[jdev] Re: Reliable presence

[Nolan Eakins]

David Waite wrote:
> The fundamental problem is 'what does a presence message mean'. In
> truth, it indicates the availability and status of an endpoint at a
> particular point in time. Over time, that presence message becomes
> next to meaningless. Unfortunately today, there is no mechanism within
> XMPP to even specify what time presence was set.
> 
> There are solutions which come to mind, but none which closely
> resemble the current presence model in XMPP.
> 
> -David Waite

Reading this I came up with another possible solution. Your definition of
presence as availability at a specific time helped. It would be possible to
periodically send presence stanzas which would solve the problem, but doing
that may end up flooding the network. Doing that would be a bad idea, but
presence stanzas could specify when the presence will be updated again.
Something like:

<presence>
<status>Online</status>
<x xmlns="http://jabber.org/protocol/presence_update">54000</x>
</presence>

That would make clients that understand the
"http://jabber.org/protocol/presence_update" namespace expect a new
presence to be sent in 15 minutes. The 54000 is in seconds. The server
would handle broadcasting it to all the contacts that are subscribed to the
client.

And I suppose if a presence is not received at that time, plus some leeway,
the receiving client could send a presence probe just to see what happened.
Though I'm unsure how presence is handled if a s2s connection can't be
made.

Regards,
Nolan
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