[Standards] MIX use of type=groupchat?

Steve Kille steve.kille at isode.com
Mon Jan 23 07:09:35 UTC 2017


> -----Original Message-----
> From: Standards [mailto:standards-bounces at xmpp.org] On Behalf Of
> Stephen Paul Weber
> Sent: 22 January 2017 19:32
> To: standards at xmpp.org
> Subject: [Standards] MIX use of type=groupchat?
> I have a question about
> <https://xmpp.org/extensions/xep-0369.html#usecase-user-message>
> Doesn't using <message type="groupchat"> defeat the purpose of building
> on / re-using PubSub?  Why have this extra special case as a way to
> items, instead of using normal publish?  And using type=groupchat seems to
> also necessitate a custom <jid xmlns="xmlns='urn:xmpp:mix:0"> to indicate
> the item publisher.
[Steve Kille] 

This is a minor tweak for messages reflected back to originator, which I do
not see as a big deal.   A simple implementation could ignore this.

> <https://xmpp.org/extensions/xep-0369.html#concepts-pubsub> says " MIX
> uses standard presence and groupchat messages to provide an interface to
> the MIX service that does not expose PubSub protocol for many of the more
> common functions" -- but wouldn't "exposing PubSub" simplify everything
> (only one protocol to support instead of more)?  If MIX were backwards-
> compatible with MUC at either client or server level, I would understand
> keeping some warts, but since both client and server support is required
> use it at all, why not clean up everything while we're at it?
> --
> Stephen Paul Weber, @singpolyma

[Steve Kille] 

There would be a definite elegance in "using PubSub" everywhere, and an
early MIX version was written this way.

A key decision at the summit 12 months back was to switch use groupchat and
presence encodings for core messages.

There was a strong consensus on this, and I don't think this is something
that will be reversed.   We can review again in Brussels if there is desire.

To me, the key issue is that MIX/MUC/Groupchat is a pretty fundamental
service for real time messaging.   I think that it makes sense to use
special/optimized encoding for core traffic.   To me, type=groupchat really
belongs in XMPP and is not something that should die with MUC.  It feels a
fundamental capability.    Clearly type=presence is fundamental and I think
it makes sense for MIX to use this and not wrap messages in PubSub.

Using type=groupchat  will help a lot with writing a client that does both
MUC and MIX (which many client writers will want to).   The core traffic
will use essentially the same encoding, which I believe will help.   I also
note that it should be possible to write a pretty reasonable end user
MIX/MUC client without use of PubSub (you will not be able to skip MAM in
the same was, as MAM is vital for an end user client to retrieve history).


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