Aydoo 07 Usecase Modeling

8/4/2019 Aydoo 07 Usecase Modeling

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OO AnalysisUse Case Modeling

User Requirements Modeling

By Jesus Zavala

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Before the UML

1960s - 70s- COBOL, FORTRAN, C

- Structured analysis and design techniques

1980s - early 1990s- Smalltalk, Ada, C++, Visual Basic

- Early generation OO methods

Mid/late 1990s- Java

- UML

- Unified Process

- Collaborative software process (open source)

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The Value of the UML

Is an open standard

Supports the entire software developmentlifecycle

Supports diverse applications areas

Is based on experience and needs of theuser community

Supported by many tools

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Creating the UML

Booch method OMT

Unified Method 0.8OOPSLA 95

OOSEOther methods

UML 0.9Web -June 96

public

feedback

Final submission to OMG, Sep 97

First submission to OMG, Jan 97

UML 1.1

OMG Acceptance, Nov 1997

UML 1.3, 1.4

UML 1.0UML partners

UML 2

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Meyer

Before and after

conditions

Harel

Statecharts

Gamma, et al

Frameworks and patterns,

HP Fusion

Operation descriptions and

message numbering

Embley

Singleton classes and

high-level view

Wirfs-Brock

Responsibilities

Odell

Classification

Shlaer - Mellor

Object lifecycles

Rumbaugh

OMT

Booch

Booch method

Jacobson

OOSE

Contributions to the UML

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Overview of the UML

The UML is a language for

- visualizing

- specifying

- constructing

- documenting

the artifacts of a software-intensive system


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Architecture and the UML

Organization

Package, subsystem

Dynamics

Interaction

State machine

Design View Implementation View

Process View

ComponentsClasses, interfaces,

collaborations

Active classes

Deployment View

Nodes

Use Case View

Use cases

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Workflows and Models

Requirements

Design

Implementation

Test

Analysis

Use CaseModel

DesignModel

Depl.Model

Impl.Model

AnalysisModel

TestModel

UML diagrams provideviews into each model

Each workflow isassociated with one ormore models.

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Analysis & Design ModelUse CaseDiagrams

CollaborationDiagrams

ComponentDiagrams

DeploymentDiagrams

ObjectDiagrams

StatechartDiagrams

SequenceDiagrams

ClassDiagrams

ActivityDiagrams

Use CaseModel

DesignModel

Depl.Model

Impl.Model

AnalysisModel

TestModel

Incl. subsystemsand packages

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User requirements

Functional requirements

Use Case Diagrams

- Actors

- Use Cases graphical

- Use Cases textual

- Test Use Cases

- Glossary

Prototypes

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Use Case Diagram

Captures system functionality as seen byusers

Built in early stages of development

Purpose- Specify the context of a system

- Capture the requirements of a system

- Validate a systems architecture

- Drive implementation and generate test cases

Developed by analysts and domain experts

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Use Case Diagram

Captures system functionality as seen byusers


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Use case diagram elements

TelephoneCustomer

In-StoreCustomer

Clerk

Identify Movie

Open Account

Return Movie

Customer

ReviewAccount Status

Actor

Use Case

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Use Case Diagram Example

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Use Case Text FormatR F - < i d d e l r e q u i s i t o > < n o m b r e d e l r e q u i s i to f u n c i o n a l>V e r s i n < n u m e r o d e v e r s i n y f e c h a >A u t o r e s < a u t o r >F u e n t e s < f u e n t e d e l a v e r s i n a c t u a l >O b j e t i v o s a s o c i a d o s < n o m b r e d e l o b j e t iv o >D e s c r i p c i n E l s i s t e m a d e b e r c o m p o r t a rs e t a l c o m o s e d e s c r i b e e n

e l s i g u ie n t e c a s o d e u s o { c o n c r e t o c u a n d o < e v e n t o d ea c t i v a c i n > , a b s t r a c t o d u r a n t e l a r e a l iz a c i n d e l o sc a s o s d e u s o < l i s ta d e c a s o s d e u s o > }

P r e c o n d i c i n < p r e c o n d i c i n d e l c a s o d e u s o >P a s o A c c i n

