[Crm-sig] subproperty - superproperty

Christian-Emil Ore c.e.s.ore at edd.uio.no
Mon Jun 11 15:47:34 EEST 2007

Dear all,
I may well be blind, but I cannot find the following specified in the 

Assume we have four class (could be two) Ei, Ej, Ek, El and two 
properties Pa, Pb

Ek is a sub class of Ei
El is a sub class of Ej

Pa: Ei <-> Ej
Pb: Ek <-> El

which can be illustrated by the diagram

   Ei   <---->   Ej
   |	  |	|
   |       |     |
   |       |     |
   Ek   <---->   El

It is clear that each instance of a Pb will be a Pa when seen as a 
property on the superclass level. That is ordinary object orientedness 
and well documented in the crm standard.

Since Ek and El are subclasses of Ei and Ej, the properties between Ei 
and Ej, that is, Pa will also be a property between Ek and El. However, 
can there exist an instance of Pa:Ek <--> El that is not an instance of Pb?


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