Tell a Story

Use Case

Function and Form

First Form: A NarrativeMake a Payment

Narrative Form

Second Form: A ScenarioRegister Customer With Automatic Activation

Scenario Form

Third Form: A ConversationMake A Payment - General Flow

Conversation Form

Comparing the Three Forms

The Benefits of Use Cases

Use Cases Aid Understanding

Use Cases Vary by AbstractionLevel

Use Cases Vary in Scope

Use Cases Vary in Detail

What Use Cases Cannot Do

Finding Use Cases

Finding Use Cases

Naming Use Cases

Primary and Secondary Actors

Naming Actors

Group individuals according to their common use of the system. Identify the roles they take on when they use or are used by the system

Each role is a potential actor Name each role and define its distinguishing

characteristics. Add these definitions to your glossary

Don’t waste time debating actor names

Actor and Use Case Checklist

Glossary

Glossaries

Build Consensus

Defining Concepts

Identify a concept and its distinguishing characteristics

More than a synonym for a word Identifies a way of mentally dividing reality for

purpose of talking or thinking

Writing Glossary Entries

Why this concept is important Typical sizes or values Clarify likely misunderstandings Show an example Explain graphical symbols Relate entries

A Good Form for Definitions

Improving Glossary Definitions

Relating Definitions

Define Acronyms and Their Concepts

Avoid Using“Is When” or “Is Where”

Explain What Is Unclear

Setting the Stage for the Use Case

Level—summary, core, supporting, or internal use case?

Actor(s)—role names of people, objects or external systems initiating this use case

Context—the current state of the system and actor

Preconditions—what must be true before a use case can begin

Completing The Picture

Variations— different ways to accomplish use case steps Exceptions— errors that occur during the execution of a step Policies— specific rules that must be enforced by the use case Issues— questions about the use case Design notes— hints to implementers Post-conditions— what must be true about the system after a use

case completes Other requirements— what constraints must this use case conform

to Priority— how important is this use case? Frequency— how often is this performed?

Make Clear What You Don’t Know

Avoid Vague Words

Write General and Specific Cases

Actor Actions

Include System Actions

Describing Actions

Condense Information Entryand/or Validation Actions

State System Actions at aReasonably High Level

Showing Optional and Repeated Actions