OWL: A Description Logic Based Ontology Language

摘要

Description Logics (DLs) are a family of class (concept) based knowledge representation formalisms. They are characterised by the use of various constructors to build complex concepts from simpler ones, an emphasis on the decidability of key reasoning tasks, and by the provision of sound, complete and (empirically) tractable reasoning services. Although they have a range of applications (e.g., reasoning with database schemas and queries), DLs are perhaps best known as the basis for ontology languages such as OIL, DAML+OIL and OWL. The decision to base these languages on DLs was motivated by a requirement not only that key inference problems (such as class satisfiability and subsumption) be decidable, but that "practical" decision procedures and "efficient" implemented systems also be available. That DLs were able to meet the above requirements was the result of extensive research within the DL community over the course of the preceding 20 years or more. This research mapped out a complex landscape of languages, exploring a range of different language constructors, studying the effects of various combinations of these constructors on decidability and worst case complexity, and devising At the same time, work on implementation and optimisation techniques demonstrated that, in spite of the high worst case complexity of key inference problems (usually at least ExpTime), highly optimised DL systems were capable of providing practical reasoning support in the typical cases encountered in realistic applications. With the added impetus provided by the OWL standardisation effort, DL systems are now being used to provide computational services for a rapidly expanding range of ontology tools and applications.