UCD in the VO registry

[Andrew Lawrence]

*(2.2) A UCD is a semantic type, not an instance. It is semantically
*different from a Name. 

I think this is the key point and absolutely correct. UCDs also don't
specify units or data type (i.e. real, string, integer) etc. To specify
a column one would need Name, semantic type (UCD), units, and data type.
This is all pretty obvious in VOTable already.

The VO needs to solve the problem of column-specification because we
want the software to know what to without us. However, shoving this
inside UCDs is wrong and indeed dangerously confusing. Don't mess with
the UCDs !

This doesn't answer the question of what we do or don't put in
Registries, just that distorting UCDs aint the answer anyway.


   andy l