- From: Bijan Parsia <bparsia@cs.man.ac.uk>
- Date: Sun, 5 Sep 2010 16:26:36 +0100
- To: Axel Polleres <axel.polleres@deri.org>
- 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>
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]). [snip] 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. Cheers, Bijan.
Received on Sunday, 5 September 2010 15:27:06 UTC