Essentials of IBM Rational Requirements Composer, v3 · 2017. 12. 16. · Module overview After...

© Copyright IBM Corporation 2010, 2011

Essentials of IBM Rational Requirements Composer, v3

Module 4: Creating a use-case model

2 © Copyright IBM Corporation 2010, 2011

Module overview

After completing this module, you should be able to:

Explain the elements of use-case model

Create a use-case specification

Create a use-case diagram


Define user and system requirements

Use case model

Vision features

Supplementary Spec

• Features

• Functional requirements

• Non-functional requirements (including

constraints)

• Use cases and user story elaborations

Userperspective

Solution

space

UI specification

Systemperspective

Storyboard

• User interface

specification

• User interface

• StoryboardUI Sketch

High-level businessrequirements

,Glossary

Businessperspective

Stakeholder needs

Business Processes

Problem

space

• Business goals and objectives

• Business processes (as-is versus to-be)

• Stakeholder needs

• Glossary

• Business rules

Features and use cases

capture what the solution

will provide from a

functional perspective.


Actor

An Actor represent roles that humans, hardware devices, or

other systems can play in relation to the system under

development.

Actors are external to the system.

A complete set of actors describes all the ways by which outside

users communicate with the system.

This illustration shows the Unified Modeling Language (UML)

notation for an actor:

Actor


Use case

A use case is…

the specification of a set of actions

performed by a system,

which yields an observable result that is, typically,

of value for one or more actors or other stakeholders of the system.

(Unified Modeling Language -UML 2.0 )

Used to specify the behavior of a system, without revealing the

internal structure of the system

Use case


Use cases contain software requirements

Each use case:

Is a coherent unit of functionality provided by a system

Describes sequences of actions that the system takes to

deliver something of value to an actor

Models a dialog between the system and actors

Is a complete and meaningful flow of events from the

perspective of a particular actor


What is a use-case model?

Describes the functional requirements of a system in

terms of use cases

Links stakeholder needs to software requirements

Serves as a planning tool

Consists of actors and use cases


Capture a use-case model

A use-case model is composed of:

Use-case diagrams

(visual representation)

Use-case specifications

(text representation)


Use-case diagram

Shows a set of use cases

and actors and their

relationships

Defines clear boundaries of

a system

Identifies who or what

interacts with the system

Summarizes the behavior

of the system

Use case 1

Use case 2

Use case 3

Actor 1

Actor 3

Use case 1

Use case 2

Use case 3

Use case 1

Use case 2

Use case 3

The system

Actor 1

Actor 2

Use-case diagram


Communicates-association

A channel of communication

between an actor and a use case.

A line is used to represent a

communicates-association.

An arrowhead indicates who initiates

each interaction.

No arrowhead indicates either end

can initiate each interaction.

Actor 1

Actor 2 Actor 3

Use Case


Use-case specification

A requirements document

that contains the text of a use

case, including:

A description of the flow of

events describing the

interaction between actors and

the system

Other information, such as:

– Preconditions

– Postconditions

– Special requirements

– Key scenarios

– Subflows

Use-case specification


Use cases in Rational Requirements Composer

Use cases exist as artifacts in the

project.

Use cases are elaborated with text in

use-case specification artifacts.

Use cases can be represented visually

in use-case diagram artifacts.


Creating a use-case specification

Create a use-case specification as you

would any other artifact. Select Use Case

Specification in Artifact Type.


Creating a use-case specification (continued)

Add and edit use-case text in the

Artifact editor. Edit attributes as

necessary.


Embedding artifacts

You can embed artifacts or images in the

use-case specification artifact.


Artifact templates

Artifact templates make it easier to

create complete and consistent

use-case specifications.


Actors in Rational Requirements Composer

Actors exist as artifacts in the

project.


Creating an actor artifact

Create an actor artifact as you would

any other artifact. Select Actor in

Artifact Type.


Creating an actor artifact (continued)

Enter a text description for the Actor,

and edit attributes as necessary.


Creating a use-case diagram

Actor

Use case

Association

System boundary

Tool palette

Create a use-case diagram as you would any other

artifact. Select Use Case Diagram in Artifact Type.

Then, build the diagram in the Use Case editor.


Lab 4: Working with use cases

Complete these tasks:

Open a use-case diagram.

Open a use-case specification.

Create a use-case diagram.


Review

What is the value of employing

use cases?

How do you represent use cases

in Rational Requirements

Composer?


Module summary

In this module, you learned how to:

Create a use-case specification

Create a use-case diagram

Essentials of IBM Rational Requirements Composer, v3 · 2017. 12. 16. · Module overview After...

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