I think you should include the Actor in the sequence diagram. Boundary, Control & Entity are Rational/IBM concepts as is the concept of "Use case realization" so they are not part of the UML standard. Specifically, in Rational Rose they use different UML representation for those types of classes. If you do decide to use "Boundary/Control/Entity", make sure you represent them as classes (maybe strereotyped) and not using the Rose notation. That's what I am doing anyway.