OO programming and UML OO programming and UML DesignDesign

Dr. Zhen Jiang

West Chester University

E-mail: zjiang@wcupa.edu

OutlineOutline

Introduction to object and classIntroduction to UML Introduction to UML design

Introduction to object and classIntroduction to object and classWhy OO programming?

– Look at this picture carefully– You need to identify it from VERY similar

pictures in the next slide

Introduction to object and classIntroduction to object and classWhy OO programming?

– Which one is shown before?

– In the next slide, your partner will see the selected picture and other two pictures together. Write down something to help your partner to pick up the same picture correctly.

Introduction to object and classIntroduction to object and classWhy OO programming?

– Partner’s job

Introduction to object and classIntroduction to object and classWhy OO programming?

– Which one?

Introduction to object and classIntroduction to object and classWhy OO programming?

– From snapshot to the action

Introduction to object and classIntroduction to object and classWhy OO programming?

– From snapshot to the action

3

2

1

Introduction to object and classIntroduction to object and classWhat’s object

– Identity– State– Behavior

Sequence Diagram Statechart Diagram

– Messages and methodsWhat’s class

– Objects and Classes– Class Attributes– Operation (Method)– Interfaces– Interfaces and Implementation

What’s objectWhat’s object

Fundamentals of Object-Oriented Programming

What’s objectWhat’s objectConceptually, there are many ways to think

of an object– something that can be seen or touched– a thing to which some action is directed– something that performs an action

The structure and behaviour of similar objects are defined in their common class

Objects have three properties: identity , state, and behaviour

Object Property 1: Object Property 1: IdentityIdentityIdentity is that property of an object which

distinguishes it from all other objectsMost programming languages use variable

names to refer to objectsKeep in mind, however, that an object may

not have a name; Similarly, an object might have multiple names (aliases)– For this reason, there is a subtle distinction

made between the concepts of "name" and "identity"

Object Property 2: StateObject Property 2: StateThe state of an object encompasses all of the

descriptions of the object plus the current values of each of these descriptions

Object Property 3: Object Property 3: BehaviourBehaviourBehaviour is how an object acts and reacts,

in terms of its state changes and message passing

The state of an object represents the cumulative results of its behaviour

In object-oriented programming, a behaviour is invoked by sending a message to an object

Example ObjectsExample ObjectsThere are many physical objects we can

examine right in this room– each person is an object – any chair is not an object– each light bulb is an object– Any book is not an object– this room itself is an object (full or not)

See if the followings are objects or not:– Desk– Lamp– Person– Log– The Earth– Clock– Machine– Computer– Saving account

Answer: N, Y, Y, N, Y, Y, Y, Y, Y

What’s the relationship among What’s the relationship among objects: Messages and Methodsobjects: Messages and Methods

A object executes a method when it sends/receives a message

For example, we can ask/tell a dog to sit by sending him the message "sit"

In object-oriented programming, objects send messages asking/telling others to perform behaviors -- those other objects invoke the method corresponding to the message in order to execute the desired behavior

What’s classWhat’s classA class describes the common structure

(attributes/state) and behaviour of its instancesFor example,

– 3.14, 2.71, and 5.5 can be classified as Floats

– the following shapes can be classified as Circles

Classes and ObjectsClasses and ObjectsAn object is called an "instance" of a classThe terms instance and object are

interchangeableCreating an object from a class is often

called instantiationFor example, there are many person objects

in this room -- each person is an instance of the person class

Classes and objectsClasses and objectsHow would we describe the state,

behaviour, and identity for each of these objects

We have looked at objects and we have seen that objects can be "classified" into classes

As programmers, we work with both classes and objects from those classes

For example, we might write a stack class and create multiple stack objects for use in our program

In a 2D drawing package, circles have a radius, a line thickness, a line colour, and a fill colour

Each individual circle (instance) drawn by the user has its own value for each attribute

The programmer writes a Circle class and the program instantiates a Circle object every time the user draws a Circle

a snowman made from 9 Circle instances

Simply, a class is a group of objects with common parts or behaviors (similar, not necessary the exact same). That common thing will be defined in class definition.

An object is an instance which meets all the description of its class.

An attribute is a named property of a class that describes the range of values that instances of the property may hold.(Booch,1999)

An attribute has a type that defines the type of its instances.

Only the object itself should be able to change the value of its attributes.

