Organizing

Data and Information

C H A P T E R

5

The Hierarchy of Data

DatabaseCollection of data organized to meet users’ needs

Database management system (DBMS) Software consisting of a group of programs that

manipulate the database and provide an interface between the database and the application programs

The Hierarchy of Data

Data is generally organized in a hierarchy that begins with the smallest piece of data (a bit) and progresses through thehierarchy to a database.

The Hierarchy of Data

Character Basic building block of information, represented by a byte

(0,1)

Field A name, number, or combination of characters that

describes an aspect of a business activity

The Hierarchy of Data

Record Collection of related fields

File Collection of related records

DatabaseCollection of integrated and related files

Data Entities, Attributes, and Keys

EntityGeneralized class of people, places, or things for which

data is collected, stored, and maintained

Attribute Characteristic of an entity

Data itemSpecific value of an attribute

Data Entities,Attributes, and Keys

Key A field or set of fields in a record that is used to identify

the recordPrimary key

A field or set of fields that uniquely identifies the record

Secondary key A field in a record that does not uniquely identify the record

Keys and Attributes

Entities (records)

Key field Attributes

The Traditional Approachto Data Management

[Figure 5.3]

Flaws in the Traditional Approach

Data redundancy Duplication of data in separate files

Data integrity The degree to which the data in any one file is accurate

Program-data dependence Potential for incompatible programs and data between

applications

The Database Approach to Data Management

Data management in which a pool of related data is shared by multiple application programs

Rather than having separate data files, each application uses a collection of data that are either joined or related in the database.

The Database Approach to Data Management

[Figure 5.4]

Advantages of theDatabase Approach

Improved strategic use of corporate data Reduced data redundancyImproved data integrityEasier modification and updatingData and program independence

Advantages of the Database Approach

Better access to data and informationStandardization of data accessA framework for program developmentBetter overall protection of the dataShared data and information resources

Disadvantages of the Database Approach

Relatively high cost of purchasing and operating a DBMS in a mainframe operating environment

Specialized staff

Increased vulnerability

Database Considerations

Content What data is to be collected at what cost?

AccessWhat data is to be provided to which users when

appropriate?

Database Considerations

Logical structureHow is the data to be arranged so that it makes sense to a

given user?

Physical organizationWhere is the data to be physically located?

Types of Database Design

Logical design An abstract model of how the database should be

structured and arranged to meet an organization’s information needs

Physical design A model of how the data will be organized and located

within the database

Data Modeling and Entity-Relationship Diagrams

Data modelA map or diagram of entities and their relationships

Enterprise data modeling Data modeling done at the level of the entire organization

Entity-Relationship(ER) Diagrams

Diagrams that use basic graphical diagrams to show the organization of and relationships between data

Relationships include:One-to-one (1:1)One-to-many (1:N)Many-to-many (N:M)

[Figure 5.5]

An Entity-Relationship Diagram

An ER diagram for a customer ordering database

Entities

Relationship

Attributes

Database Models

Hierarchical (tree) models

Network models

Relational models

Hierarchical Database Model

A model in which the data is organized in atop-down or inverted tree-like structure

[Figure 5.6]

Network Models

An extension of the hierarchical model,in which a member may have many owners

[Figure 5.7]

Relational Models

Data organized in tabular format (rows and columns)Relations: Two-dimensional tables into which data

elements are placedTuple: Each row of a table Attributes: Columns of the tableDomain: Values for attributes or columns

Relational Models

[Figure 5.8]

Data Manipulations

SelectingEliminating rows according to certain criteria

ProjectingEliminating columns in a table

Data Manipulations

Joining Combining two or more tables

LinkingJoining tables that share at least one common data element

Data Analysis and Normalization

Data analysisEvaluation of data to uncover problems with the content

of a database

Anomalies Problems and irregularities in data

NormalizationRemoving anomalies from a database

Comparison of Database Models

Hierarchical modelPrimary advantage: processing efficiency

Network modelMore flexible than hierarchical models in terms of

organizing data

Relational database modelEasier to control, more flexible, and more intuitive; by far

the most widely used

Database Characteristics

AmountDatabase size depends on the number of records or files it

contains

VolatilityA measure of the changes typically required in a given

period of time

ImmediacyA measure of how rapidly changes must be made to data

Database Management Systems

Group of programs used as an interface between a database and application programs or a database and the user

