This tutorial is an introduction to Description Logics in the context of knowledge representation and reasoning. Description Logics (DLs) are a family of logic-based knowledge representation formalisms with interesting computational properties and a variety of applications. In particular, DLs are well-suited for representing and reasoning about terminological knowledge and constitute the formal foundations of semantic web ontologies. Technically, DLs correspond to decidable fragments of first-order logic and are closely related to modal logics. There are many different flavors of description logics with specific expressiveness and applications, an example of which is ALC and on which we shall focus in this tutorial.

The outline of the tutorial is as follows: We start with an introduction to the area of Knowledge Representation and Reasoning (KRR) and the need for representing and reasoning with terminological knowledge, which stands as the main motivation behind the development of DLs. We then present the description logic ALC, its syntax, semantics, logical properties and proof methods. In particular we make explicit the aforementioned relationship between ALC and other logical frameworks. Finally we illustrate the usefulness of DLs with the popular Protégé ontology editor, a tool allowing for both the design of DL-based ontologies and the ability to perform reasoning tasks with them.

 

Lecture 1: Introduction to KRR and DLs; Introduction to the description logic ALC

Lecture 2: The description logic ALC

Lecture 3: Formal ontologies in Protégé

Bibliography:

Brachman, R. and Levesque, H. Knowledge Representation and Reasoning. Morgan Kaufmann. 2004.

Baader, F., Calvanese, D., McGuinness, D., Nardi, D., Patel-Schneider, P. (eds.): The Description Logic Handbook: Theory, Implementation and Applications. Cambridge University Press, 2 edition, 2007.

Protégé Ontology Editor: http://protege.stanford.edu

The Description Logic workshop series: http://dl.kr.org