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CSCI 528 Data Structures- Introduction to SW Design Processes, ADT, and Object Models -

Dr. Kwang Lee

School of Information

Technology

Quiz #1:

Assignment #1:

Announcement!

Copyright © Prof. K. Lee All rights reserved.

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Introduction to SW Development Processes

Lecture 1

Lecture Overview

Introduce software development approaches

SW analysis and design methods

– Study top-down and objected-oriented approaches

Introduce design aspects

– Select or build data types

– Develop algorithms for operations on data

– Investigate error types

– Discuss testing methods

Note time and effort devoted to maintenance

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1. SW Development

Usually, three basic approaches to be needed for

development SW

– Identify and Analysis

Confirm needs, solve a problems, and analysis stuff with

programming

– Design

Produce solutions without detail implementation

– Implement

Involve coding algorithm and data structures with programming

languages

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1. SW Development

Waterfall Model

Adding test and maintenance steps

5 phases of SW life cycle

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1. SW Development

Realistic Waterfall Model7

1. SW Development

(1) Identify and Analysis Steps

(2) SW Design Steps

(3) SW Implementation Procedures

(4) Testing, Executing, and Debugging

(5) Maintenance

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Identify and analyze systems requirements;

– The most important task in creating a software product

is extracting the requirements or requirements

analysis

– Customers typically have an abstract idea of what

they want as an end result, but not what software

should do

Incomplete, ambiguous, or even contradictory requirements

are recognized

– Frequently demonstrating live code may help reduce

the risk that the requirements are incorrect

Using Visual Basic or Script languages

1.1 Identify Steps

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Make a SW specification (spec)

– Specification is the task of precisely describing the

software to be written, possibly in a rigorous way

Spec will include following things;

– Purpose

– Available resources

– Pre-condition

– Post-condition

– etc

1.1 Identify Steps

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CS courses

– Small systems

• Few hundred lines of

code

• Simple, straightforward

“Real” world

– Large systems

• Thousands of lines of

code

• Complex

• Many components

• Problem initially poorly

defined

1.1 Identify Steps

Real world contracts or specifications

- Must be precise

- May be required to prove end product meets these precise

specifications

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SW design procedures

– After the purpose and specifications of software are

determined, software developers will design or employ

designers to develop a plan for a solution

– Need a process of problem-solving and planning for

a software solution

Including low-level components and algorithms

implementation issues as well as the architectural view

Determining data types, operations, and algorithms

Selecting design methods

– Structured design (top-down approach)

– Object-oriented design

1.2 SW Design Steps

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Using top-down procedures;

– Identifying major actions

– Analyzing their control flows

– Expressing solution in terms of control structures

and functions

(1) Structured Design Method

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Original problem partitioned into simple sub-

problems by actions and functions

Each of these sub-problems likewise subdivided

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(1) Structured Design Method

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Data1

Data2 Nouns

Data3

Operation1 (funtion1) {

----------

----------

} Verbs

Operation2 (funtion2) {

----------

----------

}

Example: Structured Programming

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Using object-oriented analysis

– Identifying major objects

– Analyzing their operations

– Expressing solution in terms of these objects and

operations

(2) Object Oriented Design Method

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(2) Object Oriented Design Method

Identify the objects in the problem's specification

and their types

Identify the operations or tasks to manipulate the

objects

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Record

Student

Class 1 {

Data

Methods

}

Class 2 {

Data

Methods

}

Class n {

Data

Methods

}

Example: Object-Oriented Programming

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Programs = “Data Structures” + “Algorithms”

Determining data types, structures, and algorithms

– What type of data is needed!

– What type of structures are needed!

– What type of algorithms can be performed!

