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Subject: Re: PPS Core Elements -- ontology problem


Very good point!! We have actually noticed the problem after
completion of first version of the draft. Yes, the original
specification doesn't have clear distinction between type and 
instance in representing primitive objects. 

However, the latest version, which is according to the PSLX
ontology published in the PSLX white paper in Jan 2005, has
a concept considering the problem. See also 

In primitive elements, item, resource and function (this corresponding
to operation in the first version) are type data. And 
lot, task and operation (this is dispatch in the first version)
are instances, respectively. 

In this definition, you might be confused by the term "resource", 
where we define resource as a source of capacity that can do
various tasks in real world. In other words, "Machine-001" is
a instance of item if it is produced by mother-machine. 
At the same time, it is a "type" of tasks that produce something
in a particular method.

In this sense, two physical machines are exactly equal to one 
other machine that has same capacity and capability in scheduling
and planning problem. Of course, there is another task allocation
problem to clarify the resource allocation.

Thank you for the valuable comment.
We apologise that the latest version is not readable in English
so far. The bilingual version of draft-04-jp will be uploaded 
as soon as possible.

Chair of PPS-TC, Hosei University

Date Fri, 20 May 2005 15:43:02 -0400
James Odell <email@jamesodell.com> writes:

> Hi Yasu,
> Am reviewing the document: "PPS (Production Planning and Scheduling) Part 1:
> Core Elements", Working Draft 01-b, 30 August 2004
> In it, I am finding some items that might pose serious ontological problems.
> Perhaps you can correct me if I am wrong.  My concern involves many of the
> Primitive Properties.  For example, when you use <resource>, do you mean the
> type of resource or the instance of a resource?  This is extremely important
> because when a process indicates that in needs a "resource", some processes
> may specify the type of resource and some may specify the instance.  For
> instance, if a film studio wishes to make a movie, the might say that they
> need a Film Director, i.e., the type of resource; or, the studio might say
> that they don't want just any Film Director, they want Akira Kurosawa, i.e.,
> an instance of Film Director.  In short, both Resource Type and Resource
> Instance are necessary notions in production planning and scheduling.
> This same phenomenon applies to all of the Primitive Properties (e.g. Item
> Type vs Item Instance, Operation Type vs Operation Instance, and so on).
> This dichotomy also forms the basis of power types.
> Does this make sense?  Or, have I misunderstood?  Thank you.
> Kind regards,
> Jim
> www.jamesodell.com

Yasuyuki NISHIOKA, Ph.D.
Systems Design Dept., Hosei University

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