Lecture for Chapter 2 Modeling with UML

							Modelling

with UML

CS223 Lecture 4 (see BD Ch. 2) Ananda Amatya
Notice: Surgery Sessions (Weeks 6-10)
Mon 2 - 4 in C1.01 & Fri 9 - 11 in C1.04

Please attend any one session convenient to you
Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick) 1

Overview: modelling with UML
What is modelling?  What is UML?  Use case diagrams  Class diagrams  Sequence diagrams (Collaboration diagrams)  Activity diagrams  StateChart diagrams


Bernd Bruegge & Allen H. Dutoit

Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

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What is modelling?
Modelling  building an abstraction of reality.  Abstractions simplifications:  ignore irrelevant details  focus on matters of concern.  What is relevant and what is irrelevant? depends on the purpose of the model.


Bernd Bruegge & Allen H. Dutoit

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Example: street map that models access roads

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Why model software?


More sophisticated software means more complexity: Windows XP > 40 million lines of code;

Several coders must be involved.  One developer’s code must be understood by another developer.  Complex systems must be simplified: Modelling is a way of achieving this.

Bernd Bruegge & Allen H. Dutoit

Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

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Systems, Models and Views
System: an organised set of communicating parts.  Model: an abstraction describing a subset of a system.  View: a selected aspect of a model.  Notation: a set of graphical or textual rules for depicting views.  Views and models of a single system may overlap each other.
 

Examples: System: Aircraft Models: Flight simulator, scale model Views: All blueprints, electrical wiring, fuel system
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Bernd Bruegge & Allen H. Dutoit

Systems, Models and Views

Aircraft

Blueprints
Model

Flightsimulator
2 View View 3 2

System

View

1

Model

1

Fuel System Scale Model Electrical Wiring
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Bernd Bruegge & Allen H. Dutoit

Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

Models, Views and Systems (UML)

System

*

Model

*

View

Described by

Depicted by

Airplane: System

Scale Model: Model

Flight Simulator: Model

Blueprints: View
Bernd Bruegge & Allen H. Dutoit

Fuel System: View

Electrical Wiring: View
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Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

Concepts and Phenomena
Phenomenon: An object in the world of a domain as you perceive it. Examples: this lecture, that wall clock  Concept: An abstraction that describes phenomena with common properties. Examples: Lecture, Wall clock Concept is a 3-tuple:  Name (to distinguish one concept from another)  Purpose (to determine if a phenomenon belongs to a concept)  Members (the set of phenomena that belong to the concept - instances)

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Concepts and Phenomena (contd.)
Name Purpose Members

Clock

A device that measures time.

Abstraction Classification of phenomena into concepts  Modelling Development of abstractions to answer specific questions about a set of phenomena while ignoring irrelevant details.

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Concepts in software: Type and Instance
Type: An abstraction in the context of programming languages  Name: int,  Purpose: integral number,  Members: 0, -1, 1, 2, -2, . . .  Instance: Member of a specific type  The type of a variable represents all of its possible instances




Bernd Bruegge & Allen H. Dutoit

The following relationships (<–>) are similar: “type” <–> “instance” “concept” <–> “phenomenon”

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Abstract Data Types & Classes
Abstract data type: Special type whose implementation is hidden from the rest of the system.  Class: An abstraction in the context of object-oriented languages  Like an abstract data type, a class encapsulates both state (variables) and behaviour (methods) Example Class: Watch  Unlike abstract data types, classes can be defined in terms of other classes using inheritance

Bernd Bruegge & Allen H. Dutoit

Watch time date SetDate(d)

CalculatorWatch calculatorState EnterCalcMode() InputNumber(n)

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Application and Solution Domain


Application Domain (Requirements Analysis): The environment in which the system is operating



Solution Domain (System Design, Object Design): The available technologies to build the system

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Object-oriented modelling

Application Domain

Solution Domain

UML Package
TrafficControl
Aircraft TrafficController Airport SummaryDisplay MapDisplay FlightPlanDatabase

FlightPlan

TrafficControl
System Model

Application Domain Model
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What is UML?


