Vending 3d3y2e

ECE651

Object-Oriented Analysis & Design Instructor: Krzysztof Czarnecki

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Overview ÎWhat is OO Analysis & Design? • Vending Machine Example – Analysis • Use case modeling • Domain modeling • Behavioral modeling

– Design • Interaction diagrams • Refined class diagram • Concurrency and scheduling

• Summary and Further Reading 2

OO Analysis & Design • Analysis – Domain level - modeling “real world” objects – Really: part of requirements engineering • requirements development = elicitation + analysis + specification

– Many domain objects will not make into the design – Domain structures often make poor design structures

• Design – Asg responsibilities to object – Taking “illities” (maintainability, reusability, etc.) and portability into – Devising mechanisms

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OO Analysis & Design • Many methods (OMT, Booch, Unified Process, etc.) • Similar goals and techniques

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OO Analysis Activities • Use case analysis – Mostly focused on writing text - one overview context diagram is often enough – Use cases are just a part of functional requirements (only the interactive ones)

• Structural analysis – domain modeling – Finding the “real-world” objects involved in the use cases and creating class diagrams to represent them

• Behavioral analysis – Creating activity diagrams and sequence diagrams to capture use case details • Activity diagrams for business workflow • Sequence diagrams for reactive behavior (also with timing) – Possibly creating state charts to capture external reactive behavior of the system and other domain objects 5

OO Design Activities • Creating interaction diagrams and distributing responsibilities – Devising mechanisms and introducing design objects – Creating sequence diagrams – Creating communication (collaboration) diagrams

• Creating refined class diagrams • Deciding on concurrency and scheduling model • Possibly modeling detailed behavior of design objects using state charts 6

Overview • What is OO Analysis & Design? • Vending Machine Example – Analysis ÎUse case modeling • Domain modeling • Behavioral modeling

– Design • Interaction diagrams • Refined class diagram • Concurrency and scheduling

• Summary and Further Reading 7

Use Case Diagram As a Context Diagram

Vending Machine

Customer

Use Case 1 (Buy a drink)

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Use Case Diagram As a Context Diagram

Vending Machine

Customer

Use Case 1 (Buy a drink)

Use Case 2 (Restock)

Agent 9

Different Forms of Use Cases • “Casual version” – story – A narrative

• Fully dressed – Formal sections • • • •

Preconditions Main scenario Exception list …

• See “Writing effective use cases” by Alistair Cockburn, 2000 10

Use Case 1 (“Casual Version”) Consider a simplified vending machine, which is used to dispense soft drinks. The vending machine consists of a coin slot for inserting coins, a return tray for returning the customer's money and three buttons used to select Pepsi (tm), Coke (tm) or Dr. Pepper (tm). If the customer inserts coins and does not press a button within one minute, the coins will be returned automatically (no coin-return lever). If the customer selects a beverage which is out-of-stock (none left), the coins will also be returned. This vending machine does not provide change - it is up to the customer to insert only enough money to purchase a drink. If sufficient coins are inserted and a button with available beverages is pressed, the appropriate drink is dispensed, the corresponding button is illuminated for five seconds, and the coin slot moves the coins to the general storage area (i.e. the purchase has finished). 11

Use Case 1 (“Fully Dressed” Version) Primary actor: Customer Goal in context: Customer buys a drink Level: level Stakeholders and Interests: Customer : wants to buy a drink Vendor: wants to get paid for any goods dispensed Preconditions: Machine is ready & awaiting interaction Minimum guarantee: Customer gets his coins back if no drink dispensed Success guarantees: Customer has the drink; vending machine has the money for the drink; Vending machine provides no change Trigger: Customer starts interaction with the machine 12

Use Case 1 (Cont’d) Main success scenario: 1. Customer inserts sufficient money into the coin slot 2. Customer pushes one of the three select buttons 3. The selected drink is dispensed. 4. The pushed select button lights up for 5 seconds. 5. Coins are taken by the machine. Extensions 1a. Customer inserts no or insufficient money. Pushing a selection button has no effect. 2a. Customer fails to push a button within 1 minute from insertion of the last coin. Coins are returned. 2b. Customer selects beverage out of stock. Coins are returned. Frequency of use: several per day Priority: 1 Implementation status: … 13 Open issues: …

Overview • What is OO Analysis & Design? • Vending Machine Example – Analysis • Use case modeling ÎDomain modeling • Behavioral modeling

– Design • Interaction diagrams • Refined class diagram • Concurrency and scheduling

• Summary and Further Reading 14

Noun analysis Consider a simplified vending machine, which is used to dispense soft drinks. The vending machine consists of a coin slot for inserting coins, a return tray for returning the customer's money and three buttons used to select Pepsi (tm), Coke (tm) or Dr. Pepper (tm). If the customer inserts coins and does not press a button within one minute, the coins will be returned automatically (no coin-return lever). If the customer selects a beverage which is out-of-stock (none left), the coins will also be returned. This vending machine does not provide change - it is up to the customer to insert only enough money to purchase a drink. If sufficient coins are inserted and a button with available beverages is pressed, the appropriate drink is dispensed, the corresponding button is illuminated for five seconds, and the coin slot moves the coins to the general storage area (i.e. the purchase has finished). 15

Domain Model - Initial Class Diagram Inserts coins into

Contains

CoinSlot amount

1

1

Contains 1

1

Customer Pushes

3

Button id litUp

1

Vending Machine

1

Shelf

1 0..*

Drink

Contains 1

Contains 3

Contains

1

ReturnTray 16

Overview • What is OO Analysis & Design? • Vending Machine Example – Analysis • Use case modeling • Domain modeling ÎBehavioral modeling

– Design • Interaction diagrams • Refined class diagram • Concurrency and scheduling

