I have an MVC4 web application using Thinktecture's Identity Server for claims-based authentication.
The application works off of 5 different SQL server databases. A user access only one database per session. The database schemas are identical. For each database, the user may have different roles (reader, editor, admin). 
I'm trying to define the user's authorization to the databases and roles in the Identity Server like this:
db1.reader db1.editor db1.admin db2.reader db2.editor db2.admin db3.reader db3.editor db3.admin db4.reader ... 
I then assign these roles to the user accounts. For example, user John Doe could have the following claims sent to the application:
http://schemas.microsoft.com/ws/2008/06/identity/claims/role | db1.reader Go to the complete details ...