不确定我的UML USE-CASE图是否正确

Question

I've started learning UML but it confuses me sometimes (for example what i'm allowed or not to put in my USECASE diagram, last time i was wondering if logging in can be used in usecase diagram). Anyways i've made simple usecase diagram of e-learning platform, like lynda but you have to pay for individual course you'd like to take. Any suggestions/corrections about my diagram? (i'd like to bring more usecases into it)

Answer 1

as you know, a use case is a textual representation of a flow between a user and the system. the use case should have a name that reflects that flow. when i look at your use case names i can see that you have understood this. the names are all descriptive and well thought through. well done!

so, about use case diagrams: the purpose of a use case diagram is to make it easier to understand what use cases there are, and what type of users the use cases are intended for . because of this, the arrows always go from an actor to a use case.

sometimes an actor can be a separate system, and then it should be included in the use case diagram as an actor, with a name that hints to the actor being a system. if a group of persons for some reason could have a name that include the word 'system', i think it should be clarified that the actor portraying that group of persons is not an actual system, although the name of the actor hints to it being a separate system.

Answer 2

I would split that Usecase called Register/Login into two separate Usecases. I think these steps are two separate actions and need different steps to execute. This way you are also able to transform the Usecases to Composites.

We often do it this way:

• Create the Usecase
• Create an Activity Diagram with the same name
• Right-click on the Usecase
• Advanced
• Make Composite

Then you could add more detailed steps on how to implement/execute the certain Usecase in the Activity Diagram.

This answer is specific to Enterprise Architect of course.

Answer 3

Login is not a user goal. Login is necessary to be able to satify the user goal of register. If a user logged in, did nothing else, and logged out, what value does that provide? None.