[Om] questions on the OM symbols for physical units and their prefixes

Michael Kohlhase m.kohlhase at iu-bremen.de
Wed May 31 09:55:25 CEST 2006

Dear all,

Note that there is a W3C note [1] in the  MathML group that is also 
relevant here. we should try to be compatible with that in our practices 
in OM.

A paper that also touches on the units question is our proposal for a 
Physics Markup Language to be presented at the MKM Conference. That 
proposes to equip units  with types in a dimension type sytem. We are in 
the process of developing OMDoc Content Dictionaries for these based on 
the MathML note above.


[1] http://www.w3.org/TR/mathml-units/

   Prof. Dr. Michael Kohlhase,         Office: Research 1, Room 62 
   Professor for Computer Science      Campus Ring 12, 
   School of Engineering & Science     D-28758 Bremen, Germany
   International University Bremen     tel/fax: +49 421 200-3140/-493140
   http://www.faculty.iu-bremen.de/mkohlhase <m.kohlhase at iu-bremen.de>          

Christian Groß wrote:
> Hello everybody,
> I have a question on the OpenMath symbols for physical units, in 
> combination with their prefixes, i.e., on the cd's
> units_metric1 and units_siprefix1.
> In units_metric1 you have symbols metre and metre_sqrd and in 
> units_siprefix1 you find prefixes like centi and milli.
> I guess this works well in order to express cm = centi-metre or mm = 
> milli-metre. But what about cm2 as a small unit for area?
> One could construct "(centi-metre)2" of course, using the usual power 
> symbol, etc. But if it is intended that for defining physical symbols
> one needs the power symbol anyway, then which sense has the symbol 
> metre_sqrd? It should be (metre)2 in this case, if the whole system 
> has a systematic. On the other hand, I could also use 
> centi-metre_sqrd, but in my opinion this would mean 10^(-2)*m2, 
> whereas cm2 is 10^(-4)*m2.
> Similar questions arise for the units of volumes. Why is there a 
> "litre" symbol but no "metre_cubic"?
> Finally, without giving any reference to the special case "kilo", the 
> description of "prefix" in units_ops1 doesn't make much sense:
> prefix
> Description:
>    "This symbol represents the fact that the subsequent unit has been 
> effectively multiplied by 1,000 ($10^{3}$)"
> Commented Mathematical property (CMP):     This is unit multiplication 
> by 1,000
> Thanks for any help and comments,
> regards,
> Christian Gross
> ------------------------------------------------------------------------
> _______________________________________________
> Om mailing list
> Om at openmath.org
> http://openmath.org/mailman/listinfo/om
-------------- next part --------------
A non-text attachment was scrubbed...
Name: m.kohlhase.vcf
Type: text/x-vcard
Size: 346 bytes
Desc: not available
Url : http://openmath.org/pipermail/om/attachments/20060531/f7feebf9/m.kohlhase-0001.vcf

More information about the Om mailing list