The values of the attributes define the state of the object

Class AttributesClass Attributes

Operation (Methods)Operation (Methods) An operation is the implementation of a

service that can be requested from any object of the class to affect behavior (Booch, 1999)

An operation can be:– Question (does not change the value of the

object)– Command (may change the value of the

object)

Interface and ImplementationInterface and ImplementationThe class interface is its external (public)

view The class implementation is its internal

(private) viewIt is convenient to think of the interface as

describing "what the objects of this class can do" and the implementation as "how the objects of this class do it"

The implementation of a class consists of all the "behind the scenes" operations defined in the interface of the class

Introduction to UMLIntroduction to UML

What’s UML Goals of UML Overview

– Class diagram Introduction Class icon Class relationship Constraints

– Other diagrams

UML: Unified Modeling UML: Unified Modeling LanguageLanguage

The Unified Modeling Language (UML) is an industry-standard language for specifying, visualizing, constructing, and documenting the artifacts of software systems

The UML definition was led by Grady Booch, Ivar Jacobson, and Jim Rumbaugh (all now at Rational Software)

In Essence: a tool used through the analysis and design phases of system development for expressing the constructs and relationships of complex systems

Target Usage: for building object-oriented and component-based systems

UML simplifies the process of software design, making a "blueprint" for construction

1. Provide users with a ready-to-use, expressive visual modeling language so they can develop and exchange meaningful models

2. Provide extensibility and specialization mechanisms to extend the core concepts.

3. Be independent of particular programming languages and development processes.

4. Provide a formal basis for understanding the modeling language.

5. Encourage the growth of the Object-Oriented tools market.

6. Support higher-level development concepts such as collaborations, frameworks, patterns and components.

7. Integrate best practices.

Goals of UMLGoals of UML

Many free learning materials on the web– e.g. www.rational.com/uml

Standard of UMLwww.cs.wcupa.edu/~zjiang/01-09-67.pdf

Some recommended texts on UML:– The Unified Modeling Language User Guide, [G.

Booch, J. Rumbaugh, I. Jacobson, 2000]– UML Explained, [Kendall Scott, 2001]– Applying UML and Patterns 2nd Ed., [Craig Larman,

2002]– UML Distilled 2nd Ed., [Martin Fowler with K. Scott,

2000]– UML and C++, [R. Lee & W. Tepfenhart, 2001]

UML OverviewUML OverviewUML is a language for visualizing,

specifying, constructing and documenting the artifacts of a software system

The artifacts might include requirements, architecture, design, source code, project plans, tests, prototypes, releases

Objectsomething

action

state1 state2action

attribute1 attribute2

operation/method

attributes: {attribute1, attribute2}

operations/methods

value

structure

ReviewReview

Light

On OffTurn on/off

True FalseTurn_on

attributes: {True, False}

operations/methods:

value

structure

Turn_off

Turn_on/off ( )

Class DiagramClass DiagramIntroductionClass IconRelationshipsConstraints

IntroductionIntroductionThe class diagram is fundamental to object-

oriented programmingUML’s class diagrams capture the attributes

and operations of each class as well the relationships that exist between classes

Class IconClass Icon Class Icon Hiding Details Visibility Notation Attribute Specification Operation Specification

Class IconClass Icon The UML class icon is

a rectangle with three compartments:– class name– class attributes– class operations

Attributes are specified in the following form:– object:class name

Circle

radius: float

center_x: int

center_y: int

area()

display()

Hiding DetailHiding Detail

Circle

area()

display()

Circle

radius: float

center_x: int

center_y: int

Circle

You can optionally leave out the attributes, operations, or both in a class icon:

UML Member Visibility UML Member Visibility NotationNotation

UML has three visibility prefixes for members:+ for public, # for protected, and – for private

–e.g.Circle

-radius: float

#area()

+display()

Full UML Attribute Full UML Attribute SpecificationSpecification

The full form of a UML attribute is as follows:[visibility] name [multiplicity] [: type] [= initial value] [{property}]

– The property choices are changeable, addOnly, and frozen

Student Info

-id: string

-hasGraduated: bool = false

Full UML Operation Full UML Operation SpecificationSpecification

The full form of a UML operation is as follows:[visibility] name [(parameter-list)] [:return-type] [{property}]

– The property choices are sequential, concurrent, guarded, and isQuery

The full form of a UML parameter is:[direction] name : type [= default-value]

– The direction choices are in, out, and inout

UML Class RelationshipsUML Class RelationshipsA class relationship is a connection between

two (or more) classesThe three most important class relationships

are generalizations, associations, and aggregations

UML provides a graphical representation for each of the relationships using a different line type for each relationship

Class RelationshipsClass RelationshipsGeneralizationAssociationAssociation ClassQualified AssociationTernary AssociationAggregation

GeneralizationGeneralization A generalization is a relationship between a general

thing (superclass) and a more specific kind of that thing (subclass)

In the UML, generalization requires that objects of the subclass may be used anywhere an object of the superclass appears

Person

Student

AssociationAssociationAn association is a structural relationship that

specifies that objects of one thing are connected to objects of another

Faculty Student

AssociationAssociationAssociations can be adorned with a name.

