[Pellet-users] Fw: Pellet inferred statements and BaseModel

[Evren Sirin]

On 7/25/08 8:11 AM, Paolo Bussotti wrote:
> Excuse me for this resend, but I'm having some problems with the 
> e-mail server and I guess my message has not arrived.
> Best Regards
> Paolo Bussotti
>  
> ----- Original Message -----
> *From:* Paolo Bussotti <mailto:paolo.bussotti at unifi.it>
> *To:* pellet-users at lists.owldl.com <mailto:pellet-users at lists.owldl.com>
> *Sent:* Thursday, July 24, 2008 10:44 AM
> *Subject:* [Pellet-users] Pellet inferred statements and BaseModel
>
> Hello everybody,
>  
> I have a simple question which maybe can be trivial to you. However I 
> hope you can give me an answer.
> PS I apology for sending the same question in a previous mail, but I 
> need to reformulate the questions more clearly.
>    
> I'm working with a pellet-backed ontModel and I have some basic doubts.
> Can you please tell me (1) if Pellet-inferred statements actually or 
> only virtually reside in the pellet-backed OntModel and in particular 
> if they are asserted, when required, by Pellet to the Base Model. In 
> other terms does the basemodel only contain the loaded-ontology 
> asserted contents and the possible programmatic user assertions,

Yes.

> or may it host Pellet inferences?

No, Pellet inferences will only be generated as a response to a query. 
Unless manually added by the user top the base model, base model will 
not contain these inferences. Pellet does not modify the base model in 
any way during reasoning.

>  
> This is important to me since I update the OntModel by adding to 
> it/removing from it some "updating models" which have been 
> constructed asynchronously on non-inferential OntModels which are 
> initially loaded with a copy of the basemodel of the pellet-backed 
> ontModel. Of course I arranged the ontologies so that the directly 
> loaded ontology (which imports all the other) is only devoted to user 
> assertions to be held on the basemodel, for ABox-level 
> updates.              
>  
> Besides:
> (2) In case Pellet inference were not concretely asserted to the 
> OntModel (an do not become part of its basemodel), as I guess from 
> what I've tested, where are Pellet-inferred statements physically hold 
> and managed by the Pellet reasoner? Can you indicate the name of this 
> structure (if any)?

KnowledgeBase class is the main entry point for Pellet's internal 
structures. PelletInfGraph (Pellet's implementation of Jena InfGraph 
interface) is a wrapper around a KnowledgeBase. You can look at the 
PelletInfGraph code if you want to learn mode about how Pellet-Jena 
integration works.

> (3) Which is the difference from a basemodel and a rawmodel, with 
> regards to the questions?     

RawModel (and RawGraph) is related to InfModel (and InfGraph) interfaces 
in Jena where BaseModel is related to OntModel interface. You can read 
Jena documentation to learn more about these. Typically the RawModel is 
the non-inferencing model that contains the assertions and fed to the 
reasoner. OntModel on the other hand is a view over union of models (if 
there are imported ontologies) and base model is the source ontology. 
The imported ontologies by the base will be the other elements of the 
union. In this context the RawModel that will be passed to Pellet is 
this union model that contains all the information from the imports 
closure of the source ontology. Again Jena documentation (and mailing 
list) is the place to learn more about these.

Cheers,
Evren


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