C2E2: A Verification Tool for Stateflow Models

Mathworks’ Stateflow is a predominant environment for modeling embedded and cyber-physical systems where control software interacts with physical processes. We present Compare-Execute-Check-Engine (C2E2)—a verification tool for continuous and hybrid Stateflow models. It checks bounded time invariant properties of models with nonlinear dynamics, and discrete transitions with guards and resets. C2E2 transforms the model, generates simulations using a validated numerical solver, and then computes reachtube over-approximations with increasing precision. For this last step it uses annotations that have to be added to the model. These annotations are extensions of proof certificates studied in Control Theory and can be automatically obtained for linear dynamics. The C2E2 algorithm is sound and it is guaranteed to terminate if the system is robustly safe (or unsafe) with respect to perturbations of guards and invariants of the model. We present the architecture of C2E2, its workflow, and examples illustrating its potential role in model-based design, verification, and validation.