On Tue, 21 Oct 2003 posuna-at-iso.vilspa.esa.es wrote:
> I understand that people having data in X-Y tables do NOT want to hear
> about data models: they only want to be able to perform operations with
> the columns of their tables.
I'm not sure that's entirely true. I think the problem is that three partially overlapping groups of people have been trying over several years to make sense of astronomical data, so they canclassify or organise it to make data access simpler and more uniform.
(1) Those devising UCDs, which started out exclusively for tables in VizieR. I think it is now generally agreed that some hierarchical scheme should replace the original flat namespace (though designed with components which split naturally into layers).
(2) Those devising Data Models. The problem for those outside this effort is that there have been so many data models, different in structure and detail, but all apparently equally valid. I didn't manage to attend the DM sesssion in Strasbourg, but am pleased to hear of serious convergence.
(3) Those devising query languages and data access routines, who need some DM or UCD scheme to do the job properly, except for the serious problem that a UCD does not lead to a unique column in some (many?) tables.
I thought that Tom's ideas at Strasbourg sounded good, and look forward to seeing his proposal in print. If it's true that there is now a single agreed Data Model, does that not suggest that UCDs should be assigned on the same hierarchical basis?
-- Clive Page Dept of Physics & Astronomy, University of Leicester, Tel +44 116 252 3551 Leicester, LE1 7RH, U.K. Fax +44 116 252 3311Received on 2003-10-21Z09:20:44