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Re: another aggregates test case...

From: Steve Harris <steve.harris@garlik.com>
Date: Tue, 8 Jun 2010 14:14:52 +0100
Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
Message-Id: <87EC834D-4032-44F8-9A2A-AE0C85FD33B5@garlik.com>
To: Axel Polleres <axel.polleres@deri.org>
On 2010-06-08, at 14:07, Axel Polleres wrote:

> Student of mine pointed me to a somewhat corner test case:
> 
> PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> 
> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> 
> PREFIX dcterms: <http://purl.org/dc/terms/> 
> PREFIX foaf: <http://xmlns.com/foaf/0.1/> 
> PREFIX mpp: <http://imp.deri.ie/ontology/moviePostProcessing#> 
> 
> SELECT * 
> FROM NAMED <http://imp.deri.ie/vff/ppa/projects> 
> FROM NAMED <http://imp.deri.ie/vff/ppa/people> 
> WHERE {
> 
> ?project rdf:type foaf:Project ;
>          rdfs:label ?title .
> ?person rdf:type mpp:Person ;
>          rdfs:label ?personName ;
>          foaf:currentProject ?project .
> }
> GROUP BY ?project
> 
> Actually, I *think* this should be syntactically invalid, as per:
> "In aggregate queries and sub-queries only expressions which have been used as GROUP BY expressions, or aggregated expressions (i.e. expressions where all variables appear inside an aggregate) can be projected."
> 
> interestingly, the formulation - strictly speaking - doesn't say what an aggregate query is, but GROUP BY without aggregtate doesn't make a lot of sense anyways, except that it should have the same effect as DISTINCT, right(?), but we still don't want to allow in the presence of GROUP BY some non-grouped/aggregated things to be projected, I assume.

It wouldn't have the same affect as DISTINCT as per the current draft. Cardinality is preserved.

- Steve

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Received on Tuesday, 8 June 2010 13:15:36 GMT

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