IMPLEMENTATION OF NARROWING: THE RITE WAY.

A discussion is presented of implementation issues of Rite (see N. Dershowitz and D. A. Plaisted 1985), a system that performs lazy narrowing and eager rewriting with respect to a static set of rules. A novel technique is described for representing the multiple solutions that arise from the enumerative nondeterminism (U. S. Reddy, 1985) of narrowing steps. A technique for efficiently identifying reducible subterms, based on the preprocessing of rules for partial matches/unifiers, is presented. Rewriting/narrowing is effected through demons, which annotate subterms with continuations obtained from preprocessing. The authors show how these methods can be extended to deal with conditional rules viewed as computational logic programs. An experimental implementation is discussed.