Research On Architecture-Oriented Method For Developing Software Safety Requirements

Safety-critical intensive systems (SCSIS) are emerging as software play more and more safety-critical command and control roles in safety-critical systems. Software safety requirements are seen as a major contributor to system safety.The dissertation focuses on a new architecture-oriented development method for software safety requirements, because software architecture represents basic safety tactics. And if architecture represents all safety requirements, it won't do poorly work over again at last phases of software lifecycle. The main contributions of the dissertation are as follows.Firstly, the paper surveys the state of the art of software safety. The relations of safety to system and software are analyzed to show what software safety is and what safety engineering processes can be used.Secondly, the paper focuses on how to develop and represent software safety requirement. Two revelations are derived from the existing techniques and can be used to develop software safety requirements in the phase of architecture.Thirdly, an architecture-oriented method is presented for developing software safety requirements based on integration of goal and scenario. It is essentially a co-process of developing safety requirements and designing architecture. By deviation analysis of the functionality and other quality goals allocated to architecture, anti-goals and negative scenarios are developed. Through assessment of the risk of negative scenarios, safety requirements including hazard mitigation tactics and metrics are developed for the critical negative scenarios whose risks are unacceptable and can be used to refine architecture. A simple brake-by-wire system is used to illustrate how to develop software safety requirements based on the presented method.