Description Logics

Description Logics (DLs) are a successful family of logic-based knowledge representation formalisms, which can be used to represent the conceptual knowledge of an application domain in a structured and formally well-understood way. They are employed in various application domains, such as natural language processing, configuration, and databases, but their most notable success so far is the adoption of the DL-based language OWL as standard ontology language for the semantic web. This course concentrates on designing and analysing reasoning procedures for DLs. After a short introduction of predecessor formalisms such as semantic networks and frames, it will introduce the basic features of DLs such as concepts, TBoxes and ABoxes, and basic inference problems such as the subsumption and the instance problem. The course introduces techniques for solving these problems based on tableau-algorithms, automata, and other approaches. Also, the complexity of standard DLs is analysed, identifying expressive DLs for which reasoning is expensive in the worst case, but still manageable in practice, and lightweight DLs for which reasoning is tractable.

The lecture takes place twice a week. Additionally, there is a weekly exercise session held by Marcel Lippmann. Exercise sheets will be available approximately one week before the session.

The lectures and the exercise sessions will take place in room E05 at the following times: Tuesdays 16.40–18.10, Wednesdays 14.50–16.20, and Thursdays 16.40–18.10. The exact distribution of lectures and exercise sessions can be found in the table below.

Announcements:

• The exercise sessions will start on 23 October.
• The lecture will start on 15 October.

	Tuesday	Wednesday	Thursday
14 Oct. to 18 Oct.	Lecture	Lecture	Lecture
21 Oct. to 25 Oct.	Lecture	Exercise session (exercise sheet 1)	Lecture
28 Oct. to 1 Nov.	Lecture	Lecture	Public Holiday
4 Nov. to 8 Nov.	Lecture	Exercise session (exercise sheet 2)	Lecture
11 Nov. to 15 Nov.	Lecture	Exercise session (exercise sheet 3)	Lecture
18 Nov. to 22 Nov.	Lecture	Public Holiday	Lecture
25 Nov. to 29 Nov.	Lecture	Exercise session (exercise sheet 4)	—
2 Dec. to 6 Dec.	Lecture	Exercise session (exercise sheet 5)	Exercise session (exercise sheet 6)
9 Dec. to 13 Dec.	Exercise session (exercise sheet 7)	Lecture	Lecture
16 Dec. to 20 Dec.	Lecture	Exercise session (exercise sheet 8)	Lecture
6 Jan. to 10 Jan.	Lecture	Lecture	—
13 Jan. to 17 Jan.	Lecture	Exercise session (exercise sheet 9)	Lecture
20 Jan. to 24 Jan.	Lecture	Exercise session (exercise sheet 10)	Lecture
27 Jan. to 31 Jan.	Lecture	Exercise session (exercise sheet 11)	Lecture
3 Feb. to 7 Feb.	—	Exercise session (exercise sheet 12)	—

SWS: 4/2/–

This course can be used in the following modules:

• Bachelor-Studiengang Informatik: INF-B-510 (Vertiefung), INF-B-520 (Vertiefung zur Bachelor-Arbeit)
• Master/Diplom-Studiengang Informatik: INF-BAS6 (Theoretische Informatik), INF-VERT6 (Theoretische Informatik)
• Master in Computational Logic: MCL-TCSL (Theoretical Computer Science and Logic), MCL-PI (Principles of Inference), MCL-KR (Knowledge Representation)
• Diplom-Studiengang Informatik (Studienordnung 2004): Fachgebiet Theorie der Programmierung, Fachgebiet Intelligente Systeme

A script of this lecture is not available, and students are strongly recommended to copy what is written on the blackboard.

We provide, however, the slides for the introductory sessions:

• Motivation and Chapter 1
• Chapter 2
• Chapter 3
• Chapter 4

• F. Baader, D. Calvanese, D. McGuinness, D. Nardi, and P. F. Patel-Schneider, editors. The Description Logic Handbook: Theory, Implementation, and Applications. Cambridge University Press, 2003.
• F. Baader and C. Lutz. Description Logic. In P. Blackburn, J. van Benthem, and F. Wolter, editors, The Handbook of Modal Logic, pages 757–820. Elsevier, 2006.
• F. Baader. Description Logics. In Reasoning Web: Semantic Technologies for Information Systems, 5th International Summer School 2009, volume 5689 of Lecture Notes in Computer Science, pages 1–39. Springer-Verlag, 2009.