 

UML (Unified modelling Language)  A standard for modelling object-oriented software.  Resulted from the convergence of notations from:  OMT (James Rumbaugh)  OOSE (Ivar Jacobson)  Booch (Grady Booch) Reference: OMG (Object Management Group) Supported by several CASE tools  Rational ROSE (IBM)  Poseidon (ArgoUML)  TogetherJ (Borland)  Rhapsody (ILogix)  Eclipse (IBM) …

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Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

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UML: First Pass


You can model 80% of most problems by using about 20% UML



We teach you those 20%

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Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

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UML First Pass
Use case Diagrams describe a system’s functional behaviour as seen by its user.  Class diagrams describe a system’s static structure: Classes, Associations  Sequence diagrams describe a system’s dynamic behaviour: actors, objects, messages  Statechart diagrams describe the dynamic behaviour of individual objects of the system: states, events, transitions  Activity Diagrams model a system’s dynamic behaviour: activities, workflows (flowcharts)

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UML first pass: Use case diagrams
Package
Watch

Use case

Actor
ReadTime

WatchUser

SetTime

WatchRepairPerson

ChangeBattery

Use case diagrams represent the system’s functionality from user’s point of view
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UML first pass: Class diagrams
Association Class Multiplicity
1 2 PushButton state push() release() 1 LCDDisplay blinkIdx blinkSeconds() blinkMinutes() blinkHours() stopBlinking() referesh() Watch 1 1 1 2 Battery load 1 Time now

Attribute

Operations

Class diagrams represent the structure of the system
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UML first pass: Sequence diagram
Actor
:WatchUser
:Watch blinkHours() blinkMinutes()

Object
:LCDDisplay :Time

pressButton1()

pressButton1()

Message

pressButton2()

incrementMinutes()
refresh()

pressButtons1And2() stopBlinking()

commitNewTime()

Activation

Lifeline

Sequence diagrams represent the behaviour as interactions
Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick) 20

UML first pass: Statechart (diagrams) for objects with interesting dynamic behaviour
Event
[button1&2Pressed] BlinkHours

State

Initial state
[button2Pressed]
IncrementHrs

Transition
[button1&2Pressed] BlinkMinutes

[button1Pressed]

[button2Pressed] IncrementMin.

[button1Pressed] [button1&2Pressed] BlinkSeconds

[button2Pressed]
IncrementSec.

StopBlinking

Final state
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Statecharts represent behaviour as states and transitions
Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

Other UML Notations
UML provide other notations Implementation diagrams Component diagrams (BD Chapter 7) Deployment diagrams (BD Chapter 7)  UML includes OCL (Object constraint language) Used in Design (BD Chapter 9)




And then … there is UML 2 (a major revision of UML) For a good introduction see  IBM Webcast Recorded Event Feb15 Intro.itm in http://developer.raindance.com/iccdoc
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Bernd Bruegge & Allen H. Dutoit

UML Core Conventions
Rectangles are classes or instances  Ovals are functions or use cases  Instances are denoted with underlined names Examples: myWatch:SimpleWatch, Joe:Firefighter  Types are denoted with non-underlined names Examples: SimpleWatch, Firefighter  Diagrams are graphs Nodes are entities Arcs are relationships between entities
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Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

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Use Case Diagrams
Used during requirements elicitation to capture a system’s external behaviour  An Actor represents a user’s role, that is, the type of a user of the system  A Use case represents a sequence of interactions for a type of functionality  A use case model is the set of all the use cases for a system and its environment, i.e., a complete description of all the functionalities of the system and its environment

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Passenger

PurchaseTicket

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Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

Actors
An actor models an external entity which communicates with the system: User External system Physical environment Passenger  An actor has a unique name and an optional description. Examples:  Passenger: A person using a train  GPS satellite: A Provider of GPS coordinates to the system


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Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

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Use Case


A use case represents a class of functionality provided by the system as an event flow. A use case consists of: Unique name Participating actors Entry conditions Flow of events Exit conditions Special requirements



PurchaseTicket

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Use Case Diagram: Example
Name: Purchase ticket Participating actor: Passenger Entry condition:  Passenger standing in front of ticket distributor.  Passenger has sufficient money to purchase ticket. Exit condition:  Passenger has ticket. Event flow:
1. Passenger selects the number of zones to be travelled. 2. Distributor displays the

amount due. 3. Passenger inserts money, of at least the amount due. 4. Distributor returns change. 5. Distributor issues ticket.

