Lab: RDFS

Lab 5: RDFS Programming in Jena

Topics

Basic RDFS graph programming in RDFlib. Entailments and axioms with owlrl.

Classes/Methods/Vocabularies

owlrl.RDFSClosure (RDFS_Semantics, closure, flush_stored_triples())

RDFS (label, comment, subClassOf, subPropertyOf, domain, range)

Tasks

Consider the following extensions to the task from lab 2: "University of California, Berkeley and University of Valencia are both Universities. All universities are higher education instituttions (HEIs). Having a B.Sc. from a HEI and having a M.Sc. from a HEI are special cases of gradutating from that HEI. Only persons can graduate from a HEI. That a person has a degree in a subject means that the person has expertise in that subject. Only persons can have expertise, and what they have expertise in is always a subject."

Create and output the RDFS graph in Jena (as an InfModel that wraps a default Model) - if you can, try to build on your example from lab 2!

Check that simple inference works - make sure that your graph contains triples like these, even if you have not asserted them explicitly:

• that UCB and UV are HEIs
• that Cade and Ines have both graduated from some HEI
• that Cade and Ines both have expertises
• that Cade and Ines are both persons
• that biology and chemistry are both subjects

Rewrite some of your existing code to use rdfs:label in a triple and add an rdfs:comment to the same resource.

If you have more time...

Create a new RDFS graph (or InfModel) that wraps an empty base (or raw) model. This graph contains only RDFS axioms. Write it out in Turtle and check that you understand the meaning and purpose of each axiom.

Create an RDF (not RDFS) graph that contains all the triples in your first graph (the one with all the people and universities). Subtract all the triples in the axiom graph from the people/university graph. Write it out to see that you are left with only the asserted and entailed triples and that none of the axioms remain.

Download the SKOS vocabulary from https://www.w3.org/2009/08/skos-reference/skos.rdf and save it to a file called, e.g., SKOS.rdf . Use the schemagen tool (it is inside your Jena folders, for example under apache-jena-3.1.1/bin) to generate a Java class for the SKOS vocabulary. You need to do this from a console window, using a command like "<path>/schemagen -i <infile.rdf> -o <outfile.java>".

Copy the SKOS.java file into your project in the same package as your other Java files, and try to use SKOS properties where they fit, for example to organise the keywords for interests and expertise.