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Re: Updated SPARQL Query Results XML Format draft

From: Steve Harris <S.W.Harris@ecs.soton.ac.uk>
Date: Thu, 14 Jul 2005 12:08:05 +0100
To: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-ID: <20050714110805.GI27994@login.ecs.soton.ac.uk>

On Thu, Jul 14, 2005 at 11:59:10AM +0100, Andy Seaborne wrote:
> >>Maybe you just need to know that the results are ordered - i.e. an
> >>isOrdered boolean flag.   Is isDistinct also needed?  Those seem to be
> >>the two crucial flags that tell you the four forms of variable bindings
> >>results you can get:
> >> 1. a bag (the default)
> >> 2. an ordered sequence (ORDER BY)
> >> 3. an ordered sequence with no duplicates (ORDER BY + DISTINCT)
> >> 4. a set (DISTINCT)
> >
> >
> >Maybe, I'm not clear on any situations where the client might not know, and
> >would care.
> 
> The only cases I see as being important in the result set
> 
> DISTINCTness is detectable in the results whereas ordering is not.
> 
> How about an optional attribute to the <results> element.
> 
>    <results order="true">
> 
> Then there is no consistency issue about funny index orders, missing 
> indexes, or duplicates.
> 
> The next complexity level would be to number the variable declarations in 
> the header indicating the order of the variables but that does not make 
> sense for function ordering.  So, just an indication in the <results> 
> element seems fine, if anything at all.

Why optional? order="false" seems pretty reasonable, and optional
things just make processing harder.

- Steve
Received on Thursday, 14 July 2005 11:08:41 GMT

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