Detecting Non-Termination of Term Rewriting Systems Using an Unfolding Operator

Abstract. In this paper, we present an approach to non-termination of term rewriting systems inspired by a technique that was designed in the context of logic programming. Our method is based on a classical unfolding operation together with semi-unification and is independent of a particular reduction strategy. We also describe a technique to reduce the explosion of rules caused by the unfolding process. The analyser that we have implemented is able to solve most of the non-terminating examples in the Termination Problem Data Base.