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Chapter
13-1
Chapter 13
Data Modeling
Introduction
An Overview of Databases
Steps in Creating a Database Using Rea
Creating Database Tables and Records
Chapter
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Introduction
Modern AISs use computers
to systematically record data,

in convenient and
 useful formats
to provide easy access to required
information.
Chapter
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An Overview of Databases
A database is a collection of data that is stored in related files.
Databases are important because they:
contain valuable information,
are very large in volume,
store data in all its complexity
have to maintain privacy
contain irreplaceable data
have to be complete, comprehensive, and accurate
are priceless to Internet users
Chapter
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An Overview of Databases
Question
Which of these does not characterize a typical database?
a. large number of records
b. irreplaceable data
c. high need for accuracy
d. simple systems
Chapter
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Storing Data in Databases
To be useful, the data in an organization’s
databases must be stored and organized
efficiently.
The three important concepts are
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

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Data hierarchy
Record structures
Record keys
Data Hierarchy
Storing accounting data in computer files involves
organizing the data into a data hierarchy.
The lowest level of information in a file is a binary digit or bit.
Eight bits create a byte that represents a character.
A data field combines several characters or bytes.
A record combines related data fields.
A set of records forms a file.
A database is a collection of files that
contain all the information for an application.
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Data Hierarchy
Question
Which of these is not part of the ‘‘data hierarchy’’ (within
the context of databases)?
a. Record
b. bit
c. character
d. data type
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Record Structures and
Record Keys
The specific data fields in each record of a computer
file are part of the record structure.
Record Keys are identifiers for records:
Primary keys are unique to each record
Secondary keys are

non-unique identifiers for records and
 used for searching files for specific information
Foreign keys enable database records to
reference one or more records in other files
Chapter
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Additional Database Concerns
Administration
Documentation
Data integrity
Processing Accuracy and Completeness
Concurrency
Backup and Security
Chapter
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Administration and
Documentation
A database administrator
supervises the design, development, and installation of a
large database system, and
is responsible for its maintenance, security and revision
Documentation involves descriptions of
database structures,
contents,
security features,
E-R diagrams, and
password policies
A data dictionary is a data file about data.
Chapter
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Data integrity Processing
Accuracy and Completeness
Data integrity controls are
designed by the database developers and
are customized for the application at hand.
To achieve transaction controls database
systems
maintain an auditable log of transactions
Chapter
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Data integrity Processing
Accuracy and Completeness
can recover by

verifying that a problem has happened,
 reversing whatever entries were made, and
 starting anew. In
have the ability to audit any particular
transaction to ensure

processing accuracy and
 completeness.
Chapter
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Concurrency
Backup and Security
Concurrency controls are necessary to
prevent multiple-user access to the same file
execute transactions sequentially
Information in many accounting databases
must be protected


is stored by backup procedures for retrieval
is protected from unauthorized access by use of

passwords
 encryption techniques
Chapter
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Concurrency
Backup and Security
Question
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
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Steps in Creating
Databases with REA
An events-based accounting system (EBA) records
activities that actually happen.
The REA is a tool for designing databases.
An AIS captures data about an organization’s resources,
events and agents (REA).


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Resources are an organization’s assets.
Events are identifiable activities associated with
a business processes.
Agents are the people associated with business activities.
Steps in Creating
Databases with REA
Question
In the REA model, the ‘‘A’’ stands for:
a. agents
b. additions
c. accounts
d. associations
Chapter
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Steps in Creating
Databases with REA
The REA model requires the following steps:
identify business and economic events,
identify entities,
identify relationships among entities,
create Entity-Relationship diagrams,
identify the attributes of data entities, and
create database tables and records to
validate the database.
Chapter
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Identify Events and Entities
Business processes involve two types of events:
economic events that
 impact an organization’s financial statements
business events, that
 impact an organization in a value-added way
Database entities include
business and economic events
information about the agents were involved in them
the resources that events use or generate.
Chapter
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Identify Relationships
Among Entities
An entity-relationship (ER) diagram graphically
depicts a database’s contents.
An entity relationship may be
direct relationship or
indirect relationship
ER diagrams depict
entities being modeled and
the relationships (cardinalities) among them.
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Entity-Relationship Modeling
The E-R model
uses diamond symbols to represent relationships.
include symbols (“1” or “*”) that provide information
on cardinality.
The cardinality of a relationship describes the
number of occurrences of one entity that may be
associated with a single occurrence of the other
entity.
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Cardinality Relationships
Cardinality can be
One-to-one (1:1)
One-to-many (1:*),
many-to-one (*:1), or
Many-to-many (*:*)
Cardinalities provide useful information about
the nature of the company being modeled and
the business policies that it follows.
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Cardinality Relationships
Question
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
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Organizing Database Records
The structure of a database
is a particular method used to organize records
aims to develop this efficiently so that data can be
accessed quickly and easily.
The three types of structures are:
hierarchical,
network and
relational.
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Hierarchical Structures
Accounting data are often organized in a
hierarchy.
A hierarchical structure has successive levels
of data in an inverted treelike pattern, known
as tree structures.
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
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higher level records are parent records and
lower level records are child records
two records on same level are sibling records.
Network Structures
Databases can use a network structure to link
related records together and
capture many-to-many relationships.
The linking is accomplished with pointer fields.
The pointers maintain the data relationships.
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Relational Structures
Relational databases are more flexible.
Users can define relationships
when the database is created or
at later points in time.
Chapter
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Creating Database
Tables and Records
An Introduction to Microsoft Access
Creating Database Tables
Creating Records
Creating Database Relationships
Guidelines for Creating Database Tables
and Records
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Microsoft Access and
Database Tables
Microsoft Access
is a popular relational database
used by many businesses and individuals
used for small database applications
Creating database tables requires three items:
Field Name,

names assigned to the data fields
Data Type,

to be specified for each data field
Description
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optional field that defines record structures
Creating Records and
Database Relationships
Creating records
individual records for the data fields
Database relationships
link tables together
enable users to create multitable reports
To create database relationships
launch the relationships window,
select tables, and
link the tables.
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Guidelines for Creating
Database Tables and Records
Some guidelines for creating database tables
and records:
Design first; create tables and records last.
Name tables systematically and use conventional tbl prefixes.
Use mnemonic names for data fields.
Assign correct data types to data fields.
Data fields that link tables must be the same data type.
Limit the size of text data fields to reasonable lengths.
Use input masks.
Chapter
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Copyright
Copyright 2005 John Wiley & Sons, Inc. All rights reserved.
Reproduction or translation of this work beyond that permitted in
Section 117 of the 1976 United States Copyright Act without the
express written permission of the copyright owner is unlawful.
Request for further information should be addressed to the
Permissions Department, John Wiley & Sons, Inc. The purchaser
may make backup copies for his/her own use only and not for distribution
or resale. The Publisher assumes no responsibility for errors, omissions,
or damages, caused by the use of these programs or from the use of the
information contained herein.
Chapter
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Chapter 13
Chapter
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