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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