VOUnits RFC

[Frederic V. Hessman]

On 1 Aug 2013, at 18:30, Arnold Rots <arots at cfa.harvard.edu> wrote:

> 
> > If that's not good enough, then we need an explicit mechanism to define
> > a custom unit in terms of allowed units, like 'H' = 75 km/s/Mpc
> 
> Defining other units would be necessary, I think, but (a) couldn't feasibly be done _within the unit string_, and (b) would be a natural facility for a library implementation to provide.
> 
> No, not in the unit string. I'd suggest to add the option of adding an element to
> the document that allows definition of a custom unit, like
> <defineUnit name="Myweight" unit="kg"> 88.1 </defineUnit>
> And one could add an attribute that indicates what it's intended use is to be
> (whether the value is to be taken as absolute and literally).

<defineUnit name="H_0" unit="km/s/Mpc" utype="http://ivoa.net/vocab/unit#HubbleConstants" rdf="http://ivoa.net/vocab/unit#HubbleConstantPlanck" value="67.3" error="1.2">Value from http://arxiv.org/abs/1303.5076 (yes, need to put this in Dublin format….)</defineUnit>