Enterprise & Application Frameworks

Fall 2002 SJSU -- CmpE

Enterprise & Application Frameworks

Dr. M.E. Fayad, ProfessorComputer Engineering Department – RM#

College of Engineering

San José State University

One Washington Square

San José, CA 95192-0180

URL: http://www.cmpe.sjsu.edu/~fayad

Fall 2002 SJSU -- CmpE M.E. Fayad L5-S2 OO Concepts-3

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Lesson 5:Object-Oriented Concepts-3


Lesson Objectives

Objectives

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Discuss UML Associations Discuss UML – aggregation Understand UML- inheritance Explore use case concepts Understand How to identify UML

Artifacts


An association shows a two-way relationship between

objects (instances) of two or more classes and requiring

special implementation to ensure integrity.

A particular instance of an association is often called a link.

Associations between classes are required if the objects

need to communicate.

Associations are often named, and have role-names for

each side of the link.

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Associations


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More on Associations

Association Name

Person

nameageaddress

Car

modelyear# of doors

registeredCar owner

Vehicle Registration

Roles Names


Simple example:

An association has a name and a numerical specification (multiplicity indication) of how many objects on one side of the association are connected with how many objects on the other side.

Associations are called use relationships – even if this may seem somewhat cheeky in the example below

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Window GeomFiguredisplays 0..*

Company Personemploys 0..*

Employer Employee


Associations are directed (one way), bidirectional, and undirected.

UML makes no distinction between bidirectional and undirected associations.

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Class1 Class2

StereotypeRelationName{Constraints} *

role1 Role2: interface

Multiplicity


Recursive association: A class has a relation with itself.

It is also possible to model associations that are valid only temporarily “stereotype or temporary”

Constraints may be used to restrict the relation under specific aspects.

A role name describes how the object is seen by the opposite object in the association.

An association can be described in more detail by means of constraints, tagged values, and stereotypes.

Stereotypes are noted before or above the relation name, constraints, and tagged values after or below the name. 8



Directed association is a one-way association, in which one side knows the other, but not vice versa.

Multiplicity Specification:

– 1 exactly one

– 0, 1 zero or one

– 0..4 between zero and four

– 3, 7 either three or seven

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More multiplicity specifications:

– 0..* greater than or equal to zero (default)

– * ditto

– 1..* greater than or equal to one

– 0..3, 7, 9..* between zero and three, or exactly seven, or greater than or equal to nine.

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Recursive associations are associations in which one class is involved.

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Employee

namestaffNoroomNo

Person

Patient

1manager

reports to

leads

office clerk

has

* *relative


An n-ary association is like a common (binary) association, except that more than two association roles involved in it.

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N-ary Association

Class1 Class2

Class3

N-aryassociation

Ternaryassociation


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More on n-ary Association

datetrainNo

TraincarriageNo

seatNo

Seat

nametitle

Passenger

Reservation

1 1..*

1..*

Ternaryassociation


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More on Associations• Recursive Associations• N-ary Associations• Attributed Associations (Association Class)• Association Constraints• Qualified Associations• Derived Associations• Directed Associations• Ordered Associations• Realization/Refinements• Dependency



Associations are usually bidirectional

Allows each object involved in the relationship

to refer to the object to which it is related.

Bidirectional association means at the

relationship has an inverse.

Associations do not have to be bidirectional. 15


Man WomanMarriage

husband wife

Screen WindowWindows

Nets UserAuthorization

Car Trailer

Association Type

One-to-One

One-to-Many(One-to-Zero-or-More)

Many-to-Many

Zero or One 16


Square LineSides

father mother

children

Secure Room PersonOccupants

Male FemaleTraditionalFamily

Association Type

Specified the # of instances on the “many” side

Specify the possible # ofinstances using “or”

Ternary relationship

Child 17


Server Client

Connection

baudRateprotocolwireType

disconnectrerouteLink

• These attributes don’t belongin either the Client or Serverclass.• They are attributes of the connection itself.

• The association class can have behaviors as well as attributes.

Connection

Association Class

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Aggregation is a special form of association.

Aggregation is used when the relationship is

“part/whole” or “contains/is-part-of”

Aggregation is transitive and operations on

“whole” often cascade down to “parts”.

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Aggregation & Composite


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Server

Client

Aggregation

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“whole”

“part”

Computer

CPU Disk Drive Keyboard Mouse

*


Special diamond symbol used on “whole” side to indicate

aggregation.

Aggregation is an anti-symmetric that is, if A is part of B, then B is not

part of A.

DO NOT confuse aggregation with generalization

An essential property of aggregates is that the whole acts as a proxy

for its parts.

A composition is a strict form of aggregation, in which the parts are

existence-dependent on the entirely

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Entirely

Existence-DependentPart

Part

Composition

Aggregation


Mr. Clinton’s hand is part-of Mr. Clinton & Mr.

Clinton is part-of U.S.A.

Therefore:

Mr. Clinton’s hand is part-of U.S.A. 23

Aggregation Problem

WARNING


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Keypad

Number Keys Total Key Subtotal Key

Display Drawer

display display displaydrawer

*

Cash Register Example


Attributes are simply the information associated with the object.

The data type used to hold the attributes is often a fundamental type, such as int or char.

Sometimes the attribute can be a non-fundamental type, such as String type and Address type.

Avoid using attributes which might be better implemented as an association to a new class.

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Attributes


x

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More on Attributes

TV

String modelString serialNumString manName

For example:

• Why? Using an association to a Manufacturer class, the name and address of each manufacturer will be stored in one place rather than in each of the TV objects made by that manufacturer.

TV

String modelString serialNum

Manufacturer

String nameAddress address

product manufacturer

Using Attributes Using Association

*


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More on Attributes

Employee

String namefloat salarylong clearanceNum

If attributes only make sense in some instances of a given class but not in

others. It will make sense to split the single class into two classes or more.

Employee

String namefloat salary

ClearedEmployee

long clearanceNum

openVault()

Split into two classes

• Not all employees have clearances

inheritance


When a relationship exists between classes such that

lower-level classes (called subclasses) share certain

attributes and behaviors which can be defined once in a

higher-level class (called superclasses).

Subclasses inherit properties (attributes and behaviors)

of its superclass and then adds its own unique properties

and modifies any inherited properties.

This is called Generalization or Inheritance.

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Inheritance


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More on Inheritance

Window

sizeicon

paintWindow

bitmaps

textWindow

contents


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Aggregation vs. Inheritance

Aggregation Inheritance

Instances of distinct classes Instances of a single class

“a-part-of” (APO) “a-kind-of” or “is-a” (AKO)

Contains superclass-of

Aggregate + parts Superclass + subclass

“and” relationship “or” relationship

Propagated only if specified Inheritance


• What are the other terms for attributes & operations?

• Define an object and a class in UML

• What is an association? Give examples

• Associations are usually bidirectional. Please describe.

• Describe the basic difference between aggregation and inheritance. What do they have in common?

• What do you think “multiple inheritance” means?

• Which type of association is more likely to yield savings in the amount of code required for implementation? why?

• Define the process of identifying objects, classes, inheritance, associations & aggregation, attributes, and behaviors

• Define Polymorphism with examples

• What do we mean by saying “Model/View/Controller”? 31

Discussion Questions

Documents

Enterprise & Application Frameworks