chapter 2, modeling with uml object-oriented software ...blk/cs4667/lectures/ch02.pdf · an...

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Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 2

Overview: Modeling with UML

♦ What is modeling?♦ What is UML?♦ Use case diagrams♦ Class diagrams

Next lecture♦ Sequence diagrams♦ Activity diagrams

Then♦ Apply UML to Appalcart Project


What is modeling?

♦ Modeling consists of building an abstraction of reality.♦ Abstractions are simplifications because:

They ignore irrelevant details andThey only represent the relevant details.

♦ What is relevant or irrelevant depends on the purpose of the model.


Example: Appalcart route


Why model software?

♦ Software is getting increasingly more complexWindows XP > 40 million lines of codeA single programmer cannot manage this amount of code in its entirety.

♦ Code is not easily understandable by developers who did not write it

♦ We need simpler representations for complex systemsModeling is a mean for dealing with complexity


Systems, Models and Views

♦ A model is an abstraction describing a subset of a system♦ A view depicts selected aspects of a model♦ A notation is 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


Systems, Models and Views

SystemView 1

Model 2View 2

View 3

Model 1

Aircraft

Flightsimulator

Scale Model

Blueprints

Electrical Wiring


Models, Views and Systems (UML)

System Model View**

Depicted byDescribed by

Airplane: System

Blueprints: View Fuel System: View Electrical Wiring: View

Scale Model: Model Flight Simulator: Model


Concepts and Phenomena

PhenomenonAn object in the world of a domain as you perceive itExample: The lecture you are attendingExample: My watch with a heart-rate monitor

ConceptDescribes the properties of phenomena that are common. Example: Lectures on software engineeringExample: All watches with a heart-rate monitor

Concept is a 3-tuple: Name (To distinguish it from other concepts)Purpose (Properties that determine if a phenomenon is a member of a concept) Members (The set of phenomena which are part of the concept)


♦ AbstractionClassification of phenomena into concepts

♦ ModelingDevelopment of abstractions to answer specific questions about a set of phenomena while ignoring irrelevant details.

MembersName

Clock

Purpose

A device thatmeasures time.

Concepts and phenomena


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 possible instances the variable can take

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


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 behavior (methods)

Class ArrayList♦ Unlike abstract data types, classes can be

defined in terms of other classes using inheritance

Watch

timedate

CalculatorWatch

SetDate(d)

EnterCalcMode()InputNumber(n)

calculatorState


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


What is UML?

♦ UML (Unified Modeling Language)An emerging standard for modeling object-oriented software.Resulted from the convergence of notations from three leading object-oriented methods:

OMT (James Rumbaugh)OOSE (Ivar Jacobson)Booch (Grady Booch)

♦ Reference: “The Unified Modeling Language User Guide”, Addison Wesley, 1999.

♦ Supported by several CASE tools Rational ROSETogetherJ


UML: First Pass

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

♦ We teach you those 20%


UML First Pass

♦ Use case diagramsDescribe the functional behavior of the system as seen by the user.

♦ Class diagramsDescribe the static structure of the system: Objects, Attributes, Associations

♦ Sequence diagramsDescribe the dynamic behavior between actors and the system and between objects of the system

♦ Statechart diagramsDescribe the dynamic behavior of an individual object (essentially a finite state automaton)

♦ Activity diagramsModel the dynamic behavior of a system, in particular the workflow (essentially a flowchart)


UML first pass: Use case diagrams

WatchUser WatchRepairPerson

ReadTime

SetTime

ChangeBattery

Actor

Use casePackageWatch

Use case diagrams represent the functionality of the systemfrom user’s point of view


UML first pass: Class diagrams

1

2

push()release()

1

1

blinkIdxblinkSeconds()blinkMinutes()blinkHours()stopBlinking()referesh()

LCDDisplay Batteryload

1

2

1

Timenow

1

Watch

ClassAssociation

Multiplicity

Attribute Operations

Class diagrams represent the structure of the system

state

PushButton


UML first pass: Sequence diagram

:LCDDisplay

blinkHours()

blinkMinutes()

refresh()

com mitNewTime()

:Time

incrementMinutes()

stopBlinking()

:Watch

pressButton1()

pressButton2()

pressButtons1And2()

pressButton1()

:WatchUser

Object

Message

Activation

Sequence diagrams represent the behavior as interactions

Actor

Lifeline


UML first pass: Statechart diagrams for objects with interesting dynamic behavior

BlinkHours

BlinkMinutes

IncrementHrs

IncrementMin.

BlinkSeconds IncrementSec.

StopBlinking

[button1&2Pressed]

[button1Pressed]

[button2Pressed]

[button2Pressed]

[button2Pressed]

[button1Pressed]

[button1&2Pressed]

[button1&2Pressed]

StateInitial state

Final state

Transition

Event

Represent behavior as states and transitions


Other UML Notations

UML provide other notations that we will be introduced in subsequent lectures, as needed.

