Failure Analysis and the Safety-Case Lifecycle

The failure of a safety-critical system, though undesirable, is often a source of valuable lessons that can help prevent future failures. Current analysis practices do not always yield as much knowledge as they might about possible flaws in the system safety argument. In this paper, we introduce the lifecycle for safety cases. We use it to develop a framework to guide the analysis process and the development of lessons and recommendations. We illustrate the ideas with an example using the failure history of an air-traffic-control safety system.