-Now, let's look at use cases in a little more detail. - -2
-And start by defining exactly what an actor is. An actor - -3
-represents an entity, which can be a human or a device, - -4
-that plays a role within my system, so that interacts with my - -5
-system. It's some entity from the outside world, with respect to - -6
-my system, that interacts with my system. It is important to - -7
-clarify that an entity can play more than one role. For - -8
-example, you might have somebody working in a bank that can be - -9
-both an employee of the bank, or a customer of - -10
-the bank, depending on how it interacts with the banking - -11
-system. And, obviously, more than one entity can play the - -12
-same role. Using the same example, we can have both an - -13
-employee of the bank and just a regular customer, playing - -14
-the role of the customer. So again, it all depends on - -15
-what the entity does, how the entity interacts with the - -16
-system, what kind of functionality of the system the entity uses. - -17
-And finally, actors may appear in more than one use case. - -18
-So it's fairly normal for the same actor to interact with - -19
-the system in different ways. And therefore, to appear in more - -20
-than one use case. Just think about the use cases in - -21
-scenarios of usage. If the same actor can interact with the - -22
-system in different ways, that actor will appear in multiple use - -23
-cases. Now let's go back to the description of our course - -24
-management system, and see how we can identify actors in the system. - -25
-And as we did for the class diagram before, I encourage - -26
-you to stop the video and try to identify the actors - -27
-in the system yourself, before I do it. - -28
-If we look at the description, we can see that, for example, the Registration - -29
-Manager is clearly an actor for the system. Students are actors - -30
-for the system. Professors are actors for the system. And notice - -31
-that we're not doing the same thing that we were doing - -32
-when identifying classes. Here we're identifying - -33
-entities that are from the outside - -34
-world, and have an active role in interacting with my - -35
-system. Again, Registration Manager, that we will just call registrar for - -36
-simplicity, students, and professors. So once we have identified the - -37
-actors for our example, we can simply draw them, using the - -38
-notation that we just introduced. So we have the registrar, - -39
-and notice how for every actor we clarify the role that - -40
-the actor plays. We have the professor, and we have - -41
-the student. So here, these are the three actors that we - -42
-identified for our system. -- cgit 1.4.1