TAP information schema

[Doug Tody]

On Fri, 5 Oct 2007, Ray Plante wrote:
> Knowing nothing to start with, I can imagine that the client would send a
> trivial "select *" kind of query and then analyze the header (although
> this is not much different from analyzing a FORMAT=METADATA query ;-)

Since these are narrow tables, probably nearly all IS queries are
likely to be of the "select *" type although there might be a "where
tableName=foo" clause (none of which requires ADQL).  A typical client
application wouldn't need to analyze the header of what is returned
(although it could), rather it would merely read the output returned
by the standard table i/o into some runtime descriptor such as a
result-set object or hash table, and check if a given field exists
when accessing this data.  A smart client application will probably
always do this whether or not we require all IS fields to be returned.
The main reason to require that all metadata be provided is for the
more automated expression evaluation techniques such as ADQL, where it
is probably an error if an operand cannot be resolved.

	- Doug