• Introduction
• Objectives
• What is a Requirement?
  • Types of Requirements
• Use Cases and Requirements
• Requirements Traceability

Addressing Requirements

Introduction

This section shows how to trace the results of your analysis and design work back to your user requirements.

Objectives

Upon completion of this section, students will be able to:

• Define a requirement
• Describe the nature of requirements, use cases, and functions

What is a Requirement?

• A user-specified criterion that the system must satisfy.
• Requirements define the bahvior and functionality of a proposed system.
• Usually expressed as sentences that include the word shall or must.

Types of Requirements

• Functional - ``The system shall automatically generate postings to the general ledger''.
• Data - ``The system ... international currencies ...''.
• Performance - ``The system must ... in XX seconds''.
• Capacity - ``Up to 10,000 transactions per day''.
• Test - ``Stress testing shall ... XX users ... YY computers ...''.

Use Cases and Requirements

• A use case describes a unit of behavior.
• A requirement describes a law that governs behavior.
• Several types of requirements: functional, performance, and constraints.
• A use case can satisfy one or more functional requirements.
• A functional requirement may be satisfied by one or more use cases.
• Requirements are requirements, use cases are use cases. Requirements are not use cases.

Requirements Traceability

• Make a list of the system requirements.
• Write the user manual for the system in the form of use cases.
• Iterate with your customers until you have closure of items 1 and 2.
• Make sure you can trace every piece of your design to at least one user requirement.
• Make sure you can trace every requirement to the point at which its satisfied within your design.
• Trace your design back to your requirements as you review the design during your critical design review.