VisAVis: An Approach to an VisAVis: An Approach to an Intermediate Layer between Intermediate Layer between Ontologies and Relational Database Ontologies and Relational Database Contents Contents

Nikolaos Konstantinou, Nikolaos Konstantinou, National Technical University National Technical University of Greeceof Greece

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IntroductionIntroduction VisAVis ProtVisAVis Protééggéé Plugin Plugin FeaturesFeatures

– Map between RDB and OntologiesMap between RDB and Ontologies– Execute queries expressed in RDQLExecute queries expressed in RDQL

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MotivationMotivation The Semantic Web Vision orders The Semantic Web Vision orders

that web pages need to be that web pages need to be annotated in terms of an ontology annotated in terms of an ontology languagelanguage

What happens with Data stored in What happens with Data stored in databases and is generated and databases and is generated and retrieved automatically?retrieved automatically?

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DefinitionsDefinitions An Ontology can be defined as a An Ontology can be defined as a

model of a Knowledge Basemodel of a Knowledge Base Thus, we have the Terminological Thus, we have the Terminological

and the Assertional Box (ABox & and the Assertional Box (ABox & TBox)TBox)

Simplified point of view:Simplified point of view:– TBox <-> Schema of the RDBTBox <-> Schema of the RDB– ABox <-> Instance of the actual dataABox <-> Instance of the actual data

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Mapping ProcessMapping Process Capture Database DataCapture Database Data Select an Ontology ClassSelect an Ontology Class Validate the mappingValidate the mapping Modify the resulting OntologyModify the resulting Ontology

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Mapping ProcessMapping Process Validate the mappingValidate the mapping

– Disjoint classes cannot have Disjoint classes cannot have mappings to common data. Common mappings to common data. Common data includes data in tables with a data includes data in tables with a foreign key relationforeign key relation

– Maintain subclass hierarchy in the Maintain subclass hierarchy in the databasedatabase

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Query ExecutionQuery Execution Parse requestsParse requests Instead of returning the class Instead of returning the class

resources, we check if the resources, we check if the mapping property existsmapping property exists– Yes: redirect the query to the Yes: redirect the query to the

databasedatabase– No: No changesNo: No changes

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Use-Case ScenarioUse-Case Scenario

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Use-Case ScenarioUse-Case Scenario<owl:Class rdf:about="#Hiking"> <queryString>SELECT activities.description

FROM activities, activities_types WHERE (activities.activity_type_id = activities_types.id) AND (activities_types.name = "Hiking")

</queryString> <rdfs:subClassOf> <owl:Class rdf:about="#Sports"/> </rdfs:subClassOf> </owl:Class>

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ImplementationImplementation Java, version 1.5.0 or higherJava, version 1.5.0 or higher Jena framework, tested in versions Jena framework, tested in versions

2.2 and 2.32.2 and 2.3 ProtProtééggé, tested in 3.0, 3.1, 3.1.1, é, tested in 3.0, 3.1, 3.1.1,

3.2beta3.2beta MySQL and PostgreSQL, with JDBC MySQL and PostgreSQL, with JDBC

connectionconnection

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Future WorkFuture Work Richer SQL builderRicher SQL builder Support for more databasesSupport for more databases Return results from both the Return results from both the

database and the ontologydatabase and the ontology

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QuestionsQuestions

Thank you for your attentionThank you for your attention

VisAVis plugin available at VisAVis plugin available at http://www.cn.ntua.gr/~nkons/essays_en.htmlhttp://www.cn.ntua.gr/~nkons/essays_en.html