Requirements Analysis for Safety-Critical Systems


Ryuji TSUCHIYA  Mitsuyoshi FUKUDA  Yuko UEHAN

Hideki ARAI  Yuji HIRAO  Naotugu NOZUE


 This paper describes a systematic approach to the requirements analysis for safety-critical systems in which the potential loss is very serious. When the system is relied upon to control railway operations, it is obviously critical to ensure the safety of the system. Although formal methods are considered promising for verifying safety properties of the system, they are not necessarily sufficient to ensure real safety. Since safety property depends on the environment under which the system is supposed to be operated, a system whose safety is verified by a formal method may turn out to be unsafe under unexpected environmental conditions. It should also be pointed out that safety is not the only evaluation criterion of the system. In order to be operational in real world environment, it should also be verified that the system is effective efficacious and efficient enough to fulfil the system requirements. The focus of this paper is on clarifing some issues inherent in requirements analysis for safety-critical systems and on indicating the future directions in computer-supported requirements analysis for safety-critical systems.