[Standards] Presence extensions

Ralph Meijer jabber.org at ralphm.ik.nu
Fri Feb 2 15:02:29 UTC 2007


Hi,

I was testing out Palaver, a MUC implementation, and found out the
following. MUC role changes are pushed to room occupants using presence
stanzas. However, Palaver sends them out without any other presence
information. When a user that previously sent away presence, for
example, the role change stanza doesn't include that and the client
things that the availability for this user changed to plain available.

After a small discussion with Ian, it appears this situation is
underspecified, either in XEP-0045 or in XMPP IM. The question being:
what to do on broadcasting presence stanzas, and in particular a proxy
like situation like MUC, with presence extensions.

I can think of different types of extensions:

 * Extensions that really augment availability information. You have to
resend
   them every time.
 * Extensions that add non-availability information like role changes
   or other information orthogonal to availability. These don't have to
be sent
   every time. It can be argued that these should not be in presence
stanzas.
   However, several protocols do this.
 * Extensions that contain meta information about the actual presence
stanza being
   sent. An example is a signature to be able to verify the authenticity
of the
   (proxied) presence. Note that if entities add data to presence before
   broadcasting, such a signature will cease to be valid. So in case of
MUC
   you probably cannot pass these on.

Ian suggests we need to figure out what to do here and edit RFC3920bis
accordingly. Probably XEP-0045 needs some updated examples, too.

-- 
Groetjes,

ralphm




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