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

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Fri, 03 Jun 2005 18:21:08 +0100
Message-ID: <42A09184.10401@hp.com>
To: Dan Connolly <connolly@w3.org>
CC: Steve Harris <S.W.Harris@ecs.soton.ac.uk>, public-rdf-dawg@w3.org



Dan Connolly wrote:
> 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.

Steve - is there any text you can suggest to b eclear about this.  I've noted 
Dan's suggested text in the document so it gets incorporated.  Does it address 
the point you raised?

In particular, there shouldn't be an implication that the graph is obtained at 
query execution time.  Caching can always happen and one web cache is the local 
agent.

	Andy

> 
> 
>>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
Received on Friday, 3 June 2005 17:23:08 GMT

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