Claims-Based Authorization with WIF

Hi,
I asked a question few days back about how to do AUTHRIZATION in ASP.NET MVC when roles , permission are in Database?
http://forums.asp.net/t/1678646.aspx/1?Authorization+in+ASP+NET

After spending some times, I learnt about WIF.
Can somebody please guide me How can I achieve claim based AUTHORIZATION in ASP.NET MVC when the application will
use external web servcie for authentication with different database?

Thanks
...