how the use case is similer to Contex diagrams and Level 0 Data flow diagram
The first thing that comes to mind is that use cases and context diagrams operate on the same domain: the environment in which the system will be used.
The context diagram illustrates the environment with domain and boundary objects. Actors of these objects are also illustrated and I believe the purpose of the context diagram is to illustrate the relationship between the actors and the objects in the environment.
The use case then describes what the system does in response to interactions with the environment, including actors who interact with boundary objects that alters system behaviour.
