Section: New Results

Fidelity in Real-Time Programming

Participants : Guillaume Baudart, Timothy Bourke.

Synchronous languages are a rigorous approach to programming, analyzing, and implementing embedded systems. Real-time aspects are typically handled by discretizing time using either (implicit) ticks or (explicit) named signals, and later verifying that the (necessarily bounded) execution time of a reaction is strictly less than the period of the fastest timing signal. This approach has many advantages: it separates logical behaviour from implementation concerns, yields a simple and precise programming model, and abstracts from eventual run-time environments. For an important subclass of embedded protocols and controllers, however, we believe it advantageous to add constructions that deal more concretely with real-time constraints.

We are pursuing these ideas in the enriched timing model provided by the Zélus programming language (detailed elsewhere). We continue to study the extension and application of this language to the modelling, simulation, analysis, and implementation of real-time embedded software.

This year we developed three case studies: quasi-synchronous architectures (from last year), loosely time-triggered architectures (detailed elsewhere), and a small embedded controller. These case studies motivate and drive our research and implicitly define the subclass of embedded systems that we aim to treat. They have each been modelled in Zélus and can be simulated with the existing compiler.

We made progress on defining a subset of Zélus that is ammenable to discretization techniques for more flexible simulation. A first version of an appropriate algorithm has been sketched and partially implemented. Work continues on developing it with the idea of incorporating it into the Zélus compiler and using it to treat our case studies.