...Atlas is and why you’d want to use it versus client callback (man, is that still around?) and other 3rd party AJAXproviders (Ajax.NET, MagicAjax, ...). I played with the PDC bits, and was thoroughly put off by the declarative programming...
http://weblogs.asp.net/bleroy/archive/2006/02/01/437101.aspx
...in (Flash) that’s designed to simplify RIA deployment. Managers who have concerns about small commercial Ajaxproviders or support issues with open source Ajax frameworks consider Flex a safe alternative. But there is a downside: To be productive...
http://www.effectiveui.com/whitepapers/components/assets/FlexAndAJAX.pdf