Content Summary : The basic elements for an application using the AJAX technologies,JavaScript and the XMLHttpRequest object, are not difficult to understandand there are many articles on the web that show how to use this object anddeclare that being AJAX. I think there are a lot more topics that should beunderstood and talked about. The right selection from the available technologies as well as a suitableabstraction in using these elements is important for the success of therealization of an application. One main goal behind the architecture of theAJAX engine was to build an AJAX framework that you can reuse every timeyou want some asynchronous processing or when you need a smart way torefresh information on the current web page. When targeting applications with some hundred sides and WebServices andwith in sum about a thousand methods the developer must have a clear andsimple kind and pattern for coding the JavaScript code on the client to avoiderrors and to not think about the implementation details. Only by using asimple approach a good quality and maintenance can be achieved. The idea of the AJAX engine on the client is the simplification of theimplementation of the code that we need for implementing a specificfunctionality on the client. Like with the WebService framework of ASP.NETon the server the details of communication over SOAP on the client arecompletely hidden from the developer and also the recurring code portion isonly realized once in a central place. Also all details about the differentimplementations of the XMLHttpRequest object in Internet Explorer or theFirefox browsers are hidden from your code. By using web controls or tag-libraries again a higher level of abstraction andmore productivity for the developer can be reached. Because these webcontrols have to deploy JavaScript code to the client to avoid round-trips andenable the local functionality in the browser the JavaScript technology,especially JavaScript Behaviors are a substantial part of an AJAXinfrastructure. The visual effects library adds some more polished User interface elementsthat can be used together with AJAX or as standalone client side components.