Object Oriented Analysis and Design: Object, Classes, Inheritance, Encapsulation, Polymorphism

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Information System (CS507)

LESSON 27

Object Oriented Analysis and Design

There are some terms important to explaining the concept object oriented analysis and design.

26.1 Object

An object can be defined as "A concept, abstraction, or thing with crisp boundaries and meaning of the

problem at hand. Objects serve two purposes, they promote understanding of the real world and provide a

practical basis for computer implementation."

Rumbaugh et al. (1991)

26.2 Classes

A class is defined as "The purpose of a class is to specify a classification of objects and to specify the

features that characterize the structure and behavior of those objects."

Attributes & Methods

Attributes are the characteristics of object / class and methods are the operations related to the object /

class.

In order to explain concepts of Class, Object, Attribute, Method, etc, let's consider an example. A company

may be interested in creating a database for better customer relationships. For this purpose the company

may plan to create a database in the following manner.

Example

Class

Customers

Object/Instance

A particular customer

Attribute

Name, Address, etc.

(Characteristics of the

object)

Methods (Operations Add, update, delete,

related to the objects) validate, etc.

26.3 Inheritance

Inheritance is usually identified by the phrase "is a kind of." For example, the term "automobile " is a

generalization of "van", "car", "truck", and many others. Conversely, we can say that since cars are

automobiles so they inherit all the properties common to all the automobiles e.g. engine, steering, etc. but

capacity and type of engine, size of steering will be different from each class, based on these differences

sub-classes are created. Two concepts are used in relation to inheritance; generalization and specialization.

Classification is hierarchical in nature, a vehicle may be classified as truck or car, a car may further be Sub-

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classified as hatchback or sedan or sports or SUV. Moving up the hierarchy is terms as generalization and

down the hierarchy is referred to as specialization.

More general

(Classes)

Vehicle

Truck

Car

Sedan

Sports

More specialized

(subclasses)

A real customer such as "ABC Company" is an object/instance of the class of customers. If you have

different kinds of customers, such as domestic, commercial and industrial, you can create three new classes

of customers that are derived from of the Customer class. These derived classes use inheritance to gain

access to all of the common customer class attributes and methods. Special attributes which are unique to

each class can also be defined.

Message-Passing

Several objects may collaborate to fulfil each system action. For example, "Record CD sale" is a process,

which could involve a CD stock item, a sales transaction, a sales assistant, etc. These objects involved in the

process of CD sale communicate by sending each other message.

26.4 Encapsulation

Encapsulation means information hiding. For instance, when the Play Button is pressed, the tape is played.

However the actual process of how the tape is played is not visible. Another example can be given of

banking software. The banking software contains an option of computation of profit, when the option is

activated the amount is computed as and when required, however, the actual steps when performed remain

invisible to the user.

26.5 Polymorphism

Following example will help understand the concept in a better manner.

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Message from another

`Layers of an onion'

object requests a service.

model of an object:

Operation called only via valid

operation signature.

An outer layer of

operation signatures...

Data accessed only by

object's own operations.

...gives access to middle

layer of operations...

An object's data

is hidden

...which can access

(encapsulated).

inner core of data

Hence based on the example given above, the concept can be defined. Ppolymorphism is a derived from

Greek language meaning "having multiple forms"). Polymorphism is the characteristic of being able to

assign a different meaning or usage to something in different contexts - specifically, to allow an entity such

as a variable, a method, or an object to have more than one form.

26.6 What is Business Process Reengineering?

"Reengineering is the fundamental rethinking and redesign of business processes to achieve dramatic

improvements in critical, contemporary measures of performance, such as cost, quality, service and speed."

(Hammer & Champy, 1993)

The focus of this technique or method is to smooth the procedures and approaches undertaken by various

departments of an organization to achieve their respective objectives. The term rethinking refers to the idea

of firstly studying and then analyzing all or any of the processes to any extent depending on the need and

objective of change. The objectives to be achieved according to this definition are to qualitatively enhance

the efficiency and quality of delivery and production of goods and services. to achieve qualitative

improvement in the handling of production, procedural and customer related matters.

The concept of business process reengineering can be understood in the following manner.

"The analysis and design of workflow and processes within and between organizations"

(Davenport and Short, 1990).

The definition adds another aspect to the definition. It extends the concept of BPR by studying the links of

various procedures used by and between organizations. A number of processes undertaken within the

organization may have links with external organizations either as input or output. For example, raw material

purchases from suppliers are an integral part of planning, production and sales. Hence making the supplier

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more efficient to deliver on time becomes critical, industrial customers placing regular huge volume orders

in accordance with theirs own plans. You as the supplier need this information to input into your own

planning.

Competitive Advantage

One of the main goals of introducing BPR is to provide a competitive edge to the business and that can

only be achieved by providing a better product in a timely fashion to the customers in accordance with their

needs.

For Example, a petroleum company might be faced with issues such as, the product is being tampered with

before delivery to points of sale, and the gasoline is not being delivered on time to the points of sale, the

issues to be dealt at the dealer-owned-petrol pumps. Question: Why should it be worried, if at all?

The company may after the process review resolve the above stated issues such as redefining the design of

the containers/tanker, installing tracking devices on the delivery vehicles, setting up Company owned points

of sale, eliminating storage depots and ensuring timely direct deliveries to POS, etc.

While use of BPR helps an organization in gaining competitive advantage in the use of processes,

effectiveness and efficiency should also be kept in mind.

Effectiveness

By effectiveness, it is meant that how effective is the manner in which the product or service is offered to

the customer? This may include packaging, advertising, creating customer loyalty, timely availability in the

market, understanding customer needs & requirements related to the particular product or service being

offered.

Efficiency

The concept relates to not only how efficiently a quality product is manufactured, packed, stored and

delivered to customers/points of sale but also how quickly are customer complaints responded to, in what

manner are they removed, what is the cost of not doing so as to be compared to the cost of not doing so,

and how it can be made more efficient. Efficiency is not just about being efficient at the production floor

level but the decision making at management level also has to be efficient. Customer might not be able to

see all of the process but he can see the efficiency coming out of it.

Major steps in BPR

Senior managers may begin the task of process alignment by a series of BPR steps. These steps develop a

self-reinforcing cycle of commitment, communication, and culture change. The steps may include gaining

commitment to change through the formulation of the top team, developing a shared vision and mission of

the business and of what change is required, defining the measurable objectives, which must be agreed by

the team, as being the quantifiable indicators of success in terms of the mission, identify the Critical Success

Factors (CSF's) based on the mission of the organization.

Following steps should be followed to implement BPR.

· Break down the CSF's into the key or critical business processes and gain process ownership.

· Break down the critical processes into sub-processes, activities and task and form the teams

around these.

· Re-design, monitor and adjust the process-alignment in response to difficulties in the change

process.

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