UCDs status and perspectives

[Anita Richards]

Jonathan, Patricio et al:

Regarding Jonathan's example of a table with measurements of flux density
at 3 (or more) frequencies, and Patricio's comments,
http://www.ivoa.net/forum/ucd/0006.htm
I indeed think we should get away from PHOT_FLUX_RADIO_1.4G or anything
like that, and instead have some way of identifying a flux density
measurement with the frequency at which it was made, without having a
separate UCD for every frequency anyone uses. In the long run
Ray's proposal http://www.ivoa.net/forum/ucd/0011.htm  to use Xpath seems
exactly right, that is what I was trying to say in words (i.e. we need
values and attributes etc.).

However, is there a means of transition from the present use of UCDs, e.g.
by associating columns
FREQ  FLUX_DENSITY FLUX_DENSITY_ERROR
GHz      mJy           mJy
1.4     5              1
4.8     10             1
22.0    20             3

or whatever?

I suppose there are two problems here; firstly, to respond to Sebastien's
summary of the present discussion around UCDs - to see how much consensus
there is on what one would like in an idea world - and there seems to be
general agreement on the most general data models at least, different
groups may need more detail in different aspects but all the discussions
seem to be moving in the same direction.

Secondly, however, how much can be done 'seamlessly' based on the
existing, working CDS UCD system?  It is important to keep that going, not
just because astronoemrs depend on it and want to see it do these things
they hear about in reports from VO meetings, but because we need to test
developments on the community as much as possible, and we will find
subjects much more easily if we can give people prototypes which look as
familiar as possible (as with the AVO demo).  Also many new functions e.g.
the SED tool and VOPlot are being developed based on the existing UCDs.
Is this possible, is this the direction in which IDHA is going? Or will
there come a break point, and if so, when?

cheers
a



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Dr. Anita M. S. Richards, AVO Astronomer
MERLIN/VLBI National Facility, University of Manchester,
Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL, U.K.
tel +44 (0)1477 572683 (direct); 571321 (switchboard); 571618 (fax).