- From: Peter Crowther <Peter.Crowther@melandra.com>
- Date: Sun, 4 Jan 2004 20:58:17 -0000
- 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 UTC