- From: Richard Newman <r.newman@reading.ac.uk>
- Date: Wed, 26 Oct 2005 11:52:12 +0100
- To: Xavier Noria <fxn@hashref.com>
- Cc: Semantic Web <semantic-web@w3.org>
What the cardinality constraint says is this: If x is a Person, then they have precisely one mother, whether we know who that mother is or not. If x is described as having two mothers, y and z, then y == z. So, you don't need to explicitly state that x has a mother, but x nevertheless does indeed have a mother. (Think of it this way: having a mother is a necessary condition for Personhood. Asserting that something is a Person implies that they meet all of the necessary constraints.) -R On 26 Oct 2005, at 11:30, Xavier Noria wrote: > I don't agree there (but maybe my interpretation is wrong, please > correct me in that case). > > My reading of that description is: > > IF a person has a mother THEN it has exactly one > > but you can have a person WITHOUT a mother and be consistent (not > because of the open-world assumption, but because the semantic of > owl:Cardinality does not imply that *for all*). > > -- fxn > > > >
Received on Wednesday, 26 October 2005 10:52:21 UTC