XCON is a rule-based expert system that configures computer systems. Over 7 years, XCON has grown to 6,200 rules, of which approximately 50% change every year. While the performance of XCON is satisfactory, it is increasingly becoming more difficult to change. With the goal of facilitating maintenance, DEC has developed a new rule-based language, RIME, in which the successor to XCON, XCON-in-RIME, is being written. This paper evaluates the potential for enhanced maintainability of XCON-in-RIME over XCON.