UTYPES

[David Berry]

Alberto,

> I think we have to really clarify the different roles of UCDs and UTYPEs.
> (well, if not everybody, at least *I* do need it).

And me!

> It looks to me that many people even on the DM list think that UCDs
> are a DM thing, used to refer to complex concepts.
>
> For me UCDs are solely a controlled dictionary of basic words,
> while UTYPEs are a way to map to higher level concepts.

Within the context of Quantity, I think UCDs should be simple basic words.
All the extra complication shluld be held within the Frames inside the
Quantity.

> For what I just said, and as opposed to my previous email
> ( http://www.ivoa.net/forum/dm/0456.htm ),
> I just figured out it is probably correct not to mention UTYPEs in the
> Q-DM, since Q holds very simple information.

I see the Frames as holding the complex information, one component of
which is a simple UCD for each axis in the Frame.

David

----------------------------------------------------------------------
Dr David S. Berry    (dsb at ast.man.ac.uk)

STARLINK project		 |	Centre for Astrophysics
(http://www.starlink.ac.uk/)	 |	University of Central Lancashire
Rutherford Appleton Laboratory	 |	PRESTON
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