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Re: Possible Service Description change

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Tue, 19 Jun 2012 11:10:24 +0100
Message-ID: <4FE05010.5050607@epimorphics.com>
To: public-rdf-dawg@w3.org


On 19/06/12 02:50, Gregory Williams wrote:
> I ran across an issue I was hoping for some input on. As a result of
> working on the protocol tests, and reading David Booth's recent
> comment on how datasets get constructed[1], I looked over the
> documentation for sd:DereferencesURIs[2] which can provide some
> metadata that may help David's issue (and for which I've got an
> action to respond to his comment).
>
> The motivation for sd:DereferencesURIs was that some implementations
> (including mine) were already doing dereferencing to construct a
> dataset for query, and I just extended that in the spec to cover
> update, too. But now that I think more closely about it, I'm not sure
> it makes much sense. The current SD text reads:
>
> """ sd:DereferencesURIs, when used as the object of the sd:feature
> property, indicates that a SPARQL service willdereference [AWWW] URIs
> used in FROM/FROM NAMED and USING/USING NAMED clauses and use the
> resulting RDF in the dataset during query evaluation. """
 >
> I'm worried that the "USING/USING NAMED" part of that doesn't make
> any sense. That is, if an implementation constructed a dataset on the
> fly based on a USING clause, what use is there in performing an
> update operation? Presumably next time an update is submitted with a
> USING clause, the updated content in some underlying graphstore may
> again be masked by the dereferencing feature.

In a single update request there may be operations that use USING/USING 
NAMED and some that do not.  So one operation may use USING/USING NAMED 
to get a dynamically constructed dataset and the next operation does not 
use USING* so it can see the results of an earlier operation.

	Andy

> Does anybody have any thoughts on what the best way forward on this
> is? I can imagine this could get through REC without anyone noticing,
> but I'm not sure I'd be happy with that. Do you think it's worth the
> effort to make the change before moving to CR? I'm not aware of any
> implementations that do dereferencing for update (though there may be
> some), but I suspect a change like this would require another LC(?).
> Since we're already doing another LC round for Query, would this be a
> big deal?
>
> Interested in any thoughts you might have.
>
> thanks, .greg
>
>
> [1]
> http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2012Jun/0002.html
>
>
[2] http://www.w3.org/TR/sparql11-service-description/#sd-dereferencesuris
>
Received on Tuesday, 19 June 2012 10:11:48 GMT

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