[QUANTITY] and [OBSERVATION] data models: new drafts

[Jonathan McDowell]

Dear IVOA DM Group,

  In late 2003 we were drowning in emails which were not remotely
converging. I took advantage of the co-location of a number of mailing
list participants in a couple of meetings in January  to try and build a core
consensus on Quantity and Observation with a small team representing a
spread of views in a face-to-face discussion. We now have individuals
from more than one institution agreeing (mostly agreeing, anyway) on a
model, which is progress. 

The results so far have now (at last!) been written up as a set of  WG
Internal Drafts. 

The documents are now on the IVOA TWiki at 
 http://www.ivoa.net/twiki/bin/view/IVOA/IvoaDataModel
specifically at
 http://www.ivoa.net/internal/IVOA/IvoaDataModel/qty.v0.2.ps  (or pdf)
 http://www.ivoa.net/internal/IVOA/IvoaDataModel/obs.v0.2.ps  (or pdf)
and are also available at
 http://hea-www.harvard.edu/~jcm/vo/docs/
with further commentary on Quantity at 
 http://hea-www.harvard.edu/~jcm/vo/docs/qexamples/qxml.html

I've also updated the TWiki pages extensively.

I believe these drafts, although far from perfect, can serve as the starting
point for an eventual IVOA standard. However, the other WGs are waiting for us
and the IVOA Executive Committee has decreed that "eventual" means
"VERSION 0.9 (GOOD ENOUGH TO START CODING TO) PRIOR TO THE MAY 2004
INTEROP MEETING". I would say that the Quantity model is a good 0.7 or more,
while the Observation model still needs a lot of fleshing out.

We therefore have about two months to go from the current drafts to a
full version. This will require focus and a willingness from all
participants to accept "good enough" instead of "perfect". The IVOA
Exec has also said that 100 percent consensus is not required and
that I as chair should make the hard choices about leaving some people
disappointed. Be warned. If we don't deliver by that time, the IVOA will move
on and adopt ad hoc standards, and the DM process will be ignored.

It is now time to go back to a more open process. However, I do believe
the ineffectiveness of the earlier process shows that we need such `core
team' subgroups to lead progress; input from all will be welcome, but
the Work Package Teams (WPT) will have the responsibility for doing the
real work: editing the drafts and reaching consensus. I would therefore
like to invite those members who were in the earlier face-to-face
meetings to formally compose 

 Observation WPT
    Alberto Micol, Francois Bonnarel, Mireille Louys,
    Gerard Lemson, David Giaretta.
  
 Quantity WPT
    Brian Thomas, David Berry, Patrick Dowler, Mark Cresitello-Dittmar

and create a new WPT called Catalogs.

If you would like to join one of these groups, let me know (I am
particularly eager to get Astrogrid,  Asian and Australian members to
balance things); however I want to keep the size of these groups small,
and membership will imply both a willingness to devote subtantial
amounts of time and a committment to compromise in search of consensus.

Meanwhile, I encourage comments on the new drafts, particularly
if those comments suggest specific changes to make to parts of the text
you don't like.

   - Jonathan McDowell