Anything missing? Exceptional cases!
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Bernd Bruegge & Allen H. Dutoit

Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

The <<extends>> Relationship
 

Passenger


PurchaseTicket
<<extend>> <<extend>>



<<extend>> relationships represent exceptional or seldom invoked cases. The exceptional event flows are separated from the main event flow for clarity. A use case representing exceptional event flows may extend one or more use cases. The direction of a <<extend>> relationship is to the extended use case

<<extend>>

OutOfOrder

<<extend>>

TimeOut

Cancel
Bernd Bruegge & Allen H. Dutoit

NoChange
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Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

The <<includes>> Relationship
<<include>> relationship represents behaviour that is factored out of the use case.  <<include>> behaviour is factored out for reuse, not because it is an exception. PurchaseMultiCard  The direction of a <<include>> relationship is to the using use case (unlike <<include>> <<extend>> relationships).


Passenger

PurchaseSingleTicket
<<include>>

<<extend>>

CollectMoney
<<extend>>

NoChange
Bernd Bruegge & Allen H. Dutoit

Cancel
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Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

Use Case Diagrams: Summary
Use case diagrams represent external behavior  Use case diagrams are useful as an index into the use cases  Use case descriptions (flow of events) provide meat of model, not the use case diagrams.  All use cases need to be described (flow of events) for the model to be useful.


Bernd Bruegge & Allen H. Dutoit

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Class Diagrams

TarifSchedule Enumeration getZones() Price getPrice(Zone)

*

*

Trip zone:Zone Price: Price

Class diagrams represent the structure of the system.  Used during requirements analysis to model problem domain concepts during system design to model subsystems and interfaces during object design to model classes.

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick) 31

Classes
TarifSchedule Table zone2price Enumeration getZones() Price getPrice(Zone)

Name
TarifSchedule zone2price getZones() getPrice()

Attributes
Operations

Signature
TarifSchedule

    

A class represent a concept A class encapsulates state (attributes) and behaviour (operations). Each attribute has a type. Each operation has a signature. The class name is the only mandatory information.
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Bernd Bruegge & Allen H. Dutoit

Instances

tarif_2004:TarifSchedule zone2price = { {‘1’, .20}, {‘2’, .40}, {‘3’, .60}}

 




An instance represents a phenomenon. Instance name is underlined and can show its class. The attributes are shown with their values. No operation is shown as it is the same as for its class.

Bernd Bruegge & Allen H. Dutoit

Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

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Actor vs Instances


Difference between actor, class and instance:  Actor:  external to the system  interacts with the system  E.g., “Passenger”  Class:  models an entity in the problem domain  modelled inside the system  E.g., “TariffSchedule”  Instance:  A specific instance of a class  E.g., “tarif_2004, the specific TariffSchedule being used by the passenger for purchasing a ticket from the ticket distributor”
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Bernd Bruegge & Allen H. Dutoit

Associations

TarifSchedule

TripLeg

Enumeration getZones() Price getPrice(Zone)

*

*

Price Zone

Associations denote relationships between classes.  The multiplicity at an association end denotes how many objects the source object can legitimately reference.


