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Re: SPARQL 1.1 - LeftJoin definition

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Wed, 07 Dec 2011 13:42:12 +0000
Message-ID: <4EDF6D34.5050904@epimorphics.com>
To: David McNeil <dmcneil@revelytix.com>
CC: public-rdf-dawg-comments@w3.org


On 05/12/11 14:58, David McNeil wrote:
> On Mon, Dec 5, 2011 at 8:32 AM, Andy Seaborne
> <andy.seaborne@epimorphics.com <mailto:andy.seaborne@epimorphics.com>>
> wrote:
>
>         In addition, shouldn't the "or Ω_2 is empty" condition be
>         dropped from
>
>         one of these clauses so that we only include the contents of Ω1
>         one time
>         if Ω2 is empty?
>
>
> Andy - What are your thoughts on dropping the "or Ω2 is empty" from one
> of the clauses? Is my reading of this correct, that having this in both
> clauses causes duplicate solutions to be produced in the case where  Ω2
> is empty?

David,

I've removed it from the third clause

{ μ1 | μ1 in Ω1, ∃ μ2 in Ω2,
        μ1 and μ2 are compatible and expr(merge(μ1, μ2)) is false. }

It was requested originally (SPARQL 1.0) as not every one immediately 
notices that what happen in "for all" when that's empty.

	Andy
Received on Wednesday, 7 December 2011 13:42:38 GMT

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