> Message: 6
> Date: Wed, 13 Apr 2011 14:52:26 -0600
> From: Steve Emmerson <steve at unidata.ucar.edu>
> Subject: Re: [CF-metadata] physical vs dimensional units
> To: cf-metadata at cgd.ucar.edu
> Message-ID: <4DA60D0A.1010505 at unidata.ucar.edu>
> Content-Type: text/plain; charset=ISO-8859-1
>
> On 04/13/2011 02:25 PM, John Caron wrote:
> > the point im trying to make is that it would be better to understand
> > that "mol mol-1" (canonical udunit = 1) is not the same as "m3 m-3"
> > (canonical udunit = 1).
>
> In my opinion, the distinction between "mol/mol" and "m3/m3" is better
> indicated by the name of the physical quantity being displayed rather
> than by its unit attribute. In the cases under consideration, the
> respective physical quantities would be "amount of substance fraction"
> and "volume fraction".
>
> See Table 12 of
> <http://physics.nist.gov/Pubs/SP811/sec08.html> for more
> information.
>
> For example, the Y-axis of a plot could be labeled "Amount of
> Substance
> Fraction of Carbon / 1e-9" to plot nanomoles of carbon per
> mole of whatever.
Sorry, Steve - but if I would suggest this to any of my colleagues, they would declare me as insane. And according to the principle that "short and concise is beautiful", I would also much rather continue to see plots labeled as "C2H4 [nmolC/mol]" instead of "Amount of C2H4 fraction of carbon / 1e-9".
I can see the point that this may not be solved by tweaking the units attribute. But it means that software that wants to automate the use of CF data and present them to users will have to have more "intelligence" (well, actually a rather simple dictionary) built in. It's one of those areas where good principles collide with pragmatism. Here I see a majority of the CF community tending to principles - there were other cases in this discussion list where pragmatism reigned.
Cheers,
Martin
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Received on Thu Apr 14 2011 - 13:23:49 BST
