Say method m of class A calls method n on class B, but the source code of class B does not contain n, since n is inherited from one of the superclasses of B.
How will the sequence diagram look?
Will there be message interaction between A and B by the method n or would it be with A and the superclass of B with by method n
If you're to respect the principle of encapsulation, the interaction would purely be between A and B. The fact that B's implementation uses inheritance is of no concern to the code written in A - it's sole world view is that it calls the method on B.
You can safely change the implementation in B and not affect A. This is another reason to diagram the interactions this way.
来源：https://stackoverflow.com/questions/15364595/how-will-inheritance-is-depicted-in-a-sequence-diagram