- From: Lee Feigenbaum <lee@thefigtrees.net>
- Date: Mon, 27 Jul 2009 17:41:06 -0400
- To: Eric Prud'hommeaux <eric@w3.org>
- CC: SPARQL Working Group <public-rdf-dawg@w3.org>, "Seaborne, Andy" <andy.seaborne@hp.com>
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)
Lee
Received on Monday, 27 July 2009 21:42:03 UTC