Jena Framework

1
Jena Framework

• Presentation Konstantinos Kanaris

2
Overview

• What is Jena?
• Usage of Jena
• Main Concepts
• Main Components
• Storage Models
• OWL API
• RDF API
• Reasoning
• Application-oriented issues

3
What is Jena?

• Open source Semantic Web framework for Java based
  on W3C recommendations for RDF and OWL
• Provides a suitable programming environment for
  RDF, RDFS, OWL, SPARQL and an integrated
  rule-based inference mechanism

4
Usage of Jena

• Import of owl ontologies, RDF, DAML into suitable
  models (persistent or in-memory)
• Processing of these models
• Export of these models to owl, rdf, daml files

5
Main Concepts

• Almost all ontology concepts
• Classes A class is a definition of a group of
  individuals that belong together because they
  share common properties. For example John and
  Mary both belong to the class person.
• Instances Instances are what the classes consist
  of their members, they inherit class
  characteristics and properties may be used to
  relate to one another

6
Main Concepts

• Properties binary relations
• Object Properties relations between instances of
  two classes
• Datatype Properties relations between instances
  of classes and RDF literals and XML Schema
  datatypes

7
Main Components

• com.hp.hpl.jena.rdf.model package for creating
  and manipulating RDF graphs
• Model RDF model
• ModelMaker ModelMaker contains a collection of
  named models, methods for creating new models
  both named and anonymous and opening
  previously-named models, removing models, and
  accessing a single "default" Model for this
  Maker.
• Literal RDF Literal
• Statement RDF Statement

8
Main Components

• com.hp.hpl.jena.ontology package that provides a
  set of abstractions and convenience classes for
  accessing and manipluating ontologies represented
  in RDF
• OntModel An enhanced view of a Jena model that
  is known to contain ontology data, under a given
  ontology vocabulary (such as OWL)
• OntClass Interface that represents an ontology
  node characterising a class description
• ComplementClass
• IntersectionClass
• UnionClass

9
Main Components

• OntResource Provides a common super-type for all
  of the abstractions in this ontology
  representation package
• OntModelSpec Encapsulates a description of the
  components of an ontology model, including the
  storage scheme, reasoner and language profile
• ObjectProperty Interface encapsulating
  properties whose range values are restricted to
  individuals (as distinct from datatype valued
  properties)
• DatatypeProperties Interface that encapsulates
  the class of properties whose range values are
  datatype values (as distinct from ObjectProperty
  whose values are individuals)

10
Main Components

• com.hp.hpl.jena.reasoner.Reasoner reasoner
  subsystem designed to allow a range of inference
  engines to be plugged into Jena
• com.hp.hpl.jena.reasoner.ReasonerRegistry global
  registry of known reasoner modules

11
Storage Models

• Persistent Storage
• Example Source Code
• OntModelSpec spec new OntModelSpec(OntModelSpec
  .OWL_DL_MEM) IDBConnection conn
  new DBConnection(dbURL, username, password,
  dbType) ModelMaker maker ModelFactory.createMod
  elRDBMaker(conn)
  Model m maker.createModel("http//www.icsd.ae
  gean.gr/ai-lab/projects/grid4all/ontology/grid4all
  Onto", false) m.read("fileG4Aonto-example.owl")
  
  conn.close()

12
Storage Models

• In Memory
• Source Code Example
• ModelMaker modelMaker ModelFactory.createMemMode
  lMaker() Model model 1
  modelMaker.createModel("myBase")
  java.io.InputStream inFileManager.get().open(fc.g
  etCurrentDirectory().getAbsolutePath()"\\"fc.get
  SelectedFile().getName())
  model1.read(in,
  "")
  OntModelSpec spec
  new OntModelSpec(OntModelSpec.OWL_DL_MEM )
  com.hp.hpl.jena.reasoner.Reasoner reasoner1
  PelletReasonerFactory.theInstance().create()
  spec.setReasoner(
  reasoner1 )
  OntModel
  ontTestModel ModelFactory.createOntologyModel(sp
  ec, myModel)

