UML---use case diagrams

Use cases are used to describe the user's needs and to show the function of the system from the perspective of users. It is used for the analysis of the Software development requirement analysis stage and the software testing phase to provide the test basis.

Basic Composition Elements

Graphic symbol	Name	English	Briefly
	The participant	Actor	A person or thing that interacts with a system. Located outside the system, such as: administrator
	Case	Use case	A collection of features and requirements that are implemented in detail
	Association relationship	Unidirection Association	The existence of an object knows that there is an object
	including relationships	Dependency or instantiates	The inclusion of features between use cases. A use case May include multiple use cases (required)
	Extended relationships	Dependency or instantiates	Extension of a use case (extension of functionality)
	Generalization relationships	Generalization	Inheritance relationships (inheritance and extension of functions)
	Gaze body	Note	Descriptive descriptive font
	Gaze connection	Anchor Note to item	Connection Gaze
	Boundary	Border	Division of the system, the system has clear boundaries is very important

Drawing steps:1. Understand the boundaries. A large system must design elements are multifaceted, only to understand the boundaries, talent to expand use case analysis. Detailed border search We are able to participate in this blog: http://blog.csdn.net/beijiguangyong/article/details/6226242
2. Identify the participant. Participants in the system periphery, only understand the participation, talent to the system user needs and system function design.

3. Use case design.

Use case design to always stand in the user's perspective to think about the needs of users, including the use cases of the name of the body is now the perspective of consumers. The use case description describes the requirements or functions, and generally adopts the verb-object phrase.

4. Determine the relationship.

It is more difficult to distinguish between extension and inclusion.

Include a subordinate relationship, something that is bound to happen, a naming convention, and a similar one. Extensions, however, emphasize the addition of functions that do not necessarily occur. For example:
For the doctor use case, the general situation will be taken medicine, only the case of serious illness only infusion, so the medicine is included in the relationship. Infusion is an extended relationship; In the basic query function, account input is required, not necessarily for Excel printing, so the account input is included in the relationship. Excel printing is an extension relationship.

5. Use case descriptive narrative and use case description. The use case diagram provides a good communication bridge between the system designer and the user, and the necessary descriptive narrative is indispensable.
6. Interface beautification problem.

A good project teacher is sure to make the diagram clearly visible, so that the ability to better express their intentions.

Hands -on summary UML drawing includes a lot of logical thinking and specification explanation. Hope that in a little bit of learning in the future constantly summed up in depth!

UML---use case diagrams