Lab: RDFS

Topics

• Simple RDFS statements/triples
• Basic RDFS programming in RDFlib
• Basic RDFS reasoning with OWL-RL

Useful materials

rdflib classes/interfaces and attributes:

• RDF (RDF.type)
• RDFS (RDFS.domain, RDFS.range, RDFS.subClassOf, RDFS.subPropertyOf)

OWL-RL:

• OWL-RL at PyPi
• OWL-RL Documentation

OWL-RL classes/interfaces:

• RDFSClosure, RDFS_Semantics

Tasks

Task: Install OWL-RL into your virtual environment:

pip install owlrl

Task: We will use simple RDF statements from the Mueller investigation RDF graph you create in Exercise 1. Create a new rdflib graph and add triples to represent that:

• Rick Gates was charged with money laundering and tax evasion.

Use RDFS terms to add these rules as triples:

• When one thing that is charged with another thing,
  • the first thing is a person under investigation and
  • the second thing is an offense.

To add triples, you can use either:

• simple graph.add((s, p, o)) statements or
• INSERT DATA {...} SPARQL updates.

If you use SPARQL updates, you can define a namespace dictionary like this:

EX = Namespace('http://example.org#')
NS = {
    'ex': EX,
    'rdf': RDF,
    'rdfs': RDFS,
    'foaf': FOAF,
}

You can then give NS as an optional argument to graph.update() - or to graph.query() - like this:

g.update("""
    # when you provide an initNs-argument, you do not have 
    # to define PREFIX-es as part of the update (or query)

    INSERT DATA {
        # the triples you want to add go here,
        # you can use the prefixes defined in the NS-dict
    }
""", initNs=NS)

Task:

• Write a SPARQL query that checks the RDF type(s) of Rick Gates in your RDF graph.
• Write a similar SPARQL query that checks the RDF type(s) of money laundering in your RDF graph.
• Write a small function that computes the RDFS closure on your graph.
• Re-run the SPARQL queries to check the types of Rick Gates and of money laundering again.

You can compute the RDFS closure on a graph like this:

engine = owlrl.RDFSClosure.RDFS_Semantics(g, False, False, False)
engine.closure()
engine.flush_stored_triples()

Task: Use RDFS to add this rule as a triple:

• A person under investigation is a FOAF person.
• Like earlier, check the RDF types of Rick Gates before and after running RDFS reasoning.

Task: Add in "plain RDF" as in Exercise 1:

• Paul Manafort was convicted for tax evasion.

Use RDFS to add these rules as triples:

• When one thing is convicted for another thing,
  • the first thing is also charged with the second thing.

Note: we are dealing with a "timeless" graph here, that represents facts that has held at "some points in time", but not necessarily at the same time.

• What are the RDF types of Paul Manafort and of tax evasion before and after RDFS reasoning?
• Does the RDFS domain and range of the convicted for property change?