Error column in VOResource

[Ray Plante]

On Tue, 18 May 2004, Martin Hill wrote:
> If you mean that a service returns a VOTable, and so we can ask for a 
> VOTable header, that rather implies that you know already which columns 
> to ask for, as the resultset will not (I believe?) give all the columns 
> every time.

The purpose is to discover all the possible columns.  As an example, see 
the SIA spec, section 7.1 
(http://www.aoc.nrao.edu/~dtody/sim.html#registration).  A metadata query 
returns a VOTable with no rows but all the columns that can be returned.  

SkyNode has an specific operation for retreiving column names and their 
UCDs.  This is not has rich a response (however, this spec is in 
development).

cheers,
Ray