Case-based reasoning (CBR) systems solve new problems by retrieving and ada
pting problem solving experiences stored as cases in a case-base. Success d
epends largely on the performance of the case retrieval algorithm used. Smy
th and McKenna [Lecture Notes in Artificial Intelligence LNAI 1650 (1999) 3
43-357] have described a novel retrieval technique, called footprint-based
retrieval (FBR), which is guided by a model of case competence. FBR as it s
tands benefits from superior efficiency characteristics and achieves near-o
ptimal competence and quality characteristics. In this paper, we describe a
simple but important extension to FBR. Empirically we show that this new a
lgorithm can deliver optimal retrieval performance while at the same time r
etaining the efficiency benefits of the original FBR method. (C) 2001 Elsev
ier Science B.V. All rights reserved.