UCD elements

[Roy Williams]

> At the moment we have an element called <UCD> that contains
> UCD v1 values.  We are now talking about UCD1+ which are
> different; what element name should we use
> for these?  <UCD_PLUS> ?

I think the element name UCD will be enough for now. That keeps it simple.

However, if we want to get more complex, then we should build a proper UCD
schema, separating the atoms, words, and phrases, allowing RDF statements
about relationships between various UCDs, attribute names, and ivo://
identifiers. That would be the sophisticated path forward.

Roy