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RE: "Transitive over" properties

From: Peter Crowther <Peter.Crowther@melandra.com>
Date: Sun, 4 Jan 2004 20:58:17 -0000
Message-ID: <DDBBD1E00935D144AB9563D57EF98D6253EB@raccoon.melandra.net>
To: "Jos De_Roo" <jos.deroo@agfa.com>, "Mikhail Khlopotov" <mik@chel.com.ru>
Cc: "www-rdf-logic" <www-rdf-logic@w3.org>

> From: Mikhail Khlopotov
> I found no direct way to express "transitive over"
> properties, I mean properties, which are not transitive by 
> themselves, but are transitive over another property.

I seem to recall a proof that such relations plus inverses, possibly
plus cardinality, is undecidable --- I'm out of that area at the moment,
so would have to check the literature for precise details.  I suspect a
number of the other people on the list could provide a reference from
memory.  It was for this reason of undecidability that the feature was
not included in OWL-DL.

Some other KR formalisms have them, notably GRAIL
(http://www.opengalen.org/ is probably a good place to start for GRAIL).
An alternative approach to part-whole relations that may fit with OWL-DL
uses SEP triples.  This uses three classes rather than one, to denote
(i) the thing as a whole, (ii) the thing and its parts, and (iii) the
parts.  Apparently it is then possible to represent part-whole
relationships, moderately sensibly, without needing transitive-over
relationships.  I know Professor Alan Rector at University of Manchester
has been working on using this approach with OWL; I don't know how far
he's got, as it's over a year since I last spoke to him about this.

Sorry not to have more information to hand; I hope what little I can
provide is of some use!

		- Peter
--
Peter Crowther, Director, Melandra Limited
Received on Sunday, 4 January 2004 15:58:11 GMT

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