Use Case Diagram

Updated 22 Jul 2026

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def
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  a UML diagram describing the goals of actors/objects when using a system — used both as a requirements engineering/UML technique and, in an HCI context, as a way to map user goals to system functions during task analysis
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characteristics
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  focuses on user/object interactions inside and outside the system
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  a single path through a use case is called a scenario
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notation
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  actors — users or external objects, drawn as stick figures (always outside the system boundary)
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  use cases — main system functions, drawn as ovals
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  system boundary — a box containing the use cases
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when to use
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  high-level graphical model supplemented by more detailed tabular descriptions
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  UML sequence diagrams may be used to add detail showing event processing order
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use in task analysis (HCI)
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  used in Task Analysis to map user goals to system functions
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  supplements Unavailable reference at a higher level of abstraction
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note
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  for systems with complex data flows, Data Flow Diagram (DFD) may be more appropriate
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related
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  Use Case
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  Use Case Relationships
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  Unified Modeling Language (UML)
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  Scenario-based Modeling
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  Task Analysis
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  Unavailable reference

Linked references 6