Description Logics: a Nice Family of Logics

Uli Sattler and Thomas Schneider

  • Area: LoCo
  • Level: F
  • Week: 1
  • Time: 09:00 – 10:30
  • Room: D1.03


Description Logics (DLs) form the logical underpinning of state-of-the-art ontology languages such as OWL, and have a long history in knowledge representation. OWL is used to describe the meaning of terms used, e.g., in electronic health records, in a machine-processable way. In order to engineer large ontologies such as the NCI Thesaurus, suitable tool support is required, an interesting part of which is based on DL reasoning problems and the corresponding algorithms. Both classical reasoning problems – e.g., consistency and satisfiability – and more exotic reasoning problems – e.g., explanation and module extraction – play a central role, and are well-understood both in theory and in practice. We will introduce DLs and the role they play in OWL. Starting with a basic DL, ALC, we will

  • discuss the relevant standard reasoning problems
  • describe algorithms for these problems that perform very well in practice,
  • outline the computational complexity of ALC and extensions,
  • and review two non-standard reasoning services, namely those related to explanation and modularity.

Along the way we will connect the theoretical foundations with practical aspects by

  • giving an overview of OWL and the ontology editor Protégé,
  • reviewing applications from NLP,
  • demonstrating how to use reasoners via the OWL API.

The course is on a foundational level and requires no previous knowledge (although familiarity with classical and/or modal logic would be an advantage).



The remaining slides will be made available during the week. Feel free to have a look at the material from previous versions of the course:

Additional References

For more information, have a look at

To use the Protégé OWL editor, visit their web site and install Protégé Desktop (currently version 5). Feel free to send us an email if you have any questions!