Abstract
This paper presents some of the underlying principles of description logics (also known as terminological logics or kl-one-style languages), grounding them in the lattice of terms organized by the so-called subsumption" relationship. A survey of the increasingly varied uses of description logics, including industrial applications, is presented by considering their role in a number of different operations that one can apply to a knowledge base, including languages for queries, answers, updates, rules, and constraints. Finally, we discuss some of the complexity results related to the logic of descriptions and survey a spectrum of responses to the many intractability proofs.