A use case can either specify a complete system or any model element that describes behavior, for example, a subsystem.
用例可以指定一个完整的系统，也可以指定任何描述行为的模型元素，例如子系统。
2
Then the analyst populates the quality model with the data about the systembehavior the stakeholders desire.
然后分析人员使用涉众所需要的系统行为的相关数据来填充质量模型。
3
A second, more subtle reason is that the model, not the diagrams, becomes the expression of record for the structure, semantics, and behavior of the system.