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Re: Comment on: rq25

From: Olivier Corby <Olivier.Corby@sophia.inria.fr>
Date: Mon, 21 Dec 2009 16:51:08 +0100
Message-ID: <4B2F996C.4090600@sophia.inria.fr>
To: Andy Seaborne <andy.seaborne@talis.com>, SPARQL Working Group <public-rdf-dawg@w3.org>
> 8 Negation - Testing for the absence of a pattern
> I am not really happy that the EXISTS and NOT EXISTS pattern can be used
> in a filter.
> Could you say why that is? 

It is a feeling about language design.
Graph pattern is about graph match and filter is about evaluable 
expressions. Here we  mix both and that looks strange to me...

> Yes it can be combined with any other expressions.  The effect of && 
> can be achieved anyway but not ||.
> FILTER( EXISTS {?x :tax :exempt} || ?taxCode = :special ) 
What about:

{EXISTS {?x :tax :exempt}} union  { NOT EXISTS {?x :tax :exempt} 
filter(?taxCode = :special) }

> The new variable is introduced using the keyword AS; it must not already
> be potentially bound.
> Do you have an suggestions for text changes? 
May be we can list the places where the 'variable' cannot be used ?

Received on Monday, 21 December 2009 15:51:43 UTC

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