Dear all,

  IMHO yes, you can indeed have instances of Pa:Ek <--> El that are not 
instances of Pb.

  An example : The current or previous location (P53) of a material object 
(E19) isn't necessarily an instance of current location (P55). 

  Cheers

  nick

Christian-Emil Ore <[email protected]> wrote:
  Dear all,
I may well be blind, but I cannot find the following specified in the 
crm-definition:

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

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

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?

Regards,
Christian-Emil
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Nicholas Crofts
Open World
Cultural information Management

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