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This chapter provides an introduction to Description Logics as a formal language for representing knowledge and reasoning about it. It first gives a short overview of the ideas underlying Description Logics. Then it introduces syntax and semantics, covering the basic constructors that are used in systems or have been introduced in the literature, and the(More)
ur K ¨ unstliche In-telligenz, DFKI) with sites in Kaiserslautern and Saarbrücken is a non-profit organization which was founded in 1988. The DFKI conducts application-oriented basic research in the field of artificial intelligence and other related subfields of computer science. The overall goal is to construct systems with technical knowledge and common(More)
We study the problem of evolution for Knowledge Bases (KBs) expressed in Description Logics (DLs) of the DL-Lite family. DL-Lite is at the basis of OWL 2 QL, one of the tractable fragments of OWL 2, the recently proposed revision of the Web Ontology Language. We propose some fundamental principles that KB evolution should respect. We review known model and(More)
We investigate the use of epistemic operators in the framework of concept languages (also called terminological languages). The results of this work have a twofold signiicance. From the point of view of epistemic logics, our contribution is to have identiied an effective procedure for the problem of answering epistemic queries posed to a knowledge base(More)
We investigate subsumption algorithms for logic-based knowledge representation languages of the kl-one family. We deene an attribu-tive concept description language that contains the logical connectives conjunction, disjunction, and negation, as well as role quantiication, number restrictions and role intersection. We describe a rule based calculus to(More)
Abst rac t We present two concept languages,, called PL1 and PL2 which are extensions of TC. We prove that the subsumption problem in these languages can be solved in polynomial time. Both languages include a construct for expressing inverse roles, which has not been considered up to now in tractable languages. In addition, PL1 includes number restrictions(More)