[Standards] XEP-0060, offline modifications and efficient synchronization

Matthieu Rakotojaona matthieu.rakotojaona at gmail.com
Mon Sep 14 19:22:24 UTC 2015

Excerpts from Kevin Smith's message of 2015-09-14 09:58:56 +0100:
> On 7 Sep 2015, at 23:15, Matthieu Rakotojaona <matthieu.rakotojaona at gmail.com> wrote:
> > 
> > Excerpts from Kim Alvefur's message of 2015-09-07 14:49:59 +0200:
> >> Hi!
> >> 
> >> On 2015-09-05 16:22, Matthieu Rakotojaona wrote:
> >>> - MAM only allows something like "give me everything since this moment",
> >>>  however using dates is always problematic (clocks are not
> >>>  synchronized, time can drift, ...)
> >> 
> >> FYI: MAM lets you request by archive id.  There doesn't seem to be an
> >> example describing that, but it's essentially the same as paging:
> >> http://xmpp.org/extensions/xep-0313.html#query-paging
> > 
> > Hey !
> > 
> > Yes, you can page with MAM. The problem is that there is no interaction
> > between MAM's archive ids and actual items, so whenever you receive a
> > notification you know that the latest archive id must have changed but
> > you don't know the new value. So you'll have to retrieve back from the
> > last event you retrieved.
> > 
> > My idea was to make this id central in the Pubsub XEP, and then have
> > references to other XEPs like "You can use RSM with those ids".
> > 
> > XEP-0312 does feel more lightweight and more importantly more generic
> > (it doesn't apply to only pubsub, but to everything that is based on
> > presence) but still has the issue of clocks.
> Including the archive IDs in the delivered stanzas seems to be the most sensible way to do this, such that you can then do a MAM sync on your last-seen ID.
> Yes/no?
> /K

Yes, that would allow an implementor to make only the calls that are
really needed for staying in sync.

However I don't see why it should be a MAM sync; MAM in itself only
allows you to query by date, in order to filter by IDs you use RSM which
is already usable directly with pubsub (instead of doing MAM+RSM). The
only difference will be the response: either you get a list of relevant
items through pubsub, or you get a stream of messages through MAM. I can
imagine the latter is better for huge responses because messages don't
"clog" the pipe (they can be interleaved with other stanzas); is it
really the preferred way to do it ?
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