Key difference: AJAX stands for Asynchronous JavaScript and XML. It is a group of web development programs used to design websites. The programs create interactive web applications using a combination of XHTML for basic programming, CSS for styling, DOM for interaction, data exchange using XML and XSLT, XMLHttpRequest and JavaScript. Microsoft Silverlight is an application framework for writing and running rich Internet applications. It is similar to Adobe Flash, in that it adds features and purposes to the applications. It has been developed by Microsoft and was first released in 2007.

AJAX stands for Asynchronous JavaScript and XML. It is a group of web development programs used to design websites. The programs create interactive web applications using a combination of XHTML for basic programming, CSS for styling, DOM for interaction, data exchange using XML and XSLT, XMLHttpRequest and JavaScript. AJAX enables web pages to send data to and receive data from a server without changing or hindering the web page itself. AJAX eliminates the need for the customers to wait, making interaction between the customer and the server asynchronous.

Google is the biggest known supporter of AJAX and has invested millions of dollars to advance it. Major Google products, such as Orkut, Gmail, Google Suggest, and Google Maps are AJAX applications. Amazon has also launched it’s own search engine, A9, on AJAX.

Ajax is not a single technology. It is a group of technologies. Jesse James Garrett, the one who coined the term, AJAX, lists the various technologies incorporated in AJAX:

• HTML (or XHTML) and CSS for presentation
• The Document Object Model (DOM) for dynamic display of and interaction with data
• XML for the interchange of data, and XSLT for its manipulation
• The XMLHttpRequest object for asynchronous communication
• JavaScript to bring these technologies together

Microsoft Silverlight is an application framework for writing and running rich Internet applications. It is similar to Adobe Flash, in that it adds features and purposes to the applications. It has been developed by Microsoft and was first released in 2007. The run-time environment for Silverlight is available as a plug-in for web browsers running under Microsoft Windows and OS X. hence, Silverlight is compatible with various different browsers. It is also one of the two application development platforms for Windows Phone.

Silverlight originally focused on streaming media. However, it is since expanded to support multimedia, graphics, and animation. It also gives developers support for CLI languages and development tools. Silverlight provides a retained mode graphics system that is similar to Windows Presentation Foundation (WPF). Furthermore, it also integrates multimedia, graphics, animations and interactivity into a single run-time environment.

In Silverlight applications, user interfaces are declared in Extensible Application Markup Language (XAML). Additionally, the interfaces are programmed using a subset of the .NET Framework. XAML can be used for marking up the vector graphics and animations.

Since its release, Silverlight has been used to provide video streaming for many high profile events, such as by NBC to cover 2008 Summer Olympics in Beijing, as well as the 2010 Winter Olympics in Vancouver, and the 2008 conventions for both major United States political parties. Netflix is also an avid integrator of Silverlight, using it for its instant video streaming service. Silverlight can also be used to create Windows Sidebar gadgets for Windows Vista.

Some difference between AJAX and Silverlight:

• Both are client technologies but cannot be used as replacements for each other.
• Silverlight is mainly used for rich UI.  While, Ajax can give a better user experience with Aync http requests.
• Ajax is a technology specification, with many Ajax platforms/libraries available. Silverlight is a Microsoft Technology.
• ASP.Net Ajax provides both pure client APIs and server tools like Update Panel, while Silverlight allows for server integration by using web services.
• Ajax works on JSON platform based on Javascript and Xml. Silverlight is like a browser add-on that can only understand the XMAL code used by Silverlight.
• Ajax can be used to make web applications perform better and to provide better user experience than conventional websites. It also avoids page refreshes.
• Silverlight provides a rich UI and doesn’t have a heavy server dependency.
• Silverlight is considered easier to write, but Ajax is less frustrating. However, Silverlight can be used to extend AJAX and add richness for the end-user.

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