How to connect different Use Cases without 'include' or 'extend'?

Question

I'm fairly new to UML and Use Case Diagrams and I'm not sure if I understand I'm using 'include' correctly. Also please note that this is for a coursework not an actual system so even though the below details are not set in stone, they are not really flexible either.

I have this scenario where an actor (Customer) fills out an application form. This use case is called TakeMembership.

After the Customer provides the details to the system they are taken to payment and I start another use case called TakePayment. I've included an External Payment System as the primary actor and Customer as the secondary actor for this use case.

Finally, an External Email System sends the user their login details. I've called this use case SendLoginDetails and included Email System as the primary and Member (Customer has now turned into Member and became a different actor) as the secondary actor for this case.

Now my question is this: The two latter Use Cases are part of the main flow of the first Use Case, however I have no idea how to actually connect them.

I thought about using 'extend' first but then decided against it since these two Use Cases are not an exception as they well be used every single time the system is used.

Some classmates suggested I connect them with 'include' but that doesn't make sense to me either. My understanding for 'include' was that it should be used when there are common steps in two or more Use Cases and the 'include' Use Case can't stand on its own.

Is there something about 'extend' or 'include' that I'm not aware of?

Answer 1

Use cases are not about "do A, then B, eventually C" but to show the added value an actor gets from a system. Do not try a functional decomposition (so which UC included/extends what other UC). There are only very rare case where these might be of use (actually I can live very well without a single of them). Often people create a use case where it is actually just a constraint (most famous: Login ).

Once your set up your mind about the added value you can think of scenarios on how to realize them. This can be done with pure textual description or by using activity diagrams.

My best advice: do not use include/extend and read Bittner/Spence.