A system-theoretic assurance framework for safety-driven systems engineering

Abstract

The complexity of safety-critical systems is continuously increasing. To create safe systems despite the complexity, the system development requires a strong integration of system design and safety activities. A promising choice for integrating system design and safety activities are model-based approaches. They can help to handle complexity through abstraction, automation, and reuse and are applied to design, analyze, and assure systems. In practice, however, there is often a disconnect between the model-based design and safety activities. At the same time, there is often a delay until recent approaches are available in model-based frameworks. As a result, the advantages of the models are often not fully utilized. Therefore, this article proposes a framework that integrates recent approaches for system design (model-based systems engineering), safety analysis (system-theoretic process analysis), and safety assurance (goal structuring notation). The framework is implemented in the systems modeling language (SysML), and the focus is placed on the connection between the safety analysis and safety assurance activities. It is shown how the model-based integration enables tool assistance for the systematic creation, analysis, and maintenance of safety artifacts. The framework is demonstrated with the system design, safety analysis, and safety assurance of a collision avoidance system for aircraft. The model-based nature of the design and safety activities is utilized to support the systematic generation, analysis, and maintenance of safety artifacts.