AJAX (Asynchronous Javascript and XML) is a technology for using client-side JavaScript to interact with a Web Server to manage Data and User Interface. The scriptability of the Javascript DOM inside modern web browsers makes this possible. Perhaps there will be other implementations and uses in the future.

There is a very good article by Jesse James Garrett here. It is a great place to start.

You may also want to read WikiPedia’s AJAX entry.

There are many perspectives on this subject as it is an infantile technology. It is true that AJAX capabilities have been around for quite some time. It is only now that we are seeing it used more commonly. Many features of Google leverage this technology. There was a company called WestSide in Seattle that used AJAX back in 2001-2 and built a tremendous product before being aquired by BEA Systems.

A nice advantage to using Asynchrounous technology is in many ways a web GUI can act more like a traditional application. When you have an evironment as flexible as the a script container inside a web browser combined with the ability to move data back and forth without the user’s page refreshing, and the ability to dynamically update the UI; that spells C-H-A-N-G-E.

Please note: AJAX should not be considered just a DHTML technology. It’s uses are equally applicable to XUL.

To an inexperienced developer, there can be some nasty pitfalls when working with AJAX. See Alex Bosworth’s Post about potential mistakes. These mistakes are part of the reason to develop an Open Source reference implementation of an AJAX framework and best practices guid.

XMLHttpRequest (or here) is at the Core of AJAX. The ability to send XML over an HTTP connection. Wow. Simple. Powerful. Flexible.

We’ll move on to some code in the next article. So stay tuned…