Re: quantity database

I may have misinterpreted your original posting by confusing
quantity with RealType.  Perhaps by quantity you mean a
generalization of the quantityName field in BaseUnit to
DerivedUnit (BaseUnits are things like meter, kilogram and
second whereas DerivedUnits include the combinations Tom was
talking about, like meter * second^-2).
These quantities are distinct from RealTypes.  For example,
the quantity 'density' (kilogram * meter^-3) can apply to
the densities of many different substances, which would each
be RealTypes.
To continue the example we discussed yesterday, 'speed' is
the quantity for the DerivedUnit meter * second^-1, whereas
'wind speed' and 'current speed' would likely have different
RealTypes.  Giving these different RealTypes allows them to
have different display roles, for example different magnitude
scalings for flow rendering.
Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
whibbard@xxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738

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