Re: Anyone know if RSS <cloud> is used in the real world?

Yup, I'm aware of that. Unfortunately this is layered on the XMPP Pub/Sub protocol, which is wonderful but very complex. I know of one experimental OSS server implementation, plus whatever pubsub.com has running providing their service. I would prefer something easier for publishers to adopt.

Don't worry, I've already drunk the REST kool-aid :)

Robert Sayre wrote:

Nice article! Using XMPP without the pub/sub extension is definitely a lot easier, but then you're left with the issues that pub/sub would have addressed, like how one creates or cancels subscriptions. Also, XMPP <message>s don't work well for one-to-many since they have to be individually sent to each recipient. In basic Jabber only the <presence> element does efficient multicasting; in effect, Jabber was designed with one hard-coded pub/sub channel for presence signaling, which can't be extended to other purposes without doing something on the scale of the Pub/Sub extension.

Brent Simmons wrote:

Indeed, and I've been grappling with this issue in one form or another for a while. My thinking is that you need a two-stage mechanism, where a direct <cloud>-type ping can be used from the publisher's server to another server acting on behalf of a subscriber; while a different mechanism may be needed to notify the user agent. This is what Johannes Ernst calls a "Four-Point Architecture":

Very analogous to email (where server-to-server is push, while clients use a lightweight polling protocol), or to XMPP (where the client initiates a long-lived connection to the server to receive messages.) Ernst points out that even ostensibly P2P networks often end up in a topology like this, with "superpeers" and "edge peers".