"Reducing" CLASSIC to practice: Knowledge representation theory meets reality

Most recent key developments in research on knowledge representation (KR) h ave been of the more theoretical sort, involving worst-case complexity resu lts, solutions to technical challenge problems, etc. While some of this wor k has influenced practice in Artificial Intelligence, it is rarely-if ever- made clear what is compromised when the transition is made from relatively abstract theory to the real world. CLASSIC is a description logic with an a ncestry of extensive theoretical work (tracing back over twenty years to KL -ONE), and several novel contributions to KR theory. Basic research on CLAS SIC paved the way for an implementation that has been used significantly in practice, including by users not versed in KR theory. In moving from a pur e logic to a practical tool, many compromises and changes of perspective we re necessary. We report on this transition and articulate some of the profo und influences practice can have on relatively idealistic theoretical work. We have found that CLASSIC has been quite useful in practice, yet still st rongly retains most of its original spirit, but much of our thinking and ma ny details had to change along the way. (C) 1999 Published by Elsevier Scie nce B.V. All rights reserved.