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From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Mon, 29 Jun 2009 14:21:34 +0000
To: "public-rdf-dawg@w3.org" <public-rdf-dawg@w3.org>
Message-ID: <B6CF1054FDC8B845BF93A6645D19BEA3646EFD2D60@GVW1118EXC.americas.hpqcorp.net>

> -----Original Message-----
> From: public-rdf-dawg-request@w3.org [mailto:public-rdf-dawg-
> request@w3.org] On Behalf Of Simon Schenk
> Sent: 29 June 2009 10:36
> To: public-rdf-dawg@w3.org
> Subject: UNSAID vs MINUS
> ACTION-32  http://www.w3.org/2009/sparql/track/actions/32

> To revive the discussion on negation, I would like to point you to the
> overview of options for implementation at:
> http://www.w3.org/2009/sparql/wiki/Design:Negation

> In particular, binary operators vs. FILTER expressions, and set based
> MINUS in SeRQL vs UNSAID are discussed. Note that MINUS in SeRQL !=
> MINUS in Mulgara (?), which has the same semantics as UNSAID.
> Cheers,
> Simon

Good time to revive it.

(I reorganised the page end of Friday - didn't remove any text intentionally but I put the two options in separate sections.  I generally called it NOT EXISTS.)

To make progress on this, let's take it in two steps.

1/ Decide on UNSAID vs Set-MINUS, that is resolve to explore one design in depth

2/ Then take as a sub-issue of NOT EXISTS as to have a graph operator and/or a FILTER expression.

I propose we adopt the UNSAID/NOT EXISTS design.  The Set-MINUS seems to have no advantages because it is equivalent to an NOT EXISTS form, but requires each side to be a set, which would need to be worked through the rest of the language.

On the second part, I found it to be no more work as the graph operator is the introduction of  algebra-level filter.


Received on Monday, 29 June 2009 14:22:30 UTC

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