The operation you are trying to complete is forward mapping. However during forward map we alter only the user defined tables. Modifications of view is not supported.
The only workaround I can provide you with is to create the relationship on your database server and then reverse map it.
I am sorry for the inconvenience this might be causing you.
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items