Ed and Joe, (01)
The fundamental principle I've been trying to get across is
that we are *not* defining yet another upper level ontology.
Those terms have been defined many times before in many
different upper level ontologies. (02)
If anyone wants to see a definition of them, go look at
OpenCyc, SUMO, Dolce, BFO, etc. The UoM *must* be compatible
with every one of those plus a lot more. Therefore, we
*must* not define those words. For the UoM, they must be
taken as primitives -- i.e., undefined terms. That allows
the upper level ontologies to define them according to any
philosophical principles they choose. (03)
EB> But if we take John's guidance at his word, the following
> are undefined primitives: Quantity, Kind of Quantity,
> Quantity Magnitude, Dimension, Unit of Measure. Now, what
> sort of ontology will we make with those undefined terms? (04)
We would have exactly what a UoM ontology should be: a general
purpose microtheory that is compatible with a wide range of
upper-level ontologies. (05)
JC> I think we need to have these three aspects of the meaning
> of Quantities and Units for meaningful definitions. (06)
If you want a definition, go look at OpenCyc or any of the
other upper levels. The UoM is not being defined in a vacuum.
It is *part* of a community of ontology developers. (07)
The VIM document is compatible with every one of the currently
proposed upper levels and many more that are yet to be invented.
The UoM ontology *must* be compatible with every one of them.
Those terms that are primitive for the UoM will have different
definitions in different upper levels, but that is precisely why
we must avoid presenting yet another incompatible definition. (08)
EB> Well, John, what precisely is the problem at hand? That
> is the question Gunther was trying to answer. (09)
Fundamental problem: (010)
Design an ontology for units of measure that support
interoperability among legacy systems that have no
ontology and among new systems that are based on
different upper level ontologies. (011)
The VIM document does that. We should be more formal,
but at least as compatible as they are. (012)
EB> We don't want a reasoner to use valid mathematics and
> nonsense physics to produce the proof of a conjecture. (013)
Every engineering project uses approximations because the
fundamental equations are too difficult to solve efficiently,
and they frequently use theories such as Newtonian mechanics
that are known to be wrong. (014)
As I have said many times, the UoM must be compatible with
an upper ontology based on the latest theories of physics
and an upper ontology based on 19th century physics. The
VIM document achieves that balance. So should the UoM. (015)
John (016)
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