desirable to make this kind of expressiveness available for the description of hybrid systems, that is, systems whose evolution is understood in terms of segment-wise continuous functions over the real time axis. Our approach consists of modifying Esterel concepts, most notably by replacing the discrete time frame by a continuously advancing one. We are then able to state a semantics made up of transitions with closed execution intervals of non-zero length. The Esterel notion of instant is rendered as an execution interval within this framework. Hybrid signals may change their value during such an instant, non-hybrid ones, that is, classical signals immediately settle to a specific state and keep it the whole time. Time consumption still has to be specified explicitly, namely in that instants reflect jumps among control flow locations defined by so-called pause statements; all other statements take no time in the sense that arbitrarily many of them may be sequentially executed regardless of the instant's duration. A transfer of perfect synchrony from the discrete to the continuous is in this way accomplished. After a brief introduction, the talk begins with foundations from (non-hybrid) Esterel. The new syntactic and semantic concepts of our hybrid Esterel derivative are then introduced. The rest of the talk is concerned with the pragmatics of using the language, structural operational semantics, bisimilarity and compositionality.

Joint work with Thomas Stauner (BMW Car IT, formerly Munich University of Technology)

ASTEC seminar
Monday, April 8, 2002

Place: Information technology, Uppsala University
Room: 1145
Time: 10.15-11.00 (+ discussions)

Room 1145 is in building 1, floor 1, room 45 (in the northern part of the building).

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There will be an extended period for discussions after the seminar.

Speakers are encouraged to give an short (5 min) introduction to the subject at the begining of the talk.
Listeners are excused if they have to leave after 11.00.