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Re: Standardise method for selecting extensions for DESCRIBE

From: Gregory Williams <greg@evilfunhouse.com>
Date: Sat, 31 Jul 2010 15:04:27 -0400
Cc: public-rdf-dawg-comments@w3.org
Message-Id: <3BE61EFD-7391-4F4B-B37A-E3C99200188C@evilfunhouse.com>
To: Peter Ansell <ansell.peter@gmail.com>
On Jun 22, 2010, at 6:02 PM, Peter Ansell wrote:

> It would be nice with the SPARQL review if there could be a minor
> change to the DESCRIBE query syntax to support optional selection of
> the way DESCRIBE should work.
> For example, even if I know that my SPARQL endpoint supports different
> types of DESCRIBE queries, such as Concise Bounded Description [1] and
> Symmetric Concise Bounded Description and basic Subject Predicate
> Object (with or without inferences), there is no standard way of
> telling a DESCRIBE query to use one over the other.
> A syntax may be "DESCRIBE [USING <METHODURI>] <URI>" or any other way
> that is substantially backwards compatible. The METHODURIs for some
> common methods could be suggested, with any new methods being easily
> extensible using URIs that anyone else publishes.
> This wouldn't change the best guess approach that was originally
> standardised for DESCRIBE, but it would give a user some standard way
> of selecting their preferred DESCRIBE method in some cases.


The ability to choose a DESCRIBE algorithm was one of the features proposed[1]
for inclusion in SPARQL 1.1. However, compared to several other features which
will be in SPARQL 1.1, there was little support within the working group for
standardizing a means of choosing a DESCRIBE algorithm.

> Even if this feature doesn't get through, it would be nice to have the
> DESCRIBE query method as a required element the SPARQL Service
> Description so I could at least identify the method that would be used
> by default for an endpoint.

The SPARQL 1.1 Service Description document currently describes a sd:feature
property meant for use in describing arbitrary features of a SPARQL endpoint.
Provided a URI for a DESCRIBE algorithm, a service description could describe
its implementation with:

 [] a sd:Service ;
 	sd:feature <http://www.example.org/closure/concise-bounded-desc> ;

Does this use of sd:feature fit your needs?

Gregory Williams
(on behalf of the SPARQL Working Group)

 [1] http://www.w3.org/2009/sparql/wiki/Feature:ControlOfDescribeQueries
 [2] http://www.w3.org/TR/sparql11-service-description/
Received on Saturday, 31 July 2010 19:04:58 UTC

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