TAP information schema

[Ray Plante]

Hi Doug,

I noticed that your schema marked some things as required; I take it that 
the other items are optional (always a reassuring notion).  I'm curious, 
though, how client knows what what columns are available for an IS query. 
Did you have a scenario in mind?

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 ;-) 
Alternatively, the standard might instead make all columns required, but 
possibly empty.  The intent is that all possilbe would in practice be 
queriable and no initial meta-meta query would be necessary.

cheers,
Ray