Subject: Advanced Internet Technology

Topic: RIA and Mashup

Difficulty: Low

The classic web application model works like this:

• Most user actions in the interface trigger an HTTP request back to a web server. The server does some processing retrieving data, crunching numbers, talking to various legacy systems and then returns an HTML page to the client.
• It’s a model adapted from the Web’s original use as a hypertext medium, but as fans of The Elements of User Experience know, what makes the Web good for hypertext doesn’t necessarily make it good for software applications.
• This approach it doesn’t make for a great user experience. While the server is doing its thing, the user waiting. And at every step in a task, the user waits some more.
• Obviously, if we were designing the Web from scratch for applications, we wouldn’t make users wait around. Once an interface is loaded, why should the user interaction come to a halt every time the application needs something from the server? In fact, why should the user see the application go to the server at all?

Ajax Working

• 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.