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

[Tim Turner <timturner11@bellsouth.net>]

I also do not like to start introducing more (loaded) terminology into the forum - so please lets stick to those already in use (e.g. design, planned and realized)! Of course we distinguish between a design & the (many) products relized from it.

 

The discussion on the classification of the design being *inherited* in some way by the realized (& I presume the planned) products in focus is mute if the design is ever likely to be separated from the exchange of the product itself. In other words, I do not believe that we will always want to exchange both the design & the realizaed product at the same time.

 

It is of course possible to reference the design when exchanging a realized product, but this assumes that the design is available, which again may not be true.

 

The realized product may also become out of sync (as it were) with the configuration allowed by the design authority, so it would be somewhat naive to assume that a realized product matches that of the design configuration. Remember those phrases on the seal of some products... "by removing this cover plate you revoke all warranty to the product should it then fail.."? This is the OEM's way of saying only the design configuration (options) are supported.

 

I admit that changes to the configuration in the field happens all the time, but how can we anticipate these changes and the reference data required to support them? I don't think it is possible to cater for every future possible classification in advance (nor should we try), but perhaps we should provide the basic original classification (initial?) and some mechanism for any additional classifications. This, I think, is a point that needs to be agreed or an alternative way suggested.  However, this raises the question of how to indicate the initial versus the additional classification? The PDM schema has a related issue with context which is resolved by having a distinction between an initial_context and a set of additional_contexts. How the additional classifications should be organised in PLCS is something we need to devise.

 

regards,

Tim

 

NB by *inherited* I mean thru the use of product_planned_to_realized, product_design_to_individual etc)..

-----Original Message-----
From: Nigel Newling [mailto:nfn@lsc.co.uk]
Sent: 07 March 2005 10:56
To: 'plcs-dex@lists.oasis-open.org'
Subject: FW: [plcs-dex] Classification of type and individual

I have grave reservations about using the term "typical". I will leave to my office colleagues to debate the finer point of change control but I fear the impression of imprecision that the word creates.

 

In PLCS we have always had to grapple with the bridge from the design environment to the real world of supporting realised products. In the design world, product definitions go through iterations as the design is improved to eliminate failure modes, enhance functionality and simplify manufacture. As digital data, each iteration can be identified as a new version through the application of a rigorous change control mechanism.

 

At some point we actually get round to building a few. Once built, each product takes on a life of its own, able to be referenced back to a design version only if you are lucky ( :-(  but remember I am a real world support engineer by trade so forgive the doubt!)

 

PLCS must cope with the fact that the as-built version of a realised product behaves differently from a design version. Realised products can always be defined, not necessarily by reference to an identifiable design version but always by identification of actual parts fitted (because you can go and have a look). The differences from the design may or may not be covered by authorised variances (concessions).

 

I cannot see what value a "typical"  option is adding.

 

Nigel

-----Original Message-----
From: David Price [mailto:david.price@eurostep.com]
Sent: 07 March 2005 14:31
To: plcs-dex@lists.oasis-open.org
Subject: 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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