On probabilistic term rewriting

We study the termination problem for probabilistic term rewrite systems. We prove that the interpretation method is sound and complete for a strengthening of positive almost sure termination, when abstract reduction systems and term rewrite systems are considered. Two instances of the interpretation method—polynomial and matrix interpretations—are analyzed and shown to capture interesting and nontrivial examples when automated. We capture probabilistic computation in a novel way by means of multidistribution reduction sequences, thus accounting for both the nondeterminism in the choice of the redex and the probabilism intrinsic in firing each rule. •We study the termination behavior of probabilistic abstract reduction systems.•We define a reduction relation for such systems on multidistributions.•We prove that ranking functions are sound and complete for strong a.s. termination.•We lift the interpretation method to probabilistic term rewrite systems.