1. Web Information Systems Modeling Luxembourg, June 2006 1 VisAVis: An Approach to an Intermediate Layer between Ontologies and Relational Database Contents Nikolaos Konstantinou, National Technical University of Greece

2. Web Information Systems Modeling Luxembourg, June 2006 2 Introduction VisAVis Prot é g é Plugin VisAVis Prot é g é Plugin Features Features –Map between RDB and Ontologies –Execute queries expressed in RDQL

3. Web Information Systems Modeling Luxembourg, June 2006 3 Motivation The Semantic Web Vision orders that web pages need to be annotated in terms of an ontology language The Semantic Web Vision orders that web pages need to be annotated in terms of an ontology language What happens with Data stored in databases and is generated and retrieved automatically? What happens with Data stored in databases and is generated and retrieved automatically?

4. Web Information Systems Modeling Luxembourg, June 2006 4 Definitions An Ontology can be defined as a model of a Knowledge Base An Ontology can be defined as a model of a Knowledge Base Thus, we have the Terminological and the Assertional Box (ABox & TBox) Thus, we have the Terminological and the Assertional Box (ABox & TBox) Simplified point of view: Simplified point of view: –TBox Schema of the RDB –ABox Instance of the actual data

5. Web Information Systems Modeling Luxembourg, June 2006 5 Mapping Process Capture Database Data Capture Database Data Select an Ontology Class Select an Ontology Class Validate the mapping Validate the mapping Modify the resulting Ontology Modify the resulting Ontology

6. Web Information Systems Modeling Luxembourg, June 2006 6 Mapping Process Validate the mapping Validate the mapping –Disjoint classes cannot have mappings to common data. Common data includes data in tables with a foreign key relation –Maintain subclass hierarchy in the database

7. Web Information Systems Modeling Luxembourg, June 2006 7 Query Execution Parse requests Parse requests Instead of returning the class resources, we check if the mapping property exists Instead of returning the class resources, we check if the mapping property exists –Yes: redirect the query to the database –No: No changes

8. Web Information Systems Modeling Luxembourg, June 2006 8 Use-Case Scenario

9. Web Information Systems Modeling Luxembourg, June 2006 9 Use-Case Scenario SELECT activities.description FROM activities, activities_types WHERE (activities.activity_type_id = activities_types.id) AND (activities_types.name = "Hiking")

10. Web Information Systems Modeling Luxembourg, June 2006 10 Implementation Java, version 1.5.0 or higher Java, version 1.5.0 or higher Jena framework, tested in versions 2.2 and 2.3 Jena framework, tested in versions 2.2 and 2.3 Prot é g é, tested in 3.0, 3.1, 3.1.1, 3.2beta Prot é g é, tested in 3.0, 3.1, 3.1.1, 3.2beta MySQL and PostgreSQL, with JDBC connection MySQL and PostgreSQL, with JDBC connection

11. Web Information Systems Modeling Luxembourg, June 2006 11 Future Work Richer SQL builder Richer SQL builder Support for more databases Support for more databases Return results from both the database and the ontology Return results from both the database and the ontology

12. Web Information Systems Modeling Luxembourg, June 2006 12 Questions Thank you for your attention VisAVis plugin available at http://www.cn.ntua.gr/~nkons/essays_en.html VisAVis plugin available at http://www.cn.ntua.gr/~nkons/essays_en.html