WD for the Obscoredata model and its implementation on TAP

[Doug Tody]

On Tue, 21 Dec 2010, Arnold Rots wrote:

> I have four comments:
>
> Like Tom McGlynn, I find the prescribed unit for the spectral axis
> (wavelength) very awkward. Only 1/3 of the community thinks in this
> inverse unit. I would strongly suggest allowing wavelength, frequency,
> or energy; if we really need to stick with only one, I would suggest
> frequency as the most physically meaningful one.
>
> TimeScale is missing from the list.
>
> Reference positions are missing, too. They really need to be there.
> One might require them to be the same for space and time, but the
> spectral reference needs to be separate.
>
> I commented earlier on the Redshift axis. Its specification requires a
> Redshift-Doppler toggle, Doppler definition (optical/radio/relativistic),
> a reference position, and possibly the Doppler units (though km/s is
> pretty much globally accepted).

Arnold - All of this is (except possibly adequate treatment of
redshift) is already in the full model.  But ObsCore is a simplified
subset intended only for data discovery.  Agreed something like
reference position is needed for analysis, but that level of precision
is not likely to be needed for data discovery.

Fixing the units is essential for discovery, at least if we plan to
use TAP-ADQL expressions globally.  The primary requirement is that
this work reliably as a computer interface; it does not have to try
to be a good user interface.  We will never succeed with that at this
level if we are trying to address 3/3 of astronomy - but it can be
done in the actual user interface or client application.

 	- Doug