Deriving Mode Logic for Autonomous Resilient Systems

Ensuring system resilience - dependability in presence of changes - is a complex engineering task. To achieve resilience, a system should not only autonomously cope with non-deterministically changing internal state and external operating conditions but also proactively reconfigure to maintain efficiency. To facilitate structuring and verifying such complex system behavior, in this paper, we demonstrate how to derive resilience-enhancing mode transition logic from the goals that the system should achieve. Our approach is formalised in Event-B that allows us to reason about resilience mechanisms at different architectural levels. We illustrate the proposed approach by an example - safe and efficient navigation of a swarm of drones.