RIA Services is a set of end-to-end experiences that makes it as easy to build Silverlight based n-tier applications as it is to build traditional 2 tier apps – some would say that it’s basically the new paradigm for client-server development in the 21st century…
RIA Services focuses on writing n-tier apps by treating them as one logical application, a great way to achieve n-tier goodness from the architecture/pattern without the plumbing getting in your way.
RIA Services provides a pattern for encapsulating application logic on the middle tier that can be useful in a variety of scenarios. It is DAL-agnostic and available for Multiple presentation layers.
Check out Brad Abram’s PDC09 talk at: http://microsoftpdc.com/Sessions/CL21
Here is a link to ho blog post and sample code: http://blogs.msdn.com/brada/archive/2009/11/19/pdc09-talk-building-amazing-business-applications-with-silverlight-4-ria-services-and-visual-studio-2010.aspx