Friends, after today's meeting and following this discussion,
I think it's a critical decision to set a scope for this
project. Do you want to define units or quantities? If you
want units, then you do not need to define mass or discuss
what it means to apply 180 cm to yourself. (01)
If you want to define quantities, you should consider the
VIM's is lacking much detail that can branch out from
1.1 (1.1) quantity "property of a phenomenon, body, or substance,
...". (02)
You can not apply 1.3 kg to your lump of cheese without
specifying the property. Same as 180 cm to yourself. (03)
In some standards, formalized by IUPAC (there is a book
called the "Silver Book" and the following literature: (04)
[1] Dybkaer R. An Ontology on Property for physical, chemical, and
biological systems. APMIS. 2004; 112(Suppl. no. 117).
[2] C-NPU. Subcommittee on Nomenclature, Properties, and Units in
Laboratory Medicine. Available from: URL:
http://www.iupac.org/divisions/VII/VII.C.1/
[3] LOINC®. Logical Observation Identifiers Names and Codes. Available
from: URL: http://www.regenstrief.org/loinc (05)
While the above are about laboratory medicine, the principles
apply for physics as well. (06)
To specify a property, they say, you need to specify the "system"
and it's "component" and "kind of property". (07)
So: "my (system) body (component) length (kind of quantity) is 180 cm"
or: "this lump of cheese's (system) total (component) mass (kind of
quantity) is 1.3 kg" (08)
To split out "component" from "system" does not always make sense
IMO (like above the total mass is does not require a component).
It appears even from the VIM that to recognize a property, you need
to have an object which possesses that property. Defining exactly
the property is IMO too wide for this ontology to include, because
it could be just about anything, e.g., it could be the "frequency
by which I notice that I have not eaten dinner" -- far too much
to specify in your ontology. (09)
So, you probably need to exclude defining properties from your
scope and begin with kind of quantity. But I suggest you even take
kind of quantity as a primitive and focus only on dimensions. (010)
Since you are making UML models from the VIM, I am attaching a Word
document that has a draft which I have made about a year ago based
on VIM quotations. It's one of those I showed in today's slides
without much further explanation. You may find some ideas there
to use. (011)
Finally, to the rest of the discussion: (012)
>> David Leal wrote:
>>>>> There are at least two ideas of what the members of "1.3 kg" are,
>>>>> including:
>>>>> a) the members are mass tropes of different individual quantities
>>>>> of matter;
>>>>> b) the members are different individual quantities of matter.
>> I wrote:
>>>> I don't know what David's (b) means. I would have said the members
>>>> of the equivalence class designated "1.3kg" are either:
>>>> a) 'mass tropes' of different individual things, or
>>>> b) measurements of the 'mass tropes' of individual things.
>>>>
>> Matthew West wrote:
>>> MW: I would say neither of these, but the individual things
>>> themselves.
>>> The measurements are of these.
>>>
>>> E.g. My lump of cheese is a member of the 1.3Kg equivalence class. (013)
Clearly that cannot be. It is either (014)
(a) the particular properties (this mass of this lump of cheese)
(b) the measurement results (the reading of the scale with this lump
of cheese on it) or
(c) the expression of the measurement result, i.e., my statement
that the mass of this lump of cheese is "1.3 kg". (015)
I feel that the extension of the equivalence class "1.3 kg" is
(c) or even less, and that only by a relation from the elements of
that equivalence class to the properties and ultimately objects
possessing those properties is it that we think that these properties
or objects are the elements of the equivalence class. But that is
not really useful. Of course you can always define the equivalence
class by transitively including the expression, measurement,
property and object, but that would violate Occam's razor. (016)
>> This may be true of 'mass', but it doesn't generalize. The person Ed
>> Barkmeyer is not a member of the 180cm equivalence class.
>
> Thats because 180 cm isn't a meaningful quantity applied to you,
> without further specification. It would like saying that you don't
> have a voltage, which is true but not very interesting. But as soon as
> you specify a meaningful length class (height, waist size) then the
> analogy with mass works just fine. And you are a member of an
> equivalence class of volumes, for example.
>
>> The height of
>> EdBarkmeyer is a member of the 180cm class. But the waist size of
>> EdBarkmeyer is a member of a different class (predictions of one of my
>> former students notwithstanding). In a similar way, the existence
>> of a
>> thing may be a member of one duration class, while some other property
>> is a member of a different duration class. (017)
I think that's too much already. The member of the 180 cm class is
180 cm and 0.18 m. There may be a relation between the property
instances of Ed Barkmeyer's height and/or waist circumference to that
equivalence class, but that is more than a useful theory of units
of measure requires. (018)
>>> MW: <snip> I think it is important to
>>> distinguish two concepts:
>>>
>>> 1. The mass something has,
>>> 2. A measurement of the mass something has. (019)
"Measurement" is a dangerously ambiguous concept. Nothing "has
a measurement". It is we who "make measurements". Thing have
properties which we measure. A measurement is the "process of
experimentally obtaining one or more quantity values that can
reasonably be attributed to a quantity". (020)
>> I think this is exactly the same pair as David's (a) and (b) above,
>> with
>> the substitution of "something" for
>> "individual quantity of matter", and my (a) and (b) above is the same,
>> with a slightly different substitution. It seems to me that we are
>> all
>> in violent agreement, except that we can't agree on the spelling of
>> "some thing".
>>
>>> We should not be choosing to be interested in one or the other, but
>>> both. (021)
Actually, I would say you should choose to be interested in
neither for the sake of the simplicity of the theory of units
of measure. (022)
regards,
-Gunther (023)
--
Gunther Schadow, M.D., Ph.D. gschadow@xxxxxxxxxxxxxxx
Associate Professor Indiana University School of Informatics
Regenstrief Institute, Inc. Indiana University School of Medicine
tel:1(317)423-5521 http://aurora.regenstrief.org (024)
Quantity and Units Model.doc
Description: MS-Word document
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