UCDs status and perspectives

[DIDELON Pierre]

> From Markus.Dolensky at eso.org Thu Mar 20 17:01:00 2003
> To: DIDELON Pierre <dide at discovery.saclay.cea.fr>
> CC: ucd at ivoa.net
> Subject: Re: UCDs status and perspectives
> 
> Hi Pierre,
> 
> I couldn't agree more on the notion of your second point:
> 
>  > 2) Adding UCD.
>  >
>  > As Patricio said, "the problem is not to add more UCDs", everbody
>  > would agree on that, but it is certainly _how_ to perform
>  > the metadata bank update, when _really_ needed.
>  > A very strict and tedious approvment by an "expert group",
>  > as proposed in sebastien's doc, is certainly not appropriate
>  > for a lot of cases, where quick even instantaneous
>  > response is needed.
>  > Once more, migrating to parametrized atomic Descr (PAD?),
>  > will perhaps facilitate their dynamic handling.
> 
> It would be great if we could agree on some rules for using UCDs rather 
> than looking at them individually.
 
I totally agree. What I had in mind  is not a traduction one by one of all
the existing UCD, but the definition of atoms and parameters which allow
to handle the existing UCD in a more flexible way. 
So, PAD can point to UCD, but the reverse would perhaps not always be true. 
But it is not clear to me, if the two systems coexists in the future,
which will be the needs of update synchronism and joined maintenance!

>...This might not be fully in line with 
> the original idea when UCDs were invented as some sort of table column 
> identifiers. The scope, however, is much broader now 

That's why PAD is perhaps more appropriate than UCD, because we no longer
deal only with column descriptors but with _global_ metadata.

>...- it's about meta 
> data in a more general sense. We need them in the registry, as query 
> specifiers, as a way for interpreting VOTable docs, as tags in data 
> models, ...
> 
> Markus
> 

Sorry for being unclear with rough english,
cordially,
Pierre