VOEvent registration: Ha!

[Markus Demleitner]

Dear VOEventers,

On Fri, Apr 11, 2025 at 09:06:13AM +0200, Markus Demleitner wrote:
> > updated VOEvent stream/ mentioned in the document makes a reference to
> > technologies like Apache Kafka <https://kafka.apache.org/>. Maybe people
>
> I'd be delighted if I had one of these to register, too.

So, GCN does that, and I am preparing a sample registration with
them.  For them, to subscribe to a stream, you need to know the host
name and a single parameter, the topic.  Do people expect that to be
typical?

Even if not, it seems clear that we need to *at least* communicate a
host name and one or more parameters.  Given that we have a URL to
communicate that, I am now proposing an ad-hoc URI scheme in
<https://github.com/ivoa-std/VOEvent/pull/26>.  I will freely admit
that I don't *really* know what I'm doing here, as I've never really
done anything with Kafka.  It would be great if someone who has could
chime in; in particular, I suspect someone else will already have had
the same problem ("uniquely identify a Kafka stream in an actionable
way") and has probably solved it in some other way.  If so, I think
we ought to follow their lead.

Meanwhile, thanks to the folks over at CHIME, you can now actually
try and discover a VOEvent stream in the VO Registry.  For instance,
"give me access URLs of VOEvent streams in the radio" is

  SELECT res_title, access_url
  FROM rr.resource
  NATURAL JOIN rr.capability
  NATURAL JOIN rr.interface
  WHERE
    standard_id='ivo://ivoa.net/std/voevent'
    AND 1=ivo_hashlist_has('radio', waveband)

on the RegTAP mirror of your choice (mine: http://reg.g-vo.org/tap).

That particular record also has STC coverage, so you can do better
than constraining waveband; the stream standardIDs are not yet mapped
(by me, at least), though.

So, what does everyone think?

Thanks,

          Markus