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Re: Comments on aggregation in SPARQL 1.1

From: Lee Feigenbaum <lee@thefigtrees.net>
Date: Wed, 18 May 2011 08:53:15 -0400
Message-ID: <4DD3C13B.1080604@thefigtrees.net>
To: Graham Klyne <graham.klyne@zoo.ox.ac.uk>
CC: Steve Harris <steve.harris@garlik.com>, public-rdf-dawg-comments@w3.org
On 5/18/2011 3:19 AM, Graham Klyne wrote:
> For the purposes of your formal process, please treat this as
> acknowledgement of satisfactory resolution.
>
> ...
>
> Issue 2 is certainly resolved.
>
> For issue 1, I think the test cases probably help out, but they're not
> so easy to navigate for casual enquiry. Is there a human-readable
> version of the test case manifest? It seems much of the data is there
> from which one could be generated automatically.

Hi Graham,

Over the next several weeks, we will be looking at producing a human 
readable version of the test manifest, similar to what the SPARQL 1.0 WG 
did here: http://www.w3.org/2001/sw/DataAccess/tests/r2

Do you think that that would help this out?

Lee

>
> #g
> --
>
> Steve Harris wrote:
>> In response to
>> http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2010Sep/0000.html
>>
>>
>> > 1. Editorial
>> >
>> > I'm finding the section on aggregates is quite hard to follow.
>> >
>> > More examples, especially for GROUP_CONCAT, might make it easier
>> > to understand the link between the algebra and its practical
>> consequences
>> > in SPARQL queries.
>>
>> There is a balance between providing examples, and making the document
>> too long.
>>
>> The explanatory section on aggregates has been expanded, and there are
>> now some testcases for aggregates
>> http://www.w3.org/2009/sparql/docs/tests/data-sparql11/aggregates/ -
>> which hopefully illustrate the behaviour.
>>
>> > 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.
>>
>> The group discussed the possibility of adding this feature but decided
>> to postpone it to a future working group.
>>
>> Please note: “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.
>>
>> > 2. A Nice-to-have feature
>>
>> We understand that you have now seen another solution to this issue,
>> see
>> http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2010Oct/0001.html.
>>
>>
>> Could you please respond to this message saying whether this comment
>> has been answered to your satisfaction.
>>
>> Regards,
>> Steve, on behalf of the SPARQL Working Group
>>
>
>
>
Received on Wednesday, 18 May 2011 12:53:44 GMT

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