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RE: More on MINUS vs. UNSAID

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Fri, 31 Jul 2009 13:06:18 +0000
To: Eric Prud'hommeaux <eric@w3.org>, Lee Feigenbaum <lee@thefigtrees.net>
CC: SPARQL Working Group <public-rdf-dawg@w3.org>
Message-ID: <B6CF1054FDC8B845BF93A6645D19BEA36470A49211@GVW1118EXC.americas.hpqcorp.net>


> -----Original Message-----
> From: Eric Prud'hommeaux [mailto:ericw3c@gmail.com] On Behalf Of Eric
> Prud'hommeaux
> Sent: 28 July 2009 13:34
> To: Lee Feigenbaum
> Cc: SPARQL Working Group; Seaborne, Andy
> Subject: Re: More on MINUS vs. UNSAID
> 
> * 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?
> 
> yep
> 
> > 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:
> 

With the expr as well?

>    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 }
> 
> ++++++++++++++++++++

I don't understand dom() -- is it a typo?

Did you mean 

 intersection(dom(μ), dom(μ′)) is not empty?

In full:

{ μ | μ in Ω1 such that for all μ′ in Ω2 where 
        intersection(dom(μ), dom(μ′)) is not empty, 
        μ and μ′ are not compatible }

	Andy


> > Lee
> >
> >
> 
> --
> -eric
> 
> office: +1.617.258.5741 32-G528, MIT, Cambridge, MA 02144 USA
> mobile: +1.617.599.3509
> 
> (eric@w3.org)
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> 
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Received on Friday, 31 July 2009 13:07:47 GMT

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