1 { E l < a c t o r > , E l s is t e m a } < a c c i n r e a li z a d a p o r e la c t o r o s i s t e m a > , s e r e a l i z a e l c a s o d e u s o< c a s o d e u s o R F - x >

2 S i < c o n d i c i n > , { e l < a c t o r > , e l s i s t e m a } < a c c i nr e a l i z a d a p o r e l a c t o r o s i s t e m a > > , s e r e a l i z a e lc a s o d e u s o < c a s o d e u s o R F - x >

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S e c u e n c i aN o r m a l

nP o s t c o n d i c i n < p o s t c o n d i c i n d e l c a s o d e u s o >

P a s o A c c i n1 S i < c o n d i c i n d e e x c e p c i n > , { e l < a c t o r > , e l

s i s t e m a } } < a c c i n r e a l i z a d a p o r e l a c t o r os i s t e m a > > , s e r e a l i z a e l c a s o d e u s o< c a s o d e u s o R F - x > , a c o n t i n u a c i n e s t e c a s od e u s o { c o n t i n u a , a b o r t a }

2

E x c e p c i o n e s

3R e n d i m i e n to P a s o C o t a d e t ie m p o

1 n s e g u n d o s2 n s e g u n d o s

F r e c u e n c i a e s p e r a d a < n d e v e c e s > v e c e s / < u n i d a d d e t i e m p o >I m p o r t a n c i a { s i n i m p o r t a n c i a , i m p o r t a n t e , v i t a l }U r g e n c i a { p u e d e e s p e r a r , h a y p r e s i n , i n m e d i a ta m e n t e }C o m e n t a r i o s < c o m e n t a r i o s a d i c i o n a le s >

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UC: Scenario based requirements modeling

Recommended:Booch, Rumbaugh, Jacobson:The Unified Modeling Language UserGuide.Addison Wesley, 1999

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Use Case 1

Specifies the intended behavior (the what?) of asystem.

Is a set of sequences of actions (including variants)to yield an observable result of value to an actor.

Represents a functional requirement of the system

as a whole.

It IS NOT a flow chart

Used to:

describe customer requirements (early analysis).

Validate your architecture / verify your system.

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Use Case 2

Each sequence (also called a scenario)represents the interaction of things outsidethe system (its actors) with the system itself(or parts of the system).

Separate main vs. alternative flows

Process loan

Loan Officer

ActorUse case


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Use Case Example

Name: Capture deal

Precond: Financial Officer is logged inMain flow of events:

1. Enter the client name & bank account

2. Check that they are valid

3. Enter number of shares to buy

& share ID

4. Determine price

5. Check limit

6. Prepare order to NYSE

7. Store confirmation number and give it to client

Client

Financial

Officer

Capture deal

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Use cases: terms and concepts

Unique namee.g.: Place order, Validate user

Sequence of actions (event flows)- textual (informal, formal, semi formal)

Main flow of events:The use case starts when thesystem prompts the Customerfor a PIN number.The Customercan now enter a pin number...

Exceptional flow of events:If the Customerentersam invalid PIN number

- interaction diagrams

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Actors

Role that a human/hardware device/another system plays with respect to thesystem

Actors carry out use cases- look for actors, then their use cases

Actors do not need to be humans!

Actors can get value from the use case(Client in example) or participate in it(Financial Officer in example)

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Actors

Actors can be specialized

connected to use cases only by association

association = communication relationship(both can send messages to, or receivemessages from the other one)

Officer

Loan Officer

specializationrelationship

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Use case description

Generic, step-by-step written description ofa use cases event flow- Describe precondition (initial system state)

- List sequence of steps

Includes interactions with actor(s), anddescribes what objects are exchanged

May contain extension points

Clear, precise, short descriptions

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Organizing Use Cases: Generalization Relationship

child use case inheritsbehavior and meaning ofthe parent use case

child may add or override

the parents behavior

child may be substitutedany place the parentappears

Validateclient

Checkpassword

Retinalscan


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Organizing UC: Include Relationship

Used to avoid describing the same flow of eventsseveral times, by putting the common behavior ina use case of its own

Avoids copy & paste of parts of use casedescriptions

Validateclient

Place

order

Track

order

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Include Example

Use Case: Track order

Precondition: Financial Officer is logged in

Main flow:1. Obtain and verify order number

2. Include (Validate client)

3. For each part in the order,

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Organizing UC: Extend relationship

Allows to model the part of a usecase the user may see as optional

Allows to model conditionalsubflows

Allows to insert subflows at acertain point, governed by actorinteraction

extension points (in textual eventflows)

(set priority)

Place order

Extensionpoints:

Set priority

Place rushorder

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Extend Example

Use Case: Place order

Precondition: Financial Officer is logged in

Main flow:1.

