2.Different from stereotype:
<<Boundary>>
<<Interface>>
3.Different in concept:
Interface's responsiblity is:
a.Introduce somthing to user class to use Impletentation.
Boundary's reponsiblity is:
a.Introduce somthing to user class to use Impletentation.
b.Maybe it could have other responsibites except <a>. In other words, it has states.
4.In programmer language:
Java: Implement interface.
C++: Using abstract class Implement interface.