In International CAISE Workshop on Web Information Systems Modeling (WISM\'06), Luxembourg, June 2006

1. VisAVis: An Approach to anVisAVis: An Approach to an
Intermediate Layer between OntologiesIntermediate Layer between Ontologies
and Relational Database Contentsand Relational Database Contents
Nikolaos Konstantinou, NationalNikolaos Konstantinou, National
Technical University of GreeceTechnical University of Greece

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IntroductionIntroduction
 VisAVis ProtVisAVis Protééggéé PluginPlugin
 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 thatThe Semantic Web Vision orders that
web pages need to be annotated inweb pages need to be annotated in
terms of an ontology languageterms of an ontology language
 What happens with Data stored inWhat happens with Data stored in
databases and is generated anddatabases and is generated and
retrieved automatically?retrieved automatically?

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DefinitionsDefinitions
 An Ontology can be defined as a modelAn Ontology can be defined as a model
of a Knowledge Baseof a Knowledge Base
 Thus, we have the Terminological andThus, we have the Terminological and
the Assertional Box (ABox & TBox)the Assertional Box (ABox & 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 mappings toDisjoint classes cannot have mappings to
common data. Common data includescommon data. Common data includes
data in tables with a foreign key relationdata in tables with a foreign key relation
– Maintain subclass hierarchy in theMaintain subclass hierarchy in the
databasedatabase

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Query ExecutionQuery Execution
 Parse requestsParse requests
 Instead of returning the classInstead of returning the class
resources, we check if the mappingresources, we check if the mapping
property existsproperty exists
– Yes: redirect the query to the databaseYes: redirect the query to the database
– 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 2.2Jena framework, tested in versions 2.2
and 2.3and 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 JDBCMySQL 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 databaseReturn results from both the database
and the ontologyand the ontology

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QuestionsQuestions
Thank you for your attentionThank you for your attention
 VisAVis plugin available atVisAVis plugin available at
http://www.cn.ntua.gr/~nkons/essays_en.htmlhttp://www.cn.ntua.gr/~nkons/essays_en.html