This content is reprinted from Real-World AJAX: Secrets of the Masters published by SYS-CON Books. To order the entire book now along with companion DVDs for the special pre-order price, click here for more information. Aimed at everyone from enterprise developers to self-taught scripters, Real-World AJAX: Secrets of the Masters is the perfect book for anyone who wants to start developing AJAX applications.

A Brief History of AJAX

On April 30, 1993, CERN announced that the World Wide Web would be free for anyone to use and the Web took off, jumping from 130 Web sites in 1993, to over 100,000 in 1996, to 11.5 billion sites in 2005. The main protocol used on the Web is the Hypertext Transfer Protocol (HTTP). It's a patented open Internet request/response protocol intended to publish and receive HTML pages.

The HTTP protocol was so simple it made any barriers to doing Web design and development so low that anyone could enter. However, it was a step backwards for programmers and software development. The Web was never meant to be used for applications, only mass storage or linked content. Ever since the Web came out, developers have been struggling to get around the request/response sequence.

Browser asynchronous hacks have been possible since 1996, when Internet Explorer introduced the IFRAME tag, passing through a number of techniques such as pixel gifs, Netscape layers, Microsoft Remote Scripting, Java/JavaScript gateways, stylesheet hacks, image/cookies, and most recently the XMLHttpRequest.

Microsoft's Remoting Scripting or MSRS was introduced in 1998. This device was more elaborate than previous hack attempts and used JavaScript to communicate with a hidden Java applet that was in charge of the asynchronous communication. Microsoft used this technique with the release of Outlook Web Access supplied with Microsoft Exchange Server 2000. The only problem was that it was not a strictly native browser technology and Java applets limit its reach and compatibility.

In 2002, Microsoft replaced Remoting Scripting with the XMLHttpRequest object, which was quickly copied by all the major browsers. The only difference was that until Internet Explorer 7, the XMLHttpRequest object was implemented with ActiveX. With the release of IE7, ActiveX will no longer have to be enabled to support AJAX requests.

What slowed down this technique, and any advances in browser technology, was consistency. Browsers behaved differently and were moving too fast for application development to be based on them. After the browser wars ended and there was no more money involved, their development slowed and they started to stick to standards.

Most modern browsers now implement Uniform Resource Identifier (URI), HTTP/1.1, HTML 4.01, Document Object Model (DOM), and JavaScript. This means that there is less need for conditional statements to apply different scripts depending on the browser.

Historically, Web sites improved in user experience by implementing Dynamic HTML or DHTML, a method of combining HTML, JavaScript, Cascading Style Sheets (CSS), and Document Object Model (DOM) to interact with user events. However, this interactivity was limited by having no interaction with the server. It was possible to play with manipulating the presentation layer in many ways, including new content, drag-and-drop, resorting, and deleting elements, but nothing affected the database, drastically limiting any benefits.

AJAX is only a communication layer and does not include any visual elements. However, because AJAX, like DHTML, is based on JavaScript, it can achieve amazing results.

The term AJAX was coined on February 18, 2005, by Jesse James Garret in a short essay published a few days after Google released its Maps application. Since then, the name has been controversial and dismissed in some corners as mere marketing hype for existing techniques. And in a sense this is true: AJAX does not describe a new technique but simply provides a common name to refer to existing ones.

When Google launched its AJAX services, it gave AJAX awareness, trust, and credibility. Depending on JavaScript and modern browsers somehow wasn't so bad, and was justifiable because of its splendid results.

Microsoft is currently working on its Live product series. Windows, Office, Messenger, Shopping Carts, all AJAX-based using Microsoft's Atlas technology, are still in beta.

IBM and a group of industry leaders announced on February 2006, an open source initiative to promote AJAX adoption. This initiative, known as OpenAjax (www.openajax.org), is (at the time of writing) supported by over 60 companies and organizations including BEA Systems, Borland, the Dojo Foundation, the Eclipse Foundation, Google, IBM, Laszlo Systems, Mozilla, Nexaweb, Novell, Openwave Systems, Oracle, Red Hat, Yahoo, Zend, and Zimbra.

This content is reprinted from Real-World AJAX: Secrets of the Masters published by SYS-CON Books. To order the entire book now along with companion DVDs, click here to order.