no inferences with DL queries in OWL - API

Question

I am trying to write a query

Hospitals and hasNameWithWords value "center"^^string

This query returns me the instances that has the hospitals that has "center" in its name in Protege 4.2 with FACT++ reasoner as well as Hermit reasoner

but when i input the same query in the OWL-API's DL Query Example thats available in the website http://sourceforge.net/p/owlapi/code/ci/aef6981535f07a2d0d44c394b9f4d5415f36025a/tree/contract/src/test/java/org/coode/owlapi/examples/DLQueryExample.java

I don't get any result.

But it gives me result when i write simple queries such as

Hospitals

Is it because the reasoner in the code is not able to make the inference?

What other reasoner would be better?

Answer 1

The class you use as example (DLQueryExample.java) relies on an OWL-API built-in structural reasoner (OWLReasonerFactory reasonerFactory = new StructuralReasonerFactory();).

This type of reasoner is fairly simple and is not suited for complex queries as yours. It can however provide answers on the class hierarchy: This is why you get some results with the straightforward query Hospitals.

What you need to do is to set your code to either use Hermit or FACT++. I give the example with Hermit:

• Download HermiT jar file and add it to the class path of your project.
• In your class, replace the line OWLReasonerFactory reasonerFactory = new StructuralReasonerFactory(); by: OWLReasonerFactory reasonerFactory = new Reasoner.ReasonerFactory();. You should have to import org.semanticweb.HermiT.Reasoner in order to make it work.
• We just replaced the default reasoner by HermiT. The rest of the code should stay the same and your query should now work.
• You could try FaCT++ and Pellet and compare speed, etc...