The real-time web: RSS Cloud and Google’s PubSubHubbub

It was quite a revolution when RSS became popular (created in 1999, it became wide used around 2005/2006) and integrated in almost all tools. To the point that some people were even challenging that it would use too much bandwidth… Why is that ? While RSS is a neat system to find out when something changes on a website it still requires from the client to poll the server. Bad designed client (that were not using correctly the HTTP protocol and its 304 status code) and the multiplication of tools (CMS, CRM and co.) would load servers and the network and eventually causing some problems. After a while we get it to work nicely but notifications still relies on the polling mechanism and its frequency. Good… but not enough for the real-time web. Real-time Web? one of the 5 futurs trends on the web (see also a list on ReadWriteWeb of the Top 50 Real-Time Web Companies).

RSS Cloud

RSS Cloud takes advantage of the “cloud” element in the RSS 2.0 specification. Actually “cloud” has been there since RSS 0.92, but no one paid much attention until the rising interest of real-time web. RSS Cloud effectively allows any client (like feed reader) to register to get notifications for stuff they have subscribed for beforehand.

How does it work ?

  1. The >cloud< element in your RSS2 feed tells the clients where and how to sign up for notifications requests.
  2. The publisher sends out notifications updates to the cloud when a new post is published
  3. The cloud sends out notifications to all client that have subscribed to the publisher updates

The result is that new posts from your favorite blogs arrive much faster using the RSS Cloud method than the polling method. But RSS Cloud is not alone and there are competing specifications like… PubSubHubbub.

Google’s PubSubHubbub

PubSubHubbub is a simple server-to-serve publish/subscribe protocol as an extension to Atom and RSS. The servers speaking the PubSubHubbub protocol can get near-instant notifications when a feed URL is updated. The subscriber gets not only the notification of the update but also the new/changed content.

ReadWriteWeb: Speed in the Feed: Google Reader and PubSubHubbub

Note that the Real-time Web is the main theme of LeWeb 09 conference in Paris in December.

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