Google Maps is one well-known application that uses AJAX. The interface allows user to change view and manipulate the map in real time. AJAX applications do not require installation of a plug-in and work directly with Web browser. AJAX is not a proprietary technology or a product but it the combination of technologies.
How AJAX works?
Before Ajax most Web sites were based on complete HTML pages. Each user action required that a complete new page be loaded from the server. This process was inefficient, as reflected by the user experience: all page content disappeared, and then the new page appeared. Each time the browser reloaded a page because of a partial change, all of the content had to be re-sent, even though only some of the information had changed.
This placed additional load on the server and made bandwidth a limiting factor on performance. Google made a wide deployment of standards-compliant, cross browser AJAX with Gmail (2004) and Google Maps (2005). On 5 April 2006, the World Wide Web Consortium (W3C) released the first draft specification for the XMLHttpRequest object in an attempt to create an official Web standard.
Ajax Incorporated Technologies:
* HTML and CSS: For representation.
* DOM (Document Object Model): For dynamic display and interaction with data.
* JSON and XML: For data communication
* XMLHttpRequest: For asynchronous communication.
* Web applications that use AJAX are built in a way that cannot be read by screen-reading technologies.
* Because of the asynchronous nature of Ajax, each chunk of data that is sent or received by the client occurs in a connection established specifically for that event. This creates a requirement that for every action, the client must poll the server, instead of listening, which incurs significant overhead.
* Dynamic Web page updates also make it difficult to bookmark and return to a particular state of the application.
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