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Re: Name of a graph? and FROM and FROM NAMED

From: Dan Connolly <connolly@w3.org>
Date: Thu, 02 Jun 2005 08:54:51 -0500
To: Steve Harris <S.W.Harris@ecs.soton.ac.uk>
Cc: public-rdf-dawg@w3.org
Message-Id: <1117720491.19175.210.camel@localhost>

On Thu, 2005-06-02 at 13:45 +0100, Steve Harris wrote:
> On Thu, Jun 02, 2005 at 12:26:29PM +0100, Andy Seaborne wrote:
> > > The example in 8.1 implies this. But isn't  that the URL where the subgraph 
> > > was taken from?
> > 
> > For <http://> URLs , they should be read with GET (inc web caches etc).
> > 
> > If a system does not want to do web fetching, it wouydl give an error when the
> > query asked for fetching.
> > 
> > Should rq23 explicitly say <http://> implies GET?

Well, nearly... it should use the more general term "representation"
  http://www.w3.org/TR/webarch/#def-representation
ala...

  The FROM and FROM NAMED keywords allow a query to specify
  an RDF dataset by reference; they indicate that the dataset
  should include graphs that are obtained from representations
  of the resources identified by the given IRIs (i.e. the
  absolute form of the given IRI references). The dataset
  resulting from a number of FROM and FROM NAMED clauses
  is
   - a default graph consisting of the merge of the
   graphs referred to in the FROM clauses
   - a set of (IRI, graph) pairs, one from each FROM NAMED clause.


Here I'm not only using the "representation" terminology, but
also following Andy's later suggestion that FROM and FROM NAMED
completely specify the dataset (which seems somewhat
responsive to Yoshio's proposal, though it's not quite the same).


> > Does any one have an example where it woudl nto be GETted in some way?
> 
> Yes, in the case that the service is itsself a cache, and the service has
> chosen to identify graphs by thier resolved URIs, or where there is
> application level knowledge that the service should not resolve the URI
> for security or performance reasons.

Those cases seem consistent with the "representation" terminology, to
me.

> eg. I have a service that includes a lot of data, including the
> musicbrainz RDF data. It is identified by its web resolvable URI, if you
> want to search only that with FROM the obvious way is to use FROM
> <http://server/...>, but you dont want the service to re-fetch it (its
> around 20M triples, generated live,  and changes 10+ times a day).
> 
> - Steve
-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Thursday, 2 June 2005 13:54:58 GMT

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