问题
Can I include the system as an actor on use case diagram?
The system automatically sends emails and/or automatically updates some details of another user.
回答1:
Depends. If you have a system that is responsible for sending e-mails - lets call it NOTIFY - and another system - lets call it X - that uses NOTIFY then X can be modelled as an actor of use case Send e-mail that is covered by NOTIFY. On the other hand, NOTIFY itself cannot be modelled as an actor using its own use cases.
回答2:
No.
The system under consideration is supposed to support use cases for actors interacting with the system. The use case is for the actor, not the system. In your case the use case would be Receive Mail (about X) and some actor (user) would be the primary actor. So he has some added value here.
来源：https://stackoverflow.com/questions/46008287/use-case-diagram-system-as-an-actor