Nature of the catalogs (Was: Re: Quantity-based catalog model (Was: Re: Source Catalogue DM))

[Pedro Osuna]

Dear all,

I am glad to see there start to be reactions on the Source Catalogue DM.

As you may know, it was agreed that the Catalogue Data Model subgroup of
the IVOA Data Model group would start by trying to define a Source Data
Model as a first step toward demonstrating the usability of a general
Catalogue Data Model.

There were loads of discussions on whether we were trying to model
tables, or whether a Catalogue is a table, or what the differences are
between VOTables and Catalogues, etc. You can see all those discussions
at:
http://www.ivoa.net/internal/IVOA/IVAODMCatalogsWP/Catalogue_DM_mails.txt

All these issues were discussed and it was agreed that we ought to start
by the most required and possibly useful type of catalogue model: the
one for Sources (please check the page:
http://www.ivoa.net/twiki/bin/view/IVOA/IVAODMCatalogsWP).

The only inputs received for this specific Source DM were compiled into
a model that was presented to you in Kyoto, where I insisted (Jonathan,
do not parody this....) on the need to receive more inputs to build a
solid and useful DM for everyone. 

This tries to give you an explanation on the "granularity" mentioned by
Anita and why we did go to try the Source data model. I will send my own
inputs on a separate mail on the specific issues mentioned by Anita.

With respect to the possible reactivation of work in the group, and in
view that it seems to be still some glowing embers of interest, I will
try to grab some of you during the ADASS/Interop meeting here in Madrid,
to try to find a common approach to the whole issue. In particular I
would like Brian and/or Ed plus others to be there. Will that be
possible, Brian? In case you're not coming, could Jonathan collect your
inputs/ideas/complaints and transmit them? I believe Brian/Ed model fits
in naturally in a possible general IVOA Catalogue DM and also in the
Source DM and we only have to find out how to marry the different
structures.


I will send some of you a separate mail trying to fix some date for
discussion in Madrid.

Cheers,
P.


On Thu, 2005-09-15 at 19:14, Brian Thomas wrote:
> On Thursday 15 September 2005 12:19 pm, Jesus J. Salgado wrote:
> > However, it does not solve the question of what do you need to describe
> > a Source (it only leaves a placeholder to add all the properties that
> > the source could have, but without trying to define them). I think we
> > need something more detailed if we want to use this data model as a base
> > to inter-operate in the future.
> > 
> 
> 	Jesus,
> 
> 	It is true, we have tried to side-step defining what a "source" actually
> 	is, and for the near-term, we are happy to start with the Salgado/Osuna/etc
> 	model. As you indicate, part of the reason for our side-stepping
> 	of this issue was to be able to get to critical structural issues for how to 
> 	construct a general purpose collection/catalog model. Presumably (at least, 
> 	we presume :) this model should be reusable to hold more than just sources.
> 
> 	I think the debate about sources is whether we prefer to have catalogs hold
> 	objects which are oriented towards observational characteristics only, or can
> 	we not have theoretical ones (e.g. I may want to construct a catalog of 'galaxies' or 
> 	'stars'). I believe we want both, and that we will want to have catalogs which
> 	are virtual views of other catalogs (for example, a catalog of galaxies which is
> 	cobbled together from several separate source catalogs). Our model is designed
> 	with this intention (although still some work to do in this direction, and as always,
> 	we are happy to collaborate :)
> 
> 	On a related note: what DM -related activity will happen at the IVOA? I haven't seen
> 	any information about meetings, etc (perhaps as usual hopelessly out of the loop).
> 	I would definitely like to discuss the catalog/collection issues in depth while in Spain!
> 
> 	Regards,
> 
> 	=b.t.
-- 
Pedro Osuna Alcalaya

ESA 
Science Archives System Engineer
Science Archive Team
European Space Astronomy Centre
(ESAC/ESA)
e-mail: Pedro.Osuna at esa.int
Tel + 34 91 8131314
---------------------------------                                                                                
European Space Astronomy Centre
European Space Agency
P.O. Box 50727
E-28080 Villafranca del Castillo
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