TAP1.0 Comments

[Paul Harrison]

On 2009-07 -15, at 12:38, Douglas Tody wrote:

> Basically what this would allow you to do is build an index table for
> all the 8000 or so Vizier tables.  It could be queried with a GDS  
> query
> (in TAP probably) to find the tables of interest.  These would then
> be queried individually with TAP.  Aside from being simpler, I think
> this is more convenient and flexible for the client than getting all
> the query responses in one big file from which they would then have
> to be extracted.  If we really wanted that it could be done with an
> integrator service of some sort.


Doug,

I think that you have missed the point here - Vizier *is* such an  
integrator service. This was precisely what François was saying, and  
pointing out that the client does not want the inefficiency of doing  
1+N queries where N is a large number when in fact they could do just  
one when querying Vizier. I think that the additional point that was  
made was that in an all catalogue search Vizier can return different  
columns for each table (catalogue) that matches, which is why François  
wants to be able to issue multiple tables within a single VOTable  
document. It seems rather a shame to disallow this in TAP in many ways  
as VOTable is supposed to be self describing, so that the client  
should be able to "understand" the multi table result just as easily  
as they can a single table result.

Cheers,
	Paul.