Charlie & CF-Metadaters,
On Wed, Nov 26, 2014 at 8:27 PM, Charlie Zender <zender at uci.edu> wrote:
> Now UDUnits has "molecule" and "byte". They (Steve)
> are receptive to well-justified proposals, so do not feel daunted
> in transmitting to them the suggestion for "photon".
Please don't request such "units". I beg you.
Think about it. How many things exist like "molecule" or "photon". Here's
the start of a list:
tents
clouds
giraffes
desks
people
...
etc., etc., etc. The number of such "units" is, effectively, infinite.
Adding such units is the wrong way to go about solving the problem of
adding quantity-semantics to data values. It would be much better to have
the names of the variables be things like
"number_of_tents"
"number_of_clouds"
"number_of_giraffes"
"number_of_desks"
"number_of_people"
"number_of_molecules"
"number_of_bytes"
"number_of_bits"
and whose units were "1" than to try to incorporate such semantic
information into a unit. The power of units is that there's a limited
number of them: many physical quantities can have the same unit. The US
National Institute of Standard and Technology agrees (see sections 7.4 and
7.5 of <
http://physics.nist.gov/Pubs/SP811/sec07.html>).
A *physical quantity* library should be used for situations in which it's
desirable to have a program automatically convert between, for example,
"bits" and "bytes". Such a library would do for physical quantities what
the UDUNITS library does for units. It would, for example, know how to
convert values between "bits" and "bytes". It could also know how to
perform co-ordinate system transformations, such as converting practical
salinity values to density. The algorithms for such a library have already
been worked-out in multiple packages (VisAD springs to mind, IBM and the
Laboratory for Atmospheric and Space Physics have also created such
libraries).
Please don't request that the UDUNTS package be polluted in order to do a
job that's best done elsewhere.
With regards,
Steve Emmerson
(I feel better now. Thanks! :-)
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Received on Thu Nov 27 2014 - 10:58:14 GMT
