Modularity in the ESM/RTL Framework for Real-Time Systems

Abstract

The ESM/RTL framework uses extended state machines (ESMs) for representing real-time discrete event processes in both the object to be controlled (the plant) and the controlling software (the controller). Real-time temporal logic (RTL) is used as the assertion language for specifying required plant behaviour and verifying that the controller satisfies this specification.In this paper, a first step towards modularizing the ESM/RTL framework is taken by developing a method to construct higher level ESMs from basic ESMs. ESMs are interpreted as generators of trajectories, and this interpretation can be used to provide an operational semantics for an ESM at any level. The paper concludes with a brief discussion of how the framework supports modular reasoning in RTL.