Re: federate several datasources

From: Jean-Marc Vanel (jmvanel_at_nospam.free.fr.removethis)
Date: 12/14/04 

Date: Tue, 14 Dec 2004 08:25:24 +0100

Robert Klemme wrote:
> "Jean-Marc Vanel" <jmvanel@nospam.free.fr.removethis> schrieb im
> Newsbeitrag news:41BB00A9.90406@nospam.free.fr.removethis...

>>I found these two open-source Java frameworks that seem interesting.
>>Daffodil might do what I want, but the configuration seems complicated.
>>
>>Daffodil Replicator Daffodil Replicator is a powerful Open Source data
>>replication tool that allows bi-directional data synchronization between
>>heterogeneous databases – Oracle, SQL Server, Postgre SQL, Derby,
>>Daffodil DB – supporting JDBC drivers, triggers and procedures.
>
>
> It can even replicate it's name in newsgroup postings. :-)
>
> That will actually move data around and thus make it possible that a
> single db does the join.
>
>
>>C-JDBC - Clustered JDBC gives your applications a transparent (no code
>>modification) access to a cluster of databases even if your database
>>engines are not cluster-aware.
>
>
> Thanks for that hint! That's interesting. Although, from quick glancing
> at the web site I'd say that all these databases must be schema
> compatible. I.e. the main point of C-JDBC is to route queries to
> different servers (although they can be different makes), but not to join
> results from different sources.
>
> Both products do not seem to meet your requirements perfectly but, yes,
> they could help, especially Replicator.

I'm considering still another open source product: XSB. It is an
enhanced Prolog engine writen in C++, with ODBC and Oracle connectors.
XSB can connect to *several* databases, turning the tables rows into
Prolog facts. It has a Java API. It doesn't expose the federated
databases as SQL, which can be an inconvenient if one wants to use SQL
tools. But on the other hand, Prolog is a more powerful language than
SQL, allowing to express rules and do reasoning based on these rules. 

-- 
Jean-Marc Vanel
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