Why End Users Want AJAX Applications

Users tend to view desktop applications as a sort of commitment. They install a program, usually from a disk pulled from a costly shrink-wrapped box. The program consumes hard disk space as well as a position in the program menu. The user may need to update the program periodically or perform an upgrade later on to get new features. If the program is proactive about updating itself, the user is confronted regularly with dialogs about accepting patches or downloads. In exchange for this investment of time, money, and energy, the user gets repaid by an application that is able to leverage the operating system and machine resources. It is a rich application. It has local storage capabilities, offers quick response times, and can present a compelling and intuitive graphical user interface.

More and more applications are accessible from the web browser, where the full resources of the hardware and OS are not available, but the user commitment of a desktop application is not required. Over the years, interacting with a web application has meant a predictable pattern for users. They click a link in the page and the browser flashes while the user waits until the screen is repainted (the dreaded post back). This cycle is repeated again and again. The user looks at what is presented on the page, interacts with it, and clicks somewhere. The browser produces an audible click for feedback and begins to post back to the server. The screen of the web browser flashes blank and some icon spins or flashes while the user waits for a new version of the page to be returned from the server. Many times, the new version of the page is almost exactly the same as the previous version, with only part of the page being updated. And then the cycle begins all over again. This has a sluggish feeling even when the user has a highspeed network connection.

The AJAX set of technologies has changed what users expect from web applications. JavaScript code running in the browser works to exchange data with the web server asynchronously. There is no click sound and the browser does not flash. The request to the server is nonblocking, which means the user is able to continue viewing the page and interacting with it. The script gets the updated data from the server and modifies the page dynamically using the DHTML coding methodology. The user is able to continue looking at the page while parts of it are updated in the background. AJAX is used to provide a more responsive experience, making web applications behave more like desktop installations. JavaScript is used to provide a richer experience with support for drag-and-drop, modal dialogs, and seemingly instantaneous updates to various parts of the page based on user inputs.

A big part of successfully leveraging AJAX technologies is in the perceived performance increase. Users appreciate web applications that anticipate their actions. If you also use JavaScript code in the background to pre-fetch images and data that may be needed, users can get a speedy response without the usual pause that accompanies their actions. Nobody wants to wait for data exchanges between client and server; studies have shown that a time lag between user input and subsequent UI changes can significantly reduce their productivity and give them the frustrating feeling that they are fighting the application. Users want web applications to behave like desktop installations but without the overhead associated with an installation. As more applications employ smart caching, anticipate user actions, and provide richer UI, the difference between web and desktop applications is becoming blurred. Expectations of web applications are rising. The end user has now seen that it is possible to avoid the commitment of installing a desktop application and still have a rich and responsive experience.