[Standards-JIG] rfc3921bis, RC3

[JD Conley]

> How is this expected to behave in case user sends unavailable presence
> broadcast , and then sends directed presence ?
> Notifying recipients of directed presence currently uses the
> unavailable
> presence trigger ...
> This requirement does add significantly to the server resource usage
> since there is no limitation to who all a user can send directed
> presence to.

Interesting use case. If we aren't going to store directed presence
(which a bunch of people oppose for resource issues), I would say that
instead of the last broadcast presence (in all cases) we could create a
protocol extension for probes in general. Some sort of protocol when you
just want to know the last presence you received is still valid.

<presence
    type='probe'
    from='romeo at example.net/orchard'
    to='benvolio at example.org'>
	<ping xmlns="probeping"/>
</presence>

<presence
    from='benvolio at example.org/pda'>
	<pong xmlns="probeping"/>
</presence>

-JD