UCD use cases

[Roy Williams]

Please find below some possible use cases for UCD.

-- How do the different proposed UCD/DM schemes help with these cases?

-- What does the query look like in each case, and how would that query be
coded?

-- Can you supply additional use cases? Please try to stay within the realm
of the possible here!

-- If you refer to a Data Model, please try to be concrete about
who/how/example. Please do not simply invoke "the Future IVOA Data Model".

Thank you
Roy
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(1) Cone search. How to decide which columns are the RA,Dec that was used in
the search. What frame (B1950, J2000, ...) do these come from? If there are
columns with ID, what sort of ID is it, and how do I resolve it?

(2) SIAP search. Find the column that contains the URLs where the images
are. Find out if there are other columns that have RA,Dec of the image
center.

(3) We have for example a crossmatch service that is clever enough to know
about error ellipses. How does it get from a table the most sophisticated
error info that is there: (a) position (b) circular error (c) ellipse error.

(4) We want to compare photometry in two tables covering the same star
cluster. How do I decide if they share measurements in the same filter? One
has R band, the other has Halpha. What happens if fluxes are expressed
differently -- eg number / energy /
magnitude / luminosity density.

(5) I want distances to stellar objects measured in meters, so I can make a
3D display for the children. How do I recognize a redshift (z) value, how do
I recognize a radial velocity, how do I recognize an actual distance
measure?

(6) I am looking for supernovae that have both optical and Xray
measurements. Can I (should I) use UCD to help my search?

(7) How do I find 21cm observations (that may be redshifted), which also
have polarization information?