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Subject: Re: PPS Core Elements -- ontology problem


We have to go back to your first question because I didn't
make a correct answer for it. In the case of the primitives
except for "resource", PPS can represent differences between
types and instances. However, in terms of resource, PPS
can not represent instance of resource type. This is the 
correct answer. In this sense, your first suggestion is 
quire meaningful. 

The reason why we didn't try to have a representation that
shows a instance of resource such as Kurosawa is, as I described
briefly in the previous mail, that both Kurosawa and Film 
Director perform the same role in planning and scheduling
problems. In these problems, even Kurosawa is class of
some functional objects (instances) which can take a particular

In production management, shop floor personnel are sometimes
not identified by their exact name but their skill group.
Machines are also identified by group and their total capacity
and capability. In a practical system implementation, instance
of resource (Machine-001) and type of resource (MillingMachines)
need to be operated in a single algorithm. 

However, this doesn't mean that you cannot represent Machine-001
as an instance. If you need to identify it as an instance,
Machine-001 can be represented by "lot", which can be a target
of an operation. This is not suitable and not imaginable in common 
sense though.

Let me change the subject, some ISO groups as well as ISA-95 
discuss the term "resource" as a combination of consumable and
non-consumable ones. It is clear that consumable resources mean 
materials, which are represented by "lot" in PPS.


On Mon, 23 May 2005 13:12:09 -0400
James Odell <email@jamesodell.com> wrote:

> Hi Yasu,
> Sorry that I cannot read Japanese.  It would help me very much right now.
> As for the example of "resource" in your email, I have some questions.  In
> an attempt to understand better, have attached a PowerPoint file that
> contains some of the typical PPS patterns that are used in the US.  On the
> first slide, could you tell me which of the two classes are the notion you
> call "Resource"?  The other two slides might be interesting for you, as
> well.  Is it possible for us to talk on the telephone?  I could call you
> first thing in your morning.
> Thank you again for your help.  I want to try to use your material for NASA.
> But, before I can recommend it, I need to fully understand its semantics.
> Best regards,
> Jim Odell
> www.jamesodell.com
> On 5/23/05 1:32 AM, "Yasuyuki Nishioka" indited:
> > Jim,
> > 
> > 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
> > http://www.pslx.org/en/pub/WP-01EN-ALL.pdf
> > 
> > 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.
> > 
> > Yasu
> > 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., Hosei Universiry

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