- From: Jos De_Roo <jos.deroo@agfa.com>
- Date: Fri, 14 May 2004 00:33:17 +0200
- To: andy.seaborne@hp.com
- Cc: "'RDF Data Access Working Group'" <public-rdf-dawg@w3.org>, "'Rob Shearer'" <Rob.Shearer@networkinference.com>
>> I think requirement 3.8 brings up major questions about just
>> what we consider a "query". Does a "query" include a
>> selection of the RDF source, or can the same query be
>> executed against different sources? (The latter seems much
>> more sensible to me...)
>
> +1 : I don't see why the query should need to record the
> execution but I can be persuaded by an example. At the moment,
> I see it as a protocol matter concerned more with selecting
> the service access point.
Although I was used to put the selection of the RDF source(s)
in the protocol (e.g. as command line arguments) I became more
convinced that putting them in the query expression is also
interesting. For a simple example that asks for the lat/long
coordinates of Chicago or Cambridge, see
http://eulersharp.sourceforge.net/2004/04test/danQ.n3
i.e.
@prefix owl: <http://www.w3.org/2002/07/owl#>.
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
@prefix da: <http://eulersharp.sourceforge.net/euler#>.
@prefix d: <http://eulersharp.sourceforge.net/2004/04test/danP#>.
(d: owl: rdfs:).da:from da:select
{{?C d:cityName "Cambridge";
d:latitude ?LA;
d:longitude ?LO} => {("Cambridge" ?LA ?LO) a d:Result}},
{{?C d:cityName "Chicago";
d:latitude ?LA;
d:longitude ?LO} => {("Chicago" ?LA ?LO) a d:Result}}.
where that d: is actually one of the RDF sources
and the answer I actually got is
("Cambridge" 42.3 -71.1) a d:Result.
("Chicago" 41.9 -87.6) a d:Result.
--
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Thursday, 13 May 2004 18:34:02 UTC