Comments on Image Data Model

[Markus Demleitner]

Hi François,

On Mon, Nov 05, 2012 at 05:51:03PM +0100, François Bonnarel wrote:
>     That's the reason why I thought the direct mapping of WCS
> Keywords into utypes as proposed by the SIA2 2009 draft with a more
> straightfoward solution.

I think you are right -- we should not (now) express the WCS
transformation using STC, whether or not it is expressive or not to
do that; at least we should not require the representation.  WCS is
fine for what it does, and there's broad tool support for it.  So, we
should probably just leave it like it is -- as an opaque CLOB to be
interpreted by user software.

Yes, we're tieing us to WCS in this way, but I guess that's a
reasonable price to pay; trying to disguise that fact by mapping FITS
card keywords to something that looks like utypes does not seem
helpful to me.

Whatever we want to represent that's not (or not directly) in WCS, or
what's straightforwardly done in STC -- sure, let's do it the IVOA
STC way.  But let's not redo WCS if we don't have a very strong
agenda for that.

Cheers,

          Markus