RE: [plcs-dex] Classification of type and individual

Please be careful here. Actual individuals are members of the class defined by their design. However, actual individuals are not necessarily members of all the classes of which their design is a member. Classification is not transitive. I realize that a lot of classification in PLCS replaces subtyping, however that’s not true for all PLCS classifications.

David

-----Original Message-----
From: Rob Bodington [mailto:rob.bodington@eurostep.com]
Sent: 07 March 2005 13:38
To: 'Gyllström Leif'; plcs-dex@lists.oasis-open.org
Subject: RE: [plcs-dex] Classification of type and individual

Thinking about this a bit more …..

I think that this approach will get really complicated.

Imagine I have a bike design classified as an “ordinary” bike.

I then build an individual bike from this design.

The individual bike will be classified as an “ordinary” bike.

I then make a modification to my individual bike, so it is now a “Souped up bike”.

The change was not a change to a design, but to my individual bike so “Souped up bike”

is not a classification of the design, but a classification of my individual bike.

So can we be sure that:

a) all classifications of the typical apply equally to the actual thing being classified.

b) If we classify a typical will that classification apply to all of the actual things

I’m not convinced (yet)

Regards
Rob

-------------------------------------------
Rob Bodington
Eurostep Limited
Web Page: http://www.eurostep.com http://www.share-a-space.com
Email: Rob.Bodington@eurostep.com
Phone: +44 (0)1454 270030
Mobile: +44 (0)7796 176 401

-----Original Message-----
From: Gyllström Leif [mailto:leif.gyllstrom@aerotechtelub.se]
Sent: 07 March 2005 13:11
To: plcs-dex@lists.oasis-open.org
Subject: SV: [plcs-dex] Classification of type and individual

Rob

I would suggest that we only classify the typical due to the implications that the other approach will have on the reference data library.

We have agreed that refdata should be regarded as specializations (subclasses) of PLCS Entities. This would mean that an instance of

reference data would have to be defined for both the typical and the actual thing. Yes, OWL will allow for a class being a subclass of

several Entity classes. But I'm convinced that this will cause confusion and classes for typical will only appear as specializations of

the entity representing the actual etc.

I'm stongly in favor of keeping the separation of typical and actual,and exchange both instances, and have a consistent approach

throughout PLCS.

Regards

Leif

-----Ursprungligt meddelande-----
Från: Rob Bodington [mailto:rob.bodington@eurostep.com]
Skickat: den 18 februari 2005 17:27
Till: plcs-dex@lists.oasis-open.org
Ämne: [plcs-dex] Classification of type and individual

Hi

In PLCS we make a distinction between a typical something and an actual something.

E.g

Part and product_as_realized

State_definition and State_observed

We are also able to classify things.

E.g.

A Part is classified as a Bicycle

A State_definition is classified as a Fault state.

The question is, if I classify the typical things, do I need to classify the actual thing?

For example, if I classify a Part as being a bicycle, do I need to classify the Product as realised as representing my bike, as a being a bicycle, or do I just classify the Part?

Similarly for states.

If we impose a rule that you only classify the typical – not the actual, then you will always have to exchange both the typical and the actual.

Which may be overkill.

Any thoughts?

Regards
Rob

-------------------------------------------
Rob Bodington
Eurostep Limited
Web Page: http://www.eurostep.com http://www.share-a-space.com
Email: Rob.Bodington@eurostep.com
Phone: +44 (0)1454 270030
Mobile: +44 (0)7796 176 401

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