All blogs on the WordPress.com platform and any WordPress.org blogs that opt-in (using this plug-in) will now make instant updates available to any RSS readers subscribed to a new feature called RSSCloud. There is currently only one RSS aggregator that supports RSSCloud, Dave Winer’s brand-new reader River2. That will probably change very soon. Update: Within hours another RSS reader called LazyFeed has announced that it will support RSSCloud as well.

RSSCloud is an element that’s always been present in the RSS 2.0 spec but has drawn new attention with the rise of interest in the Real-Time Web. The element was just added to the WordPress code this afternoon. The implications of this big vote of support go beyond reading WordPress blogs; this is the kind of traction that new technologies can leverage to gain support in many different applications.
Supporting feed readers will now be able to request updates from WordPress blog feeds as soon as they become available, instead of polling a server periodically to check for updates. (Your blog posts typically get picked up by RSS aggregators 15 to 60 minutes after you posted them – this will change that.) The feature is already being rolled out, several WordPress users report seeing the cloud element in the source code of their RSS feeds. Update: Here’s the official announcement from WordPress HQ.
This is like the difference between checking your email every once in awhile and using a Blackberry to get new emails pushed to you as soon as they arrive. The subscription method of RSSCloud works more like Instant Messaging than the old method of polling feeds for updates each time you fire up your feed reader.
Google Reader, the dominant RSS aggregator on the market, began a limited implementation of a related protocol called PubSubHubbub last month. Facebook-acquired FriendFeed worked with Google on that system.
Now RSSCloud has a posse. Half a million blogs are created each month on WordPress and if Google Reader keeps taking its sweet time checking those blogs for updates instead of turning on support for RSSCloud, it’s going to look slow as molasses.
Real time updates could enable several things. Faster distribution of blog posts, more compelling conversations in real-time and a renewed timeliness for blogging vs. services like Twitter are all likely consequences. The list of possible technical developments on top of RSSCloud could be as open-ended as the developments enabled by the core of RSS.
RSS has made blogging viable by freeing readers of the requirement of visiting each site they are interested in. It has made podcasts subscribable. It has made wiki change notifications trackable outside the mess of the email inbox. It has made search a persistent action, instead of a one-off occasional delayed reaction. RSS is mixable, mashable, parsable, filterabile.
Now RSSCloud could add a real-time dimension to all of that. The paradigm just got a very big vote of support.