[Standards] Removing PEP nodes?

Ralph Meijer jabber.org at ralphm.ik.nu
Fri Aug 17 08:52:30 UTC 2007


On Thu, 2007-08-16 at 09:05 -0600, Peter Saint-Andre wrote:
> Ralph Meijer wrote:
> > [..]
> > 
> > We used to have an explicit 'current' item identifier for the different
> > extended presence specs, but these seem to have been removed. I always
> > assumed extended presence to have a more transient notion than one which
> > may persist a history of changes (as each publish gets a unique id if
> > you don't provide one). Peter, could you comment on this?
> 
> I don't think the "current" ItemID was ever meant to have special
> meaning, it was just what pgmillard put into the examples. We removed
> that so that people would no longer get confused.

I don't think pgm put them in for no reason. Assuming notifications with
payload and persistent nodes (even for one item), the semantics of
providing an item identifier or not are different.

If you don't provide an item identifier, the service MUST generate one
and, although this is not explicitly specified, a unique one at that.

Whether or not you provide this unique identifier with the publish
request, this means that every published item has a different item
identifier (see also the examples in the various extended presence specs
where the notifications show a uuid). This implies all items continue to
have significance and together form a history of events.

Providing a node identifier like 'current' for all items, on the other
hand, means that every published item overrides the previously published
one. There is no sense of history here.

> > In general I think you should simply provide an identifier if you want
> > to be able to retract them at a later point in time. I don't think we
> > ever discussed how retraction works in the context of PEP.
> 
> Any use case not discussed in PEP is to be handled as defined in
> XEP-0060. That applies to item retraction as well.

Sure, but not providing an item identifier, as all examples show, makes
it hard(er) to revoke items, since you need to figure out what the
identifier was that the service assigned on your behalf. We could have
specified protocol where this item identifier is returned as part of the
result of the publish request, but I'm not sure if that is needed as
this point.

Also, should PEP clients process retraction and node deletion event
notifications? 

-- 
Groetjes,

ralphm




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