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Re: Definition: Group in query editor's draft

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Thu, 23 Sep 2010 08:36:26 +0100
Message-ID: <4C9B037A.6060408@epimorphics.com>
To: Axel Polleres <axel.polleres@deri.org>
CC: SPARQL Working Group <public-rdf-dawg@w3.org>


On 22/09/10 06:59, Axel Polleres wrote:
> I have a small question about the Definition of "Group" in the query draft:
>
> "Group((),&Omega;) = { 1 ->  &Omega; }"
>
> ... shouldn't that be:
>
> "Group((),&Omega;) = { () ->  &Omega; }"
>
> i.e., what is the 1 supposed to mean?

The 1 is any key.  When the set of groups keys is the empty, which 
happnes for

SELECT (count(*) AS ?c) { ?s ?p ?o }

then there needs to be a key value for the group.

It could be said to be slightly more sense to be (1), not 1, as it's a 
list when then the key isn't empty.  The key just needs to be unique, 
and here, there is only one key so it's arbitrary.

	Andy

>
> Thanks for clarification,
> Axel
>
>
>
>
Received on Thursday, 23 September 2010 07:37:02 GMT

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