Do We Really Need to Estimate Rule Utilities in Classifier Systems?

Abstract

Classifier systems have traditionally used explicit measures of utility (strength, predicted payoff, accuracy, etc.) to quantify the performance and fitness of classifier rules. Much of the effort in designing and implementing classifier systems has focused on getting these utilities “right”. One alternative worth exploring is the idea of using endogenous fitness; that is, reinforcing successful performance with “resources” that rules need in order to reproduce. Under this regime, the best rules are those that accumulate the most resources over their lifetime and, consequently, have the most offspring. This paper describes a classifier system designed along these lines. Rules have no associated utility measure. Instead, each rule has one or more reservoirs that can be used to store resources. When enough resources have been accumulated, a rule utilizes some of its resources to reproduce and the reservoir level is reduced accordingly. Preliminary tests of this system on the multiplexor problem show that it performs as well as utility-based classifier systems such as XCS.