Re: [h5md-user] Finalization of units module

[Felix Höfling]

Am 13.01.2014, 22:39 Uhr, schrieb Peter Colberg  
<address@hidden>:

> Hi all,
>
> Following external pressure to publish or perish, I revised the units
> module by defining the "SI" unit system to encompass SI base units,
> SI derived units, and SI prefixes [1].
>
> [1] http://www.bipm.org/en/si/si_brochure/general.html
>
> I also updated the test case in lua-units [2].
>
> [2] http://git.colberg.org/lua-units/tree/examples/h5md.lua
>
> The solution will make everybody unhappy. For the use of non-SI units,
> the unit attribute can still be written using a scalar prefix and an
> SI unit. Alternatively, the values can be converted to an SI unit
> using the cv_convert_* functions [3] of the udunits2 library.
>
> [3]  
> http://www.unidata.ucar.edu/software/udunits/udunits-2.2.2/doc/udunits/udunits2lib.html#Value-Conversion
>
> Peter

Hi Peter,

The BIPM brochure is a good basis, probably the best one. Thanks for  
implementing it and for cleaning up my list!
I think that the current implementation of "SI strict" makes many people  
happy and indeed deserves to be called version 1.0.

We don't need it now, but just to remember: The brochure also says in ch.  
4 what the "extended" set of units is, including natural units and CGS  
system. (It even resolves the conflict between "hour" and Planck's  
constant by using \hbar instead of h.) For abstract unit systems, it would  
be sufficient to specify the physical dimension instead of a "unit", which  
could be done using the symbols in  
http://www.bipm.org/en/si/si_brochure/chapter1/1-3.html.

Felix