[sldev] Question: Replacing current group chat with XMPP?

[David M Chess]

> From: "Steven Harrison" <steven.harrison at gmail.com>

> *waves to David*

:)

> I think that while pub/sub model does scale (I'm specifically thinking
> of subscribers to an RSS feed, or something along the lines of
> Twitter), is it a suitable architecture choice for group IM
> conferencing? Wouldn't something more like IRC (as Dahlia mentions) be
> more appropriate?  However, I think that pub/sub could easily be done
> with HTTP and RSS, but adding in some kind of IRC-esque functionality
> would take a lot more work,

I've probably been unclear here about what I mean by "pub/sub".  In 
particular, subscribers to an RSS feed are *not* in fact subscribers in 
this sense; they are in fact polling, which is exactly what I want to 
avoid for scalability reasons.  On the other hand, IRC basically is a 
pub/sub model: within the overlay network formed by the IRC servers, 
certain users (clients) subscribe to certain channels, and when a user 
talks ("publishes") on the channel, the message is sent (push-style) to 
all and only those servers that currently have a subscribed client.

For me (and I think traditionally in comp sci before RSS terminology came 
along and muddied it up), pub/sub (publish/subscribe) refers to a system 
where there are topics or channels or subjects or whatever, some set of 
entities subscribe to one or more channels, and then some set of entities 
publishes one or more objects into one or more channels, and each 
subscriber is sent (rather than polling for) whatever objects are 
published into the channel(s) that that subscriber subscribes to.  So the 
publisher does not (necessarily) know the list of entities that will get 
the message, and the subscribers do not (necessarily) know who the 
publishers will be; instead the association is via channels, and the 
pub/sub infrastructure takes care of it without the publishers or the 
subscribers having to do the accounting.

Something like that anyway.  :)

Dale Innis
DaleInnisEmail at gmail.com
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