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Re: Use case: AR-2: "Federated query"

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Thu, 18 Mar 2004 13:38:27 +0200
Message-Id: <C5DF32DD-78D0-11D8-9FBD-000A95EAFCEA@nokia.com>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
To: "ext Alberto Reggiori" <alberto@asemantics.com>


On Mar 18, 2004, at 13:24, ext Alberto Reggiori wrote:
>> (or have I missed something more fundamental, Alberto, in your test 
>> case?)
>
> my only concern in the AR-2 use-case was to start to consider the 
> possibility that DAWG queries might effectively spawn over the Web - 
> and then we might need some little syntactic sugar to express such a 
> federation bits into the query.
>
> (just to try to make you understanding what I meant)
>
> E.g. in an hypothetical extended RDQL syntax (almost playing here in 
> the example) i.e. "get me all items titles and they geo-position" - 
> where RSS items and their locations are sitting in two separated 
> sources
>
> SELECT
> 	?item ?title ?lat ?long
> FROM
> 	<file://my-rss-feeds.rdf>
> 	<jdbc:postgresql://www.foo.com:5555/lat-long>
> WHERE
> 	( ?db1 dc:source <file://my-rss-feeds.rdf> ) // local RDF/XML source
> 	( ?item rdf:type rss:item ?db1 )
> 	( ?item dc:title ?title ?db1 )
> 	( ?db2 dc:source <jdbc:postgresql://www.foo.com:5555/lat-long> ) // 
> remote SQL database
> 	( ?item geo:lat ?lat ?db2)
> 	( ?item geo:long ?long ?db2)
>
>
> I hope it is clearer now...


It is clearer. Your example above also relates to ongoing work on named
graphs that I find very interesting. However, I think that such issues
are out of scope for DAWG for two reasons:

1. It really is an implementational detail how one service might
    provide a unified point of access to a federation of other services,
    and I don't think it is a sufficiently acute need in the general
    community to consume WG time to innovate a solution.

2. I believe that whatever solution DAWG recommends, it should be
    in sync with the new RDF specs -- and so adding support for
    named graphs seems too significant an extension for this first round.

Of course, that's just my personal opinion, and the rest of the WG
may disagree (certainly won't be a first ;-)

Cheers,

Patrick

> cheers
>
> Alberto
>
>

--

Patrick Stickler
Nokia, Finland
patrick.stickler@nokia.com
Received on Thursday, 18 March 2004 06:39:30 GMT

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