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Re: First order logic and SPARQL

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Sun, 5 Sep 2010 16:26:36 +0100
Cc: "Bob MacGregor" <bob.macgregor@gmail.com>, "Juan Sequeda" <juanfederico@gmail.com>, "Jitao Yang" <jitao.yang@gmail.com>, <semantic-web@w3.org>, <public-sparql-dev@w3.org>
Message-Id: <8CE02387-D9FA-47F1-BF9F-29C4BC01105A@cs.man.ac.uk>
To: Axel Polleres <axel.polleres@deri.org>
On 5 Sep 2010, at 16:17, Axel Polleres wrote:

>>> The problem with SPARQL stems from the OPTIONAL operator.  A mantra
>>> of RDF has been that it
>>> has open world semantics.  The OPTIONAL operator is inherently non-
>>> monotonic.
>> ?? I don't think so. I'd be interested in a reference.
> Obviously OPTIONAL is nonmomotonic and in fact, NOT EXISTS can be  
> emulated not only
> with the widely known OPTIONAL + FILTER !Bound() trick (see [1]  
> Query #13 for an example),
> but you actually don't need the FILTER even (see Query #14 in the  
> same tutorial [1]).

Thanks, brain fart on my part. (It was a chain from relational algebra/ 
calculus correspondence. Oh well :))

However, I think the point that SPARQL/1.0 is well defined in terms of  
the relational algebra holds. Your work validates that.

Received on Sunday, 5 September 2010 15:27:06 UTC

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