classic is a recently-developed knowledge representation system that follows the paradigm originally set out in the kl-one system: it concentrates on the de nition of structured concepts, their organization into taxonomies, the creation and manipulation of individual instances of such concepts, and the key inferences of subsumption and classi cation. Rather than simply presenting a description of classic, we complement a brief system overview with a discussion of how to live within the con nes of a limited object-oriented deductive system. By analyzing the representational strengths and weaknesses of classic, we consider the circumstances under which it is most appropriate to use (or not use) it. We elaborate a knowledge-engineering methodology for building kl-one-style knowledge bases, with emphasis on the modeling choices that arise in the process of describing a domain. We also address some of the key di cult issues encountered by new users, including primitive vs. de ned concepts, and di erences between roles and concepts, as well as representational \tricks-of-the-trade," which we believe to be generally useful. Much of the discussion should be relevant to many of the current systems based on kl-one.