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Re: Draft response to GK-1

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Tue, 19 Apr 2011 21:50:10 +0100
Message-ID: <4DADF582.6080307@epimorphics.com>
To: public-rdf-dawg@w3.org


On 19/04/11 21:34, Steve Harris wrote:
> Ping?
>
> - Steve

[[
 > Also, I can't find any indication of the interaction between GROUP BY 
and ORDER
 > BY, where the ORDER BY specifies a variable not named in the GROUP 
BY: is this
 > allowed? If so, what effect does it have (e.g. on GROUP_CONCAT)?

Aggregate operations are performed on a multiset, so order is not 
preserved. We have added an ISSUE [1] about whether or not to allow 
order for aggregates, which we will address if time allows it before 
going to last call. However, since we are on a tight schedule, we might 
have to move this feature for a future working group.
]]

Suggest adding:
"""
ORDER BY after a GROUP BY must only use variables exposed by the GROUP. 
  Use of non-grouping variable outside the GROUP BY is not legal and a 
required syntax error.
"""

For example:

SELECT ?book ?title
WHERE
    { ?book dc:title ?title }
GROUP BY ?book
ORDER BY ?title

==> error.

	Andy
Received on Tuesday, 19 April 2011 20:50:43 GMT

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