Introduction

Abstract

Expert systems have been increasingly popular for commercial applications. A rule based system is a special type of expert system. The development of rule based systems began in the 1960s but became popular in the 1970s and 1980s (Partridge and Hussain in Knowledge Based Information Systems. Mc-Graw Hill, London, 1994). A rule based system typically consists of a set of if-then rules, which can serve many purposes such as decision support or predictive decision making in real applications.