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Re: grouping by expressions

From: Steve Harris <steve.harris@garlik.com>
Date: Wed, 3 Nov 2010 17:13:31 +0000
Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
Message-Id: <595BDD4F-9D8E-4BA1-8862-611F36972931@garlik.com>
To: Andy Seaborne <andy.seaborne@epimorphics.com>
On 2010-11-03, at 16:22, Andy Seaborne wrote:
> 
> On 03/11/10 15:42, Steve Harris wrote:
>>> ex:agg(?y, ?z)+1 is an expression - it needs a solution to calculate the "+".
>> Yeah, makes sense in Projection, but that doesn't apply to grouping, does it? "Naming" expressions is compulsory in SELECT already, as they have to be associated with some variable name in the result format.
>> 
> 
> And before the projection step?
> 
> If we have
> 
> SELECT (ex:agg1(?y, ?z)+ex:agg2(?y, ?z)+1 AS ?A)
> {
> ...
> }
> GROUP BY ?x
> 
> then in each row, each ex:agg?(?y, ?z) needs to turn into a value. Operator + evaluates each argument, then calls op:numeric-add.
> 
> How, in expression evaluation, does ex:agg1(?y, ?z) get mapped to a value?  I would like to avoid wholesale changes to expression evaluation unless there is no other way.

Yep, that's fair enough.

- Steve

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Received on Wednesday, 3 November 2010 17:14:08 GMT

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