Faculty StudentTeaching

AssociationAssociationAssociations can be adorned with the roles.

teacherFaculty Studentlearner

AssociationAssociationAssociations can be adorned with the multiplicity.

4..*Faculty Student

1

Association Class (relation Association Class (relation attributes)attributes)

Each object of association class is one instance of relationship (link) in an association.

1..*Faculty Student4..*

Course

Qualified AssociationQualified AssociationQualified association relates two classes and

a qualifier. The qualifier is a special attribute that

reduces the effective multiplicity of an association.

Directory Filefile name

Ternary AssociationTernary Association A ternary association is a structural relationship that

specifies that objects of one thing are connected to objects of other two’s.

Developer

LanguageProject

AggregationAggregationAn aggregation is an association that

represents whole/part relationshipThe “whole” end of the association

relationship is adorned with an open diamond shape (e.g. X is part of Y)

e.g. door:Door is part of car:Car

X Y

Generalization, Aggregation, and Generalization, Aggregation, and AssociationAssociation

See if the following pairs of classes have generalization, aggregation or association Faculty & student (as) Hospital & doctor (as) Door & Car (ag --<>) Member & Organization (ag --<>) People & student (ge <|-- ) Circle & point (ge --|>) Department & Faculty (as) Employee & Faculty (ge <|--) Item & Printer (ge <|--) Account & Checking account (ge <|-- )

ConstraintsConstraintsConstraints on ObjectConstraints on Relations (Ordering)General Constraints (Dependency)

Constraints on ObjectConstraints on ObjectThe constraints restricts the values that objects can be.Example: No employee’s salary can exceed the salary of the employee’s boss.

Employee

Salary

Employer

Salary

{salary <=boss.salary}

Constraints on Relations Constraints on Relations (Ordering)(Ordering)

{Order} indicates that the elements of the “many” end of an association have an explicit order that must be preserved.

Paper Author{ordered}

11..*

General Constraints General Constraints (Dependency)(Dependency)

A dependency is a using relationship that states that a change in specification of one thing may affect another thing that uses it (but not necessarily the reverse)

General Constraints General Constraints (Dependency)(Dependency)

Aerodrome

checkRVR( r: Runway ) Runway

Dependencies are often used when one class uses another class as an argument of the operation

Dependencies are also often used to express general constraints.

Person Committeemember-of

chair-of

{subset}

UML DesignUML DesignUML class diagram is not object diagram.UML class diagram is not data flow chart.How to describe the behaviors/actions of

objects in UML class diagram?What kind of relationship is generalization?How to keep the consistency of all the

constraints?Common mistakes in Time Sequence DiagramSamples

UML class diagram is not object UML class diagram is not object diagramdiagram

Customer Bank

Loan

Other-Loan

•Should we add relation between Bank and Other-Loans? •Can Bank change Other-loans?•Instance of Loan and Other-Loans?

UML class diagram is not object UML class diagram is not object diagramdiagram

Customer

Bank

Loan

Bank-Loan Other-Loan

UML class diagram is not data UML class diagram is not data flow chartflow chart

Customer Dealer

Product Manager

buy sell report

bargain

authorize

sign

UML class diagram is not data UML class diagram is not data flow chartflow chart

Customer

Dealer

Product

Manager

Salesman

•Customer, Dealer, and Manager•Bargain

How to describe the How to describe the behaviors/actions of objects in behaviors/actions of objects in

UML class diagramUML class diagram

?

Person

sSNaddressemail

Faculty StudentCustomer Casher

How to describe the How to describe the behaviors/actions of objects in behaviors/actions of objects in

UML class diagramUML class diagram

Use case (stories): Each use case defines an interaction between an actor and the system

Use case

Use case

Use case

Use case

Scenarios of a use case Reception

Check

Failure

Authorized

Waiting

Success Failure

?

Order

How to describe the How to describe the behaviors/actions of objects in behaviors/actions of objects in

UML class diagramUML class diagram

– In design, see www.cs.wcupa.edu/~zjiang/intro_uc.ppt.

– In programming, see time sequence diagram, see www.cs.wcupa.edu/~zjiang/intro_TS.ppt.

What kind of relationship is What kind of relationship is generalizationgeneralization

People

Student

x: inty: int

radius: doubleRectangle

PositionPoint

Circle

PositionPoint

*Tip 4: Class A is a super class of class B if and only if any object of class B can also play the role as an object of class A.

How to keep the consistency of How to keep the consistency of all the constraintsall the constraints

Ticket-buyer

Dependent

Traveler

0..6

1

1 1..6

1

1

How to keep the consistency of How to keep the consistency of all the constraintsall the constraints

Ticket-buyer

Dependent

Traveler

0..6

1

0..1 0..1

0..1

1

How to keep the consistency of How to keep the consistency of all the constraintsall the constraints

Ticket-buyer Dependent

Traveler

1 0..60..1