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Re: SPARQL Update - Clarifying correct behavior when a graph is created implicitly

From: Lee Feigenbaum <lee@thefigtrees.net>
Date: Tue, 01 Nov 2011 10:29:40 -0400
Message-ID: <4EB00254.4020704@thefigtrees.net>
To: David Booth <david@dbooth.org>
CC: public-rdf-dawg-comments <public-rdf-dawg-comments@w3.org>, eric neumann <eneumann@pangenx.com>, Ian Emmons <iemmons@bbn.com>
Hi David,

In response to: 
http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2011Sep/0008.html

 > Therefore, I suggest adding some clarification to this effect at the end
 > of the first paragraph in section 3.1:
 > http://www.w3.org/TR/sparql11-update/#graphUpdate
 > [[
 > If a graph is created implicitly by an update operation, then the
 > behavior of the Graph Store MUST be functionally equivalent to its
 > behavior if the graph had been created explicitly by a CREATE operation.
 > ]]

We have adopted this suggestion in the latest editor's draft:

http://www.w3.org/2009/sparql/docs/update-1.1/Overview.xml#graphUpdate

and would kindly ask you to acknowledge that this addresses your comment.

best,
Lee
On behalf of the SPARQL WG

On 9/13/2011 6:40 PM, David Booth wrote:
> The SPARQL Update spec indicates that "If data is inserted into a graph
> that does not exist in the graph store, it *should* be created":
> http://www.w3.org/TR/sparql11-update/#insertData
> However, I've run into an issue with one implementation (Parliament
> 2.7.1) in which the graph *is* created automatically in such
> circumstances, but the graph is not persisted in the store unless it was
> created explicitly using a CREATE operation.
>
> For example, the following query creates the named graph whether line 3
> is commented out or not:
>
>    PREFIX test:<http://example/test/>
>    DROP SILENT GRAPH test: ;
>    CREATE SILENT GRAPH test: ;   # Line 3
>    INSERT DATA
>    {
>      GRAPH test: { test:foo a test:bar }
>    }
>
> But if line 3 is commented out, then the graph is not persisted.
>
> I consider this a bug (and I assume the Parliament implementers will
> also, though I have not heard back from them yet) because it would lead
> to substantial compatibility issues for SPARQL update queries if some
> implementations persisted the graph and others did not.  But AFAICT, the
> SPARQL Update spec does not make clear that this behavior is wrong.
>
> Therefore, I suggest adding some clarification to this effect at the end
> of the first paragraph in section 3.1:
> http://www.w3.org/TR/sparql11-update/#graphUpdate
> [[
> If a graph is created implicitly by an update operation, then the
> behavior of the Graph Store MUST be functionally equivalent to its
> behavior if the graph had been created explicitly by a CREATE operation.
> ]]
>
> Thanks!
>
>
Received on Tuesday, 1 November 2011 17:10:57 GMT

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