Computer-assisted safety argument review – a dialectics approach

Abstract

There has been increasing use of argument-based approaches in the development of safety-critical systems. Within this approach, a safety case plays a key role in the system development life cycle. The key components in a safety case are safety arguments, which are designated to demonstrate that the system is acceptably safe. Inappropriate reasoning in safety arguments could undermine a system's safety claims which in turn contribute to safety-related failures of the system. The review of safety arguments is therefore a crucial step in the development of safety-critical systems. Reviews are conducted using dialogues where elements of the argument and their relations are proposed and scrutinised. This paper investigates an approach of conducting argument review using dialectical models. After studying five established dialectical models with varying strengths and drawbacks, a new dialectical model specially designed to support persuasion and information-seeking dialogues has been proposed to suit the requirements of argument review. An argument review prototype system was then iteratively developed. It adopted the model and aims to conduct argument review dialogues in a structured manner. User-based evaluations of the system suggest the usefulness of the dialectics approach to safety argument review. The evaluation also sheds light on the future development of such an application.

Keywords:

• safety-critical systems
• safety case
• safety arguments
• dialogue games
• argument review

Acknowledgements

The authors thank all the participants who took part in the evaluation of the Argument Review Tool as well as research and teaching staff of the Department of Computer Science at the University of York, UK, who have generously donated their time, effort, and knowledge towards the progress of the project.