TAPRegExt fine grained differences between tables

[Mark Taylor]

Walter,

On Wed, 10 Jun 2015, Walter Landry wrote:

> Markus Demleitner <msdemlei at ari.uni-heidelberg.de> wrote:
> > Hi Walter,
> > 
> > On Tue, Jun 09, 2015 at 04:53:51PM -0700, Walter Landry wrote:
> >> We have a variety of tables with different backends all served
> >> through a single TAP endpoint.  Because the backends are different,
> >> they support different optional components of TAP.  Reading the
> >> TAPRegExt standard, is it correct to say that there is no way to
> >> express these kind of fine-grained differences between the tables?
> > 
> > This concerns what user-defined functions are available on them?
> > Things like upload limits/formats?  These, yes, are declared globally
> > per capability.  I'd recommend per table examples (for now, as per
> > the TAP Implementation Note, if I may say so myself) to document
> > where the system behaves in ways surprising to users.
> 
> Ok, though this feels vaguely unsatisfying.

I can see how this might not fit your service very well, so I can
sympathise with the "unsatisfying" sentiment.  But I'm inclined to think
the alternative would be worse.  TAPRegExt is already reasonably
complex, and if the options are (optionally) multiplied by a number
of backends per service I can imagine this would often end up being
write-only metadata: dutifully filled in (or not) by service
providers but never actually used for anything by any client.
As an author of a TAP/TAPRegExt client, I doubt I could write
a GUI that presents per-table service capability metadata to
users in a way that they'd really digest.  Machine clients might
have more chance, but it would still add quite a bit of processing
complexity for likely not much benefit.

Just my 2p (which I reserve the right to change my mind about
if somebody persuades me differently)

Mark

--
Mark Taylor   Astronomical Programmer   Physics, Bristol University, UK
m.b.taylor at bris.ac.uk +44-117-9288776  http://www.star.bris.ac.uk/~mbt/