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Chapter 3:
Data Modeling
Introduction
An Overview of Databases
Steps in Developing a Database Using
Resources, Events and Agents Model
Normalization
Chapter
3-1
Introduction
Uses of a modern AIS
 Systematically
 Provide
 Easy
record data
convenient and useful formats
access to information
Chapter
3-2
What is a Database?
Collection of organized data
Used by many different computer
applications
Manipulated by database management
systems (DBMS)
Chapter
3-3
Significance of a Database
Critical information
Volume
Distribution
Privacy
Irreplaceable data
Need for accuracy
Internet uses
Chapter
3-4
Storing Data in Databases
Data must be stored and organized
systematically
Three important concepts:



Data hierarchy
Record structures
Database keys
Chapter
3-5
Data Hierarchy
Data organization in ascending order:
Data
field
Record
File
Database
Chapter
3-6
Record Structures
Data fields in each record of a database table
Structure is usually fixed
Example
Chapter
3-7
Database Keys
Primary Key
Unique
to each record
Foreign Keys
Enable
referencing of one or more records
Matches
primary key of related table
Chapter
3-8
Records Combined Into
Report
Chapter
3-9
Additional Database Issues
Administration
 Database
Administrator
Documentation
 Includes
a variety of descriptions
 Structures, Contents, Security Features
 Data Dictionary
 Metadata
Chapter
3-10
Data Dictionary Example
Chapter
3-11
Additional Database Issues
Data Integrity
 Data
Integrity controls
 Designed by database developers
Processing Accuracy and Completeness
 Transaction
controls
 Ensures accurate transaction processing
Chapter
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Additional Database Issues
Concurrency
 Concurrency
controls
 Prevent multi-user access at same time
Backup and Security
 Ability
to recreate data
 Prevent unauthorized access
 View controls
Chapter
3-13
Study Break #1
The part of the data hierarchy that represents one instance of
an entity is a:
A. Field
B. Record
C. File
D. Database
Chapter
3-14
Study Break #1 - Answer
The part of the data hierarchy that represents one instance of
an entity is a:
A. Field
B. Record
C. File
D. Database
Chapter
3-15
Study Break #2
Within the context of databases, the term “concurrency” refers
to the possibility that:
A. A customer of one store might also be a customer of another
store
B. Two database users might want to access the same record at
the same time
C. A credit entry for a customer requires a debit entry for a
matching account
D. None of these
Chapter
3-16
Study Break #2 - Answer
Within the context of databases, the term “concurrency” refers
to the possibility that:
A. A customer of one store might also be a customer of another
store
B. Two database users might want to access the same record at
the same time
C. A credit entry for a customer requires a debit entry for a
matching account
D. None of these
Chapter
3-17
REA Model
Resources

Organization’s assets
Events

Activities associated with a business processes
Agents

People associated with business activities
Chapter
3-18
Steps in Developing
Databases with REA
Identify Business and Economic Events
Identify Entities
Identify Relationships Among Entities
Chapter
3-19
Steps in Developing
Databases with REA
Create Entity-Relationship Diagrams
Identify Attributes of Entities
Convert E-R Diagrams into Database Tables
Chapter
3-20
Identify Events and Entities
Types of Events
 Business
 Economic
Types of Database Entities
 Entities
 Agents
 Resources
Chapter
3-21
Entity Examples
Chapter
3-22
Identify Relationships
Among Entities
Types of Relationships
Direct relationship
 Indirect relationship

Cardinalities

Nature of relationships among entities
Chapter
3-23
Cardinality Relationships
Notations

One-to-one (1:1)
 One-to-many (1:N)
 Many-to-many (N:N)
Purpose

Occurrence of one entity
 Associated with occurrence of one event of another entity
Chapter
3-24
Cardinality Relationships
Chapter
3-25
Entity-Relationship Diagram
Purpose
 Diagram
entities
 Relationships among entities
Structure
 Rectangles
represent entities
 Connecting lines represent relationships
Chapter
3-26
E-R Diagram Example
Chapter
3-27
Relationship Tables
Provide greater flexibility
Need for Relationship Tables
 Linking
tables with foreign keys
 Many-to-many relationships
Chapter
3-28
Relationship Tables
Chapter
3-29
Schematic of Database Tables
Chapter
3-30
Study Break #3
In the REA model, the “A” stands for:
A. Agents
B. Additions
C. Accounts
D. Associations
Chapter
3-31
Study Break #3 - Answer
In the REA model, the “A” stands for:
A. Agents
B. Additions
C. Accounts
D. Associations
Chapter
3-32
Study Break #4
Which of these is not a cardinality between two database
entities?
A. One-to-one
B. None-to-none
C. One-to-many
D. Many-to-many
Chapter
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Study Break #4 - Answer
Which of these is not a cardinality between two database
entities?
A. One-to-one
B. None-to-none
C. One-to-many
D. Many-to-many
Chapter
3-34
Normalization
Normalization

Methodology ensuring attributes are stored in most
appropriate tables
 Design promotes accuracy
 Avoids redundancy of data storage
Levels



First normal form
Second normal form
Third normal form
Chapter
3-35
Unnormalized Data
Chapter
3-36
First Normal Form
In First Normal Form (1 NF) when:
 All
data fields are singular
 Each attribute has one value
Problems
 Data
redundancy
 Insertion anomaly
 Deletion anomaly
Chapter
3-37
First Normal Form Example
Chapter
3-38
Second Normal Form
In Second Normal Form (2 NF) when:
 It
is in 1 NF
 All data items depend on primary record key
Benefits
 More
efficient design
 Eliminates data redundancy
Chapter
3-39
Second Normal Form
Example
Chapter
3-40
Third Normal Form
In Third Normal Form (3 NF) when:
 It
is in 2 NF
 Does not contain transitive dependencies
 Data field A does not determine data field B
Ultimate Goal
 Create
database in 3 NF
Chapter
3-41
Third Normal Form Example
Chapter
3-42
Study Break #5
A database is in third normal form (3NF) if it is second normal
form and:
A. All the data attributes in a record are well defined
B. All the data attributes in a record depend on the record key
C. The data contain to transitive dependencies
D. The data can be stored in two or more separate tables
Chapter
3-43
Study Break #5 - Answer
A database is in third normal form (3NF) if it is second normal
form and:
A. All the data attributes in a record are well defined
B. All the data attributes in a record depend on the record key
C. The data contain to transitive dependencies
D. The data can be stored in two or more separate tables
Chapter
3-44
Copyright
Copyright 2012 John Wiley & Sons, Inc. All rights reserved.
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information contained herein.
Chapter
3-45
Chapter 3
Chapter
3-46