The Open Ajax Alliance is a standards organization with the mission of ensuring interoperability within Web based Ajaxified applications. One of their standards relates to intercomponent communication - the ability to subscribe and publish messages which can then be picked up by code written by other authors.

Please note that if you don't have an interest in Open Ajax, this post may not be especially illuminating - I've talked about the addOnEvent function before, even recently.

To write an Open Ajax application, you need to subscribe to events, much like in JSF 2, by registering functions which act as listeners. For instance, suppose we had a field in our page that looked like this: