Database Design and Development

John Wiley & Sons

Chapter One

CHAPTER OBJECTIVES

Understand how the database approach is different and superior to earlier data systems

Examine how information demand and technology explosion drive database systems

Trace the evolution of data systems and note how we have arrived at the database approach

Comprehend the benefits of database systems and perceive the need for them Survey briefly various data models, types of databases, and the database industry

Consider the following scenarios:

You meet someone in a computer store. As a knowledgeable IT professional, you want to help this person. He says he is looking for database software to keep the names and addresses of his customers to do his mailings and billings. But what he really needs is a mail-merge program.

You call your travel agent to make your airline reservations for the vacation you have been waiting for all year. The agent responds by saying that she cannot do that just now because the database is down. She really means that the reservations computer system is not working.

Here is one more. You call your cellular phone company to complain about errors on the latestbilling statement. The phone company representative says that the database must have printed some incorrect numbers. What the representative really implies is that the billing application has miscalculated the charges.

In our modern society most people know the term database without understanding its full and clear meaning. Even in information technology circles, not everyone knows the concepts in reasonable detail. What is a database? Is it data? Is it software? Is it the place where you store data? Is there something special about the way you store data? Is it how you store and retrieve data? What exactly is a database system? What are the features and functions? Many more such questions arise.

Today, almost all organizations depend on their database systems for the crucial information they need to run their business. In every industry across the board, from retail chain stores to financial institutions, from manufacturing enterprises to government departments, and from airline companies to utility businesses, database systems have become the norm for information storage and retrieval. Database systems form the centerpiece of the growing and maturing electronic commerce. Database and Web technologies have merged.

The Information Technology department of today's organization has a primary responsibility: The department has to support and keep the database systems running. In this transformed computing environment, knowledge of database systems is no longer confined only to specialists such as data analysts and database administrators. Are you are a systems analyst, programmer, project leader, or network specialist? Then you also need to know the basics of database systems. You also need to grasp the significance of the database approach. All IT professionals need to study the basic principles and techniques of database design and development.

First, let us begin to understand how we got to this stage where most organizations depend on their database systems for running the business. Let us trace the evolution of data systems and see the essential need for the database approach. Let us understand what exactly the database approach is. Let us briefly survey the database industry and grasp the significance of the developments.

EVOLUTION OF DATA SYSTEMS

How were companies running their business before computers came into use? Even at that time, organizations needed information to execute the business processes, sell goods and services, and satisfy the needs of customers. Manual files supported business operations. Accounting personnel performed manual calculations and prepared invoices. Payroll departments manually wrote the checks. Business operations were reasonably satisfactory.

So, what happened? How did we get to the computer database systems of today? When computers were introduced in the 1960s, computer file systems replaced the manual files. This marked a significant leap in the way data was stored and retrieved for business operations. What has been really happening from that time until now, when database systems have become the norm? What prompted the progress toward database systems?

From the 1970s onward, two striking and remarkable phenomena were distinctly observed. Refer to Figure 1-1 indicating these two major developments.

First, demand for information has escalated in every organization. Organizations have steadily become global and widespread. Organizations have to contend with fierce competitive pressures. They need vast and complex information to stay in business and make a profit. Second, the past three decades have witnessed a huge, explosive growth in information technology. Processors have become faster, cheaper, and smaller. Operating systems have become powerful and robust. Data storage media have expanded tremendously in capacity; data storage prices have tumbled. Network and communication technology can now connect any remote site without difficulty. Application programming and people-machine interface have dramatically improved.

The escalating demand for information and the explosive growth in information technology have worked hand in hand to bring about the evolution to database systems. Ever-increasing demand for information drives the need for better methods of storing and retrieving data, for faster ways of processing data, and for improved methods of providing information. The demand for more and better information drove the technology growth. Progress in technology, in turn, spurred the capability to provide different types of information, not just to run day-to-day operations of an organization, but also to make strategic decisions.

Let us first examine the pertinent aspects of the technology explosion as related to data systems, because these are what we are specifically interested in. Then let us discuss the escalating demand for information that has prompted better and improved data systems.

Technology Explosion

If you have been in the information technology area for 5-10 years, you are certainly an eyewitness to the explosive growth. Growth is not confined to any one sector. All aspects of the technology have been improving tremendously. Here are some specifics:

Twenty-five years ago, there were only 50,000 computers in the whole world; now more than 500,000 are installed every day.

More than 60% of American households have at least one computer; more than 50% have e-mail and Internet access.

Growth of the Internet and the use of the Web have overshadowed the PC breakthrough of the 1970s; at the beginning of 2000, about 50 million households worldwide were estimated to be using the Internet; by the end of 2005, this number is expected to grow 10-fold.

About 7 years ago, there were only 50 websites; now 100,000 are added every hour.

Databases in the terabyte range are becoming common; a few years ago, even the gigabyte range was unusual.

In the mid-1960s, programmers in large corporations had to write programs that had to run on 12K machines; today even your personal computer at home has 10,000 times larger memory.

Growth has not been isolated here and there in hardware and software. We notice explosive growth in all sectors of information technology. Let us proceed further to look at specific areas of information technology that are related to data systems.

