[jdev] PEP: tracking presence

Magnus Henoch mange at freemail.hu
Sun Nov 12 18:55:34 CST 2006

I'm hacking PEP support for ejabberd.  Anyone with a PEP-capable
client is welcome to create an account on stor.no-ip.org, try it out,
and report bugs.  See also
http://www.dtek.chalmers.se/~henoch/text/ejabberd-pep.html .

I'm thinking about how to implement sending the last published item
when a contact becomes available.  Now, the server keeps track of
every available presence with non-negative priority sent to each user
of the server.  That means a space complexity of O(n^2), which is not

Is there any sensible way to do it?  Treating a presence probe as
equivalent to a contact's resource becoming available might be good
enough for explicit subscriptions, but it doesn't carry information
about entity capabilities.  Would it be good enough to have a common
table for all received presence stanzas?  Assuming that many users
have common contacts, it might reduce storage needs, but it might give
slightly incorrect results if a contact removes a presence
subscription or sends directed unavailable presence.

JID: legoscia at jabber.cd.chalmers.se

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