Can Have Parent Actor more than One Child Actors In Use Case Diagram

Question

In my Usecase Diagram :

Bidder and Seller both inherit from Guest. Is this Correct? or is there another way to do it?

Answer 1

Preliminary syntactical remark: UML shows inheritance with an arrow head that is a hollow triangle. The small plain black arrow heads are confusing and might be misunderstood.

What inheritance means: Your diagram means that a bidder and a seller are both guests. Is this what you mean to model? In other words:

• Are Bidder and Seller expected to be involved in all their associated use-cases, and on top, all the use-cases of Guest? If yes, it's fine!
• But do you really want that an existing Bidder could register as Bidder, or could register as Seller?
• If not, consider separation of concerns: distinguish a Guest actor, who could only register, and a Registered user who could login (but is login really a use-case?) and do all the common thing that all registered user can do. Bidder and Seller could then inherit from Registered user.

Other improvements:

• associate Make payment and Receive notification to Registered user, because you're not allowed to have several use-cases with the same name. I understand that if the seller makes payment, it's probably the fee for the platform.

• have a Pay the auctioned item and associate it to both the seller and the bidder, because one pays, and the other receives the payment : it's in fact two sides of the same use-case.

• simplify: use-cases should not be features to add to your software, nor functions to be decompsed. It should be independent user-goals (e.g. Browse items, filter items and view item details are probably three features of one more general use-case View items)