[TAP] data type for column metadata

[Patrick Dowler]

On 2009-03-31 23:08:05 Markus Demleitner wrote:
> Again: What would be so bad with having clients request an empty VOTable
> for the columns they are interested in to retrieve STC metadata?

We already came to the conclusion that VOTable datatypes do not fully capture 
what is needed to write queries, not to mention metadata aside from column 
descriptions. That is why we came up with the list of SQL types and once 
users have to get some metadata from VOSI or TAP_SCHEMA I don't think it is 
plausible to impose that they get the rest of it from the header of an empty 
VOTable.

Secondly, in the first example of  Section 5.1 in the doc you referred to
(http://www.ivoa.net/Documents/Notes/VOTableSTC/VOTableSTC-20081018.html) they 
use one of the standard reference systems specified in STC-Lib: 
UTC-ICRS-TOPO. That is exactly what would be done here if we adopt the 
simpler compact form and a single metadata attribute (to specify something 
like UTC-ICRS-TOPO, for example). 

my 2c,

-- 

Patrick Dowler
Tel/Tél: (250) 363-0044
Canadian Astronomy Data Centre
National Research Council Canada
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Centre canadien de donnees astronomiques
Conseil national de recherches Canada
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