VOUnits RFC

[Rob Seaman]

Hi Norman,

I must admit to not having had the chance yet to review the current version of the document, so perhaps this is addressed.

> I think 2 is a problem, but I don't think it's a bad problem.  That is, I more and more confidently agree with Rick in his message of this morning, that you've lost meaning that might be important down the line, if you lose the link between this unit and the mass of jupiter.  OK, there's a problem if the receiver doesn't recognise 'jupMass', but there are mitigation strategies (some listed by Rick), one of which is to look at the documentation, and discover "ah, _this_ exoplanet database recognises the non-standard unit 'jupMass', so I can use that in my requests to it".

A more fundamental issue is that often measurements are calibrated in terms of other measurements.  Quoting something as 1.5 jupMass might not just be a handy way to provide a sense of scale, but it might be that as measurements are refined of what the mass of Jupiter actually is, that the number quoted (in the table or what have you) ought be adjusted to suit.  Examples abound such as the Hubble constant, etc.

Rob