Functional Term Rewriting Systems
Résumé
This paper proposes the theoretical foundations of a new formal tool for symbolic verification of finite systems. Some approaches reduce the problem of system verification to the reachability problem in term rewriting systems (TRSs). In our approach, states are encoded by terms in a BDD-like manner and the transition relation is represented by a new rewriting relation so called Functional Term Rewriting Systems (FTRSs). First, we show that FTRSs are as expressive as TRSs. Then, we focus on a subclass of FTRSs, so called Elementary Functional Term Rewriting Systems (EFTRSs), and we show that EFTRSs preserve the FTRSs expressiveness. The main advantage of EFTRSs is that they are well adapted for acceleration techniques usually used in saturation algorithms on BDD-like data structures. Our experiments show that for well-known protocols (e.g. Tree Arbiter, Percolate, Round Robin Mutex protocols,...) our tool is not only better than other rewriting tools such as Timbuk or Maude, but also competitive with other model-checkers such as SPIN, NuSMV or SMART. Moreover, it can also be applied to model-checking invariant properties which are a particular subclass of linear temporal logic formula (LTL).