Data Storage Devices Have you seen an 80-column card that very early computer systems used to store data? Each column in a card had holes punched to represent a single character. So a card could hold up to 80 characters. Keypunch operators typed data and program code into the cards. In the next stage, computer systems stored data on magnetic tapes. Initially, magnetic tapes of 800 BPI (bytes per inch) were used. Then we moved on to higher densities of 1600 BPI and 6250 BPI. For a brief while, paper tapes with punched holes were used as the storage medium. Special-purpose paper tape readers were used to read data from paper tapes.

It was a large leap forward when disk drives began to replace the earlier data storage media. Disk drives in mainframes consist of sets of large circular disks arranged in parallel with a common spindle. Sophisticated disk drives have come to stay as the common storage device of choice. Today's data servers use RAID (redundant array of inexpensive disks) technology as the advanced fault-tolerant storage system. Data storage devices have progressed tremendously from the primitive punched cards to the sophisticated RAID systems.

Three-and-a-Half-Inch Disk Drives You are very familiar with the three-and-a-half-inch disk drives in your home computer system. Just review the progress in the capacities of these disk drives. See how the capacities kept doubling every year. Note the following details:

1992 1 gigabyte

1993 2 gigabytes

1994 4 gigabytes

1995 9 gigabytes

1997 18 gigabytes

2000 50 gigabytes

Computer Applications Over the years, the types of computer applications have changed and progressed from mere bookkeeping applications to multimedia and data mining applications. Some of you might remember the days when the computer department was known as the data processing department. Applications in those days just processed data in elementary ways to produce some reports. The technology explosion resulted in a grand transition of computer usage from simple to increasing sophistication. Review the following details.

Data Processing Applications (DP). In the early days of computing, computer departments built applications just to replace clerical labor. Mostly, these applications performed simple accounting and financial functions. These applications produced straightforward reports. Speed and accuracy of the computer in performing calculations were the primary factors. Computer systems stored and retrieved data from magnetic tapes and earlier versions of disk drives. Applications used sequential or flat files to organize data.

Management Information Systems (MIS). In the next stage, growth of technology manifested itself in applications that went beyond accounting and finance to supporting the entire core business of an organization. Applications began to appear to process orders, manage inventory, bill customers, pay employees, and so on. Organizations depended on their management information systems for their day-to-day business. Storage and retrieval of data mostly depended on hard disks. Many applications adopted the use of database technology.

Decision-Support Systems (DSS). Further technology growth in processor speed, storage media, systems software, and database techniques pushed the application types to systems that supported strategic decision making. These applications are not meant for supporting day-to-day operations of a business but for providing information to executives and managers to make strategic decisions. In which markets should the company expand? Where should the next distribution warehouse be built? Which product lines should be discontinued? Which ones should be boosted? These applications dealt with sales analysis, profitability analysis, and customer support. Decision-support systems made use of improved storage facilities and newer features of database technology.

Data Warehousing (DW) and Data Mining (DM) Systems. In recent years, with the enormous progress in processor scalability, mass storage, and database methods, organizations are able to forge ahead with their applications, especially in building data warehousing and data mining systems. These recent decision-support systems, much more sophisticated than earlier attempts, require large volumes of data and complex analytical techniques. These systems need large databases specially designed and built separately from the databases that support the day-to-day operational systems.

Data Systems What is the effect of the technology explosion on the way data is organized? Over the years, how were businesses organizing data? We just looked at the way applications have progressed from simpler types toward increasing sophistication. What about data systems?

Manual-Type Records. Very early computer applications worked with data stored on punched cards and paper tapes. Keypunch operators prepared data on these primitive media from manual files and records. Computer applications read data from cards and tapes to prepare reports.

Sequential Files. Improved storage media such as magnetic tapes and early disk drives enabled application developers to organize data as sequential (or flat) files. Each file contained data records of the same type arranged sequentially one after the other, usually in the order in which they were created. Sorting techniques allowed data records to be resorted in a different sequence.

Databases. Increased sophistication in data storage techniques on hard disk drives and enhancements to operating systems enabled random and quick access of data. Data systems moved to a wholly new level. Applications were able to store data in databases and retrieve data sequentially and randomly.

Demand for Information

Of the two major factors that mutually contributed to the database approach to computing, so far we have considered the explosive growth of technology. Let us now turn our attention to the other factor, namely, the escalating demand for information. It is not just more information that organizations need. The demand for information includes several dimensions.

Consider how billing requirements and sales analysis have changed. In the early years of computing, organizations were happy if they could bill their customers once a month and review total sales by product quarterly. Now it is completely different. Organizations must bill every sale right away to keep up the cash flow. They need up-to-date customer balance and daily and cumulative sales totals by products. What about inventory reconciliation? Earlier systems provided reports to reconcile inventory or to determine profitability only at the end of each month. Now organizations need daily inventory reconciliation to manage inventory better, daily profitability analysis to plan sales campaigns, and daily customer information to improve customer service.

In the earlier period of computing, organizations were satisfied with information showing only current activity. They could use the information to manage day-to-day business and make operational decisions.

Continues...

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Excerpted from Database Design and Development by Paulraj Ponniah Copyright © 2003 by John Wiley and Sons, Inc. . Excerpted by permission.
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