- From: Steve Harris <steve.harris@garlik.com>
- Date: Thu, 7 Oct 2010 10:34:48 +0100
- To: Axel Polleres <axel.polleres@deri.org>
- Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
On 2010-10-07, at 02:31, Axel Polleres wrote:
> What happens when grouping for UNBOUND variables?
>
> E.g.
>
> Graph:
> :s1 :p :o1.
> :s1 :p :o2.
> :s1 :q :o3.
> :s2 :p :o1.
> :s2 :p :o2.
>
> Query:
>
> SELECT ?Q (COUNT(?P) as ?CP)
> WHERE { ?S :p ?P OPTIONAL {?S :q ?Q } }
> GROUP BY ?Q
>
> My current understanding is:
>
> that this returns
>
> ?Q | ?CP
> =========
> :o3 | 2
That's correct. It could be made clearer in the text though.
> rather than
>
> ?Q | ?CP
> =========
> :o3 | 2
> | 2
>
> yes?
>
>
> In general, what is unclear to me is what ListEval returns when for ExprList = ?var and μ(?var) undefined?
ListEval(undefined) = error.
> It seems, strictly following the definition μ(?var) would then just amount to ?var , then again, I don't know what that
> should mean for the rest of the aggregation semantics?
I'm not sure I understand.
- Steve
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Received on Thursday, 7 October 2010 09:35:22 UTC