Object Oriented Analysis and Design Object Oriented Analysis and Design

Using the UMLUsing the UML

Introduction to Object Orientation

(abbreviated!)

Objectives: Introduction to Object Objectives: Introduction to Object

OrientationOrientation Understand the basic principles of object

orientation

Understand the basic concepts and terms

of object orientation and the associated

UML notation

Appreciate the strengths of object

orientation

Understand some basic UML modeling

mechanisms

Object Orientation

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1. Basic Principles of Object 1. Basic Principles of Object

OrientationOrientation

Know This.

Salesperson

Not saying

which

salesperson

just a

salesperson in

general!!!

Customer Product

Manages Complexity

What is Abstraction?What is Abstraction?

Improves Resiliency

What is Encapsulation?What is Encapsulation? Hide implementation from clients

Clients depend on interface only!

Clients do not need to know how the server operates or provides the services!

How does an object encapsulate?

What does it encapsulate?

DISCUSS!!!!!

Order Processing

System

Billing

Order

Entry

Order

Fulfillment

Manages Complexity

What is Modularity?What is Modularity?

The breaking up of something complex

into manageable pieces

Decreasing

abstraction

Increasing

abstraction

Asset

RealEstate

Savings

BankAccount

Checking Stock

Security

Bond

Elements at the same level of the hierarchy should be at the same level of abstraction

What is Hierarchy? What is Hierarchy?

Levels of abstraction

2. Basic Concepts of Object 2. Basic Concepts of Object

OrientationOrientation Object

Class

Attribute

Operation

Interface (Polymorphism)

Component

Package

Subsystem

Relationships

A More Formal Definition A More Formal Definition An object is a concept, abstraction, or thing with

sharp boundaries and meaning for an application

An object is something that has:

State

Behavior

Identity

Know This.

: Professor

Professor Clark

a + b = 10

ProfessorClark :

Professor

ProfessorClark

Class Name Only

Object Name Only

Class and Object Name (stay tuned for classes)

Representing Objects Representing Objects the the

beginningsbeginnings An object is represented as a rectangle with

underlined name (no class name shown

here) (unnamed object)

OO Principle: Abstraction

What is a Class?What is a Class?

A class is a description of a group of

objects with common properties

(attributes), behavior (operations),

relationships, and semantics

A class is an abstraction of objects.

An object is an instance of a class

Professor

Professor Clark

a + b = 10

Representing ClassesRepresenting Classes

A class is represented using a

compartmented rectangle

(note: no underlining)

Professor name empID

create( ) save( ) delete( ) change( )

Class Name

Attributes

Operations

Class Compartments Class Compartments a bit a bit

more developmentmore development A class is comprised of three

sections

The first section contains the class name

The second section shows the structure (attributes)

The third section shows the behavior (operations)

Objects Class

Professor Smith

Professor Jones

Professor Mellon

Professor

The Relationship Between The Relationship Between

Classes and ObjectsClasses and Objects A class is an abstract definition of an object

It defines the structure and behavior of each object in the class

It serves as a template for creating objects

:CourseOffering

number = 101

startTime = 900

endTime = 1100

:CourseOffering

number = 104

startTime = 1300

endTime = 1500

CourseOffering

number

startTime

endTime

Class

Attribute

Object

Specific

attribute values

for different

objects

What is an Attribute?What is an Attribute?

CourseOffering

addStudent

deleteStudent

getStartTime

getEndTime

Class

Operation

What is an Operation? (very What is an Operation? (very

general form here)general form here)

Really need to show more, but here, this is sufficient.

Source File

Name

Executable

Name

OO Principle:

Encapsulation

What is a Component?What is a Component? A non-trivial, nearly independent, and

replaceable part of a system that fulfills a clear

function in the context of a well-defined

architecture

A component may be

A source code component

A run time component or

An executable component

Component

Name Component

Interface

Package Name OO Principle:

Modularity

What is a Package?What is a Package? A package is a general purpose mechanism for organizing like

elements into groups A model element which can contain other model elements Think: in the Java API, similar classes are found in packages that

we may import, etc.

Uses Organize the model under development

A unit of configuration management

Think: Math class. (contains math classes such as cos() )

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Example for Data Structures Class:Example for Data Structures Class:

Think IO package you imported. Inside this package are many (often) unrelated

classes. FileReader BufferedReader FileWriter PrinterWriter, etc.

To USE any of these classes, we merely create an object of them and proceed independently of any other classes.

To USE any of these classes in the package, we go directly to the class, instantiate the class, and use the methods in the objects.

OO Principles: Encapsulation and Modularity

Subsystem Name

Interface Interface

Realization Subsystem

(stay tuned for realization relationship)

What is a Subsystem?What is a Subsystem? A combination of a package (contains other model

elements) and a class (has behaviors)

A subsystem: realizes one or more interfaces which

define its behavior

Interface is an abstract class. Subsystems implement (realize) the interface(s)

Know This.

Example of SubsystemsExample of Subsystems

Subsystem Name

Interface Interface

Realization Subsystem

Subsystem might be AccountsReceivable, AccountsPayable, Billing,

That is, a major hunk of functionality.

BUT, a client of the subsystem does NOT have access to the individual

Classes like in a Package. Rather, a client must go through the

public Interface to the subsystem, which contains the signatures of the

services provided within the subsystem.

The contents of the subsystem are NOT directly accesses;

They are protected;

Only the services shown in the interface are made available to clients.

RelationshipsRelationships

Association

Aggregation

Composition

Dependency

Generalization

Realization

Professor University Works for

Class

Association

Association Name

Professor University

Employer Employee

Role Names

Relationships: Relationships:

AssociationAssociation Models a semantic connection among classes

Student Schedule

Whole

Aggregation sometimes called

simple aggregation.

This is sometimes called a

has_a relationship

Part

Relationships: Relationships: Aggregation Aggregation

(simple aggregate)(simple aggregate) A special form of association that models a

whole-part relationship between an aggregate

(the whole) and its parts

Know This

Student Schedule

Whole

Aggregation

This one is called

composition.

Part

Relationships: Relationships: CompositionComposition

A form of aggregation with strong

ownership and coincident lifetimes

The parts cannot survive the whole/aggregate

Know This

Association: Multiplicity and Association: Multiplicity and

NavigationNavigation Multiplicity defines how many objects participate

in a relationship Multiplicity is a Structural Relationship! The number of instances (that is, objects) of one

class related to ONE instance of another class (examples ahead)

Specified for each end of the association

Associations and aggregations are bi-directional by default, but it is often desirable to restrict navigation to one direction If navigation is restricted, an arrowhead is

added to indicate the direction of the navigation

Association: MultiplicityA