Over-approximating Descendants by Synchronized Tree Languages

Over-approximating the descendants (successors) of a initial set of terms by a rewrite system is used in verification. The success of such verification methods depends on the quality of the approximation. To get better approximations, we are going to use non-regular languages. We present a procedure that always terminates and that computes over-approximation of descendants, using synchronized tree-(tuple) languages expressed by logic programs