The Unified Modeling Language User Guide

1
The Unified Modeling Language User Guide

• Chapter 17
• Use Cases Diagrams

2
Chapter 17 Topics

• Introduction
• Modeling System Requirements

3
Introduction

• Use case diagrams
• Show a set of actors, use cases, and their
  relationships.
• Facilitate communication between non-technical
  customers and developers due to their simplistic
  nature.
• Show the functionality of the system from the
  prospective of each user of the system.
• Model the context of the system.
• Model the requirements of the system.

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Use Case Diagram
5
Modeling System Requirements

• A requirement
• Is a design feature, property, or behavior of a
  system.
• States what needs to be done, but not how it is
  to be done.
• Is a contract between the customer and the
  developer.
• Can be expressed in various forms, including use
  cases.

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Modeling System Requirements

• To model the requirements of a system
• Identify all actors (users of the system).
• Identify the needs, from the system, of each
  individual actor.
• Make each need a use case.
• Identify redundant behavior within your set of
  use cases, and factor it into common base-class
  use cases. In other words, look for
  opportunities to use generalization.
• Do the same for actors.
• Show the relationships between actors and use
  cases.

7
Modeling System Context