UML Diagram: Use Case
(Free Web Tutorials)

by Michael Thomas

UML Home Page

On the UML Home page, you can download the whole UML site (all content, tutorials & examples) !!!
(Note:  All of the EclipseUML projects used in these tutorials are in .zip files located at: uml\eclipse\viewonly .  Just extract them into your workspace.)

Prerequisites

• Review the UML Overview tutorial. 

Objectives

• Get a broad over view of a UML "Use Case" diagram.

Definition & Example

• Use Case Diagram - diagram of the use cases (software functions/services) and the role of the actors (users - both humans or systems). This diagram is from the user's perspective.
• Example - (created with EclipseUML - May of 2008) - Use Case Diagram for a high level view of a Hotel Reservation system.
• Example - (created with Rational Software Modeler v6.0 - Sept of 2005) - Use Case of an online order system.
  • Example - Use Case diagram.
  • Description - description of actors.
  • Description - description of Use Case.

Goals of the Use Case diagram

• Show the roles of the actors (humans, services, etc...) as they interact with the system (Use Cases) and the desired behavior.
• Show the intended behavior of the system without trying to implemented the system.
• Create a diagram that domain experts, end users and developers can review.
• Create Use Case diagrams for key system desired behaviors (functional requirements) from a user's perspective.
• Create a "Use Case" diagram to show how actors get the system to perform a task for them.
• A "Use Case" diagram is a collection of actors and their roles in communicating with the use case.

UML Use Case Diagram Terms (used by EclipseUML for UML2)

• Actor - human, system or service which interacts with a use case
• Role - the role the actor has with the use case.
• Generalization - describes a parent / child relationship where the child is more specialized in it's task.
• Include - (make a call) - a use case invokes another use case.
• Extend - (conditional call) - a use case that may or may not invoke another use case.
• Association - use a solid line to indicate that an actor is associated or involved with a use case. It does NOT represent flow of information.
  • Aggregation - three types: None, Shared, Composition
  • Multiplicity - describes the number of elements in a set.
    • 0..1 - zero to one
    • 1 - one to one
    • *  - many to many
    • 1..* - one to many
  • Stereotype - is a way to extend an element from an existing one that is specific to your situation.
  • Router (under construction)
• Diagram Link - a link to another diagram.