Use case diagram

Definition:

• It is a model of the system’s intended functionality (use cases) and its environment (actors).
  • Define the user as a role
  • User can be another system
• Includes:
  • Use cases:
    • Represents with a circle
    • Describe a functional requirement that a system performs to achieve the user’s goal.
    • A use case must yield an observable result that is of value to the user of the system.
  • Actors: an icon for that actor
    • Represents with an icon for that actor
    • An actor represents a role of a user that interacts with the system that you are modeling.
    • The user can be a human user, an organization, a machine, or another external system.
  • Subsystems: a folder
    • Represents with a folder
    • Subsystems are a type of stereotyped component that represent independent, behavioral units in a system.
    • Subsystems are used in class, component, and use-case diagrams to represent large-scale components in the system that you are modeling.
  • Relationships in use-case diagrams:
    • Represents with a simple arrow
    • A connection between model elements.
    • A UML relationship is a type of model element that adds semantics to a model by defining the structure and behavior between the model elements.

Draw

•   skinparam monochrome true
    left to right direction
    actor Guest as g
    package Professional {
      actor Chef as c
      actor "Food Critic" as fc
    }
    package Restaurant {
      usecase "Eat Food" as UC1
      usecase "Pay for Food" as UC2
      usecase "Drink" as UC3
      usecase "Review" as UC4
    }
    fc --> UC4
    g --> UC1
    g --> UC2
    g --> UC3