OWL RDF RDFs - some muses

Was tring hard on aPoC. Came across a series of interesting facts. Typical symptoms of playinng araound with vleeding edgre open source technologoes

this time its Jena. I had made use of Jena based Fuseki triplestore server for doing the basic learning of owl,rdfs and sparql. It has been a good journey until i surfaced with comples owl reasoning.

thr was a case somethig like

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?a spr:ancestor ?b .

and

spr:ancestor rdf:type owl:TransitiveProperty

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I needed to create another property that spr:preantOf which is of the same nature as spr:ancestor but should be non-transitive

Some research bought me to a solution.(As this is a most common problem in Descriptive Logic)

If:

?a spr:someRule ?b

then if i declare something like

spr:sometestRule rdf:subPropertyOf spr:someRule

it subsumes that sometestRule is valid for all cases of someRule and then we could apply transitiveness to spr:someRule

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But when i tries the same in Fuseki .that is by adding

spr:parent rdfs:dubPropertyOf spr:ancestor

then called ?a spr:parent ?b

it dint retrieve anything..

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A little reading bought me to the fact that the reasoning in jena is rule based reasining which is good for rdfs+ based constructs. And for owl based reasoning it doesnt use

the dessciptive logic based reasoning but the rule based reasning which entirely depends on instance : As is mentione din thr site :

"The Jena OWL reasoners could be described as instance-based reasoners. That is, they work by using rules to propagate the if- and only-if- implications of the OWL constructs on instance data. Reasoning about classes is done indirectly - for each declared class a prototypical instance is created and elaborated. If the prototype for a class A can be deduced as being a member of class B then we conclude that A is a subClassOf B. This approach is in contrast to more sophisticated Description Logic reasoners which work with class expressions and can be less efficient when handling instance data but more efficient with complex class expressions and able to provide complete reasoning."

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A solution to this is to configure the Pellet reasoner with Fuseki. The current version of fuseki was 0.2.5 which uses jena version 2.7.4 and ARQ version 2.9.4 .
The pellet stablee version in maven is 2.3.0 which is based on jena 2.6.4 . I tried to recompile pellet for 2.7.4 but thr was enormous incompatibilty issues as the latest jena has moved to apache openjena. while the jena version used by pellet was still the HP jena. Issues arise with arq. So i had to drop the idea. Anyone out thr could put in your inputs!!

When i started using Pellet i also found something insterestng :

Till date i only knew about : Jena Reasoner API, Sesame API .

But pellet i found a new one OWL API. They have their pellet 2.3.0 supported by OWL API and a pellet-jena for jena based resoners :| .

To get an idea of the diff b/w the API's do refer - http://answers.semanticweb.com/questions/2568/jena-api-or-owl-api-or-protege-owl-api

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One can use jena-pellet -2.3.0,tdb-0.8.10 to successfully intergrate b/w jena and pellet reasoner.

easoner =  PelletReasonerFactory.theInstance().create();           
String directory = "data/DB1" ;           
dataset = TDBFactory.createDataset(directory);         
emptyModel = dataset.getDefaultModel();

model = ModelFactory.createOntologyModel( PelletReasonerFactory.THE_SPEC ,emptyModel);

When i tried to add multiple model data using code snippet like

<code>String source = "D:\\Project\\Store_DB\\tmp\\trail_1.rdf";
FileManager.get().readModel( tdb, source);

So i had to try to load each file into separate models and  and add those model into the main model. That way it worked. It seemed to be  some bug with the version og jena.i saw in one of the blogs. This kept me occupied 1 day ufff..Anyways good findings.Enjoi!