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What is it? use case chart？
use case The figure was created by participant（Actor）、 use case（Use Case） and the use of the relations The static view of the system used to describe the composition of the UML diagram（ This definition is taken from the Baidu encyclopedia）。 use case The diagram is able to show the various types of performers outside the system with the system in use case of relations。
What are the components of a use case diagram?
As we know from the definition, the use case diagram consists of participant（Actor）、 use case (Use Case) and between these two relations The three components, strictly speaking, use cases also include System boundary However, the use cases and participants are inside and outside the system, so the system boundary is implicitly between them, and thus the system boundary can generally be omitted when drawing the diagram.
participant： participant i.e. outside the system， But individuals who interact with functional units within the system， For example, librarians、 The borrowers are all from the library management system use case Figure. participant。 One thing to note is that， It's not just“ human” only then participant， It could also be equipment、 Other systems, etc.， Any external object that interacts with the system is part of the participant， consequently， If you go deeper into the division， It's also possible to place participant Divided into initiators（ take the initiative） and supporters（ passively）， The initiator is use case The main clients of the， Supporters are the objects that support the system。
Participants are usually represented by a small human figure, as in the figure.