VODataService 1.2

[Markus Demleitner]

Dear Registry,

In Victoria, I had promised to start a review of VODataService 1.2.
My strongest itch in that department is the new STC coverage scheme
(http://ivoa.net/documents/Notes/Regstc), but there are several more
points to review.

I've now translated VODataService into ivoatex, did some superficial
maintenance and put in the new coverage scheme.  You can see the
changes on Volute,

https://volute.g-vo.org/svn/trunk/projects/registry/VODataService

[contact me if you want commit privileges and don't have a Volute
account yet], and there's a rendered version (with plenty of todo
notes) at http://docs.g-vo.org/VODataService.pdf.

A few things I'd really appreciate input, and even more appreciate
contributions on:

(a) In contrast to the original RegSTC roadmap, I'm now saying
spectral coverage is in energy rather than wavelength; I think we
need to do this considering multimessenger astrophysics will only
become more important (and wavelength has always been a poor choice
to begin with, what with lots of wavelengths being air wavelengths in
reality).  I'm not terribly happy with using values in Joule, but at
least that puts everyone at a similar disadvantage.

What does everyone think?  Use eV so at least some people will
recognise their spectral values?  Use -log10(E) so we get prettier
values and perhaps set a good example?

(b) In addition to the in-document todos, I've listed some changes
I'd like to see in 1.2 in Victoria.  Roughly, they are

* DALI-typed interfaces (a.k.a UWSRegExt)

* schema-less tables

* tap_schema compatible names in tableset

* richer metadata on BaseParams (limits? distribution? valid values?)

* richer table metadata (#rows, coverage?)

* DALI-compatible ParamHTTP result types

* dataproduct types?

* type system cleanup

See the victoria talk for a few more hints what this was about:
http://wiki.ivoa.net/internal/IVOA/InterOpMay2018Reg/voidoi.pdf
(yes, we are behind schedule; in my defense, the ivoatex translation
was essentially on time; I just shouldn't have picked the fight with the
forklift after that commit).

I'm still (and honestly) looking for volunteers to work on and think
about any of these topics and push along their update.  Don't be shy.

(c) Of course, at this stage you are more than welcome to disagree
with any particular proposed change, and in particular propose other
things that should go into VODataServer (or be thrown out).

Thanks,

          Markus