In this book, the author develops an object-centered framework with specialized support of the part-of relation based on description logics. These logics are a family of object-centered knowledge representation languages tailored for describing knowledge about concepts and is-a hierarchies of these concepts. In addition to the representation and reasoning facilities provided by description logics for is-a, representation and reasoning facilities are introduced for part-of. Finally, the feasibility and the usefulness of the approach is demonstrated by applying the framework to various areas including domain modeling, agent-oriented scenarios, document management and retrieval, and composite concept learning.