Running out of memory in RDFS inference

[Benson Margulies]

Step 1:

 Model schema = ModelFactory.createDefaultModel();
        schema.read(RdfUtils.getJugOntology(),
RdfUtils.getJugOntologyUri(), "RDF/XML");
        return ModelFactory.createRDFSModel(schema, data);

Step 2: about 50k tuples, many of them owl:sameAs

Step 3:

NodeIterator sameAsItems = model.listObjectsOfProperty(root,
relatingProp); // prop is in fact owl:sameAs
            while (sameAsItems.hasNext()) {
            ...
            }

Runs for a very long time, using a very large amount of memory.
Eventually runs out of memory.

I am at this point about to remove all dependencies on inference and
use a plain model. Is there something I should learn from this about
what inference is and isn't useful for?