What is Scenario?
A scenario is a sequence of steps describing the interaction between a user and a system. So if we have web-based on-line store, we might have a Buy a Product scenario that would be documented as a story. Based on the story the steps for the scenario can be extracted.
A simple format for capturing a user case involves describing its primary scenario as a sequence of steps and the alternatives as variations on that sequence.
l An actor is a role that a user plays with respect to the system.
l A single actor may perform many use cases; conversely, a user case may have several actors performing it.
l It is easier to arrive at the list of actors first, and then try to work out the use cases for each actor.
l Actors don’t need to be human. An actor can also be an external system that needs some information from the current system.
Use Case relationships in UML?
l Include relationship: Use include when you are repeating yourself in two or more separate use cases and you want to avoid repetition. (如果你在兩個以上的使用案例（use cases）中重複一些行為，可是又不願意重複這個行為時，可以使用包含（Include）關係。)
l Use Case generalization: Use generalization when you are describing a variation on normal behavior and you wish to describe it casually. A given use case may be a specialized form of an existing use case. The notation is a solid line ending in a hollow triangle drawn from the specialized to the more general use case. This resembles the object-oriented concept of sub-classing.(特殊化使用案例（specificalized use case）則可能改寫或新增步驟)
l Extend relationship: Use extend when you are describing a variation on normal behavior and you wish to use the more “controlled form”, declaring your extension points in your base use case. (擴充使用案例（extension use case）是在基本使用案例（base use case）的情節中，新增步驟)
沒有留言:
張貼留言