2. Collect the clients order items

3. (set priority)

4. Submit order for processing

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Using Extends relationship

Capture the base use case if we later delete extension points,we still have to have a use caseachieving

something!

For every step ask- - what could go wrong?

- - how might this work out differently?

Plot every variation as an extension of theuse case

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Comparing extends/includes

Different intent

- extend

to distinguish variants

associated actors perform use case and all

extensions

actor is linked to base case

- include

to extract common behavior

often no actor associated with the common use

case

different actors for caller use cases possible


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Extends and Includes Relationships

Extends

IncludesFind Itemby Title

Find Items

by Actor

Search Movie

Database

includes

includesCustomer

Dependency

extends

Stereotype

Check In

MovieAssess

Late FeesClerk

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A use case diagram

Valuation

Limit

exceeded

Analyze

risks

TraderPrice

details

Capture

deal

Sales person

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When and how

When:

Requirements capture - first thing to do

How:

Use case: Every discrete thing yourcustomer wants to do with the system

- give it a name

- describe it shortly (some paragraphs)

- add details later

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Recipe / Tasks to do

Identify actors that interact with the system

Organize actors

Consider primary ways of interaction withactors

Consider exceptional ways

Organize behaviors as use cases, usinggeneralize/include/extend relationships

Describe what actors require from system,not what goes on in the system!

The EndUse Cases

A Practical Example

Compiled by Jesus Zavala

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Ski resort information system

Users should be able to query weather and snow conditionforecasts for a date they enter.

The system should allow to book single or double rooms at theresort hotel Skiers Luck online (with credit card).

Visitors should be able to book one-day beginners courses onsnowboards.

There is only one course a day.

The max. size of a course is 8 persons.

The resort offers special courses for kids. In order to builtcourses with kids of same age, the customer has to enter thekids age.

Canceling of course or room bookings are only possible up to10 days ahead.

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First Trying

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Errors you should prevent 1!

>

stereotype in actor

associations

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Associations

between actors

Unnamed

associations

between use

cases

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System

no use

case!

Name

relations!

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Wrong

understanding

of the

stereotype


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Diagram moves main

functionality outside the

system

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Data structures instead of

functions as use cases, e.g.

date, age, database

relations not named

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Example Use Case Diagram

Query

weather&snowforecast

Book room

Book kidsSB course

Visitor

Cancelcourse

Book SBcourse

Cancel

room

Enterpersonal info

(Enter kids age)

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Use Case 1

Use Case: Query weather&snow forecast

Precond: -

Main flow:

1. Visitor enters date

2. Weather & snow forecast for local region isdisplayed for specified date

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Use Case 2

Use Case: Book SB course

Precond: -

Main flow:1. Visitor enters date

2. Include (Enter personal info)

3. (Enter kids age)

4. Store reservation

5. Confirm reservation to Visitor

Exceptional flow:If number of course participants for specified date > 8, then tell

visitor so and let him choose another date

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Use Case 3

Use Case: Book kids SB course

Precond: SB course is for a kid

Main flow:1. Enter kids age

2. Store reservation

3. Confirm reservation to Visitor

Exceptional flow:If course for specified date is adult course, then tell visitor so

and let him choose another date.

Exceptional flow:If course for specified date is kids course, and the specified

age is outside the courses age range,then tell visitor so and let him choose another date.


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Literature Reference Management System

Storage and retrieval of references, e.g.

Title: The unified modeling language user guide

Authors: G. Booch, J. Rumbaugh, I Jacobson

Publisher: Addison Wesley

Publication year: 1998

Title: Software engineering in the Internet age

Authors: F. Maurer, G. Kaiser

Publisher: IEEE

Publication year: 1998

Journal: IEEE Internet Computing Magazine

Volume: 2

Issue: 5

Small exercise:Draw a Use CaseDiagram (at leasttwo use cases)

Describe usecases (at leastone)

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Use Case Diagram: Lit Ref Mgmt Sys

Addreference

Removereference

Search for

reference

User

List

references

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Event flow: List references

Precondition: user has selected listreferences functionality.

