W3C home > Mailing lists > Public > public-rdf-dawg@w3.org > July to September 2009

Re: More on MINUS vs. UNSAID

From: Eric Prud'hommeaux <eric@w3.org>
Date: Tue, 28 Jul 2009 08:34:13 -0400
To: Lee Feigenbaum <lee@thefigtrees.net>
Cc: SPARQL Working Group <public-rdf-dawg@w3.org>, "Seaborne, Andy" <andy.seaborne@hp.com>
Message-ID: <20090728123413.GA3192@w3.org>
* Lee Feigenbaum <lee@thefigtrees.net> [2009-07-27 17:41-0400]
> Eric Prud'hommeaux wrote:
>> ISSUE-29
>> I believe this definition of Minus in SPARQL algebra is practical for all use cases:
>>   Definition: Minus
>>   Let Ω1 and Ω2 be multisets of solution mappings. We define:
>>   Diff(Ω1, Ω2, expr) = { μ | μ in Ω1 such that for all μ′ in Ω2, μ and μ′ are not compatible }
>>   card[Diff(Ω1, Ω2, expr)](μ) = card[Ω1](μ)
>> which is the same as Diff (Ω1, Ω2, true)
>>   http://www.w3.org/TR/rdf-sparql-query/#defn_algDiff
> That's the same as the MINUS-AntiJoin from my message  
> (http://lists.w3.org/Archives/Public/public-rdf-dawg/2009JulSep/0030.html), 
> right?


> I don't think that matched the intuition of most people that advocated  
> MINUS on the teleconference, who preferred this definition with the  
> added restriction that prevented removing solutions from the left-hand  
> side that share no variables in common with any solutions from the  
> right-hand side. (MINUS-AntiJoin+Restriction)

yes again, let's fix that:

   Diff(Ω1, Ω2, expr) = { μ | μ in Ω1 such that for all μ′ with non-empty dom() in Ω2, μ and μ′ are not compatible }
> Lee


office: +1.617.258.5741 32-G528, MIT, Cambridge, MA 02144 USA
mobile: +1.617.599.3509

Feel free to forward this message to any list for any purpose other than
email address distribution.

There are subtle nuances encoded in font variation and clever layout
which can only be seen by printing this message on high-clay paper.
Received on Tuesday, 28 July 2009 12:35:00 UTC

This archive was generated by hypermail 2.3.1 : Wednesday, 7 January 2015 15:00:57 UTC