Dear Jonathan,
thanks for your encouraging mail and the specific questions. Please find
my reply below:
* What if there is more than one compound involved in a standard name? This
could be the case with the existing construction using expressed_as, and you
can probably imagine better than me other situations where standard_names might
want to name more than one species.
According to my understanding, these names will still refer to one
particular "compound" (or "species" if you like).
"Nitrogen_dioxide_expresses_as_nitrogen" is still the same as
"nitrogen_dioxide", only that the mass units are given relative to "N" rather
than "NO2". I cannot think of a good example where you will indeed find more
than one compound name in the standard_name and where you actually aim at
pointing to more than one compound at the same time. An example like
"photolysis_frequency_of_nitrogen_trioxide_decomposing_into_nitrogen_dioxide_and_atomic_oxygen"
(hypothetical example at present) lists 3 compounds, but it is not the
compound that is at the center here, but rather the rate (or "frequency"), so
in this case I would argue not to include a "compound_name" tag.
* Is it specifically only compounds that you want to identify, that is,
excluding elements, lumped groups of components, ions or other chemical
species? In my draft lexicon, I have a category "species". This includes all
chemical species, but also biological species and some other things such as
aerosol and grapel. That's because they appear in similarly patterened
standard_names. Do we need to draw a semantic distinction? That would increase
the number of standard_name patterns.
This is indeed a tough decision. Without having thought through this in all
detail, my gut feeling tells me that it might be more useful to distinguish
between fields or applications here and adopt a rather cautious approach when
adding such tags. Otherwise we will soon end up in a similar situation where
the tags are so broad that they cannot be parsed automatically, and we will
invent yet another level of classification. What I have in mind would be an
application that would lexically parse the standard_name table and then can use
such information to offer "informed choices" to the user. For example, you
create a plot of ozone concentrations (sorry, that is
"mole_fraction_of_ozone_in_air"), and the program would then tell you which
other variables about ozone are in the dataset (or available from some web
service). So far, this should also work if, for example, marine biological
species were labeled by the same token. But if you want to make the relations
one level bigger a
nd get suggestions for "other relevant atmospheric chemical compounds", then
the marine bacteriae, algae, fish and mammals would literally flood the system.
As to "aerosol" and "graupel", this will require some more discussion,
because aerosol is seen by some also as a medium, rather than a compound. I am
not sure at present which concept would be more meaningful for these.
Best regards,
Martin
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