SYS366

The Last Stage in Analysis:System Use Case Descriptions

created through the Use Case Authoring Process

Where did we come from? Identified Stakeholder categories/types Identified business areas & basic processes Completed interviews with stakeholder rep. Identified Business Use Cases Built a Business Use Case Diagram Wrote Business Use Case Descriptions Created Actor/Activity Tables from the

Business Use Case Descriptions

System Use Cases Identify actors for System Use Cases

look for an actor who specifically interacts with the system humans, devices, other systems, etc

Actors are not part of the system. They are just outside the system boundary and are visible to the system.

Identify activities for System Use Cases Anything the system must do to achieve the use case

result Happens only inside the system boundary

Systems Use Case Diagram Systems Use Case Descriptions Systems Use Case Authoring Process

Systems Use Cases convert Business Use Cases

to system requirements. How?

B.U.C. description leads to B.U.C. actor/activity table leads to System Use Case Diagram &

Description

Documenting Systems Use Cases Systems Use Case Diagram

Shows the functionality that the system will provide and which users (actors) will communicate with the system

Done using Rational Rose acts as a place holder for the

Systems Use Case Description is a visual index, providing a context

for the descriptions

Systems Use Cases Diagram Actors are represented by

a ‘stick’ figure

Systems Use Cases are shown as an oval

Associations are a customer ID labeled arrow line —–—–––

Designing Dialogs

The process of designing the overall sequences that users follow to interact with an information system

the sequence in which information is displayed to and obtained from the user

Sequence

understanding how the user will interact with the system clear understanding of user, task,

technological and environmental characteristics

Systems Use Case Descriptions The (systems) use case descriptions

provide the substance of the (systems) use case model and they are the basis for most of the …modeling work…More than 90% of the (systems) use-case model lies beneath the surface, in the textual use-case descriptions themselves. *

*Use Case Modeling, Kurt Bittner & Ian Spence, Addison-Wesley, 2003, p. 30

Systems Use Case Descriptions “(Systems) use cases are more than

just a named ellipse and a brief description. For each (systems) use case there will also be a (systems) use-case description where the full story of the use case is told.”*

*Use Case Modeling, Kurt Bittner & Ian Spence, Addison-Wesley, 2003, p. 30

Systems Use Case Descriptions “The use case description tells a story of

how a system and its actors collaborate to achieve a specific goal

This collaboration takes the form of a dialog between the system and its actors

It is a step-by-step description of a particular way of using a system”*

*Use Case Modeling, Kurt Bittner & Ian Spence, Addison-Wesley, 2003, p. 24

Systems Use Case Descriptions “Just like a story, every use case should

have a clear beginning (how the actor starts

the use case) Middle (how the system and actors

work together) End how the use case is concluded”*

*Use Case Modeling, Kurt Bittner & Ian Spence, Addison-Wesley, 2003, p. 24

Systems Use Case Description Describes typical ways (or cases) of using

the system* with processing details Not a complete description of all possible

ways that some task is performed by actor Does not say how the system is designed or

implemented (e.g. J2EE or .NET)

*Use Case Modeling, Kurt Bittner & Ian Spence, Addison-Wesley, 2003, pp. 24-25

Systems Use Case Descriptions

The systems use case description must include:

Who the actors are and how many of them are interacting with the system at any point in time

What data is used and how All normal logic: sequential, decision,

looping All exception and error logic

Today Systems Use Case Descriptions Systems Use Cases Authoring

Systems Use Cases Authoring The Systems Use Cases and its

description evolves through the authoring process.*

*Systems Use Cases Modeling by Bittner & Spence, Page 152

The Authoring Life Cycle

Discovered Briefly Described

BulletedOutline

EssentialOutline

DetailedDescription

Systems Use CaseSpecification

The Authoring Life Cycle State 1: Discovered *

Through Interviews with the Stakeholders

Through experience Shown on a Systems Use Case diagram

Place holder for the Systems Use Case description

A visual index, providing a context for the descriptions

*Systems Use Cases Modeling by Bittner & Spence, Pages 153 - 154

The Authoring Life Cycle State 2: Briefly Described

Once the Systems Use Case has been identified, it should be described

Example: Create Vehicle Reservation by Phone

This Systems Use Cases describes how the actor, a Call Centre Employee, uses the system to reserve a vehicle for a specified period at a customer’s request.

The Authoring Life Cycle State 3: Bulleted Outline

Captures the simple steps of the use case in short sentences organized sequentially

Bulleted Outline Example of a Systems Use Case

Bulleted Outline Let’s create a bulleted outline for

one of your use cases