In a role-based access control system with context roles, when a user does not satisfy the context constraints, the user can not activate a context role to execute operation on the objects. But if there are dependencies between the operations on the objects, when an operation on an object could not be executed, subsequent operations on other objects can not be executed as well. In this thesis, we propose a method to combine context roles and isolated roles. When a user can not activate a context role, she can access the object by using an isolated role in the isolation environment temporarily. After some waiting period, depending on whether the context conditions are satisfied or not, the action will either be committed or canceled. The combined model can be used in workflow applications to avoid some delay or interruption. Finally, a document flow system was implemented to illustrate this model.