Automating modular verification

Modular techniques for automatic verification attempt to overcome the state-explosion problem by exploiting the modular structure naturally present in many system designs. Unlike other tasks in the verification of finite-state systems, current modular techniques rely heavily on user guidance. In particular, the user is typically required to construct module abstractions that are neither too detailed as to render insufficient benefits in state exploration, nor too coarse as to invalidate the desired systemproperties. In this paper, we construct abstractmodules automatically, using reachability and controllability information about the concrete modules. This allows us to leverage automatic verification techniques by applying them in layers: first we compute on the state spaces of system components, then we use the results for constructing abstractions, and finally we compute on the abstract state space of the system. Our experimental results indicate that if reachability and controllability information is used in the construction of abstractions, the resulting abstract modules are often significantly smaller than the concrete modules and can drastically reduce the space and time requirements for verification.