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[protege-owl] how to query an owl ontology

James Howison james at howison.name
Wed May 21 04:36:59 PDT 2008


On May 20, 2008, at 7:13 PM, Martin O'Connor wrote:

> anuj kumar wrote:
>
>> SPARQL is used to query RDF , so does that mean OWL is first  
>> converted
>> to an RFD representation while implementing SPARQL queries with jena
>> and since RDF is not as rich as OWL we don't get good results using
>> SPARQL with OWL. Is my understanding correct?
>
> Yes. When applied to OWL, SPARQL is typically used to query the
> serialized RDF representation of an OWL ontology. This is problematic
> because this serialization can be extremely complex and is not
> deterministic.

Thanks, this is interesting.  I had thought that the RDF  
representation of OWL was deterministic and that SPARQL against a  
'fully-reasoned' model, while not always as convenient as one would  
want, was at least fully capable.  Are there any resources around that  
explain the non-determinacy of OWL as RDF?

This is helpful on SPARQL-DL:

http://clarkparsia.com/weblog/2007/10/26/towards-sparql-dl-evaluation-in-pellet/

Although I've been doing SPARQL queries via Jena that look very  
similar to the examples using the current implementation of SPARQL  
against a 'fully-reasoned' (ie writeAll) model.

Thanks,
James

>
> Martin
>
>>
>> Anuj
>>
>> On Tue, May 20, 2008 at 6:28 PM, Martin O'Connor
>> <martin.oconnor at stanford.edu <mailto:martin.oconnor at stanford.edu>>  
>> wrote:
>>
>>
>>    SPARQL is pretty poor at querying OWL because it has no
>>    understanding of
>>    its semantics. You could try SQWRL, which is based on OWL:
>>    http://protege.cim3.net/cgi-bin/wiki.pl?SQWRL
>>
>>    Martin
>>
>>    anuj kumar wrote:
>>
>>> Hi,
>>>
>>> I have an owl ontology and my objective is to query the file
>>    based on
>>> the parameters passed by a user. I am at the very beginning of this
>>> implementation. I went through the tutorial of jena and sparql and I
>>> have some very basic questions:-
>>> Q1) Sparql is used to query RDF and not owl files correct? Then how
>>> does jena query the owl files using sparql.
>>> Q2) Which is the most widely used language to query owl files?
>>>
>>> Anuj
>>>
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