VOUnits: _another_ version, based on implementation feedback

[Norman Gray]

Arnold and François, hello.

On 2013 Dec 26, at 15:05, Arnold Rots <arots at cfa.harvard.edu> wrote:

>> > * About the units listed in Table 2: I tend to agree with Arnold that the abbreviations
>> >  "Ba" and "ta" proposed for the Besselian and tropical years look strange -- if such
>> >  units are required, "Byr"  and "tyr" would likely reach a better consensus;
>> 
>> I think that Arnold's concern was that he was torn between being reluctant to include these units in the 'known units' list, but at the same time being reluctant to discard them completely.  They're currently in the document as known-but-deprecated in FITS, and unknown in VOUnits.
>> 
> No, Arnold's concern was (and is) that these are troublesome units since they are not well understood
> by most people and certainly not SI. So they definitely should be deprecated.
> However, they have been used and there is a fair body of archival data that contain temporal information
> expressed in these units. For that reason I feel we have no choice but to accept them.

In that case, I see no harm in including them in the list of VOUnits 'known units', but deprecated, either on Arnold's grounds here, or alternatively on the grounds that they're listed in FITS, and we're aiming not to be surprising.

I'll adjust the Unity list of units, unless anyone shouts promptly.

I should stress that the only real difference this makes is that doing so reserves the strings 'Ba' and 'ta' as meaning _exclusively_ bessellian and tropical years.  Still, that's enough of a rationale. 

Best wishes,

Norman


-- 
Norman Gray  :  http://nxg.me.uk
SUPA School of Physics and Astronomy, University of Glasgow, UK