Bernd Bruegge & Allen H. Dutoit

Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

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1-to-1 and 1-to-many Associations
Country
name:String

Has-capital

CapitalCity name:String

One-to-one association
Has-vertex
Point

Polygon

*

x: Integer y: Integer

draw()

One-to-many association
Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick) 36

Many-to-Many Associations

StockExchange

*

Lists

*

Company tickerSymbol

* StockExchange

Lists

tickerSymbol

1

Company

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From Problem Statement To Object Model
Problem Statement: A stock exchange lists many companies. Each company is uniquely identified by a ticker symbol
Class Diagram:

StockExchange* Lists

*

Company tickerSymbol

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From Problem Statement to Code
Problem Statement: A stock exchange lists many companies. Each company is identified by a ticker symbol
Class Diagram:
StockExchange

*
Lists

*

Company tickerSymbol

Java Code:

public class StockExchange { private Vector m_Company = new Vector(); }; public class Company { public int m_tickerSymbol; private Vector m_StockExchange = new Vector(); };
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Bernd Bruegge & Allen H. Dutoit

Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

Aggregation
 

An aggregation is a special case of association denoting a “consists of” hierarchy. The aggregate is the parent class, the components are the children class.
Exhaust system Exhaust system

1
Muffler diameter

0..2
Tailpipe

1
Muffler diameter

0..2
Tailpipe diameter

diameter



A solid diamond denotes composition, a strong form of aggregation where components cannot exist without the aggregate.
TicketMachine

3
ZoneButton
Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick) 40

Qualifiers
Without qualification 1 Directory With qualification Directory filename * File filename

1

0…1

File

Qualifiers can be used to reduce the multiplicity of an association.  Directory uses filename to make the association 1:1
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Bernd Bruegge & Allen H. Dutoit

Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

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Inheritance

Button

CancelButton

ZoneButton

The children classes inherit the attributes and operations of the parent class.  Inheritance simplifies the model by eliminating redundancy.


Bernd Bruegge & Allen H. Dutoit

Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

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Object modelling in Practice: Class Identification
Foo

Quantity
CustomerId Deposit() Withdraw() GetBalance()

Class Identification: Name of Class, Attributes and Methods

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Object modelling in Practice: Encourage Brainstorming
Foo
Quantity CustomerId Deposit() Withdraw() GetBalance()

Account Quantity CustomerId

Naming is important! Is Foo the right name?

Deposit() Withdraw() GetBalance()

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Object modelling in Practice contd.
Account Quantity AccountId CustomerId Deposit() Withdraw() GetBalance() Customer Name CustomerId

Bank Name

1) Find New Objects

2) Iterate on Names, Attributes and Methods

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Object modelling in Practice: A Banking System
Account Quantity Bank Name AccountId CustomerId Deposit() Withdraw() GetBalance()

*

Customer Has Name CustomerId

1) Find New Objects 2) Iterate on Names, Attributes and Methods 3) Find Associations between Objects 4) Label the associations 5) Determine the multiplicity of the associations
Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick) 46

Practice Object modelling: Iterate, Categorize!
Account Bank Name

*

Customer Amount AccountId Deposit() Withdraw() GetBalance()

*

Has

Name CustomerId CustomerId()

Savings Account

Checking Account

Mortgage Account

Withdraw()

Withdraw()

Withdraw()

Bernd Bruegge & Allen H. Dutoit

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Packages
A package is a UML mechanism for organizing elements into groups (usually not an application domain concept)  Packages are the basic grouping constructs with which you may organise UML models to increase their readability.


DispatcherInterface

Notification

IncidentManagement



A complex system can be decomposed into subsystems, where each subsystem is modelled as a package
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Bernd Bruegge & Allen H. Dutoit

Class Diagrams: Summary
Class diagrams: system structure  Class: name, attributes (types), operations (signatures)  Instances: underlined names, attribute values  Associations between classes, multiplicities  Qualified Associations: from many:many to 1:1  Aggregation, composition  Inheritance  Iterate udring class identification, naming, attributes and methods, associations  Packages


Bernd Bruegge & Allen H. Dutoit

Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

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UML sequence diagrams
Used during requirements analysis TicketMachine Passenger  To refine use case descriptions selectZone()  to find additional objects (“participating objects”)  Used during system design insertCoins()  to refine subsystem interfaces  Classes are represented by pickupChange() columns  Messages are represented by arrows pickUpTicket()  Activations are represented by narrow rectangles  Lifelines are represented by Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick) dashed lines


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Nested messages

Passenger
selectZone()

ZoneButton

TarifSchedule

Display

lookupPrice(selection) price

Dataflow

displayPrice(price)

…to be continued...
   

