When I was growing up, Atlas was a mythical guy with big muscles who held the world on his shoulders. There was — and still is — a wonderful statue of him at Rockefeller Center in New York City. And Ajax was something you used to clean the bathtub.

But among us computer geeks, these terms have quite different meanings and are generating a lot of buzz lately. If you are feeling left out, you are not alone. In this article I will try to present some fundamentals of Ajax and Atlas to give you at least some idea of what people are all talking about.

Ajax

In a nutshell, Ajax is a technology for creating browser-based applications that have the look and feel of traditional desktop applications — sometimes called rich client applications — along with the ease of deployment of web applications. It's not new, having gotten its start in the 1990s, but the term Ajax was coined only last year, coinciding with a sudden burst of interest in the developer community.

The sudden interest is also fueled by continued adoption of browser standards. Ajax development is feasible only when you can be confident that essentially all the browsers that will be used to access your application not only support the required Ajax technologies, but implement them in a standard and defined manner.

Ajax is really a set of technologies including Javascript, dynamic HTML, and XmlHttp (which lessens the need for Web clients to interact with the Web server). It's already in use with some popular Web services including Gmail, Google Maps, and Microsoft's Virtual Earth. It's an approach to web development, rather than a specific tool you buy.

So-called rich internet application tools, such as Flash and Flex, have been around for years. Is Ajax reinventing the wheel? Not really. Ajax is filling the gap between these high-end Web development tools, which combine great power and sophistication with proprietary standards and complexity of development, and the traditional browser-based interface.

What does Ajax let a developer do? That's a tough question, because it is so flexible. It is certainly user interface-oriented, and permits actions such as dragging elements around in a browser and creating mash-ups that present information from various web sites. It also permits the development of web-based versions of traditional desktop applications, such as word processors and task managers.

In reality, anything you can do with Javascript, DHTML, and XmlHttp could be considered Ajax, so it's hardly a precise definition. Not that anyone expects Ajax applications to replace mainstream productivity applications such as Word and Photoshop; the speed, local storage, and responsiveness of desktop applications will not be replaced by anything browser-based, at least not for a while!