A brief summary of UML & Rational Rose – Use Case Diagram, Part II
根据一些UML知识和项目经历，利用业余时间，我简单总结了一系列关于UML和Rational Rose的文章，包括一些易混淆的概念和UML Diagrams的基本使用规则。希望这些对你有帮助，如果发现有错误，请告诉我。谢谢！
－－－－－－
For my knowledge and project experience, I write a series of postings about how to use UML and Rational Rose in my spare time, which contain some confused concepts and some basic rules to use UML diagrams. I hope it's helpful for you. However, if there is something wrong, please let me know. Thanks.
*************************************
The following will show you all UML diagrams.
4. Use Case Diagram
Use case diagram is a high-level piece of functionality that the system will provide. In other words a use case illustrates how someone might use the system.
The following is a sample of Use Case Diagram.
In general, Use Case Diagram mainly contains the foll
owing elements.
Actor represents a person or external system that initiates a use case in order to get some value from the application.
Use Case is a well-defined unit of functionality that he system providers to one or more actors.
Communicates shows that a particular actor makes use of a particular use case.
An abstract use case is one that is not started directly by an actor. Instead, an abstract use case provides some additional functionality that can be used by other use case. Abstract use cases are the use cases that participate in a uses or extend relationships.
Relationships
There are three types of relationships in a Use Case Diagram.
- Communication relationships describe the relationship between the actors and the use cases.
- Uses and extends relationships describe the relationships between the use cases.
- Actor generalization relationships describe the relationships between actors.
Notes
There are two types of notes you can add, a note and text box.
- Notes are used to include a comment that applies to a single item on the diagram.
- Text boxes are used to place the diagram name or other general information on the diagram.
Packages
Items such as actors, use cases, classes and components can be grouped together into packages in order to organize them.
