- From: Pat Hayes <phayes@ihmc.us>
- Date: Fri, 20 Mar 2009 12:43:46 -0500
- To: "Michael Schneider" <schneid@fzi.de>
- Cc: Reto Bachmann-Gmür <reto.bachmann@trialox.org>, "Semantic Web" <semantic-web@w3.org>, "Bijan Parsia" <bparsia@cs.man.ac.uk>
On Mar 20, 2009, at 11:59 AM, Michael Schneider wrote: >> -----Original Message----- >> From: semantic-web-request@w3.org [mailto:semantic-web- >> request@w3.org] >> On Behalf Of Reto Bachmann-Gmür > >> The example 2 violates what's the convention described by RDF >> semantics, >> however I see no way to add tbox statements with the (current) >> expressivitiy of OWL that would contradict this graph. > > Me neither. > > [...] > >>> (2) Lists should not be cyclic, though this is possible with RDF >>> lists: >>> >>> A -> B >>> ^ | >>> | v >>> D <- C > > Try to express such a general cycle prohibition axiom! This would > roughly > need to say something like: > > For any non-negative integer n: > there must not be nodes x1,...,xn > such that > x1 rdf:rest x2 > x2 rdf:rest x3 > ... > xn rdf:rest x1 > > If the cycle size would be restricted, one could express this by a > finite > set of axioms (I'm not necessarily talking about OWL here). But the > cycles > may be arbitrarily large, so this is not possible. Yes. This isn't a problem that can be hacked around. Basically, FOL plus a min-fixed-point recursion is intrinsically more expressive than plain FO logic. We've been exploring this space in the Common Logic effort, in order to make better sense of the sequence-marker construction, which provides a form of recursive extension. In CL, this axiom would do what you want here: (forall (x y ...)(not (and (rdf:rest x y)(RestLoopEnd x y ...)))) (forall (x y)(iff (RestloopEnd x y)(= x y))) (forall (x y z ...)(iff (RestloopEnd x y z ...)(and (rdf:rest y z) (RestloopEnd x z ...) Pat > > Michael > > -- > Dipl.-Inform. Michael Schneider > Research Scientist, Dept. Information Process Engineering (IPE) > Tel : +49-721-9654-726 > Fax : +49-721-9654-727 > Email: michael.schneider@fzi.de > WWW : http://www.fzi.de/michael.schneider > = > ====================================================================== > FZI Forschungszentrum Informatik an der Universität Karlsruhe > Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe > Tel.: +49-721-9654-0, Fax: +49-721-9654-959 > Stiftung des bürgerlichen Rechts, Az 14-0563.1, RP Karlsruhe > Vorstand: Prof. Dr.-Ing. Rüdiger Dillmann, Dipl. Wi.-Ing. Michael > Flor, > Prof. Dr. Dr. h.c. Wolffried Stucky, Prof. Dr. Rudi Studer > Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus > = > ====================================================================== > ------------------------------------------------------------ IHMC (850)434 8903 or (650)494 3973 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32502 (850)291 0667 mobile phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
Received on Friday, 20 March 2009 17:44:29 UTC