Construct “data structure”

– Simple data type

int, float, long, double

– Build structured

arrays

structures

class objects

Think of them as

Containers

(3) Determine Data and Operation Types

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Select a best algorithm, or construct/design an

algorithm considering following points;

– Simple

– Definite and unambiguous

– Finite

– Correct and efficient

– Well structured

Before starting final coding for the algorithm, many

cases use pseudocode

(3) Determine Data and Operation Types

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A sequence of statement that are close programming

languages, but more English like, and without the syntax

requirements of the formal computer language

Pascal can be usually used for Pseudocode well

e.g. Regular Code:

if ( is_valid($cc_number) )

{ execute_transaction ($cc_number, $order); }

else

{ show_failure (); }

Pseudocode:

if credit card number is valid

execute transaction based on number and order

else

show a generic failure message

Example: Pseudocode

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Implementation is the realization of an

application, or execution of a plan, idea, design,

specification, algorithm, or others

Encode the design (coding procedure). Select

languages, C, C++, Java, C#, etc to implement

– Insure quality

Program and sub-programs will be well-structured, and

documented

All source code must be correct, understandable, and

formatted for readability

– Verify integration

Combining program units into a complete software system

1.3 SW Implementation Procedures

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Testing in real environments if possible

Finding and reducing the number of bugs,

defects, or errors in a computer program or a

piece of electronic hardware thus making it

behave as expected

(1) Validation test

(2) Verification test

1.4 Testing, Executing, and Debugging

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Validation test:

"Are we building the right product?" Check that documents, program modules and others are

matched with the customer's requirements

Verification test:

"Are we building the product right?" Check that products are correct,

Complete,

Consistent with each other and with those of the preceding

phases

1.4 Testing, Executing, and Debugging

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Completing three type of tests required

– Unit tests

Each individual program unit works?

Program components tested in isolation

– Integration tests

Units combined correctly?

Component interface and information flow tested

– System tests

Overall system works correctly?

System programs, sub-programs, and libraries

(1) Kinds of Tests

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Syntax errors

– Errors in the grammar of the programming language

Link errors

– Errors in the link programs to make an executable

Run-time errors

– Errors happen during the duration of its execution

from beginning to termination

Logic errors

– Errors produces unintended or undesired output or

other behavior

(2) Types of Errors

Difficulty

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Enhancing software to cope with newly discovered

problems or new requirements

– It can take far more time than the initial development of the

software

Necessary modifications because …

– To add new SW or HW features

– Poor performance, poor structure, poor documentation, poor

style, and so on

Bug finding and fixing is tougher

Impedes implementation of enhancements

Large % of

– Computer center budgets and programmer's time

– Software development cost

1.5 Maintenance

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Appendix: “V” Life Cycle Model

The "V" Life Cycle Model Test by Dorothy

Graham

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Fusion Method by Hewlett-Packard

Requirement Doc

Object Models Interface Models

Object Interaction Graphs

Visibility Graphs

Class Descriptions

Inheritance Graphs

Programs

Analysis Part

Design Part

Implementation Part

Appendix: Fusion Method

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Summary

Discussed Software Development Processes

– Identify and analysis steps

Identify and analyze systems requirements

– SW design steps

Choose top-down and objected-oriented approaches

Select or build data types

Develop algorithms for operations on data

– Implement SW code procedures

Select languages, C, C++, Java, C#, etc to implement SW

– Discuss testing methods

Investigate error types

– Set maintenance

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Introduction to ADT and Object Models

Lecture 1

Introduce and define ADTs

– Process abstraction

– Data abstraction

– What is ADT?

Why OOP need?

– Object-oriented concept

– Object-oriented programming (OOP) features

Elements of Object Models

– The meaning of abstraction

– The meaning of encapsulation

– The meaning of modularity

– The meaning of hierarchy

Lecture Overview

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1. What is Abstraction?

Abstraction arise from a recognition of

similarities between certain objects, situations, or

processes in the real world

Abstraction is one of the fundamental ways

that we as human cope with complexity

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Example: Abstraction

Visual Icons

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1. What is Abstraction?

In the programming, abstraction is a

“representation” of an entity that includes only

the most significant attributes

Using abstraction concept in a programming is

important to reduce program complexity and

difficulty

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Example: Abstraction

How to make „6‟ using data 1 and + operation?

– 1 +1 + 1 + 1 + 1 + 1 = 6

How to make ‟21‟?

– 1 +1 + 1 + ,……., + 1 = 21

How to make „10 million‟?

