Use case diagram of UML9 diagram (i.)

Use case diagram is used in the requirement Analysis stage, describes the functional requirements of a system to be developed, the use Case view emphasizes the function of the system, and is the first design view of the software development design process. It describes the user's snowball from the user's point of view, describing the function of the system, and pointing out the performer of each function and what functions the performer has completed.

Use case diagrams consist of three parts: use case, role, and relationship. The key is the use case and the role, and the relationship is the bridge between the connection role and the use case, indicating the relationship between the role of the use case. As shown in the figure below:

How does a system look for performers? To see who uses this feature of the system, who will maintain the system, what hardware the system needs to interact with, and what hardware the system needs to operate. The principle of looking for a function is to think of the system as a black box, to understand the system from the perspective of the user of the external performer, without regard to how the function is implemented, just consider what functions the system needs, and who interacts and executes the function.

To become a good use case diagram, if the use case too many, can lead to the system is too complex, and the use case too little, can cause the maintenance of the system more difficult. This requires controlling the granularity and scope of the use case diagram. Start with the properties of the use case diagram and accurately draw the use case diagram.

Use case diagram is good or bad influence code implementation difficulty and system patching difficulty, use case diagram and the other view behind the other link together, so to give the fine use case granularity.

Use case diagrams are composed of use cases that specifically describe the behavior of the system that can be seen by end users, analysts, and testers, who use use case diagrams to describe the user's needs, communicate with users and designers, and end users using use case views to understand the functionality of the system to be completed, to confirm compliance with their requirements, The tester verifies that the implemented system conforms to the user's needs according to the use case diagram. The use case diagram drives the development of each stage after the demand analysis to a certain extent.

Use case diagram should also pay attention to clearly define the system boundary, from the performer's point of view to name the use case, avoid inconsistent with the name of the performer, avoid the relationship between the performer is too complex. Use cases can describe the requirements of the system well, but there are situations where the use case is not appropriate, which needs to be used for document description,

By doing a computer room charge system, one of the administrator role of the use case diagram:

Drawing a good use case diagram is the first step in a software architecture, a driver of demand analysis, used by analysts, testers, and end users, and is the first view of software development. Software development, there is a good starting point to have a perfect software.