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Re: negation as failure

From: Matthew Pocock <matthew.pocock@ncl.ac.uk>
Date: Wed, 4 Aug 2010 13:57:21 +0100
Message-ID: <AANLkTi=VUe12F1iqvYCUV1N3rg9k43ngjmV13vdL+c0T@mail.gmail.com>
To: Steve Harris <swh@ecs.soton.ac.uk>
Cc: Lee Feigenbaum <lee@thefigtrees.net>, "public-sparql-dev@w3.org" <public-sparql-dev@w3.org>

Using Joseki's web form, I've run the same queries. In this case, I get the
same number of results for:

?a rt:sim ?b . ?b rt:bi_to ?c . ?a rt:bi_to ?c

and the equivalent query using OPTIONAL/BOUND/FILTER:

?a rt:sim ?b . ?b rt:bi_to ?c
. OPTIONAL { ?a rt:bi_to ?c2 . FILTER(?c = ?c2) }

at 2,734 hits each. This differs from 4store which appears to be returning
5,800 hits for the first (simple) query but 2,734 for the latter (complex).
By eye, it looks like may of the 'extra' results from 4store contain nulls
for ?b which smells buggy to me.

Received on Wednesday, 4 August 2010 12:57:57 UTC

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