On 23/05/12 11:38, [email protected] wrote:
Dear Jena users,
I was wondering if, in the case of large datasets, it would be more
appropriate to store inferences immediately on disk rather than create an in
memory model and afterwards adding the inferred statements to the base model.
Until now I managed to achieve only the second solution.
String directory = "MyDatabases/Dataset1";
dataset = TDBFactory.createDataset(directory);
Model base = dataset.getDefaultModel();
OntModel o = ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM,base);
printStatements(o); // check base model content
load(base); // some reading from owl files (only for the first run)
OntModel m = ModelFactory.createOntologyModel( OntModelSpec.OWL_MEM_RULE_INF,
base );
m.prepare();
base.add(m); // if this line is removed the next time the model is created
printStatements(o) won't show the inferred knowledge
base.close();
dataset.close();
Is there a way to make the reasoner work directly on the tdb model without
needing for base.add(m)?
What you have does work directly over TDB, "base" is not an in memory
copy but a reference to TDB.
When the reasoner runs all of its internal workings, together with all
results, will be stored in memory and typically those are larger than
your base model.
If there are many entailments could I get an
outofmemory over the m model?
Yes, the inference itself is in memory. Keeping your based data in TDB
just has the effect of slowing reasoning down, it doesn't increase the
scaling.
If you only need a subset of RDFS inference then you can compute then on
the fly as you load (I believe tdbloader has some options to enable this).
If you need more inference then at present you'll just need enough
memory. Indeed you'll get a lot better performance by reading the TDB
model into a memory model and reasoning over that.
What you can do is take the results of inference and add() them to a tdb
model for storage. Then on future occasions use that materialized set of
results instead of using a reasoner.
Dave
I tried creating an InfModel, beacuse I found this suggestion at http:
//answers.semanticweb.com/questions/956/how-to-set-up-jena-sdb-with-inference-
capability using the following implementation:
String directory = "MyDatabases/Dataset1";
dataset = TDBFactory.createDataset(directory);
Model base = dataset.getDefaultModel();
OntModel o = ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM,base);
printStatements(o); // check base model content
load(base); // some reading from owl files (only for the first run)
Reasoner r = OWLFBRuleReasonerFactory.theInstance().create(null);
InfModel inf=ModelFactory.createInfModel(r, base);
inf.prepare();
base.add(m); // if this line is removed the next time the model is created
printStatements(o) won't show the inferred knowledge
base.close();
dataset.close();
... same results :( at the second run printStatements(o) print the same things
BR, Paolo
