- 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>
> -----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) > 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 Friday, 31 July 2009 13:07:47 UTC