On Sun, Apr 22, 2012 at 6:17 PM, Gunaratna, Dalkandura Arachchige
Kalpa Shashika Silva <gunaratn...@wright.edu> wrote:
> Hi,
> I have a simple requirement and that is to read
> <http://www.w3.org/2002/07/owl#sameAs> object values (sameAs link value) in a
> rdf file. For that I create an ontology model and read the whole file.
> Following is a code sample I sue for that.
>
> model=ModelFactory.createOntologyModel(OntModelSpec.RDFS_MEM);
> SysRIOT.wireIntoJena() ;
> model.read(url);
> StmtIterator stmtItr=model.listStatements();
>
> This way of processing has a huge processing overhead for my program since
> for every rdf file I just need to read the whole file to get sameAs links. Is
> there any other way of doing this kind of work or only possible way is to
> read the whole file to get the specific property type we want?
>
> And also, what happens if we do not call model.close() at the end? Will it be
> a problem which will cause heap out of space problem?
>
> Thank you,
> Kalpa
Hi Kalpa,
If you are simply interested in parsing an RDF file in a streaming
fashion, you can do something like below. If you know that you don't
have any duplicate triples, then you can eliminate the HashSet.
final Set<Triple> sameAsTriples = new HashSet<Triple>();
Sink<Triple> sink = new Sink<Triple>()
{
@Override
public void send(Triple t)
{
if (OWL.sameAs.asNode().equals(t.getPredicate()))
{
// You can either do something immediately with this
triple, or stick it a HashSet to enforce uniqueness
sameAsTriples.add(t);
}
}
@Override
public void flush() { }
@Override
public void close() { }
};
// To enable RDFS inferencing uncomment the following two lines.
// You need to have your T-Box (ontology) loaded into some model
//Model ontologyModel = ...
//sink = InfFactory.infTriples(sink, ontologyModel);
String filename = ...
RiotReader.parseTriples(new FileInputStream(filename),
Lang.guess(filename), null, sink);
// Now do something with sameAsTriples
