Use Case Diagram
用例图中的事物及解释：
| 名称 | 解释 | UML表示 |
|---|---|---|
| Actor 参与者 | external entities that interact with the software system and affect the system functions |  |
| Use Case 用例 | text desciptions of the interaction between outside entities and the software system |  |
用例图中的关系及解释：
| 关系 | 解释 | UML表示 |
|---|---|---|
| Association 关联 | shows the communication path between a use case and an actor |   |
| Generalization 泛化 | exists among the actors that have similar behavior and properties |   |
| Entend 扩展 | indicates that an existing use case is extended by additional behavior to obtain another use case |  |
| Include 包含 | indicates that the function of one use case are included in the functions of another |  |
System Boundary
The system boundary enables you to focus on the functions performed by the software system in each iteration.