TAP basics

Following the recent discussions on TAP, I feel it's still necessary to agree first on some basic points:

1. Questions of vocabulary

   It is fundamental in the discussions to ensure that we are sharing a    common vocabulary. Tables, columns, catalogs, databases, (primary) datasets,
(virtual) tablesets, protocol ... seem to have varying meanings.
   All these terms ought to be defined rigourously in the final document.    Would this be possible ?

2. The role of the protocol(s)    

   Assuming that the protocol represents the dialog which takes place    between the application (client) and the data provider (server),    we have to distinguish clearly the roles of the connection layer
(HTTP or SOAP) from our protocol (the TAP). These should remain
   as independant as possible -- or we would have to reconsider TAP    if we move to another connection protocol. Therefore using HTTPspecific     codes to indicate an empty result does not seem to be a    good approach for me.

   Having simple / complete access possibilities (ESA TAP draft doc)    is certainly useful. I've however problems to understand exactly how    it works (esp. section 3.1.2.4)

3. DAL commonalities

   Yes, having similar basic methods for accessing VO data is desirable,    for instance having the "queryData" and "getData" -- which I see as    a way of asking "how should I formulate my request" and "this is my    request" -- introduces a flexibility which looks fundamental. However    from Doug's document I could not get a clear idea on how to get only    metadata (i.e. detailed description of the tabular material involved) ?    Looks like "queryData" can return full results or just table descriptions

• who decides (client or server) and on which grounds ?

   I would also like to be sure that tabular data which are not of the    "astronomical catalog" type (e.g. atomic data) are not forgotten in    this approach.

4. Output results  

   For the metadata, an empty VOTable OR an XML serialisation using the    Registry schema should be OK -- if a tool to translate between these    2 formats does not yet exist, it should be done at some point.

Cheers, francois

Francois Ochsenbein       ------       Observatoire Astronomique de Strasbourg
   11, rue de l'Universite F-67000 STRASBOURG       Phone: +33-(0)390 24 24 29
Email: francois-at-astro.u-strasbg.fr   (France)         Fax: +33-(0)390 24 24 17
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