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Re: Go ahead with pub

From: Steve Harris <steve.harris@garlik.com>
Date: Mon, 2 Oct 2006 10:29:00 +0100
Message-Id: <71774F3D-82E8-4D66-BE9E-130FB52B7C4C@garlik.com>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
To: Bijan Parsia <bparsia@cs.man.ac.uk>


On 2 Oct 2006, at 10:14, Bijan Parsia wrote:

>
> Sorry to be late, but there was some confusion about what was going  
> on and then I hit the class part of the week.
>
> I think the status part should point to the issues list.
>
> """Costs: Tableau-based reasoners (at least, the Pellet Demo  
> example 7) rely on the current, more expressive semantics to match  
> implications that are not in a materializable RDF graph."""
>
> No. Pellet uses BNodes as syntax for non-distinguished variables,  
> as that's what we were told was the likely syntax for non- 
> distinguished variables in SPARQL/DL. The semantics of *all*  
> variables in SPARQL/RDF is semi-distinguished.
>
> I thought the alternative proposal (e.g., from conversation with  
> Jeen, Jorge and others) was to *drop* BNodes in triple patterns.  
> That does solve all the problems of scope, meaning etc., but it  
> means that certain combinations of the axes of distinguishedness  
> will be harder to specify (but heck, we can always introduce syntax  
> later).
>
> """@@ Now we are in CR, shouldn't this be deleted?  Need chair's  
> permission.
> The working group decided on this design and closed the disjunction  
> issue without reaching consensus. The objection was that adding  
> UNION would complicate implementation and discourage adoption. If  
> you have input to this aspect of the SPARQL that the working group  
> has not yet considered, please send a comment to public-rdf-dawg- 
> comments@w3.org."""

I believe that at the time OPTIONAL did not allow shared variables on  
OPTIONAL clauses that weren't in the parent clause. It makes a big  
difference to the complexity of the implementation.

- Steve
Received on Monday, 2 October 2006 09:29:15 GMT

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