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Re: [limit per resource] implementation experience and/or concerns?

From: Steve Harris <steve.harris@garlik.com>
Date: Fri, 17 Apr 2009 13:15:24 +0100
Cc: public-rdf-dawg@w3.org
Message-Id: <F1EF4ED5-AA5D-4133-9A02-9E5542E9CE29@garlik.com>
To: Kjetil Kjernsmo <Kjetil.Kjernsmo@computas.com>
On 17 Apr 2009, at 09:51, Kjetil Kjernsmo wrote:

> On Friday 17 April 2009 06:34:13 Lee Feigenbaum wrote:
>> (just looking to get a bit of background discussion in advance of
>> tuesday, to save time on the teleconference)
>>
>> http://www.w3.org/2009/sparql/wiki/Feature:LimitPerResource
>
> So, this is our main feature. If I had only one vote this would be  
> it. :-)
>
>> LIMIT, in SPARQL, normally just limits the total number of results
>> returned. Combined with DISTINCT, it limits the total number of  
>> distinct
>> tuples returned. Combined with an aggregate/grouping extension, it  
>> can
>> limit the total number of groups returned.
>
> Yes, but that's only for SELECTs, while we work mainly with DESCRIBE  
> queries,
> so it has wider applicability than that.

Hm, interesting. The wiki page gives SELECT examples, and it's a  
little hard (for me at least) to imagine what it would look like in  
DESCRIBE land. Is it something you could do in CONSTRUCT? Or do you  
have a lot of per-schema smarts in your DESCRIBE implementation?

>> 2/ does anyone implement this elsewhere (e.g. in SQL)?
>
> It isn't very relevant to SQL, since SQL databases typically deal  
> with fixed
> schemas and uniform data. Since one of the main reasons why people  
> go to RDF
> and SPARQL is its usefulness in dealing with heterogenous data, this  
> is a
> feature that would distinguishing it from the rest, so in that sense  
> I don't
> see this question as very relevant. :-)

Agreed, but there are parallels. Subqueries + aggregates in SQL can do  
something like this.

- Steve

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Steve Harris
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Received on Friday, 17 April 2009 12:15:59 GMT

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