[Crm-sig] subproperty - superproperty

Christian-Emil Ore c.e.s.ore at edd.uio.no
Tue Jun 12 19:49:14 EEST 2007


Dear all,
I have now got the explanations and examples I needed, thanks: There can 
be instances of the super property and the sub property in the example 
below.

I asked because in many object oriented programming languages this will
not be allowed. On the subclass level the sub property will hide the
super property. This is apparently also the case in Telos which is the
underlying formalism for CRM.

It is easier not to assume/use such a hiding mechanism. A strict hiding 
mechanism would have required a lot of "dummy" sub properties.

The sub property/sub class mechanism need perhaps a somewhat more 
elaborated description/definition in the introduction?

Regards,
Christian-Emil

On 12.06.2007 17:43, Stephen Stead wrote:
> My understanding is: yes there can be such an instance.
> For instance An Actor can be present at a Measuring Event without actual
> performing it.
> Rgds
> SdS
> 
> 
> 
> Stephen Stead
> 
> Tel +44 20 8668 3075 
> 
> Mob +44 7802 755 013
> 
> E-mail steads at paveprime.com
> 
> 
> -----Original Message-----
> From: crm-sig-bounces at ics.forth.gr [mailto:crm-sig-bounces at ics.forth.gr] On
> Behalf Of Christian-Emil Ore
> Sent: 11 June 2007 13:48
> To: crm-sig
> Subject: [Crm-sig] subproperty - superproperty
> 
> 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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