Towards Conflict Detection and Resolution of Safety Policies

Safety policy sets out the rules that govern safe system interaction within a system of systems (SoS). These rules are derived from high-level policy goals informed by a hazard analysis. They are expressed in terms of behaviour that the system is allowed to exhibit and that which it is required to exhibit. Nevertheless, this process can lead to describing rules that conflict with one another, both in obvious and subtle ways. The first challenge this presents is detecting a conflict, or at least the potential for conflict, before it arises. Conflicts can be identified in part by considering the context in which the system operates. The second challenge is how then to resolve such conflicts. Several types of conflict exist, such as modality conflicts, authority conflicts and conflicts of resources. It is necessary to classify and understand these conflict types before safety policy conflict detection and resolution can become a systematic process.