Classified by the type of database model they supportHierarchicalNetworkRelational

Storing and Retrieving Data

Logical access path Application requests data

from the DBMS

Physical access pathDBMS accesses a storage

device to retrieve the data

[Figure 5.14]

Data Control

Concurrency controlLocks out simultaneous access to a record that is being

updated or used by another program

SchemaThe logical and physical structure of the data and

relationships among the data in the database

Providing a User View

User viewPortion of the database a user can access

Subschema A file that contains a description of a subset of the

database and identifies which users can perform modification on the data items in that subset

Developed to create different views

The Use of Schemas and Subschemas

[Figure 5.15]

Creating and Modifyingthe Database

Data definition language (DDL)Collection of instructions and

commands used to define and describe data and data relationships in a specific database

[Figure 5.16]

Creating and Modifyingthe Database

Data dictionaryA detailed description of all data used in the database

[Figure 5.17]

Data Dictionary

Provides a standard definition of terms and data elements

Assists programmers in designing and writing programs

Simplifies database modifications

Data Dictionary

Helps achieve advantages of the database approachReduced data redundancyIncreased data reliabilityFaster program developmentEasier modification of data and information

Manipulating Data and Generating Reports

Data Manipulation Language (DML)Contains the commands used to manipulate the databaseAllows managers and other database users to access,

modify, and make queries about data contained in the database to generate reports

Structured Query Language (SQL)

A standardized data manipulation language that has become

an integral part of most relational database packages

Selecting a Database Management System

Begins by analyzing database needs and characteristicsPerformanceIntegrationFeaturesThe vendorCost

Emerging Database Trends

Distributed databasesActual data may be spread across several smaller

databases connected via telecommunications devices

Replicated databaseHolds a duplicate set of frequently used data

Distributed Database

HCIA p223

HCIA, Inc. uses a distributed database to provideup-to-date information to their customers.

Data Warehouse

A relational database management system designed specifically to support management decision making

[Figure 5.21]

Data Warehouse

Data mart Subset of a data warehouseBrings the data warehouse concept to small and medium-

size businesses

On-line analytical processing (OLAP) Consists of programs used to store and deliver data

warehouse information

Data miningAutomated discovery of patterns and relationships in a

data warehouse

Open Database Connectivity (ODBC)

Standards that help ensure that specific software can be used with any ODBC-compliant database

[Figure 5.22]

Object-Oriented Databases

Databases that store data as objects, which contain both the data and the processing instructions needed to complete

the database transaction

[Table 5.6]

Image, Hypertext, and Hypermedia Databases

Image databasesStore data in the form of images

Hypertext databasesAllow users to search and manipulate alphanumeric data

in an unstructured way

Hypermedia databasesAllow businesses to search and manipulate multimedia

forms of data

Spatial Data Technology

Involves the use of an object-relational database

Stores and accesses data according to the locations it describes

Permits spatial queries and analysis

Aspects of Database Administration

Overall design and coordination of the databaseDevelopment and maintenance of schemas and

subschemasDevelopment and maintenance of the data

dictionaryImplementation of the DBMS

Aspects of Database Administration

System and user documentation User support and trainingOverall operation of the DBMSTesting and maintaining the DBMSEstablishing emergency or failure-recovery

procedures

Database Use, Policies, and Security

What data should users have direct access to?

Under what circumstances can data be transferred from a PC or small computer system to the large mainframe system (uploading)?

Database Use, Policies, and Security

Under what circumstances can data be transferred from a mainframe system to PCs or small computer system (downloading)?

What procedures are needed to guarantee proper database use?