Safety Case Development: Current Practice, Future Prospects

Abstract

Safety-critical and safety-related systems are becoming more highly integrated and continue to increase in complexity. In parallel with this, certification standards for such systems are becoming more stringent, requiring more extensive and more detailed analyses. Safety cases, therefore, are themselves growing in size and complexity and are becoming increasingly costly to produce. It has become necessary to re-examine how and why safety cases are built in order that we might provide a means for managing their inherent complexity and reduce production costs.

In this paper, we examine some of the key issues in current industrial safety case development, in particular:

• The Purpose of the Safety Case — examining how stakeholders place demands upon the content and style of the safety case;

• Safety Analysis Techniques — examining the problem of ensuring consistency and completeness of results;

• Safety Case Production — examining how and when safety cases are produced through the development life-cycle;

• Safety Case Structure — examining how the reasoning and evidence aspects of the safety case are combined;

• Safety Case Maintenance — examining the need and support for safety cases that can be more readily maintained and reused.

We propose to address these issues through the use of a goal based notation for more effective structuring, a data model to tightly integrate the safety analysis techniques, and a process model to integrate the safety case activities into the overall development process. We demonstrate our approach using an integrated example from the automotive industry.