WD-AccessData-1.0-20140312

[Markus Demleitner]

Hi DAL,

On Thu, Jul 31, 2014 at 09:42:59AM +0200, François Bonnarel wrote:
>    I encourage people to (re)start to send comments on the current
> draft (see below) and have in mind we had on this before and during
> the last interop in may.
> 
>    What we have for interface is basically sufficient for the first
> priority cutouts and selection requirements from the CSP. It has the
> great advantage to be consistent with the SIA query interface. An
> update of the draft to take into account last evolutions of SIAV2 is
> needed

I'd *really* like AccessData to not only work with SIAv2; we have our
SSAP use cases, for instance.  Hence, while I've given up resistance
against the POS alphabet soup, I *really* think (in particular
version 1) of AccessData should contain the "three-factor semantics"
(as discussed in my Madrid talk
http://wiki.ivoa.net/internal/IVOA/InterOpMay2014DAL/flexdatalink.pdf)
-- a.k.a. simple, atomic parameters with strong metadata.

In that vein I'd also argue that consistency with the SIA "query
interface" is not a goal in itself; as I won't tire to mention, the
conventional DAL S*AP interfaces have serious issues (mainly in
interface discoverability), and I'd prefer not to be consistent with
those.

The big advantage of adopting three factor semantics for "non-magic"
parameters is that we don't have to wait for "getMetadata" or
a similar mechanism to allow clients to discover allowed ranges and
such and actually provide meaningful user interfaces.  

The POS alphabet soup could still be part of this; it'd be another
parameter, possibly even a mandatory one if you insist (although I'd
consider this unwise), identified through a UCD and without further
metadata until the time ImageDM is ready and we have good ways to
serialise instances of it.

TIME, BAND, POL, SELECT from the existing AccessData could fit fairly
well into the sanitised parameters (ok, TIME should become TIME_MAX
and TIME_MIN, BAND LAMBDA_MIN, LAMBDA_MAX, but that's details).

I'd be happy to contribute the prose for this.  For that, however, I
believe the standard text should go into version control.  I've been
planning to do an ivoatex package for authoring IVOA standards in
LaTeX (based on what Mark Taylor uses for VOTable and SAMP) since
Madrid; can the authors imagine moving over the document to such a
system?

Cheers,

         Markus