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Re: Reasoning over millions of triples - any working reasoners?

From: William Waites <ww@styx.org>
Date: Tue, 18 Jan 2011 22:30:04 +0100
To: Ivan Mikhailov <imikhailov@openlinksw.com>
Cc: Harry Halpin <hhalpin@ibiblio.org>, Semantic Web <semantic-web@w3.org>
Message-ID: <20110118213004.GX19921@styx.org>
* [2011-01-19 01:48:27 +0600] Ivan Mikhailov <imikhailov@openlinksw.com> écrit:

] Virtuoso deals with owl:sameAs in a scalable way, so you can try. Of
] course, a single chain 50 million connections long would cause problems,
] but more traditional cases should work fine. Google for "virtuoso
] owl:same-as input:inference" may be the fastest way to get more hints.

Maybe I'm doing something wrong but in my experience
Virtuoso's owl:sameAs handling is not great. For example
in bibliographca we have,

foo a bibo:Book ; 
  dc:contributor [
     foaf:name "Bob";
     owl:sameAs <http://some/author>
  ].

When the http://some/author is dereferenced it will first
look for graph named that in the store. If it doesn't it
goes and asks the store for all triples that have that as 
a subject with sameAs processing turned on (would be nicer to
have a bnode closure, actually). If there are many books that
have contributor sameAs that (where many is maybe 50) the 
query takes too long and times out.

At this stage I would not recommend using Virtuoso's sameAs
processing and am going to materialise these graphs...

As far as strategies for dealing with sameAs are concerned,
I've been meaning to do some experiments regrouping them into
a congruence closure or bundle as its sometimes called, then
doing things like migrating all properties from the leaves
to the root. Some preprocessing that worked like that would
bake a database structure that was much easier to work with
instead of trying to solve things by implementing the formal
definition directly (and recursively!).

Cheers,
-w
-- 
William Waites                <mailto:ww@styx.org>
http://eris.okfn.org/ww/         <sip:ww@styx.org>
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Received on Tuesday, 18 January 2011 21:30:33 UTC

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