Stepwise Formal Modeling and Verification of Self-Adaptive Systems with Event-B. The Automatic Rover Protection Case Study

Abstract

For a long time, formal methods have been effectively applied to design and develop safety-critical systems to ensure safety and the correctness of desired functional behaviors through formal reasoning. The development of high confidence self-adaptive autonomous systems, such as Automatic Rover Protection(ARP), is one of the challenging problems in the area of verified software that needs formal reasoning and proof-based development. In this paper, we propose a methodology that reveals the issues involved in the formal modeling and verification of self-adaptive autonomous systems using correct by construction approach. This work also provides a set of guidelines for tacking the different issues to avoid collision by preserving the local and global properties of an autonomous system. We cater for the specification of functional requirements, timing requirements, spatial and temporal behavior, and safety properties. We present a refinement strategy, modeling patterns to capture the essence of a self-adaptive autonomous system, and a substantial example based approach on an industrial case study: TwIRTee. For developing the formal models of autonomous system, we use the Event-B modeling language and associated Rodin tools to check and verify the correctness of required system behavior and internal consistency under the given safety properties.