Gunther Schadow wrote:
> Martin S. Weber wrote:
>> Gunther,
>>
>> the question at hand was not asked for multiplication, which, due to its
>> definition, is working the way you expect. It was asked about comparison,
>> which, by ITS definition, works only when you're talking about the same
>> kind-of-quantity.
>>
>> IIUC, a Nm * Nm is a (Nm)^2 no matter what, but it might be the case that
>> a Nm=/= a Nm.
>
> But multiplying 1 N.m with 1 m / m gets you 1 N.m and how do you carry
> whatever distinction you like to preserve in the unit through the
> computation? (01)
Obviously, by looking at the quantities involved. That's what is necessary to
correctly reason about equality of units. Quantities. And how they evolve from
the underlying operations on the units. You need the dimensioning, you want to
know which unit it is, and you have to take care of the quantities involved.
Which the VIM states... (02)
Imagine you take a Nm and make a torque out of it by multiplying with m/m.
That gives a different quantity. This information has to be preserved /
presented. The set of the quantities over the operations of '*' and '/' sadly
doesn't give a regular structure, but, luckily, the set of agreed-upon
quantities is finite. (03)
Honestly, I lost overview of whether the majority of UoM-involved people now
think that quantities should not be accounted for (which, imo, is bad) or
should. And of course the examples easily fall back to involving dimensionless
units. Of course because that's where the quantity makes the difference.
Which, due to SI/VIM has the final say on whether two things are comparable
[without further thought] or not. Which is something that UoM instance data
should be able to provide. Which is ... turning in circles. (04)
Regards, (05)
-Martin (06)
_________________________________________________________________
Message Archives: http://ontolog.cim3.net/forum/uom-ontology-std/
Subscribe: mailto:uom-ontology-std-join@xxxxxxxxxxxxxxxx
Config/Unsubscribe: http://ontolog.cim3.net/mailman/listinfo/uom-ontology-std/
Shared Files: http://ontolog.cim3.net/file/work/UoM/
Wiki: http://ontolog.cim3.net/cgi-bin/wiki.pl?UoM_Ontology_Standard (07)
|