- From: Dan Connolly <connolly@w3.org>
- Date: Tue, 27 Jul 2004 09:32:10 -0500
- To: Simon Raboczi <raboczi@tucanatech.com>
- Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
On Tue, 2004-07-27 at 05:22, Simon Raboczi wrote: > The current (CVS revision 1.128) text is > [[ > 4.5 Aggregate Query > > It should be possible to specify two or more RDF graphs against which a > query shall be executed; that is, the result of an aggregate query is > the merge of the results of executing the query on each of two or more > graphs. > ]] > > Previous discussion about "aggregate query" versus "union query" > occurred in a thread starting from [1]. > > We can build on top of the "merge" defined in RDF Semantics[2], and the > guarantee that "a set of graphs can be treated as equivalent to its > merge, i.e. a single graph, as far as the model theory is concerned." > I suggest text as follows: > [[ > 4.5 Querying multiple sources > > It should be possible for a query to specify which of the available RDF > graphs it is to be executed against. If more than one RDF graph is > specified, the result is as if the query had been executed against the > merge[3] of the specified RDF graphs. > ]] > > Processors with a single available RDF graph should trivially satisfy > this objective. I'd prefer to note that in the document. And I'd like a short discussion of the down-side of this feature. Perhaps: ... specified RDF graphs. Some services only offer to query one graph; they are considered to trivially satisfy this objective. While a variety of use cases motivate this feature, it is not a requirement because it is not clear whether this feature can be implemented in a generally scalable fashion. > > > [1] > http://lists.w3.org/Archives/Public/public-rdf-dawg/2004AprJun/ > 0777.html > [2] http://www.w3.org/TR/rdf-mt/ > [3] http://www.w3.org/TR/rdf-mt/#graphdefs -- Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Tuesday, 27 July 2004 10:31:55 UTC