Chain Properties of Rule Closures

This article presents an introduction to the generalization of the crossed rule approach to the detection of Knuth-Bendix completion procedure divergence. It introduces the closure chains, which are special rule closures constructed by means of particular substitution operations and operators, as a suitable formalism for a progress in this direction. Supporting substitution algebra is developed first, followed by considerations concerning rule closures in general, and concluded by investigation of closure chain properties.