Bridging EMF applications andBridging EMF applications andRDF Data SourcesRDF Data Sources

Guillaume Hillairet, Frédéric Bertrand, Jean Yves Lafaye{guillaume.hillairet01, fbertran, jylafaye}@univ-lr.frLaboratoire L3I, Université de La Rochelle, France.

SWESE’08: Semantic Web Enabled Software Engineering @ ISWC’08. SWESE’08: Semantic Web Enabled Software Engineering @ ISWC’08. 26 October 2008

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AgendaAgenda

Semantic Web Applications

Modeling Support for Semantic Web Apps

emf4sw: Eclipse Modeling Framework for Semantic Web

Conclusion

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refers to

refers to

Semantic Web ApplicationsSemantic Web Applications

RDF Store

RDF Store

RDF Store

Ontology(OWL)

Ontology(OWL)

described bydescribed by

described by

described by

SPARQL endpoint

onlinelocal

access rdf data

access rdf data

provides

OOM

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Semantic Web ApplicationsSemantic Web Applications

Web Applications: Centralized, fixed schema, single data source …

Semantic Web: Decentralized, arbitrary schema, many data sources …

From Web to Semantic Web Applications: Using Semantic Web data in existing Web Applications. Embedding Semantic Web data in common web development

processes.

Our contribution: Modeling support for Semantic Web Applications. Use of RDF Data as EMF Objects

Similar approaches: ActiveRDF, Topaz platform, …

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---- Table structure for table `a`--CREATE TABLE `a` ( `e_id` bigint(20) NOT NULL auto_increment, `dtype` varchar(255) NOT NULL, `e_version` int(11) NOT NULL, `a` varchar(255) NOT NULL, `b` varchar(255) default NULL, PRIMARY KEY (`e_id`))

---- Table structure for table `b_tocs`--CREATE TABLE `b_tocs` ( `b_e_id` bigint(20) NOT NULL, `c_e_id` bigint(20) NOT NULL, `b_tocs_idx` int(11) NOT NULL, PRIMARY KEY (`b_e_id`,`b_tocs_idx`), KEY `FKACAC0DE8ACA50134` (`b_e_id`), KEY `b_tocs` (`c_e_id`), CONSTRAINT `b_tocs` FOREIGN KEY (`c_e_id`) REFERENCES `c` (`e_id`), CONSTRAINT `FKACAC0DE8ACA50134` FOREIGN KEY (`b_e_id`) REFERENCES `a` (`e_id`))

<?xml version = '1.0' encoding = 'ISO-8859-1' ?><rdf:RDF> <rdf:Description rdf:about = 'http://www.example.org/library/MySci-FictionLibrary'> <library:name>My Sci-Fiction Library</library:name> <library:writers rdf:resource = 'http://www.example.org/library/authors/IsaacAzimov'/> <library:books rdf:resource = 'http://www.example.org/library/books/Robots'/> <rdf:type rdf:resource = 'http://www.example.org/library#Library'/> </rdf:Description> <rdf:Description rdf:about = 'http://www.example.org/library/books/Robots'> <library:title>Robots</library:title> <library:pages>305</library:pages> <library:author rdf:resource = 'http://www.example.org/library/authors/IsaacAzimov'/> <rdf:type rdf:resource = 'http://www.example.org/library#Book'/> </rdf:Description> <rdf:Description rdf:about = 'http://www.example.org/library/authors/IsaacAzimov'> <library:name>Isaac Azimov</library:name> <library:books rdf:resource = 'http://www.example.org/library/books/Robots'/> <rdf:type rdf:resource = 'http://www.example.org/library#Writer'/> </rdf:Description></rdf:RDF>

Modeling Semantic Web ApplicationsModeling Semantic Web Applications

JSF/HTML JSF/HTML GenerationGeneration

SQL SQL GenerationGeneration

OWL/RDF(S) OWL/RDF(S) GenerationGeneration

User InterfaceRelational Persistence

Semantic Web Data

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emf4swemf4sw

Uses Eclipse Modeling Framework (EMF). Links EMF applications with RDF Data Sources:

Mapping between OWL Ontology and EMF Model. Load RDF data into M1 model. Save M1 Model into RDF. Manipulate RDF Data as EMF Objects.

Acts as an ORM but for RDF data.

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emf4sw: main componentsemf4sw: main components

Resource Provider Object/Ontology Mapping. Loads/Saves objects.

Model Manager Manages EMF Resources Provides Model Transformations

Query Engine Builds queries. Provides query rewriting:

HQL to SPARQL, SPARQL to HQL.

Data Source Manager Accesses online data sources (SPARQL endpoints, …). Supports access to multiple data sources. Distributes/Federates query results.

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emf4sw usage: initializationemf4sw usage: initialization

First generate Java Classes from EMF Model. Then, init a resource provider:

Add EPackages corresponding to the EMF Model Add corresponding mapping file

Adding an RDF Data Source (RDF File, RDF DB, SPARQL endpoint):

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Object/Ontology mappingObject/Ontology mapping

Need to explicitly define links between EMF Model and OWL Ontology

Proposition Mapping language for Ecore/OWL

Map Ecore & OWL (MEO)

Ecore

EMF Model

OWL

OWL ModelMapping

MEO

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A AA2A

Ontology OaEPackage A

A’’

Ontology Ob

A2A’’

Object/Ontology MappingObject/Ontology Mapping

Mapping EMF Classes to OWL Classes Map one EClass to one OWLClass Map one EClass to many OWLClass

Have different views on same EClass, Use of OCL constraints to define views.

A’A2A’

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Object/Ontology MappingObject/Ontology Mapping

Mapping EStructuralFeatures to OWLProperties Map EAttribute to DataProperty Map EReference to ObjectProperty

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Object/Ontology MappingObject/Ontology Mapping

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OOM: Model TransformationsOOM: Model Transformations

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emf4sw: Loading and Saving objectsemf4sw: Loading and Saving objects

Loading an EObject:

Saving an EObject:

Loading/Saving EMF Resources:

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emf4sw: Querying RDF Data Sourceemf4sw: Querying RDF Data Source

Query RDF Data Source in HQL:

Or directly in SPARQL:

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ConclusionConclusion

The goal of our approach is to ease import/export of Semantic Web data within current applications.

Object/Ontology mapping is necessary for embedding Semantic Web data in current applications (not only Web App.).

Model Driven Engineering simplifies and automates implementation and use of such complex process.

Well defined OWL ontologies are needed for describing RDF data sources.

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Thank you, Questions ?Thank you, Questions ?