Reachability Analysis of Term Rewriting Systems with Timbuk

We present Timbuk - a tree automata library - which implements usual operation- s on tree automata as well as a completion algorithm used to compute an over-approximation of the set of descendants R*(E) for a regular set E and a term rewriting system R, possibly non linear and non terminating. On several examples of term rewriting systems representing programs and systems to verify, we show how to use Timbuk to construct their approximations and then prove unreachability properties of these systems