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Re: Aggregation Set Functions

From: Steve Harris <steve.harris@garlik.com>
Date: Fri, 11 Feb 2011 15:09:29 +0000
Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
Message-Id: <4D4CE635-F4F0-4DC9-ADAC-4D9561599603@garlik.com>
To: Matthew Perry <matthew.perry@oracle.com>
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
>>> 
>>> 
> 

-- 
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 15:10:05 GMT

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