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umlmodelinguse-case

Is it possible for use case to have different action depending on which Actor triggers it?

Is UML allowing this?

Can I define how an actor is interacting with use case? In other words, can an use case have a different action depending on who triggered it? For example in the following picture, Client pays for food, and waiter accepts the payment, but client and waiter are connected to the same use case. Wouldn't it be more convenient, to make separate use case called "Receive the payment" for waiter?

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Solution

  • If you want to follow very strict way describing how Client interacts with a restaurant as System under Discussion then you don't have Waiter as an actor, it's part of the System and does not belong to diagram of this level.

    Is it possible for use case to have different action depending on which Actor triggers it?

    Technically yes, but it smells bad. Consider to split the common part into separate scenario (this probably would require creation of a new common role as well). Anyway this is not related really to the main part of your question.

    Client pays for food, and waiter accepts the payment, but client and waiter are connected to the same use case.

    Here goes the tricky part. They aren't connected to the same use case, only client is connected to your "Pay for food". A use case describes interplay of Actor and the system under discussion. In "Pay for food" Waiter is a part of the system, you just don't have it as an actor on this level.

    Wouldn't it be more convenient, to make separate use case called "Receive the payment" for waiter?

    It's not about convenience actually, but yes. You have "Client pays for food" step in some high level "Client eats in restaurant" scenario. You can expand it into a scenario one level lower with steps like "System provides a receipt", "Client gives cash", "System returns change".

    Now you can expand "System provides a receipt" into yet another scenario now on Subfunction level where you can finally introduce Waiter as an actor and describe steps how he goes to cash register, unlocks it with a badge, selects table, click "print receipt"... And on diagram of this level you will finally put Waiter as an actor.