Spectral DM VOTable serializaiton issues

[Doug Tody]

Hi Igor -

This is not a direct response to your comments, but one thing I did
recently with SSAP (which I think has largely gone unnoticed) is enter
both the SSAP and Spectrum data models into a spreadsheet.  This makes
it much easier to get a uniform view of things like UTYPEs, UCDs, units,
what is provided and what is missing, etc., than trying to work all
this out from the documents.  You can find this at

    https://webtest.aoc.nrao.edu/ivoa-dal/ssap-keywords.xls

The spreadsheet should display in either Excel or OpenOffice.

In doing this I found some cases where things like the UTYPEs were
inconsistent in the Spectrum document; these cases should be fixed in the
spreadsheet, but may not yet have been resolved in the specification.
Also, there are detailed examples of suggested UTYPE usage (both in
queries and in spectrum datasets) in the output that comes back from
the SSAP reference services.  Some of the details of how this is done
probably need further discussion.

I still need to go back and note any differences from our current
specifications, but in considering further changes to Spectrum I suggest
we try to reference both the specification and the spreadsheet.

	- Doug