An extended finitely recursive process model for discrete event systems

Abstract

In the area of Discrete Event Systems (DES) a growing need is being felt for new classes of models to describe both logical and timed behaviors efficiently. Among the frameworks presented recently, the Finitely Recursive Process model is a powerful one. However it is solely based on a characterization of the event strings generated in the DES. In this work an augmented version of the above model is presented, where the notion of a collection of system related variables, forming the ‘state-space’ of the system, is introduced. A concept of a ‘silent transition’ is introduced for effective modelling of concurrent DES. To allow nonuniqueness of the initial state, an extended process framework is presented and a recursive characterization is made in terms of a collection of constant processes and process operators. A general Timed Transition Model (Ostroff, 1990) is modelled as an extended process to show the describing power of the framework. A model of a robot controller is presented to show the usefulness of its different features in modelling real systems.