RE: [d2rq-dev] is it possible that we can keep D2RQ's dynamic fea ture when doing OWL inference when

[Krishnamurthy, V. <Ven...@gs...>]

I actually dealt with a similar case last year...One of the ways I explored
(didnt do it finally) was to construct map models on the fly - since I used
Jena's general rules parser (which I think the owl inferencer uses anyway) -
I thought of parsing out rules to see what resources/properties they wanted,
and then filter the overall map model by selecting only those resources
required to answer the rule and further restricting this set using
d2rq:conditions...Didnt get a chance to fully test it...Actually I think I
asked for the D2RQModel(Model someModel) constructor specifically for this
purpose
 
But it illustrates that this is a Jena question - because the rule engine
ultimately has to query an underlying model somehow - a D2RQ model  is just
one special kind of underlying model. The trick I think is to optimize the
'path' that Jena takes to get the data related to the rule...As Walker
points out, it seems to get ALL data and then runs through it (not sure) -
maybe someone could build a general-purpose bridge that creates an 'optimal'
query when the rule engine is used? Any thoughts?
 
Venkat
 
------ 
Venkat Krishnamurthy, FRM | Management Controls Department | Goldman, Sachs
& Co.| 212-855-6074| ven...@gs...

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From: d2r...@li...
[mailto:d2r...@li...] On Behalf Of Walker She
Sent: Wednesday, December 07, 2005 2:54 AM
To: d2r...@li...
Subject: Re: [d2rq-dev] is it possible that we can keep D2RQ's dynamic
feature when doing OWL inference when



Hi Richard,
 
thanks for your replying. well, it really does work except that there's an
error. This error, however, dosen't mean much thing. The Owl inference can
still go on and sometimes with unexpected answers. I don't know whether it's
the matter of Jena or D2RQ.
 
You mean if i want to do owl inference on D2RQ Model, the performance will
be almost the same whether or not i preload the virtual statements into
database to obtain persistence Jena Model?
 
To inference on subset of the full data seems really good, but you know,
it's hard to obtain the exact subset data from the Model.
 
-Walker
 

Richard Cyganiak <ri...@cy...> wrote:

Hi Walker,

The short answer: Doing inference over a D2RQ model should be 
possible, but it's going to be very, very slow.

I've not tried this, but in theory, it *should* work:

Model baseModel = new ModelD2RQ(...);
OntModel withReasoning = ModelFactory.createOntologyModel 
(OntModelSpec.PICK_YOUR_REASONER, baseModel);

This creates an ontology model with reasoner on top of the D2RQ 
model. The ontology model should query the D2RQ model (which then 
queries the database) when inference is performed.

It's the same basic approach as using Jena reasoners with persistent 
Jena models, see [1].

However, this will result in *lots* of queries against the database, 
and it's likely to be very slow.

I don't know an easy way around this. Maybe run the inference only on 
one or more smaller subsets of the data.

Richard

[1] http://jena.sourceforge.net/ontology/#persistence

On 6 Dec 2005, at 10:20, Walker She wrote:







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