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Re: Negation decision : unexpected effects

From: Andy Seaborne <andy.seaborne@talis.com>
Date: Tue, 06 Apr 2010 09:07:39 +0100
Message-ID: <4BBAEBCB.2090400@talis.com>
To: Steve Harris <steve.harris@garlik.com>
CC: Lee Feigenbaum <lee@thefigtrees.net>, SPARQL Working Group <public-rdf-dawg@w3.org>


On 05/04/2010 10:16 PM, Steve Harris wrote:
> On 2010-04-05, at 21:51, Lee Feigenbaum wrote:
>>>>
>>>> I wouldn't be in favor of this proposal - I'd find it very difficult to
>>>> justify adding 2 forms of negation to SPARQL that seem virtually
>>>> indistinguishable from one another in most scenarios.
>>>
>>> We are doing that under the F2F3 resolution (the second one) regardless
>>> of my proposal and under the first proposal of the F2F, negation used
>>> the syntax "NOT EXISTS".
>>
>> I believe that most of the user world would simply accept that the words used for negation as a graph pattern and negation in a filter are different. I don't think any such easy explanation can be given when both can be used as graph pattern keywords.
>
> Indeed, SQL has the MINUS table operation, and NOT EXISTS in the WHERE/FILTER operation as well.

In SQL, MINUS goes outside SELECT, making it outside GROUP BY and 
separate from the join condition part of the SQL query.

	Andy
Received on Tuesday, 6 April 2010 08:08:11 GMT

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