Introduction to Ajax

Ajax is a common approach to building Web 2.0 applications. Ajax is not a technology in itself, rather it’s a combination of existing technologies – XHTML, CSS, DOM, XML, XSLT, the XMLHttpRequest object and JavaScript. Most of these technologies have been around for quite a while. It’s the way they’re used together that creates the Ajax approach to developing Web applications.

In this article, I want to introduce you to Ajax. I want to cover:

An explanation of the term
The key technologies involved
The processes used in Ajax-style applications.

It’s worth remembering that Ajax is a client-side technology so it can’t carry out server-side tasks such as accessing databases or sending emails because of security constraints. You can use Ajax on the client-side and couple it with a server-side language such as PHP, VB .NET or C# if you need to carry out these types of tasks.

Overview

What is Ajax?

Jesse James Garrett first coined the term Ajax in 2005 to refer to a technique involving Asynchronous JavaScript and XML. You can read the essay where the term was first used at http://adaptivepath.com/publications/essays/archives/000385.php.

Ajax describes an approach to working with Web applications involving:

Technology	Purpose
XHTML and CSS	Describes the interface using W3C standards
DOM	Used as an API for the interface and for loaded XML data
XML and XSLT	Describes and transforms the application data
XMLHttpRequest	This object is used for connecting to external data sources, usually XML documents
JavaScript	Binds the other technologies together to load data, manipulate the interface and respond to user interactions

Let’s look more closely at each component.

Sas Jacobs

Sas Jacobs Hello. I'm the Principal of Anything Is Possible, an Australian web development business specialising in web applications development and training. I'm interested in using Flash with dynamic content and I've presented at a number of International conferences on topics relating to applications development, XML and scripting components. I have recently released my second print book Beginning XML with DOM and Ajax to match the first one - Foundation XML for Flash. I have a business web site
and a personal web site.

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