utype questions

[Rob Seaman]

Isn't the intended usage for utype something like:

	<whatisit utype="ns:target.class">whatitis</whatisit>

When Doug says:

> A major point of UTYPEs is to provide a simple, direct, and *unique*  
> way to specify the field of a specific data model.

Isn't this in reference to the value of the utype attribute in the  
example above?

But surely the value assigned to the enclosing element will depend on  
which field of which data model is being described?  One would  
certainly think that sometimes a vocabulary specification might be  
appropriate for "whatitis".  Describing things like RadioQuietAGN is  
precisely why vocabularies (in either the VO sense or the real world  
sense) exist.

More to the point, it isn't clear how such values (of the element, not  
the attribute) could be legislated against.  This is just a fancier  
version of the VOEvent param mechanism, mapping generic keyword=value  
pairs onto an implicit or explicit data model.  The same strengths and  
limitations apply.

Rob