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Re: Comments on aggregation in SPARQL 1.1

From: Graham Klyne <Graham.Klyne@zoo.ox.ac.uk>
Date: Wed, 18 May 2011 15:14:41 +0100
Message-ID: <4DD3D451.7020606@zoo.ox.ac.uk>
To: Lee Feigenbaum <lee@thefigtrees.net>
CC: Steve Harris <steve.harris@garlik.com>, public-rdf-dawg-comments@w3.org
Yes, that's the sort of thing I had in mind :)

#g
--

Lee Feigenbaum wrote:
> 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 14:25:22 GMT

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