Counterexample Guided Spotlight Abstraction Refinement

This paper addresses the formal verification of distributed systems comprising a dynamically changing and potentially unbounded number of processes. We employ the spotlight principle to obtain a concise finitary abstraction of the system and devise an abstraction refinement strategy guided by the analysis of abstract counterexamples. It turns out that the key problem for spotlight refinement is the identification of spurious counterexamples. We observe that the problem is in general undecidable, and provide a sound but incomplete method that is able to solve the problem for many practically relevant systems. Our method is driven by a three-valued satisfaction relation for temporal specifications that accounts for the fact that concrete counterexamples can be identified in the abstracted system if they occur within the spotlight.