W3C home > Mailing lists > Public > public-rdf-dawg-comments@w3.org > June 2010

Standardise method for selecting extensions for DESCRIBE

From: Peter Ansell <ansell.peter@gmail.com>
Date: Wed, 23 Jun 2010 08:02:39 +1000
Message-ID: <AANLkTik_Cb9sAGDZW1_DMoGj0gm0yxTnG9AuThqwP388@mail.gmail.com>
To: public-rdf-dawg-comments@w3.org

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.

Virtuoso currently offer this ability using SQL define commands
attached to the front of a SPARQL query [2].

Personally I never use SPARQL DESCRIBE because I have no way of
knowing which method is going to be used, and I don't want to be
flooded with triples if the method is Symmetric Concise Bounded
Description for instance, and the URI is in the object position of a
large number of statements that are not relevant to me right now. It
would nice to be able to get the ability to discover Blank Nodes in an
Asymetric way, as you can't iteratively find Blank Nodes using the
results of past queries that you can do if all subjects and objects
are URIs.

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.

Sorry if this feature has been brought up before. I couldn't find it
with my searching.



[1] http://www.w3.org/Submission/CBD/
[2] http://docs.openlinksw.com/virtuoso/rdfsparql.html#rdfsqlfromsparqldescribe
Received on Tuesday, 22 June 2010 22:03:12 UTC

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