UML Tutorial --Use Case Diagram
Use case diagram
A use case diagram shows the relationships among actors and use cases.An actor is a role of an object or objects outside the system that interacts directly with it in a use case.The actor has class-like properties.A use case is an unit of functionality of the system or a class.One physical object may have different orles and therefore be modeled by several actors.There are three types of use case relationships:
Communicates:This relationship shows participation of an actor in a use case.This relationship is shown as a solid line between the actor and a use case,and is the only relationship between actors and use cases.
Extends:An extends relationship from use case A to use case B indicates that an instance of use case B may include the behaviour of use case A.This is shown as a generalization arrow from the use case providing the extension to the base use case.The arrow is labeled with the stereotype <<extends>>.
Uses:A uses relationship from use case A to use case B indicates that an instance of the use case A will also include the behaviour specified by use case B.This is shown as a generalization arrow from the use case doing the use to the use case being used.The arrow is labeled with the stereotype<<uses>>.
A use case diagram shows the relationships among actors and use cases.An actor is a role of an object or objects outside the system that interacts directly with it in a use case.The actor has class-like properties.A use case is an unit of functionality of the system or a class.One physical object may have different orles and therefore be modeled by several actors.There are three types of use case relationships:
Communicates:This relationship shows participation of an actor in a use case.This relationship is shown as a solid line between the actor and a use case,and is the only relationship between actors and use cases.
Extends:An extends relationship from use case A to use case B indicates that an instance of use case B may include the behaviour of use case A.This is shown as a generalization arrow from the use case providing the extension to the base use case.The arrow is labeled with the stereotype <<extends>>.
Uses:A uses relationship from use case A to use case B indicates that an instance of the use case A will also include the behaviour specified by use case B.This is shown as a generalization arrow from the use case doing the use to the use case being used.The arrow is labeled with the stereotype<<uses>>.
posted on 2009-09-15 20:55 Joshua Leung 阅读(337) 评论(0) 编辑 收藏 举报
