Page 95 - DCAP516_COMPUTER_SECURITY

Unit 8: Introduction to Databases

Objectives Notes

After studying this unit, you will be able to:
Define a database

Explain need, advantages and disadvantages of database
Describe various types of database models
Know about the database system and its application

Introduction

Information is measured in bits, just as length is measured in metres and time is measured in
seconds. Of course, knowing the amount of information is not the same as knowing the
information itself. Different scales of length are needed in different circumstances. Sometimes
we want to measure length in kilometers and sometimes in inches. Similarly, other scales for
information besides ‘bits’ are sometimes needed; in the context of physical systems information
is often measured in Joules per Kelvin. Some important facts about information are as follows:
Information can be learnt through observation, experiment, or measurement.
Information is subjective, or observer dependent. What A knows may be different from
what B knows. If informations were not subjective, there would be no need to communicate
it.

A person’s uncertainty can be increased upon learning that there is an observation about
which information may be available, and then can be reduced by receiving that information.

Information can be lost through loss of the data itself.
The physical form of information is localized in space and time. As a consequence –
information can be sent from one place to another and can be stored and then retrieved
later.

The information useful for communication and storage requires the processing of data. Data is
a collection of numbers, characters, alphabets, and special symbols etc. that can be processed to
produce some meaningful information.

8.1 Data Concepts

The word, data, is a plural of datum, though data is commonly used to represent both the
singular form and plural form. Now before proceeding further let us have a look to the definition
of data. “Data is commonly defined as raw facts or observations”. These facts can be from
physical processes, business transactions, surveys, investigations, etc. For example, if a person
went to the Mount Everest and when he returns, he will provide lot of data for the next person
going to the Mount Everest. Data are the objective measurements of the attributes of entities
such as place, people, things, and events. These measurements are usually represented by symbols
such as numbers and words or by codes composed of a mixture of numerical, alphabetical, and
other characters. However, data commonly takes a variety of forms including numeric data,
text, voice and images.
Data and information are often used interchangeably. But it is helpful to view data as raw
material. This data when processed got, converted into finished information product. But data is
usually not useful until subjected to a value added process where:
Its form is aggregated, manipulated and organized.

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