♦ Implementation diagramsComponent diagramsDeployment diagramsIntroduced in lecture on System Design

♦ Object constraint languageIntroduced in lecture on Object Design


UML Core Conventions

♦ Rectangles are classes or instances♦ Ovals are functions or use cases♦ Instances are denoted with an underlined names

my Watch:SimpleWatch

Joe:Firefighter

♦ Types are denoted with non underlined namesSimpleWatch

Firefighter

♦ Diagrams are graphsNodes are entitiesArcs are relationships between entities


Use Case Diagrams

♦ Used during requirements elicitation to represent external behavior

♦ Actors represent roles, that is, a type of user of the system

♦ Use cases represent a sequence of interaction for a type of functionality

♦ The use case model is the set of all use cases. It is a complete description of the functionality of the system and its environment

Passenger

PurchaseTicket


Actors

♦ An actor models an external entity which communicates with the system:

UserExternal systemPhysical environment

♦ An actor has a unique name and an optional description.

♦ Examples:Passenger: A person in the trainGPS satellite: Provides the system with GPS coordinates

Passenger


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


Use Case Diagram: Example

Name: Purchase ticket

Participating actor: Passenger

Entry condition:♦ Passenger standing in front of

ticket distributor.♦ Passengerhas sufficient money

to purchase ticket.

Exit condition:♦ Passengerhas ticket.

Event flow:1. Passengerselects the number of

zones to be traveled.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!


The <<extends>> Relationship♦ <<extends>> relationships

represent exceptional or seldom invoked cases.

♦ The exceptional event flows are factored out of the main event flow for clarity.

♦ Use cases representing exceptional flows can extend more than one use case.

♦ The direction of a <<extends>>relationship is to the extended use case

Passenger

PurchaseTicket

TimeOut

<<extends>>

NoChange

<<extends>>OutOfOrder

<<extends>>

Cancel

<<extends>>


The <<includes>> Relationship

♦ <<includes>> relationship represents behavior that is factored out of the use case.

♦ <<includes>> behavior is factored out for reuse, not because it is an exception.

♦ The direction of a <<includes>>relationship is to the using use case (unlike <<extends>>relationships).

Passenger

PurchaseSingleTicket

PurchaseMultiCard

NoChange

<<extends>>

Cancel

<<extends>>

<<includes>>

CollectMoney

<<includes>>


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 provide meat of model, not the use case

diagrams.♦ All use cases need to be described for the model to be useful.


Class Diagrams

♦ Class diagrams represent the structure of the system.♦ Used

during requirements analysis to model problem domain conceptsduring system design to model subsystems and interfacesduring object design to model classes.

Enumeration getZones()Price getPrice(Zone)

TarifSchedule

* *Trip

zone:ZonePrice: Price


Classes

♦ A class represent a concept♦ A class encapsulates state (attributes) and behavior (operations).♦ Each attribute has a type.♦ Each operation has a signature.♦ The class name is the only mandatory information.

zone2pricegetZones()getPrice()

TarifSchedule

Table zone2priceEnumeration getZones()Price getPrice(Zone)

TarifSchedule

Name

Attributes

Operations

Signature

TarifSchedule


Instances

♦ An instance represents a phenomenon.♦ The name of an instance is underlined and can contain the class of the

instance.♦ The attributes are represented with their values.

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

tarif_1974:TarifSchedule


Actor vs Instances

♦ What is the difference between an actor, a class and an instance?

♦ Actor: An entity outside the system to be modeled, interacting with thesystem (“Passenger”)

♦ Class: An abstraction modeling an entity in the problem domain, must bemodeled inside the system (“User”)

♦ Object: A specific instance of a class (“Joe, the passenger who is purchasing a ticket from the ticket distributor”).


PriceZone

Associations

♦ Associations denote relationships between classes.♦ The multiplicity of an association end denotes how many objects the source

object can legitimately reference.

Enumeration getZones()Price getPrice(Zone)

TarifSchedule TripLeg

* *


1-to-1 and 1-to-many Associations

Country

name:String

City

name:String

Has-capital

Polygon

draw()

Point

x: Integer

y: Integer

One-to-one association

One-to-many association

*


Many-to-Many Associations

StockExchange Company

tickerSymbol

Lists **

StockExchange CompanyLists 1*

tickerSymbol SX_ID


From Problem Statement To Object Model

Problem Statement: A stock exchange lists many companies. Each company is uniquely identified by a ticker symbol. A company may be listed on more than one stock exchange.

