WD-TAP-1.1 : tap_schema and VOSI-tables

[Markus Demleitner]

Hi DAL,

On Mon, Oct 03, 2016 at 03:28:49PM -0700, Patrick Dowler wrote:
> VODataService would be unneeded/obsolete. The whole datatype mapping
> and handling would be much simpler and direct. I can't see any
> downside to this aside from it being different from then ad-hoc things
> we did in 1.0 :-)
> 
> * proposal *
> So, although it would delay implementations somewhat, I propose that
> we add an xtype column to tap_schema.columns and use the data_type
> column for the underlying primitive type in TAP-1.1

>From a server-side perspective: I'm all for it; it clearly should
have done like this from the start.

But then I suppose by the letter of the law, it would be an
incompatible change, because clients that so far have been looking
for adql:point (or whatever) will be finding char (or something like
that).  I wonder if clients so far actually do that.  I suppose
TOPCAT looks at types to try and produce meaningful examples (does
it?).  Is anyone else out there using TAP_SCHEMA datatypes in a way
that'd break with this change?

Assuming there's no winces from the client side: As such, the change
makes everyone's lives a lot easier.  Weighed against the trouble of
having to work out what version a TAP_SCHEMA in those cases people
care about the data types at all (and I'm shuddering to think what
I'll do with GloTS): I'm not enthusiastic, but I'm not opposed to the
change either.

Cheers,

          Markus