The application scenario or also Use Case (e.g., buying coffee at a coffee vending machine) describes all steps of interaction between a consumer or user with a system (e.g., inserting money, selecting product) and all externally perceivable reactions of the system (e.g., requesting more coins to be inserted, ejecting a coffee cup, producing the coffee, etc.). The result of the use case can be success (e.g., issuing the coffee) or failure (aborting the operation because the coin falls through, aborting the operation because the coffee or water container is empty, etc.).
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