Use case diagram

One 、 participants ： The trigger of the use case , The trigger may be the user , It may be the agent of the event . The so-called time agent is the operation of the timing function set automatically for the system , When it reaches a certain time , The system will automatically perform the corresponding functions

Two 、 Use cases ： A use case is a series of actions performed in a system , These actions will generate value results visible to specific performers . A use case defines a set of use case instances .

Identify use case pithy ： The performer uses the system to use cases

3、 ... and 、 Relationship ： It describes the relationship between the performer and the use case . The relationships involved in use case diagrams are ： relation 、 generalization 、 contain 、 Expand .

The relationship between the performer and the use case

In the use case diagram , The performer interacts with the use case , The relationship between them is represented by a straight line , It is called Correlation (Association) Or communication relationship (Communication)

The generalized relationship between executors

There can be generalization between executors (Generalization) Relationship （ Also known as “ Inherit ” Relationship ）

Between use cases Inclusion relation

Describe common behaviors that exist in multiple use cases , By use case A Point to use case B, Represents a use case A Use cases are used in B The act or function of , Containment is achieved by applying <<include>> Structural type （ stereotype ） To represent the

Between use cases Extended relationship

a, Extended use cases can add new behaviors on top of the base use cases , But the base use case must declare something specific “ The extension point ”, And extension use cases can only extend new behaviors on these extension points .
b, Expanding （extend） In relationship , Basic use cases (Base) There are one or more named extension points defined in , Extending a relationship means extending a use case (Extension) The event flow of is inserted into the basic use case according to the corresponding extension point under certain conditions (Base) in .
c, Extended relationships are achieved by applying <<extend>> Structural type （ stereotype ） To represent the .

Between use cases Generalization relation

a, When multiple use cases share a similar structure and behavior , Their commonalities can be abstracted as parent use cases , Other use cases as sub use cases in generalization relationship .
b, In the generalization of use cases , A child use case is a special form of a parent use case , The child use case inherits all the structure of the parent use case 、 Behavior and relationships .
c, Generalized relationships are rarely used .