Class Diagram:


tickerSymbolLists

**


From Problem Statement to Code

public class StockExchange{private ArrayList m_Company = new ArrayList();};

public class Company{

public int m_tickerSymbol;private ArrayList m_StockExchange = new ArrayList();

};

Class Diagram:

Java Code


tickerSymbolLists **

Problem Statement: A stock exchange lists many companies. Each company is uniquely identified by a ticker symbol. A company may be listed on more than one stock exchange.


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.

♦ A solid diamond denotes composition, a strong form of aggregation where components cannot exist without the aggregate. (Bill of Material)

TicketMachine

ZoneButton3

Exhaust system

Muffler

diameter

Tailpipe

diameter

1 0..2


Book ChapterN

composed-of

Booch

Book Chapter

composed-of

UML1 *

Figure 2-7, Example of describing a model with two different notations.


Qualifiers

♦ Qualifiers can be used to reduce the multiplicity of an association.

DirectoryFile

filename

Without qualification1 *

With qualification

Directory File0…11

filename


Inheritance

♦ The children classes inherit the attributes and operations of the parent class.

♦ Inheritance simplifies the model by eliminating redundancy.

Button

ZoneButtonCancelButton


Object Modeling in Practice: Class Identification

Foo

AmountCustomerId

Deposit()Withdraw()GetBalance()

Class Identification: Name of Class, Attributes and Methods


Object Modeling in Practice: Encourage Brainstorming

Foo

AmountCustomerId


Account

AmountCustomerId


Naming is important! Is Foo the right name?

“Dada”

AmountCustomerId



Object Modeling in Practice

Account

Amount


Customer

NameCustomerId

1) Find New Objects

CustomerIdAccountId

2) Iterate on Names, Attributes and Methods

Bank

Name


Object Modeling in Practice: A Banking System

Account

Amount


Customer

NameCustomerId

CustomerIdAccountIdBank

Name

1) Find New Objects

2) Iterate on Names, Attributes and Methods

3) Find Associations between Objects

Has

4) Label the assocations5) Determine the multiplicity of the assocations

*


Practice Object Modeling: Iterate, Categorize!

Customer

Name

CustomerId()

Account

Amount


CustomerIdAccountId

Bank

Name Has**

SavingsAccount

Withdraw()

CheckingAccount

Withdraw()

MortgageAccount

Withdraw()


Watch

timedate

CalculatorWatchSetDate(d)

EnterCalcMode()InputNumber(n)

calculatorState

Figure 2-8, A UML class diagram depicting two classes: Watch and CalculatorWatch. CalculatorWatch is a refinement of Watch, providing calculator functionality normally not found in normal Watches.


OrganicCompound

Benzene

Figure 2-9, An example of abstract class.


Watch

CalculatorWatch

simpleWatch1291:Watch

calculatorWatch1515:CalculatorWatch

«instanceOf»

«instanceOf»

Figure 2-10, A UML class diagram depicting instances of two classes.


Packages

♦ A package is a UML mechanism for organizing elements into groups (usually not an application domain concept)

♦ Packages are the basic grouping construct with which you may organize UML models to increase their readability.

♦ A complex system can be decomposed into subsystems, where each subsystem is modeled as a package

DispatcherInterface

Notification IncidentManagement


UML sequence diagrams

♦ Used during requirements analysisTo refine use case descriptionsto find additional objects (“participating objects”)

♦ Used during system design to refine subsystem interfaces

♦ Classes are represented by columns

♦ Messages are represented by arrows

♦ Activations are represented by narrow rectangles

♦ Lifelines are represented by dashed lines

selectZone()

pickupChange()

pickUpTicket()

insertCoins()

PassengerTicketMachine


Nested messages

♦ 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

selectZone()

PassengerZoneButton TarifSchedule Display

lookupPrice(selection)

displayPrice(price)

price

Dataflow

…to be continued...


Iteration & condition

♦ Iteration is denoted by a * preceding the message name♦ Condition is denoted by boolean expression in [ ] before the message

name

PassengerChangeProcessor

insertChange(coin)

CoinIdentifier Display CoinDrop

displayPrice(owedAmount)

lookupCoin(coin)

price

[owedAmount<0]returnChange(-owedA mount)

Iteration

Condition

…to be continued...

…continued from previous slide...

*


Creation and 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.

PassengerChangeProcessor

…continued from previous slide...

Ticket

createTicket(selection)

free()

Creation

Destruction

print()


Sequence Diagram Summary

♦ UML sequence diagram represent behavior in terms of interactions.

♦ Useful to find missing objects.♦ Time consuming to build but worth the investment.♦ Complement the class diagrams (which represent structure).


State Chart Diagrams

BlinkHours

BlinkMinutes

IncrementHrs

IncrementMin.

BlinkSeconds IncrementSec.

