Abstract
This is the second report in a series on the PROTODL system, which is an *extensible* knowledge representation and reasoning system based on Description Logics (DLs). We have motivated elsewhere [Borgida&Brachman92, Borgida92] the utility of being able to add new concept constructors to a DL, and, while in previous papers we have concentrated on subsumption reasoning, in this paper we consider reasoning about individuals. We present the modular implementation of a Description Logic-based KBMS which performs inferences about individuals in such a way that the addition of each new concept constructors is achieved by introducing a series of functions (and possibly modifying some old ones). Considerable emphasis has been placed on the efficient handling of *incremental* updates. This is accomplished by combining the primitive procedures in different ways in order to obtain variants of the standard procedures for inferring concept (non)membership -- variants that take into account the fact that the previous state of the KB was consistent, and that we know what specific kind of update has been performed, and when dependency links have been set.