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Re: Negation decision : unexpected effects

From: Andy Seaborne <andy.seaborne@talis.com>
Date: Mon, 05 Apr 2010 20:52:07 +0100
Message-ID: <4BBA3F67.7060005@talis.com>
To: Steve Harris <steve.harris@garlik.com>
CC: SPARQL Working Group <public-rdf-dawg@w3.org>


On 03/04/2010 8:45 AM, Steve Harris wrote:
> On 2010-04-02, at 22:05, Andy Seaborne wrote:
>> The FILTER could be artificially forced using a extra {}
>>
>> { { ?s rdf:type :T
>>     FILTER NOT EXISTS { ?s :p ?v . }
>>    }
>>     ?s :q ?v
>> }
>>
>> This is unnecessary - the more direct syntax is closer to the OPTIONAL/!BOUND idiom that I think it the important thing to make easier.
>
> !BOUND can only be used inside a FILTER as well (though OPTIONAL is not mobile) and users must be used to this, so I'm not sure this is a significant problem.
>
> The main reason I thought the compromise that was found at F2F3 was good was that it made it clear that NOT EXISTS was executed per solution, like a FILTER, and not as an algebraic operator.

FILTER is an algebra operation just like all the others.

	Andy

>
> - Steve
>
Received on Monday, 5 April 2010 19:52:41 GMT

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