Download Chapter 6

Core Concepts of
ACCOUNTING INFORMATION SYSTEMS
Moscove, Simkin & Bagranoff
Developed by:
Marianne Bradford, Ph.D.
Bryant College
John Wiley & Sons, Inc.
Chapter 6
Databases and Data Modeling
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Introduction
Database Concepts
Database Design and Data Modeling
Database Structures, Object-Oriented
Databases, and Multimedia Databases
• Database Management Systems
Database Concepts
• A database is a collection of data that is stored
in related files. Reasons why databases are
important are:
• Valuable information
• Volume
• Complexity
• Privacy
• Irreplaceable data
• Storage costs
• Internet users
Storing Data in Databases
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To be useful, the data in an
organization’s databases must be stored
and organized efficiently.
Three important concepts are
1. Data hierarchy
2. Data warehouses
3. Record structures
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.
• Eight bits create a byte that represents a
character.
• A data field combines several characters.
• 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.
Characteristics of a
Data Warehouse
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A data warehouse pools data from separate
applications into a large common body of
information.
Characteristics of data warehouses
1. Data are “clean” of errors and defined uniformly.
2. Data are stored in several databases, not just one.
3. Data Warehouses span a longer time horizon than
the company’s transaction systems.
4. The data relations are optimized for answering
complex questions.
Advantages of
Data Warehouse
• Make organizational information available on a
corporate-wide basis, which is central to the
concept of enterprise-wide databases.
• Facilitates data mining and enables users to
identify target markets or its most desirable
customers.
Record Structures and
Record Keys
• The specific data fields in each record of a
computer file are part of the record structure.
• 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
REA Framework
• An events-based accounting system (EBA) records
activities simply because they happen not because
the system requires it.
• The REA is a tool for designing databases.
• Using this model, an AIS captures data about an
organization’s resources, events and agents (REA).
• Resources are an organization’s assets.
• Events are identifiable activities associated with a
business processes.
• Agents are the people associated with business
activities.
Normalization
• Flat files are files with no sequence or
order to them, except perhaps
chronological.
• Flat files make it almost impossible to
find a particular record easily or use
file data productively.
• Normalization is a process of examining
and arranging file data in a way that enables
designers to avoid problems when files are used
or modified later.
First Normal Form
• A database is in first normal form (1NF)
if all the record’s attributes (data fields)
are well defined and the information can
thus be stored in a flat file.
• Problems:
– data redundancy
– insertion anomaly
– deletion anomaly
Second Normal Form
• A database is in second normal form
(2NF) if it is in 1NF and all the data items
in each record depend on the record’s
primary record key.
• This approach results in a more efficient
design and eliminates much of the first
file’s data redundancy.
Third Normal Form
• Our goal is to create a database that is
minimally in third normal form (3NF).
• A database is in third normal form if it is
in second normal form and contains no
transitive dependencies - i.e., no
relationships in which data field A
determines data field B.
Entity-Relationship Modeling
• An entity-relationship (ER) diagram
graphically depicts a database’s contents.
• Entities are resources, events and agents.
• ER diagrams depict entities being
modeled and the relationships
(cardinalities) among them.
Entity-Relationship Modeling
• The E-R model uses diamond symbols to
represent relationships.
• E-R diagrams 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.
Cardinality Relationships
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One-to-one (1:1)
One-to-many or many-to-one (1:*), (*:1)
Many-to-many (*:*)
Cardinalities provide useful information
about the nature of the company being
modeled and the business policies that it
follows.
User Views
Schemas and Subschemas
• The database schema is a map or plan of the
entire database.
• Any particular user or application program
will be interested in only a subset of the
schema, called the subschema.
• A database must be flexible enough
to satisfy the subschema
uses required.
Online Analytical Processing
• Complex multidimensional data analysis
performed on database information is
called online analytical processing
(OLAP).
• OLAP packages allow end users
to perform their own database
analysis, including data mining.
Data Dictionaries
• A data dictionary describes the data fields
in each database record.
• It is usually a separate computer file that is
created and maintained by the
administrators of the database.
• Uses
– Documentation aid
– Audit trail
– Investigating internal controls
Database Concerns for AISs
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Data integrity
Processing Accuracy and Completeness
Concurrency
Security
Database Structures
• A particular method used to organize
records in a database is called the
database’s structure.
• The objective is to develop this
structure efficiently so that data
can be accessed quickly and easily.
• Three types of structures are:
1) hierarchical, 2) network
and 3) relational.
Hierarchical Structures
• Accounting data are often organized in a
hierarchy.
• A hierarchical structure has successive levels of
data in an inverted treelike pattern, also known
as tree structures.
• 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.
Relational Structures
• Relational databases are more flexible.
• Users can define relationships at the time
the database is created or at
later points in time.
Object-Oriented and
Multimedia Databases
• The object-oriented database (OODB)
contains both the text data of
traditional databases plus information
about the set of actions that can be
taken on the data fields.
• Many OODBs are multimedia
databases that include graphics,
audio information and animation.
Database Management
Systems
• A database management systems (DBMS) is a set
of separate computer programs that enable users
to create, modify, and utilize database
information more efficiently.
• The data definition language (DDL) of a DBMS
enables users to define the record structure of any
particular database table.
• The data manipulation language (DML) enables
users to perform tasks such as querying, changing
records and deleting records.
Data Manipulation
Languages
• Many relational databases support
structured query language (SQL).
• Hypertext can also be used for finding
information in a database.
• End-user programming allows users
to perform their own data
processing without technical
assistance from IT professionals.
Copyright
Copyright 2001 John Wiley & Sons, Inc. All rights reserved.
Reproduction or translation of this work beyond that permitted in
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the use of the information contained herein.
Chapter 6