Re: federation use case

Seaborne, Andy wrote:

>
> Could this be addressed with a general paramterised queries (see also 
> [1]) mechanism?  If CDDB and IMDB were on the same site it would be 
> nice to flow the paramters from the first query to the second without 
> a round trip back to the client.

I do not yet see the connection between federated queries and either 
parameterized queries or aggregate queries [1]. Parameterized queries 
(and Aggregate Queries) may be federated or not. I feel that federation 
is an orthogonal concept.

As an aside, I wanted to observe that the ebXML Registry use case is 
also touching on both the federated query and parameterized query.

-- 
Regards,
Farrukh


>
>     Andy
>
> [1] 
> http://lists.w3.org/Archives/Public/public-rdf-dawg/2004JulSep/0090.html
>
> Eric Prud'hommeaux wrote:
>
>> Joe wants to see what top 10 movies of also had top-ten soundtracks.
>> IMDB has information about movies and CDDB has info about music. Joe
>> writes a query that gets the titles of all the top 10 movies. These
>> are boudn to the variable ?t. He uses those bindings for ?t to then
>> query IMDB to filter out the ones that did not have top 10
>> soundtracks.
>>
>> from CDDB:
>> CONSTRUCT (?t foo bar)
>> WHERE (?m tt:rank ?rc)
>>       (?m cddb:soundtrack ?s)
>>       (?s dc:title ?t)
>> AND ?rc <= 10
>>
>> from IMDB:
>> SELECT ?t
>> WHERE (?r tt:rank ?ri)
>>       (?r dc:title ?t)
>> AND ?ri <= 10
>>
>>
>> This needs the ability to use variables bound in an earlier query to
>> constrain later queries. It also requires some sort of query
>> targeting. In algae, this looks like:
>>
>> ns tt=<...> ns cddb=<...> ns dc=<...>
>> attach <http://www.w3.org/...#remoteQuery> ?cddb (
>>             server=<http://cddb.com/rq>)
>> ask ?cddb ( ?m tt:rank ?rc {?rc <= 10} .
>>         ?m cddb:soundtrack ?s .
>>         ?s dc:title ?t )
>> attach <http://www.w3.org/...#remoteQuery> ?imdb (
>>             server=<http://imdb.com/querySrvc>)
>> ask ?cddb ( ?r tt:rank ?ri {?ri <= 10} .
>>         ?r dc:title ?t )
>> collect (?t)
>>
>>
>> This is very different from (more rigorous and expensive than) our
>> current definition of aggregate query [1]. Such a query would, if the
>> data is divided as the above queries suggest, return zero results.
>>
>> [1] http://www.w3.org/2001/sw/DataAccess/UseCases#d4.5
>
>

Received on Wednesday, 28 July 2004 09:33:51 UTC