[Om] Questions about representing units

Professor James Davenport jhd at cs.bath.ac.uk
Sat Feb 21 04:37:28 CET 2009

On Fri, February 20, 2009 11:51 pm, Christoph LANGE wrote:
> Dear James, dear Jonathan, dear all,
> An easy one first:  I didn't find a concrete example for prefixing, but
> may I
> assume that the following is correct?
> <!-- 1 kilometre -->
> <OMA>
>   <OMS cd="arith1" name="times"/>
>   <OMI>1</OMI>
>   <OMA>
>     <OMS cd="units_ops1" name="prefix"/>
>     <OMS cd="units_siprefix1" name="kilo"/>
>     <OMS cd="units_metric1" name="metre"/>
>   </OMA>
> </OMA>
That's right.
> Then, how about compound units?  There are some convenience symbols like
> metres_per_second, but what do we need them for?  Wouldn't it make more
> sense
> to do without them (as you suggested to do without metre_squared) and
> write instead: <snip>divide</snip>
It probably would do. As and when we can declare individual symbols
obsolete, I will propose doing so to MOST of these - memroy says there are
some odd ones, but i can't remember offhand.

> BTW, does your unit converter
> (http://klein.activemath.org:90/~jonathan/units/converter.php) support
> such compound units for which no explicit symbol has been defined?
One for Jonathan.
> Then, a final question about that unit converter: I can convert hours to
> minutes, but for minutes to seconds, and hours to seconds, it tells me
Ditto this one.
>> The two units were known, but found to be different dimensions. Please
>> supply a definition for the units to reconcile this difference,
>> remembering
>> to ensure the new definition has a different name.
>> 1 hour to second is incalculable.
> Is there any better place for reporting this bug?
> BTW, we are planning to add a unit conversion service to our active
> document framework (https://jomdoc.omdoc.org/wiki/JOBAD); see
> https://jomdoc.omdoc.org/ticket/254 if interested in further details.
Thanks for this.

James Davenport
Visiting Full Professor, University of Waterloo
Hebron & Medlock Professor of Information Technology and
Chairman, Powerful Computing WP, University of Bath
OpenMath Content Dictionary Editor
IMU Committee on Electronic Information and Communication

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