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Re: SPARQL Query language for RDF

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Mon, 06 Aug 2007 09:48:26 +0100
Message-ID: <46B6E05A.9000108@hp.com>
To: Malcolm Crowe <CROW-CI0@wpmail.paisley.ac.uk>
CC: public-rdf-dawg-comments@w3.org



Malcolm Crowe wrote:
> 
> Hi,

Hi Malcolm,

> I have noticed some small errors in section 12:
> 12.2.1 in the algorithm, LeftJoin(G,A,true) should read LeftJoin(G,SA,true)

In the conversion from query string to algebra expression, OPTIONAL translates 
to LeftJoin so OPTIONAL.  When SA is OPTIONAL(A), that is the syntax word 
OPTIONAL and a term already converted because the algorithm works bottom-up,
then the outcome is LeftJoin (G,A,true), the A being taken from the OPTIONAL. 
  The document is correct.

> 12.5 the evaluation of Filter(P,F) should read
> eval(D(G),Filter(P,F)) = Filter(eval(D(G),p),F)

Yes - it seems to have lost the pattern - correected to:

eval(D(G), Filter(F, P)) = Filter(F, eval(D(G), P))

The pattern and filter were the wrong way round as well.

Thank you for your comments,

	Andy


> Best wishes
> Malcolm
>  
> 
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Received on Monday, 6 August 2007 08:48:42 GMT

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