Publish-Subscribe Internet

From Jon Udell:

The Internet isn’t one giant LAN. It works remarkably well much of the time, but variable latency and sporadic failures are no longer exceptions, they are the rule. HTTP’s statelessness was the first major adjustment to this new reality. Hit the InfoWorld home page, and your browser will make a dozen separate requests of our server. If a few of those fail, it’ll keep trying until it finally assembles the whole page.

Of course, why were you hitting our site in the first place? Presumably to find out about topics that interest you. Since you’ve got better things to do than poll the site to find out what’s new, we publish feeds that you can subscribe to in order to be notified when updates occur. If you’re reading this column, you’ve subscribed to one of those feeds, in the form of an e-mail newsletter. (There are others[1] as well.) You might also be using an RSS (Rich Site Summary) newsreader to follow one of our syndicated XML newsfeeds[2,3,4,5]. These are all simple examples of a publish/subscribe services architecture. As pub/sub and asynchronous messaging get baked into the Web services stack, things are going to get a whole lot more interesting.

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Rajesh Jain

An Entrepreneur based in Mumbai, India.