StopBlinking

[button1&2Pressed]

[button1Pressed]

[button2Pressed]

[button2Pressed]

[button2Pressed]

[button1Pressed]

[button1&2Pressed]

[button1&2Pressed]

StateInitial state

Final state

Transition

Event

Represent behavior as states and transitions


Group Work

The following sequence of diagrams are taken from an example developed in the textbook. We will review UML notation by trying to understand these diagrams.


Report Emergency

FieldOfficer DispatcherOpenIncident

AllocateResources

FRIEND

Figure 2-13, An example of a UML use case diagram: Incident initiation in an accident management system.


OpenIncident

AllocateResources

HelpDispatcher«include»

«include»

Figure 2-16, An example of an «include»relationship.


Figure 2-18, An example of an «extend»relationship.

OpenIncident

AllocateResources

ConnectionDown«extend»

«extend»


EmergencyReport Incident

FieldOfficer

name:StringbadgeNumber:Integer

Dispatcher


author

incidentsGeneratedreportsGenerated

initiator

reports

1

*

1

*1..*

1

Figure 2-22, An example of a UML class diagram: classes that participate in the ReportEmergency use case.


report_1291 incident_1515bob:FieldOfficer

name = “Bob D.”badgeNumber = 132

john:Dispatcher

name = “John D.”badgeNumber = 12

alice:FieldOfficer

name = “Alice W.”badgeNumber = 23

Figure 2-23, An example of a UML object diagram: objects that participate in the warehouseOnFirescenario.


IncidentFieldOfficer


Allocates

role:StringnotificationTime:Time

resourcesincident

1

1..*

Figure 2-25, An example of an association class.


Incident

FieldOfficer


Allocation

role:StringnotificationTime:Time

resources

incident 1

1..*

11

Figure 2-26, Alternative model for Allocation.



FieldOfficer Dispatcherauthor initiator

reportsGenerated incidents

1

*1

*

1..*

1

PoliceOfficer


Figure 2-32, An example of a generalization.


Report Emergency

FieldOfficer

DispatcherOpenIncident

AllocateResources

ArchiveIncident

SearchArchive

ManageUsers

ManageTerminalsLibrarian SysAdmin

SysAdministrationIncidentArchive

IncidentManagement

Figure 2-45, Example of packages: use cases of FRIEND organized by actors.


FieldOfficer Dispatcher

Librarian SysAdmin

IncidentArchive SysAdministration

IncidentManagement

Figure 2-46, Example of packages.


DispatcherStation



FieldStation

Figure 2-47, Example of packages.


EmergencyReport

DispatcherStation

Incident


FieldStation

The EmergencyReportclass is defined in FieldStationand used in both stations.

Figure 2-48, An example of a note. Notes can be attached to a specific element in a diagram.


Activity Diagrams

♦ An activity diagram shows flow control within a system

♦ 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 furtherHappens “instantaneously” with respect to the level of abstraction used in the model

Activity state:Can be decomposed furtherThe activity is modeled by another activity diagram

HandleIncident

DocumentIncident

ArchiveIncident


Statechart Diagram vs. Activity Diagram

HandleIncident

DocumentIncident

ArchiveIncident

Active Inactive Closed Archived

Incident-Handled

Incident-Documented

Incident-Archived

Statechart Diagram for Incident (similar to Mealy Automaton)(State: Attribute or Collection of Attributes of object of type Incident)

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

TriggerlessTransitionCompletion of activity

causes state transition

Event causesState transition


Activity Diagram: Modeling Decisions

OpenIncident

NotifyPolice Chief

NotifyFire Chief

AllocateResources

[fire & highPriority]

[not fire & highPriority]

[lowPriority]


Activity Diagrams: Modeling Concurrency

♦ Synchronization of multiple activities ♦ Splitting the flow of control into multiple threads

OpenIncident

AllocateResources

CoordinateResources

DocumentIncident

ArchiveIncident

SynchronizationSplitting


Activity Diagrams: Swimlanes

♦ Actions may be grouped into swimlanes to denote the object or subsystem that implements the actions.

OpenIncident

AllocateResources

CoordinateResources

DocumentIncident

ArchiveIncident

Dispatcher

FieldOfficer


What should be done first? Coding or Modeling?

♦ It all depends….

♦ Forward Engineering:Creation of code from a modelGreenfield projects

♦ Reverse Engineering:Creation of a model from codeInterface or reengineering projects

♦ Roundtrip Engineering:Move constantly between forward and reverse engineeringUseful when requirements, technology and schedule are changing frequently


UML Summary

♦ UML provides a wide variety of notations for representing many aspects of software development

Powerful, but complex languageCan be misused to generate unreadable modelsCan be misunderstood when using too many exotic features

♦ For now we concentrate on a few notations:Functional model: Use case diagramObject model: class diagramDynamic model: sequence diagrams, statechart and activity diagrams

chapter 2, modeling with uml object-oriented software ...blk/cs4667/lectures/ch02.pdf · an...

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