Using 1 + 1 = 2, 1 + 1 + 1 =3, then abstracted

data „2‟ and „3‟

– 2 + 3 + ,…, + 2 = 21

Create another abstracted operation (×),

multiplication

– (3 × 2 × 3) + 3 = 2136

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1. What is Abstraction?

Knowing the concept of abstraction is a

fundamental way to learn programming and

computer science

Generally all programming languages support

“process abstraction” using subprograms

Nearly many programming languages designed

since 1980 support “data abstraction”

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(1) Process Abstraction

All programming languages support process

abstraction using subprograms

– They provide a way for a program to specify that some

process is to be done, without providing detail of how it

is to be done

main()

{

int avg, find;

sortdata(~~);

avg=average(~~);

find = search(~~);

~ ~

return 0;

}

void sortdata(~~)

{ }

int average(~~)

{ }

int search(~~)

{ }

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Since 1980, nearly all programming languages

designed support data abstraction, called

abstract data type (ADT)

– Smalltalk, Object Pascal, C++, Java, C#, and others

Abstract data type (ADT) is user-defined

abstraction type. It enclosure that includes;

– Data representation of one specific data type

– Subprograms that provide the operations for that type

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(2) Data Abstraction

Example: Data Abstraction

Suppose an abstract data type is to be constructed for a

stack that has the following abstract operations:

– Create(stack) :creates a stack object

– Destroy(stack) :deallocates the storages for the stack

– Empty(stack) :predicate function for checking the stack

– Push(stack, element) :pushes the specified element

– Pop(stack) :removes the top element from the stack

– Top(stack) :returns a copy of the top element

A client of the stack type could have a code sequence such

as the following:

create(stk1);

push(stk1, color1);

if (!empty(stk1)) temp = top(stk1);

…. 40

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Abstract data type (ADT) is a user-defined data

type that satisfies the following two conditions:

1. The declaration of the type and the operations on objects

of the type are contained in a single syntactic unit

e.g. Unit = {type + operations (protocol)}

2. The representation of objects of the type is hidden from the

program units that use the type, so the only direct

operations possible on those objects are those provided in

the type's definition

e.g. Manipulate objects

unit 1 unit 2

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2. What is ADT?

2.1 ADT Implementations

ADT is a basic unit in programming languages

- Unit = { Storage structures for the data items +

Algorithms for the operations

- Called an Abstract Data Type (ADT) ≈ Objects

For a programming task, we must identify

(1) The collection of data items

(2) Basic operations to be performed on them

Taken together (data items and operations)42

Unit Data

Operations

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In the point of Java or C++, ADT is an object to

make one unit procedure;

unit procedure = { data + functions} = class

e.g.

class abc

{ data;

functions;

}

=> abc is an object

=> abc a, b; then a, b are objects (instances)

2.2 ADT Implementations in C++, Java

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2.3 Advantages of Data Abstraction

Modularity -- everything associated with a data

structure is together so that program have a

strong organization and modifiability

Reliability -- by hiding the data representations

(encapsulation), user code cannot directly access

objects of the type or depend on the

representation, allowing the representation to be

changed without affecting user code

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3. Why OOP need?

Software crisis in 1980

– Conflicting requirements have always hindered the

software development process

– The roots of the software crisis are complexity,

expectations, and change

- It refers to the difficulty of writing correct, understandable, and

verifiable computer programs

Trying to find easier maintenance and reusable

SW method

Widespread abstraction method in software

engineering fields

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3. Why OOP need?

ADT concept can make data and basic

operations to be merged into one single entity,

called “object”

– ADT is the fundamental way to support object model

for finding an object, and developing ADT

Object modelling programming skill provide lots

of advantages for SW engineering processes,

such as easier maintenance and reusable SW

components with an obvious mapping from real

world entities to system

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3. Why OOP need?

