Modular termination of basic narrowing

Abstract

Basic narrowing is a restricted form of narrowing which constrains narrowing steps to a set of non-blocked (or basic) positions. Basic narrowing has a number of important applications including equational unification in canonical theories. Another application is analyzing termination of narrowing by checking the termination of basic narrowing, as done in pioneering work by Hullot. In this work, we study the modularity of termination of basic narrowing in hierarchical combinations of TRSs, including a generalization of proper extensions with shared subsystem. This provides new algorithmic criteria to prove termination of basic narrowing. © 2008 Springer-Verlag.