Title: A comparative study of Process Algebras for Hybrid Systems

By: Uzma Khadim

Abstract:
A hybrid system is one that exhibits both discrete and continuous behaviour. Embedded systems are typical examples of hybrid systems in which a digital component controls a continuous environment. Examples are a thermostat, storm surge barriers, fire alarms etc. With the advancing integration of software technology in our daily lives and safety critical systems, the interest in use of formal methods in specifying hybrid systems is increasing.

We take four rather recent process algebras for describing hybrid systems namely Process Algebra for Hybrid Systems (by Bergstra and Middelburg), Phi- Calculus (by Rounds and Song), HyPA (by Cuijpers and
Reniers) and Hybrid Chi (by Man and Schiffelers). We compare operators and constructs offered by them for specifying hybrid systems. We point out special features of each process algebra and try to determine what advantages are achieved through these features in terms of expressiveness and ease of modelling. We also present a case study of a railway gate controller that helps us to identify similar constructs of each process algebra and determine its expressiveness.