- From: Jeff Pan <pan@cs.man.ac.uk>
- Date: Thu, 6 Jan 2005 10:54:52 -0000
- To: "NANNI Marco RD-BIZZ-SOP" <marco.nanni@francetelecom.com>, <public-swbp-wg@w3.org>

C is satisfiable because of the semantics of (all R P), which is the set {x | for all y. <x,y> in I(R) implies y in I(P)}, where I is the interpretation function. In other words, any object x that does NOT relate to any other objects via R is an instance of C. How to make it more understandable? If we add the following axiom in the TBox :top <= (some R :top), where :top is the concept name for the object domain, which asserts that each object in the domain must relate to some object with R, then C is no longer satisfiable. For the same reason, D subsumes C. In fact, we can generalise D as D', where D'= (and (all R P') (all R E)), and we still have D' subsumes C. Informally (I mean, I am not giving a proof but only some hopefully intuitive description here), any object x that does not relate to any other objects via R is still an instance of D', AND any object x' that relates to instances of (and P' E) is also an instance of D'. Hope this helps. Greetings, Jeff -- Dr. Jeff Z. Pan ( http://DL-Web.man.ac.uk/ ) School of Computer Science, The University of Manchester ----- Original Message ----- From: "NANNI Marco RD-BIZZ-SOP" <marco.nanni@francetelecom.com> To: <public-swbp-wg@w3.org> Sent: Wednesday, January 05, 2005 4:55 PM Subject: Tutorial scope or [OEP] Hi, First of all happy new year to all. Here 2 definitions to illustrate my questions : C = (and (all R P) (all R (not P) ) D= (and (all R P') (all R (at-most 4 S)) I have to admit that all the OWL newcomers and even people who have already built some not only little academicals examples of OWL ontologies to which i have showed such examples dont understand that : - C is satifiable (consistent ?) - D subsume C. It'is very diificult to explain such (classification) results. So my questions are ? 1) do you think that "ordinary" people MUST be capable to clearly explain themselves these examples or is this kind of case only for experts of the domain (the member of this WG - not me of course) ? The problem is that i can't find a "real life" (with concrete classes names) to show that if, i don't understand this point i could make some mistake in creating "real" ontologies. In other words is the example - or the fact to not understand it - the visible part of a huge Iceberg or the symptom of a deeper incomprehension problem for potentials mistakes in using OWL regularly 2) do you think that such points are covered by the tutorial material in http://www.w3.org/2001/sw/BestPractices/Tutorials ? 3) do you think it is in the scope of the WG ? Thanks a lot Best regards Marco NANNI

Received on Thursday, 6 January 2005 10:55:27 UTC