An Engineering Approach to Hard Real-Time

System Design ?y

H. Kopetz, R. Zainlinger, G. Fohler

H. Kantz, P. Puschner, W. Sch?utz

Institut f?ur Technische Informatik

Technische Universit?at Wien

Treitlstr. 3/182

A-1040 Vienna, Austria

Abstract

This paper presents a systematic methodology for the design of distributed fault tolerant real-time systems. The methodology covers the stepwise refinement of the given requirements, expressed in the form of real-time transactions, to task and protocol executions. It also includes a timing analysis and dependability evaluation of the still incomplete design. The testability of the evolving system is considered to be of essential concern. A set of coherent tools for the support of the methodology is described in some detail. The methodology assumes that the run-time architecture is based on static scheduling and a globally synchronised time-base is available to co-ordinate the system actions in the domain of real-time.
Keywords: System Design, System Evaluation, System Testing, Design Methodology, Design Environments, Real-Time Systems

1 Introduction

Real-time systems have to produce the correct results within the specified time intervals. If a result is incorrect or arrives too late, then the real-time system has failed. The potential consequences of such a failure depend on the characteristics of the particular application context. If these consequences are possibly catastrophic, then we call the system a hard real-time system. Examples of such systems are flight control systems or train signaling systems. In this paper we discuss an engineering approach to the design of hard real-time systems.

?This work was supported in part by the ESPRIT Basic Research Project 3092 Predictably Dependable Computing Systems"
yA related version of this paper has been accepted for publication in the IEE Software Engineering Journal"