What is a trigger in the use case specification?

What is a trigger in the use case specification?

• A. The event that gets the use case started
• B. The scenario (sequence of steps) in which nothing goes wrong
• C. The postconditions
• D. The subject

Answer: (A)

The trigger is the initiating event that starts the use case. It’s the external action that kickstarts the whole sequence of interactions between the actor and the system. For example, in a checkout use case, the trigger might be the customer clicking the "Place Order" button. This tells you when the use case should begin. The other elements describe what happens after start or who is involved: the scenario where nothing goes wrong is the basic flow, postconditions are the outcomes after completion, and the subject is the actor or system itself, not the starting event.

The trigger is the initiating event that starts the use case. It’s the external action that kickstarts the whole sequence of interactions between the actor and the system. For example, in a checkout use case, the trigger might be the customer clicking the "Place Order" button. This tells you when the use case should begin.

The other elements describe what happens after start or who is involved: the scenario where nothing goes wrong is the basic flow, postconditions are the outcomes after completion, and the subject is the actor or system itself, not the starting event.