On Jul 14, 2009, at 5:52 PM, Ed Barkmeyer wrote: (01)
> David Leal wrote:
>
>> This is good progress.
>
> Thanks, but real progress would be if we had captured chapter and
> verse
> from various reference documents and put this someplace.
>
>> You say:
>>> But what is important is that there are 4 distinct concepts:
>>> - particular quantity = a physical instance to be quantified
>>> - kind of quantity = a category of comparable particular quantities
>>> - magnitude of quantity = an abstract quantification of particular
>>> quantities
>>> - quantity value = the expression of a magnitude as a number and a
>> measurement unit (where the number is the ratio of the magnitude to
>> the unit)
>>
>> Probably we need to look at two "kinds of quantity":
>> - categories such as that which includes Ed Barkmeyer's height,
>> width of the
>> Thames at London Bridge, the diameter of the earth's orbit;
>> - categories such as that which includes ultimate tensile strength,
>> yield
>> strength in tension, yield strength in compression (all are
>> stresses).
>
> If I understand you right, yes. (02)
Can anyone elaborate on the distinction here? I don't follow it. (03)
> There is a set of categories that are
> 'kinds of quantity', such that all instances of any 'kind of quantity'
> category are comparable and no pair of instances from two different
> kinds of quantity are comparable. (04)
Why the second requirement? If length and width are different
quantities (why not?) they are nevertheless comparable. (05)
> There are other categories that must
> be subclasses of the 'kinds of quantity' (each of which is a
> subclass of
> the general category 'quantity'), which is your second bullet. (As I
> mentioned in the email to Martin, these might be "roles" instead of
> subclasses. I don't know. (06)
I think subclass vs. role vs. property is a function of the underlying
formalism we decide to use. I can transcribe everything into CLIF or
IKL in any case, whatever we decide. (07)
> )
>
> I notice that Pat Hayes uses 'dimension' for 'kind of quantity'. (08)
I did, but I think 'kind of quantity' is better. So I will use that
from now on. So, to check my understanding, the following are kinds of
quantity: lengths, masses, weights, tensile strengths, time
durations, .... The KOQ Length is a class (or class-like thing, ie
something with members or instances) whose instances are particular
lengths, such as the distance from the earth to the moon, the width of
my left third finger, a light year, etc., all thought of in a pre-
measure-unit way. In general, all the elements of a given KOQ are
numerically comparable, so that for any two of them A, B, there is
some number N such that A is N*B. (Or maybe we need to generalize
number here to some ordering scale, I'm not sure about that.) (09)
> I
> think the VIM also uses the term 'dimension', but I can't recall what
> meaning VIM assigns to it. (010)
It would make sense to allow each KOQ to have an associated dimension,
but the association be many-one, so that length, width, distance, etc.
all are different KOQs but all associated with the one physical
dimension, which is spatial distance. But that requires relaxing the
'incomparable with other kinds' restriction you mention above. NOt
sure about this. (011)
Pat (012)
>
> -Ed
>
> --
> Edward J. Barkmeyer Email: edbark@xxxxxxxx
> National Institute of Standards & Technology
> Manufacturing Systems Integration Division
> 100 Bureau Drive, Stop 8263 Tel: +1 301-975-3528
> Gaithersburg, MD 20899-8263 FAX: +1 301-975-4694
>
> "The opinions expressed above do not reflect consensus of NIST,
> and have not been reviewed by any Government authority."
>
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> (013)
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