VOUnit for solar density or metallicity?

[Tom Donaldson]

Hi Sébastien and Norman,

Thank you for the responses!  I think I am content with continuing to use Sun as the most reasonable available unit to describe the FIELDs we have, but I am less clear on why it would be considered valid according to the standard.

Sun is a valid vounit symbol. It is described in the current Recommendation, and this
should not change in version 1.1 currently in preparation. The problem comes from the
validator that ignored Sun, but this should get fixed, see :
https://heptapod.host/nxg/unity/-/issues/11<https://urldefense.com/v3/__https:/heptapod.host/nxg/unity/-/issues/11__;!!CrWY41Z8OgsX0i-WU-0LuAcUu2o!0C37XentP6REz1B5JpwoHuwQX6BYnX6-RUFiwlrFqMrpjaGG3s9iZpejm7qfPwwfoyVpyN8bKvrduzFJYMfRBJHzQu6Qc2LBgKed$>

My reading of the document is that Sun appears in Tables 5 and 14.  The wording around and within those tables does suggest that it is a VOUnit.  However appendix C.4, which is the normative definition of the grammar, does not refer to either of those tables so would seem to say that Sun could not be recognized by the grammar.

I note that essentially all of the other units mentioned in Table 5 are also present in Table 2 which is referenced by the grammar definition.  Was Sun left out of Table 2 on purpose or an error?  Should C.4 have referenced more tables?  (or most likely, am I just misreading the document?)  Although all of section 2 is labelled “normative”, and section 2.8 contains Table 5, the wording there is just ambiguous enough to me that if I were implementing a validator I would probably favor the more explicit appendix C.4.

I’m not just asking to be pedantic (and to decide whether to surround our Sun with single quotes).  It turns out that astropy’s VOUnit validation also does considers Sun to be unknown (but does recognize all the other units in Table 5 that are also in Table 2).  Before starting an issue or PR with astropy regarding Sun, I want to make sure that it is indeed “officially” recognized by the standard.

Thanks!

Tom


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