An attempt to confront asynchronous reality to synchronous modelization in the ESTEREL language

Abstract

Programming in ESTEREL a large real-time application with various specific problems issued from the domain of applications (automatic manufacturing process) shows the problem of an asynchronous reality opposed to a synchronous expression. Since the application has an asynchronous nature and the language was synchronous, we therefore searched to develop systematic methods to adapt synchronous programming to asynchronous context. In order to help us and to define accurately the problems, we classified the events by their nature so as to find a systematic implementation for each class.

We found systematic solutions for most of the problems but some persist and look like a shadow over the programmer who wants to use ESTEREL. If memorizing the state of a component is no more a problem, controlling the number of states produced by the compiler remains one. The programmer will always be haunt by the risk to make the automaton explose but, maybe, he is better driven than before.

This study comes within the framework of the development of the ELECTRE language we designed. ELECTRE is a reactive language which is intended to the expression of asynchronous applications. That is to say:

• • actions have a no-null execution duration and they may be either resumed or restarted and they may be assigned a non-interruptible property

• • events are complex entities which may be assigned properties so that either they are fleeting or they have single or multiple occurrences memorization.

Moreover, its operational semantics makes it possible to compile the ELECTRE programs into Finite State Automata. We are currently working on the translation from ELECTRE to ESTEREL.