Ontologies and Databases

Tutorial at the
Reasoning Web 2009 Summer School
Bressanone, Italy, Aug. 31 - Sep. 4, 2009

Diego Calvanese

KRDB Research Centre
Free University of Bozen-Bolzano

Slides of the tutorial


Both knowledge base (KB) and database (DB) systems are used to maintain information about a domain of interest and provide mechanisms to access and manipulate such information. However the assumptions that traditionally are at the basis of these two kinds of systems are fundamentally different. On the one hand, in KB systems, data is assumed to be incomplete, i.e., the open-world assumption is made, and extensional information is stored together with an ontology. The latter maintains complex relationships at the intensional level and is used at query time to infer new knowledge. On the other hand, DB systems work under the closed-world assumption and do not exploit intensional information at query time, which makes them capable of managing efficiently very large amounts of data. Recently, various application domains, ranging from biological to enterprise data management, require to combine the assumptions underlying both types of systems, namely the management of very large amounts of data, as in DBs, under the open-world assumption and in the presence of complex constraints in an ontology, as in KBs. Several novel challenges arise in this context and need to be addressed, such as: (i) the trade-off between the expressive power of the ontology language and the efficiency of computing answers to queries; (ii) the impedance mismatch between the abstract objects in the ontology and the values appearing in data sources; (iii) the processing of queries posed over the ontology by accessing the data stored in relational sources. In this tutorial, we will analyze these issues in depth and will propose solutions based on recent research results for tractable Description Logics and in Ontology-Based Data Access. We will also allow participants to familiarize with state-of-the-art technology recently developed in this area.

Presentation style: lectures with slides

Prerequisite knowledge: basic knowledge in first-order logic and relational databases; background in Description Logics is preferable, but not strictly necessary

Tutorial duration: full day (8 hours)

Outline of the tutorial content

  1. Introduction to ontology-based data access
  2. Description Logics and the DL-Lite family
  3. Reasoning in the DL-Lite family
  4. Linking ontologies to relational data
  5. Conclusions and References

Back to home page of Diego Calvanese
Last modified: Tuesday, 17-Aug-2010 14:38:43 CEST