[CATALOGUE]Starting Data Model Subgroup

[Jonathan McDowell]

> VOTable is the XML serialization of whatever it
is that the Catalogue DM group come up with, so isn't this more a case of
reverse engineering?

No - the other working groups have made it clear they have requirements
for a standard model for astronomical source catalogs. The VOTable
is a serialization of a simple table, but an astronomical catalog
is more than a table - it will have extra standard metadata linking
the sources to their parent observations and extraction algorithms,
for instance. One output of the Catalogue data model effort will
certainly be a more formal statement of the VOTable model, but another
output will be recommendations for ways to serialize this extra metadata
in VOTable (particular PARAM and FIELD values for certain things, for
example). And yet another output will be an XML schema for those who
prefer to use generic XML, although in the particular case of catalogs
I hope that a VOTable-based serialization will be the preferred 
approach. But just saying "write a VOTable" is not a sufficient spec.
I hope the CDS folks can say a little about how a Vizier README is
converted to VOTable, and others can comment on how pipeline-generated
catalogs should be recorded, and what extra metadata (wavelet scales,
data characterization like wavelength band, etc) are appropriate.

  - Jonathan