Therefore, programmers need a language (OOP)

which can handle the above requests technically

with supporting manageable coding mechanisms

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3.1 Object-Oriented Concept Development

Object-oriented analysis (OOA):

– concerned with developing an object model of the

application domain by discovering the classes and

objects

Object-oriented design (OOD):

– concerned with developing an object-oriented system

model to implement requirements with inventing the

abstractions and mechanisms

Object-oriented programming (OOP):

– concerned with realising/implementing an OOD using

an OO programming language such as C++ or Java

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Example: Object-Oriented Systems

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An object-oriented system is made up of interacting

objects that maintains their own local state and

provide operations on that state

3.2 Elements of the Object Models

For all things object-oriented, the conceptual

framework is the object model

There are four major elements as follows;

(1) Abstraction

(2) Encapsulation

(3) Modularity

(4) Hierarchy

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Object Orientation

En

cap

sula

tio

n

Ab

stra

ctio

n

Hie

rarc

hy

Mo

du

lari

ty

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3.2 Elements of the Object Models

Abstraction is the process or result of

generalization by reducing the information

content of a concept

– Abstraction is one of the fundamental ways that we

as human cope with complexity

A good abstraction is one that emphasis

significant part to the reader and suppresses

detail immaterial and diversionary

– Abstraction focuses on the outside view of an object

and serves to separate an objects' essential behavior

from its implementation

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(1) The Meaning of Abstraction

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Sales Person

Not saying which

salesperson – just

a salesperson in

general!!!

CustomerElectronic Product

Example: Abstraction

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(2) The Meaning of Encapsulation

Abstraction focuses on the observable behavior

of an object, whereas “Encapsulation” focuses

on the implementations that gives rise to this

behavior

The definition of “Encapsulation” is the process

of compartmentalizing the elements of an

abstraction that constitute its structure and

behavior

– Abstraction should be treated as a secret and hidden

from most client in implementation

– Encapsulation serves to separate the contractual

interfaces of an abstraction and its implementation54

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(2) The Meaning of Encapsulation

Encapsulation is most often achieved through

“Information Hiding”

– All secrets of an object is hidden, as well as the

implementation of its method

– Hiding is the one level of abstraction may be represent

the outside view at another level

– “Hiding is for the prevention of accidents, not the

prevention of fraud”

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Example: Encapsulation and Hiding

Hiding implementation from clients

– Clients depend on interface

How does an object encapsulate?

What does it encapsulate?

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(3) The Meaning of Modularity

Modularity is that the action of partitioning a

program into “individual components” can

reduce its complexity to some degree

Modularity is the property of a system that has

been decomposed into a set of cohesive and

loosely coupled modules

– The goal of the decomposition into modules is the

reduction of software cost by allowing modules to be

designed and revised independently

– It creates a number of well-defined, documented

boundaries within the program

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Order Processing

System

Billing

Order

Entry

Order

Fulfillment

Example: Modularity

The breaking up of something complex into

manageable pieces

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(3) The Meaning of Modularity

Modularization consists of dividing a program into

modules which can be compiled separately, but

which have connections with other modules

In object-oriented design, modularity provides a

crisp boundary around a single abstraction

– Both encapsulation and modularity provide barriers

around the abstraction

The principles of abstraction, encapsulation, and

modularity are synergistic

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(4) The Meaning of Hierarchy

Abstraction, encapsulation, and modularity are

necessary as the following;

– Abstraction help to find/create objects by recognizing

similarities between certain functions, situations, or

processes in the real world

– Encapsulation help manage the complexity by hiding the

inside view of our abstraction

– Modularity help giving us a way to cluster logically related

abstraction

To “simplify” the whole problem, identifying the

hierarchies in design is needed so that a set of

abstractions often forms a “hierarchy structure”

– Hierarchy is a ranking or ordering of abstractions

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(4) The Meaning of Hierarchy

Two most important hierarchies in a complex system

are its class structure (the “is-a” hierarchy) and its

object structure (the “part-of” hierarchy)

– “is-a” relationship

Single inheritance

Multiple inheritance

– “part-of” relationship

Aggregation

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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

Example: Hierarchy

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Introduced and define ADTs

– Process abstraction

– Data abstraction

Studied object-oriented models and programming

– Object-oriented concept

– Object-oriented programming (OOP) features

Looked at four elements of object models

– Meaning of abstraction

– Meaning of encapsulation

– Meaning of modularity

– Meaning of hierarchy

Summary

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Thank You!

Quiz #1:

Assignment #1:

Note and Thank You

Copyright © Prof. K. Lee All rights reserved.