Ajax: A New Approach to Web Applications

Ajax isn’t a technology. It’s really several technologies, each flourishing in its own right, coming together in powerful new ways. Ajax incorporates:

• standards-based presentation using XHTML and CSS;
• dynamic display and interaction using the Document Object Model;
• data interchange and manipulation using XML and XSLT;
• asynchronous data retrieval using XMLHttpRequest;
• and JavaScript binding everything together.

How Ajax is Different

An Ajax application eliminates the start-stop-start-stop nature of interaction on the Web by introducing an intermediary — an Ajax engine — between the user and the server. It seems like adding a layer to the application would make it less responsive, but the opposite is true.

Instead of loading a webpage, at the start of the session, the browser loads an Ajax engine — written in JavaScript and usually tucked away in a hidden frame. This engine is responsible for both rendering the interface the user sees and communicating with the server on the user’s behalf. The Ajax engine allows the user’s interaction with the application to happen asynchronously — independent of communication with the server. So the user is never staring at a blank browser window and an hourglass icon, waiting around for the server to do something.