- From: Farrukh Najmi <Farrukh.Najmi@Sun.COM>
- Date: Wed, 28 Jul 2004 09:33:19 -0400
- To: andy.seaborne@hp.com
- Cc: "Eric Prud'hommeaux" <eric@w3.org>, public-rdf-dawg@w3.org
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