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Re: [uom-ontology-std] retitled: magnitude of a quantity

To: edbark@xxxxxxxx, uom-ontology-std <uom-ontology-std@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Thu, 16 Jul 2009 06:55:01 -0500
Message-id: <33F90A03-28EA-4963-AD4B-8D5FF3861E07@xxxxxxx>

On Jul 15, 2009, at 7:00 PM, Ed Barkmeyer wrote:    (01)

> James Davenport wrote:
>
>> Personally, I'm not sure that I would give 'length' and 'width'
>> different kinds, but that's why we will (when we actually get down to
>> talking about populating the ontology) be having these debates. Two
>> better examples are torque and energy,
>
> Torque and energy are different kinds of quantity, and their instances
> are not comparable.  The confusion here arises from the fact that they
> differ in their dimensional formulations by multiplication by a kind  
> of
> quantity (angle) that has no "unit".  (Its model is arc length/radius,
> i.e. length/length.)    (02)

It always bothered me that dimensional analysis made angles  
dimensionless, when they are of such profound physical significance.  
Clearly, direction of length matters. The fact is, 'length' should be  
treated as a vector rather than a scalar. This also, btw, helps with  
distinguishing length from width from height. BUt this is probably  
going too far out in left field for this forum :-)    (03)

>
>> or the distinction between relative and non-relative temperatures
>
> Pandora's box number 2.  Absolute temperatures (which is the usual  
> kind)
> and date-time are very special problems.  They don't work like other
> measurements.    (04)

Date/time is a mess because the scales aren't additive (months screw  
things up), but the underlying model of time-intervals is quite  
coherent. Temperature is interesting: another dimensionless  
dimension :-)    (05)

PatH    (06)

>
> -Ed
>
> -- 
> Edward J. Barkmeyer                        Email: edbark@xxxxxxxx
> National Institute of Standards & Technology
> Manufacturing Systems Integration Division
> 100 Bureau Drive, Stop 8263                Tel: +1 301-975-3528
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>
> "The opinions expressed above do not reflect consensus of NIST,
>  and have not been reviewed by any Government authority."
>
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>    (07)

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