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Re: Aggregation Set Functions

From: Matthew Perry <matthew.perry@oracle.com>
Date: Fri, 11 Feb 2011 10:16:52 -0500
Message-ID: <4D5552E4.9040600@oracle.com>
To: Steve Harris <steve.harris@garlik.com>
CC: SPARQL Working Group <public-rdf-dawg@w3.org>
Ok. That works for me.

- Matt

On 2/11/2011 10:09 AM, Steve Harris wrote:
> It does as written, but that's an unintended consequence, the def'n of Count() will need to be change to not count error values.
>
> - Steve
>
> On 2011-02-11, at 14:00, Matthew Perry wrote:
>
>> Hi Steve,
>>
>> Lets say M = (1, 2, 3, "a", "b")
>>
>> Does this change COUNT(xsd:int(?x)) from 3 to 5?
>>
>> - Matt
>>
>> On 2/11/2011 7:03 AM, Steve Harris wrote:
>>> I've spoken with Andy on IRC, and he also agrees that it's probably better without it, so the current draft of rq25 doesn't have the error count argument.
>>>
>>> Following some discussion on IRC last night, I've also clarified the return types of the set functions.
>>>
>>> - Steve
>>>
>>> On 2011-02-11, at 10:55, Steve Harris wrote:
>>>
>>>> Hi all,
>>>>
>>>> Currently the Set Functions in Aggregates (ie. the underlying functions) are defined like:
>>>>
>>>> Func(M, errors, scalars)
>>>>
>>>> where M a multiset of the values from the group, e.g. if you have SUM(?x) and ?x is 1,2,3 in the group, then M = (1,2,3). But M is defined used ListEvalE(), so all the results which are errors are removed from the multiset.
>>>>
>>>> errors is a count of the errors (which where removed from M).
>>>>
>>>> I think it would be much simpler if instead M included the errors, and the error count argument was dropped, then it would be:
>>>>
>>>>    M = ListEval(exprlist, range(g))
>>>>
>>>>    func(M, scalarvals), for non-DISTINCT
>>>>    func(Distinct(M), scalarvals), for DISTINCT
>>>>
>>>> Dave B also complained about the error count argument saying it was redundant in his comment.
>>>>
>>>> I don't quite remember why it was included? I think Andy S might have suggested it, something about future extensibility? But I don't see what function it performs.
>>>>
>>>> So, my question is, can anyone think of a good reason to keep it?
>>>>
>>>> - Steve
>>>>
>>>> -- 
>>>> Steve Harris, CTO, Garlik Limited
>>>> 1-3 Halford Road, Richmond, TW10 6AW, UK
>>>> +44 20 8439 8203  http://www.garlik.com/
>>>> Registered in England and Wales 535 7233 VAT # 849 0517 11
>>>> Registered office: Thames House, Portsmouth Road, Esher, Surrey, KT10 9AD
>>>>
>>>>
Received on Friday, 11 February 2011 15:18:48 GMT

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