Introduction
Ajax means Asynchronous JavaScript + XML which enable the rich application user interface without the page reloading concept.
Technologies incorporated by Ajax
Ajax incorporates several technologies to derive the Ajax web application model.
The technologies are:
1.standards-based presentation using XHTML and CSS;
2.Dynamic display and interaction using the Document Object Model;
3.Data interchange and manipulation using XML and XSLT;
4.Asynchronous data retrieval using XMLHttpRequest;
5. JavaScript binding everything together.
Classic Web application Model
The classic web application model works like this: Most user actions in the interface invoke an HTTP request back to a web server. The server does some processing and then returns an HTML page to the client with page refreshment. And at every step in a task, the user waits some more.
How Ajax is Different
An Ajax application eliminates the page reloading by introducing an Ajax Engine between the user and the server. Instead of loading a webpage, at the start of the session, the browser loads an Ajax engine — written in JavaScript and usually in a hidden frame.
This engine is responsible for both rendering the interface the user sees and communicating with the server on the user’s behalf. The Ajax engine allows the user’s interaction with the application to happen asynchronously — independent of communication with the server. So the user is never staring at a blank browser window and an hourglass icon, waiting around for the server to do something.
The Ajax engine is responsible for both rendering the interface the user sees and communicating with the server on the user’s behalf. The Ajax engine allows the user’s interaction with the application to happen asynchronously — independent of communication with the server. So the user never stares at a blank browser window waiting around for the server to do something. Every user action that normally would generate an HTTP request takes the form of a JavaScript call to the Ajax engine instead.
Benefits of Ajax
Any response to a user action that doesn’t require a trip back to the server — such as simple data validation, editing data in memory, and even some navigation — the engine handles on its own. If the engine needs something from the server in order to respond — if it’s submitting data for processing, loading additional interface code, or retrieving new data — the engine makes those requests asynchronously, usually using XML, without stalling a user’s interaction with the application.
Ajax enabled Applications:
1.Google Suggest
2.Gmail
3.Orkut
4.Google Maps