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Re: When is HAVING processed?

From: Alex Miller <alex@puredanger.com>
Date: Thu, 8 Dec 2011 16:37:30 +0000
Message-ID: <CAOdgdgyeFm9TEqYyh3B8_-Erm3HRVUJ-iVeLpwS5iqLdf-Bikg@mail.gmail.com>
To: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
Cc: Alex Miller <amiller@revelytix.com>, public-rdf-dawg-comments@w3.org
Acknowledged... thanks.

On Thu, Dec 8, 2011 at 11:07 AM, Birte Glimm
<birte.glimm@comlab.ox.ac.uk> wrote:
> Alex,
>
> Thank you for your comment about the SPARQL 1.1 Query specification.
>
> We agree that there was some inconsistency in the specification and
> your observation about the wrong order of items at the beginning of
> 18.2.4 is fixed in the current editors' draft, see
> http://www.w3.org/2009/sparql/docs/query-1.1/rq25.xml#convertGroupAggSelectExpressions.
>
> We would be grateful if you would acknowledge that your comment has
> been answered by sending a reply to this mailing list.
>
> Birte, on behalf of the SPARQL-WG
>
> On 3 November 2011 16:06, Alex Miller <amiller@revelytix.com> wrote:
>> I've been puzzling over the SPARQL spec trying to determine the intent as to
>> when the HAVING clause is executed.
>>
>> In particular, re section 18.2.4:
>> http://www.w3.org/TR/sparql11-query/#convertGroupAggSelectExpressions
>>
>> The link above lists processing in the order of: Grouping, Aggregates,
>> Bindings, Select exprs, and Having.
>> However, the sub-sections of 18.2.4 are listed in the order of: Grouping and
>> Aggregation, HAVING, BINDINGS, SELECT Expressions.  Note that HAVING is
>> listed in a different order than #1.
>> In the Grouping and Aggregation section (18.2.4.1), the algorithm given
>> shows the HAVING filters being executed at the end of the Grouping step.
>> In the Having section (18.2.4.2) it says "Note that, due to the logic
>> position in which the HAVING clause is evaluated, expressions projected by
>> the SELECT clause are not visible to the HAVING clause."  This seems to be
>> in alignment with #2.
>>
>> #2-4 seem consistent and I thus conclude that the list at the beginning of
>> 18.2.4 is ordered incorrectly and should say:
>>
>> Grouping
>> Aggregates
>> Having   // moved from end
>> Bindings
>> Select exprs
>>
>> Have I correctly interpreted the intent?  If so, can this issue be resolved
>> in a future draft?
>>
>> Thanks,
>> Alex Miller
>> Revelytix
>>
>
>
>
> --
> Dr. Birte Glimm, Room 309
> Department of Computer Science
> University of Oxford
> Parks Road
> Oxford
> OX1 3QD
> United Kingdom
> +44 (0)1865 283520
>
Received on Thursday, 8 December 2011 16:38:23 GMT

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