Bonsai: Cutting Models Down to Size

In model checking, abstractions can cause spurious results, which need to be verified in the concrete system to gain conclusive results. Verification based on multi-valued model checking can distinguish conclusive and inconclusive results, while increasing precision over traditional two-valued over- and under-abstractions. This paper describes the theory and implementation of multi-valued model checking for Promela specifications. We believe our tool Bonsai is the first four-valued model checker capable of multi-valued verification of parallel models, i.e. consisting of multiple concurrent processes. A novel aspect is the ability to only partially abstract a model, keeping parts of it concrete.