13
OWL API
14
OWL API

• Source Code Example
• private ObjectProperty getAllPropertiesWithSameD
  omainAs(ObjectProperty oP)
  ObjectProperty oPznew ObjectProperty0
• OntClass domainClasseslistDomainClasses(oP)
• OntModel oMoP.getOntModel()
• ExtendedIterator itoM.listObjectProperties()
• while(it.hasNext())
• ObjectProperty oP2(ObjectProperty)it.next()
• if(oP2.getLocalName().compareTo(oP.getLocalName
  ())!0)
• OntClass domainClasses2listDom
  ainClasses(oP2)
• if(isSubclass(domainClasses,domainC
  lasses2))
• oPzextendArray(oPz,oP2)
• it.close()
• return oPz

15
OWL API
16
OWL API

• private String getAllSiblingClasses(OntClass
  Class2)
• OntClass supClassClass2.getSuperClass()
  
• int iNoOfSubClassessupClass.listSubClass
  es().toList().size()
• String siblings new
  StringiNoOfSubClasses-1
• int iCounter0
• for(int i0 iltiNoOfSubClasses i)
• OntClass oC(OntClass)supClass.listSu
  bClasses().toList().get(i)
• if(!oC.equals(Class2))
• siblingsiCounteroC.getLocalNam
  e()
• iCounter
• return siblings

17
RDF API
18
RDF API

• ExtendedIterator iter ontModel1.listDatatypePro
  perties()
• while(iter.hasNext())
• DatatypeProperty dP
  (DatatypeProperty)iter.next()
• if(dP.getRange().getLocalName().c
  ompareTo("int")0 dP.getRange().getLocalName()
  .compareTo("double")0)
• String sProtnew
  String4
• ExtendedIterator iter3
  ontModel1.listIndividuals()
• while(iter3.hasNext())
• OntResource oRes
  (OntResource)iter3.next()
• NodeIterator
  sitoRes.listPropertyValues(dP)
• while(sit.hasNext())
• com.hp.hpl.jena.rdf.m
  odel.impl.LiteralImpl pr(com.hp.hpl.jena.rdf.mode
  l.impl.LiteralImpl)sit.next()
• String
  sSubjectoRes.getLocalName()
• String
  sObjectpr.getString()
• String
  sPredicatedP.getLocalName()

19
Reasoning

• Internal Reasoning
• com.hp.hpl.jena.reasoner.ReasonerRegistry
  ,mediocre reasoning ability
• Source Code Example
• OntModelSpec spec new OntModelSpec(
  OntModelSpec.OWL_DL_MEM ) com.hp.hpl.jena.reasone
  r.Reasoner reasoner1 ReasonerRegistry.getOWLReas
  oner() spec.setReasoner( reasoner1 )
  ontTestModel ModelFactory.createOntologyModel(s
  pec, myModel)
• External Reasoning
• E.g.Pellet Reasoner, complete reasoning ability
• Source Code Example
• OntModelSpec spec new OntModelSpec(
  OntModelSpec.OWL_DL_MEM ) com.hp.hpl.jena.reasone
  r.Reasoner reasoner1 PelletReasonerFactory.theIn
  stance().create()spec.setReasoner( reasoner1 )
  ontTestModel ModelFactory.createOntologyModel(sp
  ec, myModel)

20
Application-oriented issues

• Jena 2.5.4 used
• One in memory RDF model used
• A persistent model approach was initially
  introduced but was rejected
• Two in memory ontology models used
• One with a reasoner attached
• One without reasoner
• Pellet 1.5.1 reasoner used is some occasions only
  to determine subsumptions between subclasses and
  superclasses and their individuals respectively

21
Application-oriented issues

• Only ontology files imported (OWL-DL)
• No alterations on the imported ontology
• Only Knowledge Extraction
• Use of this knowledge to create Multiple Choice
  Questions
• No SPARQL Queries developed

22
Application-oriented issues

• Limited use of the RDF API
• Used only to create ontology models and in some
  occasions to detect certain statements.
• Extended use of the Ontology API
• Knowledge extracted concerning
• Classes
• Individuals
• Object Properties
• Datatype Properties

23
Questions???

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