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[Support #ZZS-676605]: [udunits] Need to represent Celsius and Fahrenheit with C & F


> I want to use UDUnits2 with a Chemical Engineering simulator called Aspen 
> Plus.  Aspen Plus doesn't require coulombs or farads, but it represents 
> Fahrenheit and Celsius with F and C.  I thought adding these definitions 
> would just be a matter of editing the udunits2-common.xml file like so:
> ...
> <symbol>&#x2109;</symbol>   <!-- DEGREE FAHRENHEIT -->
> <name> <singular>fahrenheit</singular> </name>
> ...
> To
> ...
> <symbol>&#x2109;</symbol>   <!-- DEGREE FAHRENHEIT -->
> <name> <singular>fahrenheit</singular> </name>
> <name> <singular>F</singular> </name>
> ...
> And maybe I would have to delete coulombs and farads out of the 
> udunits2-derived.xml file.  However, any attempt to do any of those things, 
> the deletion of farads or coulombs, or the addition of new names "F" or "C" 
> and udunits2 appears to fail to parse the XML file.
> I don't think I'm messing up the XML, because I can add additional, more 
> unique, names to Fahrenheit, like "earwax" or "degrees_Jim."  But "F" and "C" 
> seem to be illegal.  I haven't dug into the UDUnits code yet, does anyone 
> know how to get this to work?

I STRONGLY advise against doing this. Your datasets will loose interoperability 
and the workarounds are trivial (use instead "deg_C", "celsius", "\xB0C", or 
any of the other identifiers, for example).

I hate to say it but, in my personal opinion, the authors of Aspen Plus are 
exposing a lack of knowledge, professionalism, and/or rigor on their part by 
not adhering to internationally agreed-upon standards.

If you insist on changing the standard definition of, for example, the symbol 
"C", then you will have to modify all occurrences of that symbol in the 

    cd $prefix/share/udunits
    grep -w C udunits2-*.xml
    udunits2-accepted.xml:            <def>2.58e-4 C/kg</def>
    udunits2-common.xml:            <def>1.602176487e-19 C</def>
    udunits2-common.xml:            <def>9.64957e4 C</def>
    udunits2-common.xml:            <def>9.65219e4 C</def>
    udunits2-common.xml:            <def>9.648531e4 C</def>
    udunits2-common.xml:            <def>3.335640e-10 C</def>
    udunits2-derived.xml:        <symbol>C</symbol>
    udunits2-derived.xml:        <def>C/V</def>
    udunits2-derived.xml:        <symbol>&#xB0;C</symbol>            <!-- 

The last entry should be left alone; the 3rd-to-last entry should be deleted; 
and all other entries should have the "C" replaced with "coulomb".

> Thanks,
> Jim
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Steve Emmerson

Ticket Details
Ticket ID: ZZS-676605
Department: Support
Priority: Normal
Status: Closed