Another use case diagram of UML

A use case diagram is primarily a graph that represents the main event flow of a system. It is mainly used to describe the needs of customers, that is, users want the system to complete a certain function of the ability to understand the use case is the SOFTWARE function module. The designer creates and interprets a use case diagram based on the customer's needs to describe what functional modules the software should have and the call relationships between them.

Composition:use-case diagrams include: actors (actor), use cases, system boundaries, relationships
The participants and use cases are connected in order to reflect the whole structure and function of the system to the user, and the structure and function decomposition of the software is the corresponding.
Relationships between use cases: generalization, inclusion, extension
Relationship Refinementinclude include

use the include use case to encapsulate a set of similar actions (behavior fragments) that span multiple use cases so that multiple base use cases can be reused. The relationship between the base use case control and the containing use case, and whether the event stream containing the use case will be inserted into the event stream of the base case. The base use case can depend on the results that contain the execution of the use case, but neither side has access to the other's properties. A typical application of a containment relationship is reuse, which is what the definition says. But sometimes when the event of a use case flows through complexity, in order to simplify the description of the use case, we can also abstract an event stream into a contained use case, instead, when the use case is divided too thin, you can also abstract a base use case to contain the use cases of these fine particles. This situation is similar to the process design language in which a piece of the program's algorithm is encapsulated into a sub-procedure, and then called from the main program. said for a long while too official, difficult to understand, draw a diagram to illustrate.

Example

Extended Extend

The extended relationship encapsulates a relatively independent and optional action in the base case with an extension (Extension) use case, and then extends it from the extension point (Extension points) declared in the base use case to make the base case more concise and more focused. The extension use case adds new behavior to the base use case. An extension use case can access the properties of the base use case, so it can determine whether to execute itself based on the current state of the extension point in the base case. However, the extension use case is not visible to the base use case.

Example

generalization generalize

Generalization represents a general and special relationship. The generalization relation between the use cases is similar to the generalization relation between the classes, that is, in the use case generalization, the child use case represents the special form of the parent use case. Child use cases inherit behaviors and properties from the parent use case, and you can add behaviors or overrides, and change inherited behavior. Use case generalization is used when one or more use cases in a system are specific to a generic use case.

Example

use case diagram

The following is the computer room charge system use case diagram, welcome to correct, continuous modification, common progress ...

Another use case diagram of UML