Re: federation use case

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.

	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 09:14:49 UTC