Use Case Diagram having trouble with extends and includes in my diagram

3
votes

I'm very new to UML, especially use case diagrams. I attempted to draw a use case diagram for my application which includes a renter, a seller, and a general user. My renter and seller extend general user. I am having trouble with includes and extends. For example, When you view an office space, you can also see the reviews for it at the bottom of the page. As well as when a renter wants to write a review, he/she must do this on the view office space page. I am not sure if this is an extends or an include. Please correct me if I am wrong with any of my arrow directions. Also, is it okay to say that Renter and Seller include logging in?

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2
umluse-case

2 Answers

2
votes

As Jim states: I/E are for UCs, not for Actors. I assume you meant a generalization here, so both inherit from General User.

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Some further observations:

  • Use verb-substantive for UCs titles
  • Think of the "use" in use cases. IOW: the added value. If you don't find it's added value, then it's no use case.
  • Avoid I/E in general. They often indicate that you try to use functional decomposition which is not the aim of a UC synthesis.
  • The relation you draw between the UCs is wrong in any case. There is no relation which has a filled triangle and is dotted. You probably meant to use some <<include>> dependency (with an open arrow). But as said above: avoid it. Just create an association to the actors. It's sufficient to just draw one between Reviews and General User as Renter will inherit the relation.
  • Login/out are no UCs (no added value). The are constraints to other UC (write {must be logged in} and attach to the connector)
2
votes

You generally should not model login use cases, as they don't directly help the user accomplish anything he or she cares about.

Includes and extends are relationships between use use cases, not actors. The UML 2.5 specification says:

  • An extension is:

    A relationship from an extending UseCase to an extended UseCase that specifies how and when the behavior defined in the extending UseCase can be inserted into the behavior defined in the extended UseCase.

  • An include is:

    An Include relationship specifies that a UseCase contains the behavior defined in another UseCase.

A generalization / specialization relationship between actors is perfectly fine. That's just a generalization arrow. (e.g., a solid line with a hollow arrow head.)