The Salmon Protocol (http://salmon-protocol.org) leverages PubSubHubbub and web hooks to build a real time, decentralized commenting and annotation system. The basic idea is that commentary swims upstream to the thing being commented on, which can then redistribute comments back out via PubSubHubbub to interested subscribers. There's a demo available at http://salmon-playground.appspot.com/ros which posts comments back to a Blogger blog (by proxying to an existing API, just for demo purposes).
Aside from evangelizing Salmon, I'm also interested in getting feedback on the use of PubSubHubbub. One specific question: At the moment, Salmon specifies that subscribers should follow the rel="comment" link for each entry in an Atom feed to find the comment feed to subscribe to. This could lead to a lot of subscriptions that have initial activity but then die out; not sure if this is a problem for PubSubHubbub or not. It might be better to define a feed for, and there fore a way to subscribe to, "all comments for items in this feed" as a whole -- but there's no standard way to do this at the moment. Also, Salmon definitely needs some extensions to get passed through un-modified (like crosspost:source, thr:in-reply-to, etc.) so the discussion about what hubs may/may not change is very relevant. Comments, critiques, feedback of all kinds welcomed. -- John Panzer / Google [email protected] / abstractioneer.org <http://www.abstractioneer.org/> / @jpanzer
