I agree with John's comments (below). (01)
I think that for the UoM we can adopt the principle that the dimensions
(time, distance, mass, temperature, etc.) that are standardized by the basic
units are themselves "primitive" and logically undefinable, whose meanings
and usage in programs are generally understood. However the standards
against which they are measured and the techniques by which they are
measured can be related to the basic dimensions by semantic relations, and
the values of those relations may change over time. For those other
dimensions that are not directly definable as combinations of the basic
dimensions (e.g. hardness, and I would include force, whose meaning is not
just 'ma'), it may be best to also treat them as "primitive". For the
primitive dimensions our main concerned would be how to relate those
different dimensions of measure to the way the unit is defined and measured
at any given time in history. This entails that the question - of whether
any given measure is or is not multiplicative versus some basic unit - is
not the question that determines whether we treat a particular dimension as
primitive or derived. (02)
Pat (03)
Patrick Cassidy
MICRA, Inc.
908-561-3416
cell: 908-565-4053
cassidy@xxxxxxxxx (04)
> -----Original Message-----
> From: uom-ontology-std-bounces@xxxxxxxxxxxxxxxx [mailto:uom-ontology-
> std-bounces@xxxxxxxxxxxxxxxx] On Behalf Of John F. Sowa
> Sent: Monday, August 10, 2009 1:37 AM
> To: uom-ontology-std
> Subject: Re: [uom-ontology-std] uom-ontology-std - strawman UML
>
> Ingvar and Pat,
>
> I certainly agree that scientists today know far more about the
> underlying principles than they did one or two centuries ago.
> But the point I was trying to emphasize is that the same units
> of measure that they used back then can still be used in the
> same way (but with greater precision) for the same kinds of
> applications. More people use the meter for measuring roads
> and houses than they do for measuring stars and atoms.
>
> That implies that any ontology for UoM should be *neutral* with
> respect to Newtonian physics, quantum mechanics, relativity,
> string theory, or whatever anyone might discover in the future.
>
> IJ> I would say that it is only after the acceptance of statistical
> > thermodynamics that the "absolute zero" became generally regarded
> > as the temperature that theoretically is the lowest possible
> > temperature.
>
> That's probably true. But Lambert proposed the term 'absolute zero'
> in 1779 and gave the very good approximation of -270 C. The fact
> that the underlying principles became better understood a century
> or so later does not invalidate the use of the concept and its
> estimated value during the 19th century. Nor does it invalidate
> mundane uses of the temperature scale today by people who have
> never studied statistical thermodynamics.
>
> Implications for computational uses of a UoM ontology:
>
> 1. Whatever system of ontology we propose should support multiple
> "microtheories" or whatever else one would like to call them.
>
> 2. Some of those microtheories might assume good old Newtonian
> mechanics, others might use relativity, others might use a
> nonrelativistic quantum mechanics, and others might use the
> latest and greatest theories anybody has proposed.
>
> 3. But all of them can use the same words and values for the
> basic units of measure.
>
> 4. Those points imply that a microtheory for units of measure
> should *not* contain detailed axioms and definitions of the
> underlying physical principles and theories.
>
> 5. The detailed axioms and definitions should be contained in
> microtheories for whatever physical theories are assumed for
> any particular application.
>
> PC> I think that 'force' is a concept that means a lot more than
> > just "ma", and also happens to be directly experienced by many
> > sentient animals.
>
> I agree. The UoM should contain the equations that relate the
> measures of force to the basic units such as m, kg, and s.
> But it should not contain detailed axioms and definitions that
> might conflict with any application. Detailed axioms needed
> for each kind of application can be contained in microtheories
> designed for those applications.
>
> John
>
>
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