Eliminative Argumentation for Arguing System Safety - A Practitioner’s Experience

Safety cases are an essential artifact for establishing the safety of complex systems. Industrial use of safety cases varies between industries. Due to inconsistent regulatory guidance, numerous different strategies, notations, and techniques have been developed for safety case construction. Eliminative Argumentation (EA) has been proposed as a technique to systematically improve confidence in a safety case via `defeasible reasoning' wherein reasons to doubt safety claims are introduced and subsequently eliminated. Elimination of doubt results in increased confidence. This paper reports on the application of EA to seven different software-intensive systems in the automotive, rail, and industrial control industries. Our experiences suggest that EA's doubt-driven approach to safety argumentation increases confidence in a safety case and can be used to support activities such as independent safety assessments and safety verification and validation. From our experiences we synthesized into a set of lessons learned.