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Re: [Fwd: Unexpected DISTINCT?]

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Mon, 05 Mar 2007 09:29:13 +0000
Message-ID: <45EBE2E9.1080303@hp.com>
To: Bijan Parsia <bparsia@cs.man.ac.uk>
CC: Lee Feigenbaum <feigenbl@us.ibm.com>, RDF Data Access Working Group <public-rdf-dawg@w3.org>

Bijan Parsia wrote:
> In SQL, SELECT has two parameters, ALL and DISTINCT with ALL being  
> implicit.
> One way to handle the sort of variability in result set desired here  
> is to make ALL *not* be implicit, but have the bare SELECT mean  
> something like "something between ALL and DISTINCT depending on the  
> implementation".
> SQL defaults to ALL because, I think, of the strong perception that  
> it is "always" cheaper (which in fact depends on the relative cost of  
> pruning dups and transmitting them). Making the default "whatever the  
> implementation thinks is cheapest" seems in the spirit of this and  
> ALL allows access to the max sane result set (plus, implementations  
> can chose not to support it...it can be tricky in OWL since you'd  
> have to get all derivations...not impossible but non-trivial).
> Cheers,
> Bijan.

The cardinality for extensions of BGP matching isn't prescribed by the spec - 
it's just a matter of an extension deciding what is appropriate for it's 


which does not include anything on cardinality induced from blank nodes in 
BGPs.  Hopefully, that should give freedom to extended matchings such as OWL-DL.

Received on Monday, 5 March 2007 09:29:25 UTC

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