Safe requirements engineering: A scenario-based approach for identifying complete safety-oriented requirements

In order to construct low-risk, software-intensive safety-critical systems, it is crucial to identify and prevent risks during the early stages of software development, since most safety-critical decisions are made at that time. Even if limited information is available about the system under development, a detailed safety analysis should be applied, for example to derive safety-oriented requirements for safety-critical systems. Certain faults of software-controlled systems that are caused, e.g., by missing requirements can lead to fatal consequences such as death, environmental pollution, etc. However, traditional requirements engineering techniques do not focus on identifying hazards and their associated risks, but rather on identifying functional requirements consistently and completely, and safety analysis techniques are generally applied unsystematically when deriving safety requirements, without consideration of the completeness of the functional requirements. Only few approaches have been proposed to identify the functional requirements (expected behavior) and the safety requirements (non-expected behavior) concurrently. But even the most closely related methods do not identify these requirements in a complete, systematic, intuitive, and effective way. Therefore, an approach for effectively and completely identifying both functional requirements and safety requirements is desired. To resolve these open issues, SafeRE is proposed in this thesis. SafeRE (Safety-oriented Requirements Engineering) is a novel method for concurrently and completely determining functional requirements and safety requirements. It defines a general structure and a grammar for accommodating both functional and safety requirements and proposes a systematic safety analysis based on the identified type-based functional requirements for deriving safety requirements. The combined safety-oriented requirements are then generated in a finite state machine and presented in an HTML-based specification. For obtaining the complete set of functional and safety requirements, a sequence-based specification methodology and its corresponding tool are extended. The extended tool is named SafeSBS. This approach was validated in one industrial case study and one research case study. The results of these case studies show that SafeRE is effective for identifying the safety-oriented requirements completely both in theory and in practice.