Note on enabling STC queries in the Registry

[Markus Demleitner]

Dear IVOA community,

I have just published a Note on 

  A Roadmap for Space-Time Discovery in the VO Registry

on the document repository: http://ivoa.net/documents/Notes/Regstc

When encountering the Registry, our users are very typically
bewildered that the Registry cannot really cope with very obvious use
cases such as:

* Where can I find data in the near infrared for sources within two
  degrees of the Galactic center?
* Where can I find photometry on the southern sky for the first half
  of the 20th century?
* Where can I find X-ray spectra for objects in the Large Magellanic Cloud?

Fixing this defect has turned out to be surprisingly complicated,
with the initial plan reaching back to at least 2007 not really
having come to fruition -- I'd say partly from lack of experience,
partly because some key components (specifically, MOC and RegTAP)
were still missing.

However, I think we can fairly easily do it now (and Aladin 10 shows
what kind of cool functionality is enabled over and above the basic
user expectations).

Still, several standards have to be touched until we're there, which
is what this roadmap lays out.  Comments on this are highly welcome
(the note contains several points that I still consider open), as
well as, of course, any help you can give.

Most importantly, however: It would be great if data centers could
see if they can produce the metadata as described in the note.  I'm
in negotiations with the RofR to make it so your Registry won't
become invalid if you add it -- it is really important to understand
whether the scheme proposed works for you early on, and it's
important to have good STC metadata on as many services as possible
so it becomes attractive for clients to offer interfaces to it.

Thanks,

          Markus