A Process-Algebra-Like Framework for Modelling Hybrid Systems
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
Place: Information technology, Uppsala University
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.
Everyone is welcome !
Updated 26-Mar-2002 16:49 by Roland Grönroos
e-mail: info -at- astec.uu.se