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Introductory Data Management Principles

Module F01c

In this "information age" business, government, and individuals depend more and more on storing and retrieving facts using computers.

Data management is one of the most complex and awesome tasks facing computer users and professionals. Just think: as information about the world and its people piles up, how can we keep track of it? How can we find what we need when we need it? This module will introduce you to principles and techniques used in this great task.

 

Three main types of data stored in computers


To set the scene, let's think about what types of information computers store. There are three main types:
  1. Numbers (after all, we call it a "computer" so it must be able to do the numbers!)
  2. Characters (letters, digits, and symbols - using number codes)
  3. Instructions (they work like phone numbers)

In addition, computers store lots of other kinds of information, such as...

  • Dates (remember the Y2K fuss?)
  • Graphic images
  • Sounds
  • Video

New kinds of data are put into the computer all the time, but the secret is: they're all numbers. Anything can be stored in a computer, as long as someone can figure out a way to represent it with numbers. For more information how how computers store things, see module G15c, "Data Storage Principles" http://www.wccnet.org/dept/cis/mod/g15c.htm.

 

Types of storage used in Data Management Systems

 

To store all this information, computers use numbers, characters and special codes. These are usually put into Fixed-length records and fields.

What does this look like?

  • There is no separation between records or fields
  • Character and number data mixed together

Here's an example:

     ¤ kT  ÇkT  @kT  ÇkT  ÇkT  `kT  ákT  ` kT ` k kT  ákT ¤ `fT _ 1  ]T É ]T   ]T ¶ _  Salutation -c _¤  LastName _Æ _c  _¤  Fi _¤  Country _Æ Yc  _¤  Phone F _Æ uc¤ ¤ _¤  Notes F _Æ æc

The strange characters ( ¤ á Æ) are actually numeric data mixed in with the character data. Since Web browsers and computer printers always work with character data, they try to show everything as a character, even if it isn't meaningful to us humans! So...

How can a program tell...

It must get data format information.

 

What is Data Format Information?

 

Data format information = "data about data"

Data format information includes things like...

  1. Type of storage: is this data character, numeric, or some variation?
  2. Size: How big the fields are
  3. What fields' names are
  4. How to display the information on screen or on paper.
  5. ...and any other information needed internally.

Two places for data about data 

There are two places data about the data are ordinarily placed. Take a look at the advantages and disadvantages of each:

With the Program

Data Processing Programs

With the Data

Data Management Systems

 

Advantages:

  • Simpler and more straight-forward to write data processing programs
  • Historically, this was "the way it was always done"

 

Advantages:

  • One program can read many types of data files
  • You don't have to be a programmer to create a data file
  • It's relatively easy to add or change types of information stored

Disadvantages:

  • A new program must be written for each new type of data file
  • It can be very complicated to add new types of information to an old file

Disadvantages:

  • It's complicated to write a program that can read many types of data files
  • One data management system usually cannot read files created by a different data management system.

Data management comes in 2 styles 

The two main "flavors" of data management systems are File Management Systems (FMS) and Database Management Systems (DBMS). Here's a comparison of the two types:

File Management Systems (FMS):

Database Management Systems (DBMS):
One data file at a time
  • Simpler to use, less expensive but limited capability.
  • Good for personal use; small business, simple files.
  • Examples: address lists, (home) inventory... Popular FMS: Windows CardFile; Microsoft Works
 Several related data files handled
  • More flexible, more powerful, more difficult to learn

    • (Many can be used as FMS initially.)
  • Good for organizational use.
  • Examples: personnel, products, business inventory...
  • Popular DBMS: Oracle, Microsoft Access, Lotus/IBM Approach, Borland Paradox, Claris FileMaker Pro
  • Why would anyone want to handle more than one data file at the same time?...a business example - catalog order processing:

    • Customer file
    Inventory file
    Accounts Receivable file
    Personnel file (to assign commissions)

General Procedure for Data Management System Use 

Building under Construction

 

Want to put some data on the computer? Data Management Systems make it relatively easy to put information in the computer and get it back in useful ways. Of course, setting up a large database for an organization can be quite complex, but the process is fundamentally the same in both cases. Here's a simple overview:

1. Plan the data requirements:

  • This is often hurried over too fast, with long-lasting consequences.
  • We need to think ahead -plan for the future.
  • Consider the information to be stored, its size and data type.
  • Consider the overall file organization: how should it be sorted, what are the keys, and how is information in the database related.

2. Define file(s): supply data format information

  • Use file definition feature of the data management system

3. Enter data: data management systems have a data entry feature

  • Uses information supplied during definition (step 2)

4. Verify and correct the data:

  • Remember GIGO principle!
  • Use the editing feature of the data management system.

5. Organize and output data:

  • The data management system needs to know which records to show;
  • It needs to know what order to put them in;
  • It needs to know how you want them printed out.
  • It puts all this together with data format information to produce a report.

Important Data Management Tools

RDBMS
ODBMS
SQL


As you get more familiar with data management, you'll hear a number of tools mentioned. Let's take a look at a few of the more important ones, and the names you'll hear them called:

RDBMS: Relational DataBase Management System

Relational databases are organized into multiple simple tables which are related to one another by common data fields. Now the most widely used of the high-powered DBMSs, RDBMS was not the first historically. This way of organizing information has all but replaced earlier DBMS models ("hierarchical" and "network") because of its flexibility and simplicity. [For more detail visit WhatIs.com: http://www.whatis.com/relation.htm]

ODBMS:: Object-oriented DataBase Management System

Some database designers are looking to a new model inspired by "object-oriented programming" as an alternative to the RDBMS model. Object-oriented programming takes the database idea one step further: data becomes "intelligent" in that in "knows" how to behave - that is, data is associated not only with data format information but also with instructions for handling it. [For more detail visit WhatIs.com: http://www.whatis.com/relation.htm]

SQL: Structured Query Language (often pronounced "sequel")

The closest thing we have to a universal language among the diverse database systems, SQL is a systematic way of asking a database for specific information, and is implemented by most database programs. [For more detail visit WhatIs.com: http://WhatIs.com/sql.htm]

 

Review Link

 Click here to study review questions for this module. (http://courses.wccnet.org/computer/mod/f01cr.txt)

Audience

 
This is for people who are familiar with data storage principles (see module G15c), and who want to know about programs to store information on computers. 

Objectives 
When you successfully complete this lesson, you will demonstrate understanding of...
  • The basic principles of data management systems:
    • what data format information is;
    • Why programs need data format information;
    • Separation of program and format information;
  • The difference between file management and database management systems;
  • The applications for which each type of data management system is most useful;
  • The general procedure for using data management systems, from file definition through data input and listing of output;
  • The role of data file definition in data management systems;
  • The role of report formatting in data management systems.

About this Document 

Module F01c:

This document is part of a modular instruction series in Computer Information Systems. For more information, see the overview or the list of modules in this series, F: File Management Systems. This document has been used in the following classes: 
Author:
Laurence J. Krieg
Institution:

Department of Computer Information Systems, Washtenaw Community College
History:
Original: 22 March 1988
Amplified HTML version 15 October 1996; Revised 16 November 1999;
"Tools" section split into X60c 20 March 2005
Copyright:
Copyright © 1999-2005, Laurence J. Krieg, Wahstenaw Community College
Instructors: You may point to this file in your Web-based materials. 
Students: you may make a copy for your personal use. 
All other uses: contact the author, Laurence J. Krieg for permission.
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