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2009 Pearson Education, Inc. Publishing as Prentice Hall 1

Lecture 8

Chapter 1: The Database Environment

Modern Database Management

9thEdition

Jeffrey A. Hoffer, Mary B. Prescott,

Heikki Topi

Presentation Adapted by

Dr. Mahmoud Youssef

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Important!

This lecture includes significant amount oftheoretical information.

In order to study the materials in thislecture correctly, check the objects

Exam questions will be based on these

objectives

2

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Objectives

Definition of terms

Name limitations of conventional file processing

Explain advantages of databases

Identify costs and risks of databases

List components of database environment

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Definitions I

Database: organized collection of logicallyrelated data

Data is organized in some way, usually tables

Logically related. There are relationships between thedata elements that reflect the nature of the business.

For example, when there is a relationship between customerdata and order data, such relationship follows from thebusiness practices that orders are places by customers.

Notice also that this relationship is needed to satisfyinformation needs. E.g., when we want to have a reportabout orders made by each customer from year beginninguntil today (Y-T-D).

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Definitions II

Data: stored representations of meaningfulobjects and events

Objects (things) such as customers, orders, products

Events (actions or activities) such as placing an order,depositing money, issuing national card.

Data can be classified into two types

Structured: numbers, text, dates

Unstructured: images, video, documents

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Definitions III

Information: data processed to increaseknowledge in the person using the data

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Figure 1-1a Data in context

Context helps users understand data

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Graphical displays turn data into usefulinformation that managers can use for

decision making and interpretation

Figure 1-1b Summarized data

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Definitions IV

Metadata: data that describes the properties andcontext of user data

Usually, the term metadata is used to mean

data about data or simpler data that describedata.

For a book, the title, the author name, and allthe front matter can be considered metadata.

In databases, metadata is usually the data thatdescribe the data in the database

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Descriptions of the properties or characteristics of thedata, including data types, field sizes, allowable

values, and data context

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File Processing I

Before the use of databases in informationsystems, data used to be stored in files. Thisapproach has many problems that led to thedevelopment of databases and using them in

information systems.

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File Processing II

12

09100400, Ahmed Mohamed Hussein, 12 Tahrir St. Dokki, Cairo, 13/3/1990, Finance09100401, Samy Ibrahim Saber, 15 Korneish Road, Cairo, 28/8/1989, Marketing

Only the programmer who designed this file knows what these fieldsare and how they can be used and that is coded in the application notwith the data. In other words, the metadata is maintained withinapplicationsNotice also that other files may use another separator such as the TABcharacter rather than the comma in this case. As such there is noconsistent file structureThese are just a few limitations of the file approach.

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Problems with Data Dependency

Each application programmer must maintainhis/her own data

Each application program needs to includecode for the metadata of each file

Each application program must have its ownprocessing routines for reading, inserting,updating, and deleting data

Lack of coordination and central control Non-standard file formats

Teaching Note:If you dont understand the above dont memorize it

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Disadvantages of File Processing

Program-Data Dependence All programs maintain metadata for each file they use

Duplication of Data Different systems/programs have separate copies of the same data

(see slide 14)

Limited Data Sharing No centralized control of data

Lengthy Development Times Programmers must design their own file formats

Excessive Program Maintenance 80% of information systems budget

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Duplicate Data

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SOLUTION:

The DATABASE Approach Central repository of shared data

Data is managed by a controllingagent (Database ManagementSystem)

Stored in a standardized, convenientformRequires a Database Management System (DBMS)

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Database Management System

DBMS manages data resources like an operating system manages hardware resources

A software system that is used to create, maintain, and providecontrolled access to user databases

Order FilingSystem

InvoicingSystem

Payroll

System

DBMSCentral database

Contains employee,order, inventory,

pricing, and

customer data