• Summary and Further Reading 17

Sequence Diagram for Use Case 1 (Main Scenario + Extensions 1a & 2b) customer

machine

insertMoney(x) insertMoney(y) push(z) m:=checkAmount(x+y)

a:=checkAvailability(z) [!a] return()

[m&a]

5 sec

dispenseDrink() lightUp() moveCoins() lightDown()

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Activity Diagram for Use Case 1 (Main Scenario + Extension 1a) Customer

VendingMachine

Insert money

Select drink money Sufficient money?

no

yes

Dispense drink drink

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State Chart for Vending Machine (Full behavior) Push button Z [no drink Z]/ return money

Insert money (x) after (60 seconds)/ return money

Ready Push button Z [sufficient money & drink Z in stock]

after (5 seconds)/light down

Dispensing Entry/ dispense drink, light up button, take money

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Hierarchical State Chart Insert money (x)

Coin slot empty Push button Z [sufficient money & drink Z in stock]

Coin slot has money

after (60 seconds)/return money Push button Z [no drink Z]/return money

after (5 seconds)

Dispensing Entry/ dispense drink, light up button, take money

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Overview • What is OO Analysis & Design? • Vending Machine Example – Analysis • Use case modeling • Domain modeling • Behavioral modeling

– Design ÎInteraction diagrams • Refined class diagram • Concurrency and scheduling

• Summary and Further Reading 22

Sequence Diagram customer

coinSlot

button1

controller

shelfRel1

shelfSens1

insertMoney(x) insertMoney(y) push()

request(1) close() m:=checkAmount() getTotal() a:=checkAvailability() isEmpty() [!a] return()

[m&a]

lightUp()

release()

moveCoins()

5 sec

open() lightDown()

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Extension 2a customer

coinSlot

button1

controller

insertMoney(x)

set(60)

insertMoney(y)

set(60)

timer

60 sec

checkTime() checkTime()

timeOut() return() insertMoney(x)

set(60)

insertMoney(y)

set(60)

< 60 sec push()

request(1) close()

reset() 24

Communication Diagram (Used to be collaboration diagram) 2: push()

button1 2.1: request(1)

timer1 1.1: set(60) 2.1.1.1: reset()

2a: timeOut()

coinSlot 1: insertMoney(x)

2.1.1: close() 2.1.2.1: getTotal() 2.1.4a [!a]: return() 2.1.7 [m&a]: moveCoins() 3.1.1: open()

2.1.5 [m&a]: lightUp() 3.2.2: lightDown() 2.1.4 [m&a]: release()

shelfRel

controller 2.1.3.1: isEmpty() «self» 2.1.2: m:=checkAmount() 2.1.6: set(5)

2.1.3: a:=checkAvailability() 3: timeOut()

shelfSens

timer2 25

Additional Design Technique: CRC Cards • CRC (class-responsibilitycollaborator) cards – Index cards – Written in a design session – Focus on asg responsibilities – Can be used in addition to interaction diagrams – Pioneered by ward Cunningham & Kent beck

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Overview • What is OO Analysis & Design? • Vending Machine Example – Analysis • Use case modeling • Domain modeling • Behavioral modeling

– Design • Interaction diagrams ÎRefined class diagram • Concurrency and scheduling

• Summary and Further Reading 27

Refined Class Diagram Timer CoinSlot amount: Integer opened: Bool insertMoney(Int) close() open() getTotal() return() moveCoins()

1

3

ShelfSens empty: Bool isEmpty()

1 1

1

Button id: Integer litUp: Bool push() lightUp() lightDown()

set() reset() checkTime() Signals timeOut()

1 3

1 Controller price: Integer request(Integer) checkAmount() checkAvailability()

1

1

ShelfRel 3

release()

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Overview • What is OO Analysis & Design? • Vending Machine Example – Analysis • Use case modeling • Domain modeling • Behavioral modeling

– Design • Interaction diagrams • Refined class diagram ÎConcurrency and scheduling

• Summary and Further Reading 29

Single Thread With ive Objects • Requires a top level control loop – Read input, compute, write output

• Calls to procedures performing the processing steps need to be scheduled manually • Simple: no synchronization of concurrent threads or processes necessary • May waste computing resources – “Polling style” 30

ive objects design with a main control loop // main control loop while(true) { If (coinSlotSensor.coinInserted()) coinSlot.insertMoney(coinSlotSensor.amount()) ; If (buttonSensor1.pressed()) button1.push(); If (buttonSensor2.pressed()) button2.push(); If (buttonSensor3.pressed()) button3.push(); timer1.checkTime(); timer2.checkTime();

} 31

Active Objects • Define a statechart for each object • Communication through signals – E.g., SDL: asynchronous send, synchronous receive – Synchronous communication requires sending a request and waiting for the response – Avoid variables shared between processes

• No direct by most programming languages – Need a framework/library

• Better utilization of computing resources • Automatic scheduling 32

Overview • What is OO Analysis & Design? • Vending Machine Example – Analysis • Use case modeling • Domain modeling • Behavioral modeling

– Design • Interaction diagrams • Refined class diagram • Concurrency and scheduling

ÎSummary and Further Reading 33

Summary • Analysis – Use case analysis - writing stories – Structural analysis/domain modeling - finding “real-world” objects – Behavioral analysis • Creating activity diagrams and sequence diagrams to capture use case details • Creating state charts to capture external reactive behavior of the system and other domain objects

• Design – – – –

Creating interaction diagrams and distributing responsibilities Creating refined class diagrams Deciding on concurrency and scheduling model Possibly modeling detailed behavior of design objects using state charts 34

Further Reading • Recommended OO Analysis & Design book: – Applying UML & Patterns: An Introduction to Object-Oriented Analysis and Design and Iterative Development” by Craig Larman, 3rd edition, Prentice Hall, 2004

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