By the way,
I thought of using oracle-xe and dblinks to federate the RDBS. does d2rq
allows a table to be called, say, "ext_db.ext_ta...@my_link"?
Diogo F.C. Patrão
Manager of Medical Informatics
Biotechnology Laboratory
Hospital A.C. Camargo
http://www.accamargo.org.br/
On Wed, Dec 1, 2010 at 8:11 AM, Diogo FC Patrao <[email protected]>wrote:
> Hello Richard
>
> As for the practical needs I have, ETL seems the way to go, unfortunately.
> But I found a good tool (Pentaho community - download it at sourceforge)
> that seems very good to design and keep such a repository running.
>
> We're starting today a study group on d2rq source to try to contribute with
> d2rq, in the sense of fully supporting multiple databases connection by
> keeping queries over them separated. Could you suggest some starting point
> for us to begin with?
>
> Thanks!
>
> Diogo F.C. Patrão
> Manager of Medical Informatics
> Biotechnology Laboratory
> Hospital A.C. Camargo
> http://www.accamargo.org.br/
>
>
> On Wed, Dec 1, 2010 at 7:53 AM, Richard Cyganiak <[email protected]>wrote:
>
>> On 29 Nov 2010, at 14:13, Diogo FC Patrao wrote:
>>
>>> The rewriting engine is not designed to work with multiple DBs, so
>>>> sometimes it works by accident, but in general it won't.
>>>>
>>>
>>> Do you think that if we configure the query rewriting module to not JOIN
>>> databases, that would work?
>>>
>>
>> The easiest way of achieving this is running multiple instances of D2R
>> Server.
>>
>>
>> It would certainly be great if D2RQ had that ability. It's an open
>>>> source project and contributions are always welcome ...
>>>>
>>>
>>> That's definitely something I'm interested into, and would gladly give
>>> some
>>> of my employee's time to solve. Do you have an idea how exactly to solve
>>> this? Contact me in pvt if you wish.
>>>
>>
>> This goes into the direction of federated SPARQL queries. There is quite a
>> bit of research already out there, but I don't think that any really
>> practical solution has been described in the literature yet, so solving this
>> likely requires a fair bit of original research.
>>
>>
>> Anyways, if you want to integrate several data stores, at this point
>>>> I'd recommend either using the basic federated query feature of Andy
>>>> Seaborne's ARQ, or Extract-Transfer-Load them all into one triple store.
>>>>
>>>
>>> you mean this ? http://jena.sourceforge.net/ARQ/service.html
>>>
>>> So I would have several instances on D2R-Server mapping different
>>> databases
>>> to the same ontology, then query them with ARQ using this SERVICE
>>> statement?
>>>
>>
>> Yes. As stated on this page, it doesn't do any smart query planning, so
>> essentially you have to do the query planning yourself when writing the
>> query, but at least you can get results. See also:
>>
>> http://seaborne.blogspot.com/2007/07/basic-federated-sparql-query.html
>> http://www.w3.org/2009/sparql/docs/fed/service (just a draft, I think
>> it's not being further pursued by the working group at this point)
>>
>> Best,
>> Richard
>>
>>
>>
>>
>>> ETL is not the ideal for me, I have several production databases I want
>>> to
>>> integrate, and I would avoid dealing with DW updates.
>>>
>>> Thanks,
>>>
>>> dfcp
>>>
>>>
>>>
>>>
>>>> Best,
>>>> Richard
>>>>
>>>>
>>>>
>>>>> Regards
>>>>> Dr Christian Brenninkmeijer
>>>>> University of Manchester
>>>>>
>>>>>
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>>>>
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>
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