Actor Function vs System Function

Can anyone explain to me, thoroughly, the difference between Actor function and System function?
From my understanding, actor function is the activity by the actor. And system function is the activity by the system.
Can anyone please elaborate on that? They are really confusing.

You are perfectly right. Just to illustrate this, imagine you are designing a cash dispenser.
If you want to describe the use of the dispenser, then you will define :

  • actions to be done by the user of the system (an actor), by means of actor-allocated functions : e.g. ‘introduce credit card’, ‘select cash amount’, etc.
  • reactions expected from the system, by means of system-allocated functions : e.g. ‘check credit card validity’, ‘check bank account balance’, ‘deliver bank notes’, etc.
  • and interactions between them, by means of functional exchanges (‘credit card’, ‘bank notes’…).
    These elements will constitute the dataflow, spread among the system and actors, on which you will be able to define for example test scenarios, or functional chains, using these functions and exchanges.
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