A Small Model Theorem for Rectangular Hybrid Automata Networks

Rectangular hybrid automata (RHA) are finite state machines with additional skewed clocks that are useful for modeling realtime systems. This paper is concerned with the uniform verification of safety properties of networks with arbitrarily many interacting RHAs. Each automaton is equipped with a finite collection of pointers to other automata that enables it to read their state. This paper presents a small model result for such networks that reduces the verification problem for a system with arbitrarily many processes to a system with finitely many processes. The result is applied to verify and discover counterexamples of inductive invariant properties for distributed protocols like Fischer’s mutual exclusion algorithm and the Small Aircraft Transportation System (SATS). We have implemented a prototype tool called Passel relying on the satisfiability modulo theories (SMT) solver Z3 to check inductive invariants automatically.