Software Engineering Principles

Ajit K Nayak, Ph.D.

ajitnayak@soauniversity.ac.in

Domain & Behavioural Modelling

Acknowledgements• Slides of Prof. Rajib Mall, IIT, KGP

Domain Modelling• Represents concepts or objects appearing in the

problem domain.

• Also captures relationships among objects.

• Three types of objects are identified

– Boundary objects

– Entity objects

– Controller objects

• Three different stereotypes on classes are used:

– <<boundary>>

– <<entity>>

– <<control>>

Cashier Interface

Withdrawal

Account

Object Types• Boundary Objects are objects that Interact with actors:

– User interface objects like screens, menus, forms, dialogs etc.

– Do not perform processing but validates, formats etc.

• Entity Objects are objects that Hold information:– Such as data tables & files, e.g. Book, BookRegister

– Normally are dumb servers responsible for storing data, fetching data etc.

– Elementary operations on data such as searching, sorting, etc.

– Entity Objects are identified by examining nouns in problem description

• Controller Objects Coordinate the activities of a set of entity objects– Interface with the boundary objects

– Realizes use case behaviour– Embody most of the logic involved with the use case

realization

– There can be more than one controller to realize a single use case

Modelling Behaviours• A behavioural model

shows the interactions between objects to produce some particular system behaviour that is specified as a use-case.

• Sequence diagrams, Activity diagrams, state diagrams, collaboration diagrams are used to model interaction between objects.

• Where are people coming from?

• Where are they going?

• How do they move from one space to the other?

Modelling Behaviour

• How do we use the SMS Server interface?

• What is the order of executing the operations?– sendMessage, getStatus, Resend?

– getStatus, sendMessage, checkForMessages?

• When do we use resend?

• We use Interaction diagrams to model this

Phone

handleMessage(text, reciepient)

SMS Server

sendMessage(sender, text, reciepient):msgID

getStatus(msgID): status

resend(msgID)

checkForMessages(receipient):msgID[]

Sequence Diagrams• A sequence diagram is an interaction diagram that

shows how objects send messages with one another and in what order?

Object Control

Corresponding Class Diagram

Message types• Synchronous message

– Used when the sender waits until the receiver has finished processing the message, only then does the caller continue (i.e. a blocking call).

• Asynchronous message– the sender does not wait for the

receiver to finish processing the message.

– An open arrowhead is used to indicate that a message is sent asynchronously.

• Return message

If-Else (Alternatives)

Loops - Iteration

Example 1: Tic-Tac-Toe Computer Game

• A human player and the computer make alternate moves on a 33 square.

• A move consists of marking a previously unmarked square.

• The user inputs a number between 1 and 9 to mark a square

• Whoever is first to place three consecutive marks along a straight line (i.e., along a row, column, or diagonal) on the square wins.

• As soon as either of the human player or the computer wins, – A message announcing the winner should be displayed.

• If neither player manages to get three consecutive marks along a straight line, – All the squares on the board are filled up,

– Then the game is drawn.

• The computer always tries to win a game.

Domain Modelling• Use Case Model

Tic-tac-toe game

Play Move

Player

• Initial and Refined Domain Model

Board

Initial domain model

PlayMoveBoundary PlayMoveController Board

Refined domain model

Sequence Diagram

:playMoveBoundary

:playMoveController

:board

move acceptMove checkMoveValidity

[invalidMove]announceInvalidMove

[invalidMove]

announceInvalidMove

[game over]announceResult

announceResult[game over]

checkWinner

playMove

checkWinner

[game over]announceResult

[game over]announceResult

getBoardPositionsdisplayBoardPositions

[game not over]promptNextMove

Class Diagram

Board

int position[9]

checkMove ValiditycheckResultplayMove

Controller

announceInvalidMoveannounceResult

PlayMoveBoundary

announceInvalidMoveannounceResultdisplayBoard

Supermarket Prize Scheme - I• Supermarket needs to develop software to encourage

regular customers.

• Customer needs to supply his:

– Residence address, telephone number, and the

driving licence number.

• Each customer who registers is:

– Assigned a unique customer number (CN) by the

computer.

• A customer can present his CN to the staff when he makes any purchase.

– The value of his purchase is credited against his CN.

Supermarket Prize Scheme - II• At the end of each year:

– The supermarket awards surprise gifts to ten

customers who make highest purchase.

• Also, it awards a 22 carat gold coin to every customer:

– Whose purchases exceed Rs. 10,000.

• The entries against the CN are reset:

– On the last day of every year after the prize winner’s

lists are generated.

Use Case Model

SupermarketPrize scheme

registercustomer

registersales

selectwinners

Customer

Sales Clerk

Manager

Clerk

Initial Domain Model

SalesHistory

SalesRecords

1

*CustomerRecord

CustomerRegister

1

*

Refined Domain Model

SalesHistory

SalesRecords

1

*CustomerRecord

CustomerRegister

1

*

RegisterCustomerBoundary

RegisterSalesBoundary

SelectWinnersBoundary

RegisterCustomerController

RegisterSalesController

SelectWinnersControllers

Sequence Diagram:Select Winners Use Case

:SelectWinnerBoundary

:SelectWinnerController

:SalesHistory

:SalesRecord

:CustomerRegister

:CustomerRecord

SelectWinners

SelectWinners

announces

SelectWinners*computeSales

*browse

[for each winner]find WinnerDetails [for each winner]

browse

Sequence Diagram: Register Customer Use Case

:RegisterCustomerBoundary

:RegisterCustomerController

:CustomerRegister

:CustomerRecord

registerregister

*match

displayCIN

create:CustomerRecord

checkDuplicate

[duplicate]

showError

generateCIN

register

showError

Sequence Diagram: Register Sales Use Case

:SalesRecord

create

RegisterSales

:RegisterSales

Boundary

:SalesHistory

:RegisterSales

Controller

registerSales

confirm

registerSales

confirm

Sequence Diagram: Refined Register Sales Use Case

:RegisterSales

Boundary

:SalesHistory

registerSales

confirm

:SalesRecord

create

RegisterSales

Class Diagram

SalesHistory

selectWinnersregisterSales

CustomerRegister

findWinnerDetailsregister

SalesRecords

computerSalesbrowsecreate

salesDetails

CustomerRecord

browsecheckDuplicatecreate

nameaddress

1

*

1

*

Thank You