W3C home > Mailing lists > Public > public-rdf-dawg@w3.org > April to June 2010

Re: Negation decision : unexpected effects

From: Steve Harris <steve.harris@garlik.com>
Date: Tue, 6 Apr 2010 10:19:01 +0100
Cc: Lee Feigenbaum <lee@thefigtrees.net>, SPARQL Working Group <public-rdf-dawg@w3.org>
Message-Id: <2EBA03AE-ED39-41B2-977C-45C21F1D04A1@garlik.com>
To: Andy Seaborne <andy.seaborne@talis.com>
On 2010-04-06, at 09:59, Andy Seaborne wrote:
> On 06/04/2010 9:20 AM, Steve Harris wrote:
>> On 2010-04-06, at 09:07, Andy Seaborne wrote:
>>> 
>>> 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.
>> 
>> Yup, but so do the other table operations, UNION and friends.
> 
> SPARQL UNION does not need the column compatibility rules.  We don't have INTERSECTION directly ... yet.

Well, SQL UNION has rules that there must be the same number of columns, and of the same type - SPARQL's UNION is much laxer. This is a good thing IMHO, though I wasn't convinced of that during the previous WG :)

SQL doesn't really have a notion of "compatibility" beyond that.

- Steve

-- 
Steve Harris, Garlik Limited
1-3 Halford Road, Richmond, TW10 6AW, UK
+44 20 8439 8203  http://www.garlik.com/
Registered in England and Wales 535 7233 VAT # 849 0517 11
Registered office: Thames House, Portsmouth Road, Esher, Surrey, KT10 9AD
Received on Tuesday, 6 April 2010 09:19:30 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 16:15:42 GMT