Asynchronous Javascript And XML web applications combine several technologies, in an attempt to match a desktop application experience over the Internet.
Something old is new again, as the concept of remote scripting returns. Now, it’s referred to as Ajax, and it powers some of the more interesting applications arriving on the Web today.
When working with a Web-based application, the user experience becomes one of a start-stop nature, according to Adaptive Path’s founder, Jesse James Garrett. It’s an experience derived from the earliest days of the World Wide Web and the exchange of hypertext between client browser and HTTP server.
By placing an intermediary between the client and server, in this example an Ajax engine, some of the delays associated with the user experience can be eliminated.
One typical delay for users involves the web page itself. Submitting a request for information means the client browser usually redisplays the same navigation and other page elements every single time. Some sites force the browser to go back to the server over and over again to do this.
Now look at Yahoo! News, particularly the various blocks of news categories on the page. By clicking on a news source within the navigation of one of those blocks, like Science, the content inside the block changes to headlines from that news source. The page doesn’t reload, and the latency is nearly non-existent.
Ajax brings together several technologies to accomplish this trick: JavaScript, XML, CSS, DOM, XSLT, and others. The most important seems to be JavaScript, which powers the Ajax engine downloaded first by a browser. The engine renders the page the visitor sees, and communicates with the server in the background.
As the user submits requests and queries, the Ajax engine handles the interaction with the server. The user sees the same interface as it updates with responses and answers from the server as collected by the Ajax engine.
Other sites like Google Suggest and Google Maps use Ajax approaches to fulfill site requests. And other developers will continue to utilize Ajax, as its focus on application development rests on open standards.
David Utter is a staff writer for Murdok covering technology and business. Email him here.
