@INPROCEEDINGS{AntoyBrasselHanus03PPDP,
author = "Antoy, S. and Bra{\ss}el, B. and Hanus, M.",
title = "Conditional Narrowing without Conditions",
year = "2003",
pages = "20-31",
publisher = "ACM Press",
booktitle = "Proc.\ of the 5th International ACM SIGPLAN Conference on
             Principle and Practice of Declarative Programming (PPDP'03)"
abstract = {
We present a new evaluation strategy for functional logic programs
described by weakly orthogonal conditional term rewriting systems.
Our notion of weakly orthogonal conditional rewrite system extends a
notion of Bergstra and Klop and covers a large part of programs
defined by conditional equations. Our strategy combines the
flexibility of logic programming (computation of solutions for logic
variables) with efficient evaluation methods from functional
programming. In particular, it is the first known narrowing strategy
for this class of programs that evaluates ground terms
deterministically.  This is achieved by a transformation of
conditional term rewriting systems (CTRS) into unconditional ones
which is sound and complete w.r.t. the semantics of the original
CTRS. We show that the transformation preserves weak orthogonality
for the terms of interest.  This property allows us to apply a
relatively efficient evaluation strategy for weakly orthogonal
unconditional term rewriting systems (parallel narrowing) on the
transformed programs.
}
}