We have a SL application and many users who use this system with different data and access roles. For example, each user can have some devices and each device will send its locations every 5 minutes to server.
One approach is defining a User table in database and have many tables which connect an entity to a user Id, but this is not a good idea as that creates many tables between users and other entities.
It will be a time consuming process to select user data or reporting, so I wanted to know what the best way is for handling such behavior in Silverlight?
You can use AuthenticationDomainService. This is a popular service for authorization users with roles. You can get more information there: http://msdn.microsoft.com/en-us/library/ee707361(v=VS.91).aspx