The system prompts the user to select thedevice: printer or file.

The system prompts the user to select theprint order: by name or by title.

The use case finishes with the systemprinting the list on the requested device.

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Event flow: Add reference

Precondition: user has selected add new referencefunctionality.

The system prompts the user to select if he/she wantsto add a normal reference or a book.

The system prompts the user to enter title, author, andpublisher of the reference(Add journal paper)(Except-1).

The user is notified that the reference has beensuccessfully added.

Except-1: The reference already exists. The user canre-enter the data or terminate the use case.

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Use case: Add journal paper

Add journal paper: If the paper is a journal,then the system additionally asks for thejournals name, the volume number and theissue number.

Add journal

paperAdd reference

Use Case Example

ElevatorBy Jesus Zavala

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Elevator -- Use Case

press an elevator button

press a floor button

User

Elevator

enter and exit through a door

1 elevator, n

floors

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Example: Bank Account Manager

Use case for withdrawal

Use case for depositing

Use case for balance query

Small Test:

Draw a Use Case Diagram(Organize use cases)

Describe use cases

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Small Test: Bank Account Manager

System has to run on an automated teller machine.

User must be able to deposit checks into the account.

User must be able to draw money from the account.

User should be able to query the balance of his/heraccount.

The user should get a receipt for a transaction onrequest. The transaction type (withdrawal or deposit),the transaction date, the account number, the amount,and the new balance should be visible on the receipt.

After each transaction the new balance should bedisplayed to the user.

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Errors regarding arrows (connections)

connection between actors and use cases haveno direction

Connections between use cases are dotted( ) and should be labeled or

:arrow points from use case describing thealternative event flow to the standard case

:arrow points from calling use case to use casethat describes actions to include

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Errors regarding relation graph & desc

If use cases are connected then in thetextual description we have to mirror this:

-

- include (verify user)

- - (print receipt)...

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Errors regarding textual desc of use cases

Preconditions not given

No connection to graphical representation

Different names in graphical and textual

representation:user vs visitoruse case name different

bank info vs user info

But also: use case name appearing severaltime in diagram


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Other often occuring errors

Flow charts instead of use casesremember: use case = sequence of actionsachieving a goalnot: action = use case

Exceptional flow: not only exceptioncondition, but also actions if it occurs

Exceptional flow: indicate in main flow atwhich point to check for this exception (ifnot obvious)!

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Good solution 1

User

withdraw

deposit

check

balanceVerify user

withdraw withreceipt

deposit with

receipt

(print receipt)

(print receipt)

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Good solution 2

Use case: withdraw

Precondition: User has selected withdraw option

Main flow:

Include (Verify user)

Prompt user for amount to withdraw

Check available funds of user

Check available money of ATM

Remove amount from account

Give money

(print receipt)

Print current balance

Exceptional flow

If not sufficient funds or money available, prompt user for loweramount

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Good solution 3

Use case: deposit

Precondition: User has selected deposit option

Main flow:

Include (Verify user)

Prompt user for amount of deposit

Open slot

Get check

(print receipt)

Print (balance + deposited amount)

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Good solution 4

Use case: check balance

Precondition: User has selected balance

option

Main flow: Include (Verify user)

Print balance

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Good solution 5 (not required in test)

Use case: verify user

Precondition: none

Main flow:

User enters ID card User enters PIN number

System checks validity of card and number

Exceptional flow:

If combination is not valid, reject user


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Good solution 6 (not required in test)

Use case: withdraw with receipt

Precondition: User has selected withdraw option andprint receipt option

Use case: deposit with receipt

Precondition: User has selected deposit option andprint receipt option

...

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Acceptable solution 1

User

withdraw

deposit

checkbalance

withdraw withreceipt

deposit withreceipt

(print receipt)

(print receipt)

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Acceptable solution 2

Use case: withdraw

Precondition: User is verified and hasselected withdraw option

Similar for other use cases

The End

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Aydoo 07 Usecase Modeling