Applications Messaging Standard

[Thomas Boch]

Hi John,

> >> I can see that not worrying about handover from one hub to another
> >> would simplify things.  So we need to decide how to fire up such a
> >> daemon if it's not already running.  We could just ask the user to
> >> start it, I guess.  No doubt some app authors will still want to make
> >> it seamless by spawning off a hub themselves.  In that case we'll
> >> have to rely on good etiquette so that such hubs don't "bump" an
> >> already running hub, and when the user tries to shut them down they
> >> give fair warning if there are applications still using their hub
> >> (and if closing the app implies shutting down the hub).

That's more or less how Aladin is behaving (in the PLASTIC framework).
It starts its own hub automatically at startup, only if no other running
hub has been detected (this behaviour can be disabled in preferences in
order not to automatically launch the embedded hub). If the running hub
shuts down, the user is warned, and he can startup manually the embedded
hub.

Now, the case of multiple applications already connected to a hub which
shuts down is more problematic. You can't just fire up a new hub and
assume everything will be ok, as applications would have to re-register
with the new hub.

Generally, as Alasdair and you are stating, we should let maximum
freedom to the user, as well as imposing as little as possible to
developers willing to support the messaging standard in their
applications. Embedded hubs should of course not be compulsory, but they
can be useful.

Cheers,

Thomas