Re: why are properties decoupled from classes

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
>
>
>
>