PlantUML Use Case Diagram: System Requirements

Use Case Diagrams for System Requirements

Use case diagrams capture what a system does from the perspective of external actors. They are essential for requirements gathering and stakeholder communication.

Basic Structure

@startuml
left to right direction

actor Customer
actor Admin
actor "Payment Gateway" as PG

rectangle "Online Store" {
  usecase "Browse Products" as UC1
  usecase "Add to Cart" as UC2
  usecase "Checkout" as UC3
  usecase "Manage Inventory" as UC4
  usecase "View Analytics" as UC5
}

Customer --> UC1
Customer --> UC2
Customer --> UC3
Admin --> UC4
Admin --> UC5
UC3 --> PG
@enduml

Layout Direction

left to right direction arranges actors on the left and the system on the right. The default is top to bottom, which works better for smaller diagrams.

Include and Extend

usecase "Checkout" as UC3
usecase "Apply Coupon" as UC6
usecase "Process Payment" as UC7
usecase "Verify Address" as UC8

UC3 ..> UC7 : <<include>>
UC3 ..> UC8 : <<include>>
UC3 <.. UC6 : <<extend>>

Include: UC3 always requires UC7 and UC8 to complete. The arrow points from the base use case to the included use case.

Extend: UC6 optionally extends UC3. The arrow points from the extension to the base use case.

Actor Generalization

actor User
actor Admin
actor SuperAdmin

User <|-- Admin
Admin <|-- SuperAdmin

Admin inherits all of User's use cases, and SuperAdmin inherits all of Admin's.

System Boundaries

Use rectangle to draw the system boundary. Actors sit outside the boundary (they are external to the system). Use cases sit inside.

Package Grouping

rectangle "E-Commerce Platform" {
  package "Shopping" {
    usecase "Browse" as B
    usecase "Search" as S
  }
  package "Checkout" {
    usecase "Pay" as P
    usecase "Ship" as SH
  }
}

Packages within the system boundary organize related use cases into logical groups.