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Re: Question on the SPARQL spec

From: Lee Feigenbaum <lee@thefigtrees.net>
Date: Sun, 28 Oct 2007 15:05:12 -0400
Message-ID: <4724DD68.1080808@thefigtrees.net>
To: Francis McCabe <frankmccabe@mac.com>
CC: public-rdf-dawg-comments@w3.org

Yes. This is correct in the editor's draft.

http://www.w3.org/2001/sw/DataAccess/rq23/rq25.html

Lee

Francis McCabe wrote:
> 
> The semantics of LeftJoin read
> 
> Definition: LeftJoin
> Let Ω1 and Ω2 be multisets of solution mappings and F a filter. We define:
> 
> LeftJoin(Ω1, Ω2, expr) = Filter(expr, Join(Ω1, Ω2)) set-union Diff(Ω1, 
> Ω2, expr)
> 
> card[LeftJoin(Ω1, Ω2, expr)](μ) = card[Filter(expr, Join(Ω1, Ω2))](μ) + 
> card[Diff(Ω1, Ω2, expr)](μ)
> 
> 
> 
> Presumably, this should read
> 
> Definition: LeftJoin
> 
> Let Ω1 and Ω2 be multisets of solution mappings and expr a filter. We 
> define:
> 
> LeftJoin(Ω1, Ω2, expr) = Filter(expr, Join(Ω1, Ω2)) set-union Diff(Ω1, 
> Ω2, expr)
> 
> card[LeftJoin(Ω1, Ω2, expr)](μ) = card[Filter(expr, Join(Ω1, Ω2))](μ) + 
> card[Diff(Ω1, Ω2, expr)](μ)
> 
> 
> 
> 
> Frank McCabe
> 
> 
> 
Received on Sunday, 28 October 2007 19:05:27 GMT

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