Description Logics

This chapter discusses description logics (DLs), which are a family of logic-based knowledge representation languages that can be used to represent the terminological knowledge of an application domain in a structured and formally well-structured way. It discusses their provenience and history and explains the way the field has developed. It describes the basic DL ALC in some detail, including definitions of syntax, semantics, and basic reasoning services, and discusses important extensions such as inverse roles, number restrictions, and concrete domains. It discusses (1) the relationship between DLs and other formalisms, in particular first order and modal logics, (2) the most commonly used reasoning techniques, in particular tableau, resolution, and automata based techniques, and (3) the computational complexity of basic reasoning problems. After reviewing some of the most prominent applications of DLs, in particular ontology language applications, the chapter discusses other aspects of DL research.