Final answer:
The principal components of a textual use-case description include the actor, trigger, preconditions, main flow, alternative flows, and postconditions.
Step-by-step explanation:
The principal components of a textual use-case description include:
- Actor: The actor is the person, system, or external entity that interacts with the system being described in the use-case. It represents the users or entities that initiate the use-case and receive the outcome.
- Trigger: The trigger is an event or condition that initiates the use-case, such as a user action or a change in the system's state.
- Preconditions: Preconditions are the conditions that must be true before the use-case can be executed. They represent the initial state of the system.
- Main Flow: The main flow is the sequence of steps or actions that occur in the use-case. It describes the normal or expected behavior of the system when the use-case is executed.
- Alternative Flows: Alternative flows describe deviations from the main flow that may occur in certain situations. They represent different paths or options within the use-case.
- Postconditions: The postconditions are the conditions that must be true after the use-case is executed. They represent the resulting state of the system.