What does the term "alternative flow" refer to in use cases?

The term "alternative flow" in use cases refers to the different paths that can be taken to achieve an actor's goal, aside from the main or primary flow. In the context of use cases, the primary flow outlines the main sequence of actions that lead to the expected outcome when everything goes as planned.

Alternative flows provide a way to capture scenarios that diverge from this main path. These could include variations due to different conditions, user choices, or additional interactions that still allow the actor to eventually reach their goal but through different means or under different circumstances. For example, an alternative flow might outline what happens if a user enters invalid data, thus leading them through a different sequence of steps to correct that mistake before proceeding.

This concept of alternative flow is vital because it helps to ensure that all possible user interactions and outcomes are considered during the requirement analysis phase. By clearly defining these flows, developers and stakeholders can better understand the system's functionality and anticipate how users will interact with it in real-world scenarios.