IVOA Note on UCD maintenance

[Thomas McGlynn]

Marco C. Leoni wrote:
> The Note can be found here: http://www.ivoa.net/Documents/latest/UCDmaintenance.html
> 
> Cheers,
>    Marco
> 
> 

In addition to the procedure for approving changes, I'd suggest one needs to
be clearer about the nature of the change that is being contemplated.

Here are some of the kinds of changes I can imagine:

Deletion: The UCD word is to be removed from the list of standard UCDs.
           Normally a deletion request should include a statement of what
           UCD would be used in place of the original UCD.
           A list of deleted UCDs (e.g., all of UCD1) and their replacements
           should be maintained.  Another example here might be the FITS 'EPOCH'
           keyword which was originally misdefined and is now deprecated and
           replaced by EQUINOX.  There is a pending request to replace
           UCDs for mean and variance with the moments of various orders.

Modification: The role of the UCD word is being changed (preferably expanded
           so that existing uses of the word are not made invalid).  E.g., this
           might come up when a concept is originally split into too fine granularity
           and it's decided that in the future only one of a set of original UCD's
           should be used.

Amendment: The description of the UCD is to be corrected, but its intended usage
           is not changed.

Addition: A new UCD word to be added.  This is what most of the fuss has been about.
           In addition to the general description, I believe that there needs to be
           some very specific roles about how this word can be combined with other words.
           Can it be a primary word or is it primarily intended as a modifier?


This last point leads to the issue that so far we have discussed the maintenance
of the vocabulary only at the level of UCD words.  Some management of the
use of atoms and maintained guidelines on how given words can be combined into UCDs
are probably also needed.  E.g., I'd suggest that  re-use of atom strings be
forbidden or at least be strongly discouraged.



A little nit ...

Looking at the proposed UCDs I'd like to ask that some standard on the capitalization of
UCDs be promulgated.  There are suggestions for
     pos.htm  (as the Hierarchical Triangular Mesh index) and
     phys.IMF (as the Initial Mass Function)
Personally I would prefer lower case in both of these, but so long as it's consistent
I don't care much.



	Tom McGlynn