What is Ajax?

Ajax is like the materials that go into making a high-rise building. High rises are made of steel instead of wood, and their exteriors are modern and flashy with metals and special glass. The basic structure is still there, walls run parallel and perpendicular to one another at 90-degree angles, and all the structure's basic elements, including plumbing, electricity, and lighting, are the same - just enhanced.

The structure of an Ajax application is built on an underlying structure of XHTML, which is an extension of HTML. Tools used to build Ajax web applications include:

• Extensible HyperText Markup Language (XHTML)
• Document Object Model (DOM)
• Cascading Style Sheets (CSS)
• Extensible Markup Language (XML)

Obviously, other things can also be used when building Ajax applications, but XHTML is the core structure of any Ajax applications. XHTML holds everything that is going to be displayed on the client browser, and everything works off of it. The DOM is used to navigate all of the XHTML on the page. Javascript has the most important role in an Ajax application. It is used to manipulate the DOM for the page, but more important, JavaScript creates all the communication between client and server that make Ajax what it is. CSS is used to affect the look of the page, and is manipulated dynamically through the DOM. Finally, XML is the protocol that is used to transfer data back and forth between clients and servers.