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Use fields specified in a CU into another CU

I have a CU that extends another CU, let's say: Add inventory extends Add product, so in one product interface I need to use fields from inventory CU, how I can described this in a CU?

Solution

  • "Extends" means that during the "execution" of the extended UC, execution of the extending UC has been voluntarily invoked by an actor. Each UC is described by several scenarios. Scenario is decribed as an ordered sequence of "steps".

    You have to specify so called extension points - steps in the scenario(s) of the extended use case, in which the Actor can invoke the extending UC's execution. It can be a single step or a range...

    You can think of the extension point as of a method with parameters, tmplemented in the extending UC and invoked by the extended UC. These parameters could be these fields, you need to "pass" to another interface.

    In my projects I always "back up" the my case model with the domain model (class diagram) and use elements of it in the specification of the UCs (preconditions, postconditions, scenarios, extension points).

    UPDATE (after the comment)

    UML does not define the concrete format of the use case specification, it only defines the concepts and their semantic meaning. A UC can have so called Behavior, can extend another one (or be extended), has Extension points.

    The way you define Behavior and Extension points are your own choice.

    So, in my example:

    • Behavior of both UC is defined as a textual sequence of steps, as performed by System or User (alternative is a state machine, activity diagram, even user interface prototype)
    • Extension Point is defined as a step in the sequence and additionally described by this "method" signature, to illustrate the exchanged information

    Remember that UCs show INTERACTIONS beetween the System and the outside world. For them is the System kind of black box. Conceptual model I've used here is therefore NOT a DB or system design, but rather a conceptual, implementation-agnostic view on the entities used by the app. They can even be mapped on 2 different systems on the implementation level! Relationships between the UCs similarly exist purely on the user-system interaction level of abstraction, and DO NOT BY ANY MEANS reflect some internal system dependencies! (note added after Gangnus's comment)

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    (Scenarios and concepts are fully invented for the example sake)