http://www.inf.unibz.it/~calvanese/teaching/2009-09-ReasoningWeb-school-ontologies-dbs/
Ontologies and Databases
Summary
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
- Introduction to ontology-based data access
- Introduction to ontologies
- Ontology languages
- Query answering in databases
- Querying databases and ontologies
- Description Logics and the DL-Lite family
- Quick overview of DLs
- Reasoning and query answering in DLs
- The DL-Lite family of tractable DLs
- Reasoning in the DL-Lite family
- TBox reasoning
- TBox and ABox reasoning
- Beyond DL-Lite
- Linking ontologies to relational data
- The impedance mismatch problem
- Ontology-Based Data Access systems
- Query answering in OBDA systems
- The QuOnto OBDA system
- Conclusions and References
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Last modified:
Tuesday, 17-Aug-2010 14:38:43 CEST