School of Computer Science

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MOWS08 TUTORIAL Jena A Semantic Web Framework
for Java 2 July 2008

• Deshen Moodley
• School of Computer Science
• University of KwaZulu-Natal

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Software setup

• SWOOP 2.3 beta
• JDK 1.5 Eclipse 3.2.1
• Open workspace
• Jena_tutorial_workspace_MOWS_2JUL08.zip
• Compile and execute
• src-example/mows.examples/CreateKBTest.java

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SWOOP

• Ontology editor similar to Protégé in terms of
  being used to edit ontologies
• Extract SWOOP-2.3beta3.zip
• Execute runme.bat
• Browse to and open fruit.owl
• TASK Create your own simple test ontology at
  least 3 classes, subclasses, 2 properties, 2
  instances, e.g. cars, animals etc

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Overview of Jena

• Jena is a Java framework for building Semantic
  Web applications. It provides a programmatic
  environment for RDF, RDFS and OWL, SPARQL and
  includes a rule-based inference engine.
• Jena is open source and was intiated by Hewlitt
  Packard (HP) Labs Semantic Web Programme.
• The Jena Framework includes
• A RDF API
• Reading and writing RDF in RDF/XML, N3 and
  N-Triples
• An OWL API
• In-memory and persistent storage
• SPARQL query engine
• Support is provided by the jena-dev mailing list.

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JENA

• Semantic Web development environments
• Jena framework
• Protégé OWL- API
• WonderWeb OWL API
• Recent survey of SW users (Cardosa 2007)
• 68.2 use Protégé as their ontology editor
• 75.9 use OWL as the ontology language
• 53.6 use Jena as their reasoning engine

Jorge Cardoso, The Semantic Web Vision Where
are We? IEEE Intelligent Systems,
September/October 2007, pp.22-26, 2007
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Creating and reading an ontology model

• Create an OntModel
• Sample code CreateKBTest
• Model specification using the OntModelSpec class
• Load an OWL ontology into the model directly from
  a local file or from a URI or a locally cached
  ontology ReadKBTest, ReadKBTestWithCache
• TASK Modify the code to read in your own
  ontology

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Manipulating classes

• Listing the existing classes in the model
• Creating a new class
• Retrieving a specific class and listing its
  subclasses
• Adding a class and a subclass
• TASK List all classes in your ontology, add
  another class to your ontology and make it a
  sub/superclass of an existing class

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Writing a model

• An OntModel can be written to a local file
• WriteKBTest
• TASK Write the changed model to a another local
  file

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Manipulating properties

• Datatype properties
• RDF Literals, XML Schema data types
• Object Properties
• relations between classes, link individuals to
  individuals
• Listing, retrieving and creating properties
  PropertiesKBTest

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Manipulating instances

• List all instances in the model
• Listing instances of a class
• Listing properties and property values of an
  instance
• Adding a new instance and populating it with
  appropriate property values
• TASK List instances of a particular class in
  your ontology, add a new instance to this class
  with appropriate property values, and check that
  the instance has been created.

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Querying

• Querying using RDF triples
• Jena represents a triple as a statement of the
  form
• subject, predicate, object
• A model consists of a collection of statements
• QueryKBTest
• TASK. Perform a triple query on your ontology

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SPARQL query

• http//www.ibm.com/developerworks/xml/library/j-sp
  arql/
• http//jena.sourceforge.net/ARQ/Tutorial/
• SparqlQueryTest
• TASK Perform the same query using SPARQL

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Inferencing

• Inference engines are also called reasoners
• Jena reasoner rule based reasoner, rule sets
  for RDFS OWL
• Other reasoners are Pellet, FaCT
• file///C/Research/docs/tutorial/workspace/Jena-2
  .5.1/doc/inference/index.html

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Inferencing

• InferenceKBTest
• Checking ontology data for consistency
• ValidityKBTest
• TASK Create an inference model on your ontology

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Advanced features

• Persistence
• Storing ontology data in databases
• Connections to other reasoners such as Pellet
• Generic Rule based reasoner
• Custom inference rules
• Built-ins

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References

• Cardosa J., Programming the Semantic Web, in
  Cardosa J. Sheth A. P. (eds), Semantic Web
  Services, Processes and Applications, Springer,
  pp.351-380, 2006.
• Cardoso J. , The Semantic Web Vision Where are
  We? IEEE Intelligent Systems, September/October
  2007, pp.22-26, 2007