The source of an arrow indicates the activation which sent the message An activation is as long as all nested activations Horizontal dashed arrows indicate data flow Vertical dashed lines indicate lifelines
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Bernd Bruegge & Allen H. Dutoit

Iteration & condition
…continued from previous slide...
Passenger
ChangeProcessor CoinIdentifier Display CoinDrop

*insertChange(coin)
Iteration

lookupCoin(coin) price displayPrice(owedAmount)

[owedAmount<0] returnChange(-owedAmount)

Condition
…to be continued...
 

Iteration is denoted by a * preceding the message name Condition is denoted by boolean expression in [ ] before the message name
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Bernd Bruegge & Allen H. Dutoit

Creation and destruction
…continued from previous slide...
Passenger
ChangeProcessor

Creation
Ticket

createTicket(selection)

print() free()

Destruction

  

Creation is denoted by a message arrow pointing to the object. Destruction is denoted by an X mark at the end of the destruction activation. In garbage collection environments, destruction can be used to denote the end of the useful life of an object.
Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick) 53

Bernd Bruegge & Allen H. Dutoit

Sequence Diagram Summary
UML sequence diagram represent behaviour in terms of interactions.  Useful to find missing objects.  Time consuming to build but worth the investment.  Complements the class diagrams (which represent structure).


Bernd Bruegge & Allen H. Dutoit

Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

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State Chart Diagrams
Event
[button1&2Pressed] BlinkHours

State

Initial state
[button2Pressed]
IncrementHrs

Transition
[button1&2Pressed] BlinkMinutes

[button1Pressed]

[button2Pressed] IncrementMin.

[button1Pressed] [button1&2Pressed] BlinkSeconds

[button2Pressed]
IncrementSec.

StopBlinking

Final state Represent behaviour as states and transitions
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Bernd Bruegge & Allen H. Dutoit

Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

Activity Diagrams


An activity diagram shows flow control within a system
Handle Incident Document Incident Archive Incident

 

An activity diagram is a special case of a state chart diagram in which states are activities (“functions”) Two types of states:  Action state:  Cannot be decomposed any further  Happens “instantaneously” with respect to the level of abstraction used in the model  Activity state:  Can be decomposed further  The activity is modelled by another activity diagram Note: UML 2 uses rounded rectangles for action and activity nodes.
Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick) 56



Bernd Bruegge & Allen H. Dutoit

Statechart Diagram vs. Activity Diagram
Statechart Diagram for Incident (similar to Mealy Automaton) (State: Attribute or Collection of Attributes of object of type Incident)
Event causes State transition
Active IncidentHandled Inactive IncidentDocumented Closed IncidentArchived Archived

Activity Diagram for Incident (similar to Moore) (State: Operation or Collection of Operations)
Handle Incident Document Incident Archive Incident

Completion of activity causes state transition
Bernd Bruegge & Allen H. Dutoit

Triggerless Transition
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Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

Activity Diagram: modelling Decisions

[lowPriority] Open Incident Allocate Resources [fire & highPriority] [not fire & highPriority] Notify Fire Chief Notify Police Chief

Bernd Bruegge & Allen H. Dutoit

Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick)

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Activity Diagrams: modelling Concurrency
Synchronisation of multiple activities  Splitting the flow of control into multiple threads

Allocate Resources

Splitting
Open Incident Coordinate Resources

Synchronisation
Archive Incident

Document Incident



Now Read BD Chapter 2
Object-Oriented Software Engineering: Using UML, Patterns, and Java L4 (Adapted For ISE 2005/6 By Ananda Amatya, University of Warwick) 59

Bernd Bruegge & Allen H. Dutoit