uml - When a system should be included as an actor in use case diagram? -

I am creating a case diagram for a new system. I am thinking that when any system should be included in the diagram as an actor in terms of use?

Thank you.

As stated in another answer, an actor is a system Conversation role If you should include the system as an actor out of developing the system, and if it contacts the system directly, then you are developing.

This is important because you need to define your system limit, which means that its scope and interface include a system as an actor, clearly required for your system It will be clear about the actor to provide the appropriate interface for the system.