What are extensions in a use case specification?

What are extensions in a use case specification?

• A. Alternative sequences of steps branching off of the main success scenario
• B. The postconditions
• C. The event that starts the use case
• D. The subject

Answer: (A)

Extensions are the alternate flows that can occur in a use case, separate from the main success path. They represent variations, exceptions, or optional functionality that can be invoked from a specific point in the main flow. In modeling terms, you define extension points in the base use case and create extension use cases that describe the steps to take when triggered, branching off from the main scenario. This differs from postconditions (the state after completion), the event that starts the use case (the trigger), or the subject (the system or actor). For example, in a “submit payment” use case, an extension might handle a payment method failure, branching away from the main payment steps to retry or select another method.

Extensions are the alternate flows that can occur in a use case, separate from the main success path. They represent variations, exceptions, or optional functionality that can be invoked from a specific point in the main flow. In modeling terms, you define extension points in the base use case and create extension use cases that describe the steps to take when triggered, branching off from the main scenario. This differs from postconditions (the state after completion), the event that starts the use case (the trigger), or the subject (the system or actor). For example, in a “submit payment” use case, an extension might handle a payment method failure, branching away from the main payment steps to retry or select another method.