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Systems Analysis and Design

9thEdition

Chapter 9

Data Design

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Chapter Objectives

Explain file-oriented systems and how they differ

from database management systems

Explain data design terminology, including entities,

fields, common fields, records, files, tables, and keyfields

Describe data relationships, draw an entity

relationship diagram, define cardinality, and use

cardinality notation

Explain the concept of normalization

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Chapter Objectives

Explain the importance of codes and describe

various coding schemes

Explain data warehousing and data mining

Differentiate between logical and physical

storage and records

Explain data control measures

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Introduction

Begins with a review of data design conceptsand terminology, then discusses file-basedsystems and database systems, including Web-

based databases Concludes with a discussion of data storage

and access, including strategic tools such asdata warehousing and data mining, physicaldesign issues, logical and physical records,data storage formats, and data controls

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Data Design Concepts

Data Structures

Each file or table

contains data about

people, places, things orevents that interact with

the information system

File-oriented system

Database managementsystem (DBMS)

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Overview of File

Processing

File processing can be

efficient and cost-effective in certain

situations

Potential problems

Data redundancy

Data integrity

Rigid data structure

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Overview of File Processing

Various types of files

Master file

Table file

Transaction file

Work file

Security file

History file

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The Evolution from FileSystems to DatabaseSystems A database management

system (DBMS) is acollection of tools,features, and interfacesthat enables users to add,update, manage, access,and analyze the contentsof a database

The main advantage of aDBMS is that it offerstimely, interactive, andflexible data access

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The Evolution from File Systems to Database

Systems

Some Advantages

Scalability

Better support for client/server systems

Economy of scale

Flexible data sharing Enterprise-wide applicationdatabase administrator

(DBA)

Stronger standards

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DBMS Components

Interfaces for Users,

Database Administrators,

and Related Systems

Users

Query language

Query by example (QBE)

SQL (structured query

language)

Database Administrators A DBA is responsible for

DBMS management and

support

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DBMS Components

Interfaces for Users, Database Administrators,

and Related Systems

Related information systems

A DBMS can support several related information

systems that provide input to, and require specific data

from, the DBMS

No human intervention is required for two-way

communication

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DBMS Components

Data Manipulation Language

A data manipulation language (DML) controls

database operations, including storing, retrieving,

updating, and deleting data

Schema

The complete definition of a database, including

descriptions of all fields, tables, and relationships,is called a schema

You also can define one or more subschemas

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DBMS Components

Physical Data Repository

The data dictionary is transformed into a physical

data repository, which also contains the schema

and subschemas

The physical repository might be centralized, or

distributed at several locations

ODBCopen database connectivity JDBCJava database connectivity

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Web-Based Database Design

Characteristics of Web-Based Design

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Internet Terminology

Web browser

Web page

HTML (Hypertext Markup Language)

Tags

Web server

Web site

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Internet Terminology

Intranet

Extranet

Protocols

Web-centric

Clients

Servers

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Connecting a Database to the Web

Database must be connected to the Internet orintranet

Middleware Adobe ColdFusion

Data Security

Well-designed systems provide security at threelevels: the database itself, the Web server, and thetelecommunication links that connect thecomponents of the system

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Data Design Terminology

Definitions

Entity

Table or file

Field

Record

Tuple

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Key Fields

Primary key

Candidate key

Foreign key

Secondary key

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Referential Integrity

Validity checks can helpavoid data input errors

In a relational database,

referential integritymeans that a foreign keyvalue cannot be enteredin one table unless itmatches an existing

primary key in anothertable

Orphan

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Entity-Relationship Diagrams

Drawing an ERD

The first step is to list the

entities that you identified

during the fact-finding

process and to considerthe nature of the

relationships that link them

A popular method is to

represent entities as

rectangles and

relationships as diamond

shapes

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Types of Relationships

Three types of

relationships can exist

between entities

One-to-one relationship

(1:1)

One-to-many

relationship (1:M)

Many-to-many

relationship (M:N)

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Cardinality Cardinality notation

Crows foot notation

Unified Modeling

Language (UML)

Now that you understand

database elements and

their relationships, you

can start designing tables

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Normalization

Standard Notation Format

Designing tables is easier if you use a standard

notation format to show a tables structure, fields,

and primary key

Example: NAME (FIELD 1, FIELD 2, FIELD 3)

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Normalization

Repeating Groups and Unnormalized Design

Repeating groups

Often occur in manual documents prepared by users

Unnormalized

Enclose the repeating group of fields within a

second set of parentheses

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Normalization

First Normal Form

A table is in first normal form (1NF) if it does not

contain a repeating group

To convert, you must expand the tables primary

key to include the primary key of the repeating

group

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Normalization

Second Normal Form

A table design is in second normal form (2NF) if it is in1NF and if all fields that are not part of the primarykey are functionally dependent on the entire primary

key

A standard process exists for converting a table from1NF to 2NF

The objective is to break the original table into two or

more new tables and reassign the fields so that eachnonkey field will depend on the entire primary key inits table

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Normalization

A Normalization Example

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Using Codes During Data Design

Overview of Codes

Because codes often are used to represent data,

you encounter them constantly in your everyday

life They save storage space and costs, reduce data

transmission time, and decrease data entry time

Can reduce data input errors

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Developing a Code

1. Keep codes concise

2. Allow for expansion

3. Keep codes stable

4. Make codes unique

5. Use sortable codes

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Developing a Code

6. Avoid confusing codes

7. Make codes meaningful

8. Use a code for a single purpose

9. Keep codes consistent

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Database Models

A Real-World BusinessExample

Imagine a company that

provides on-site service

for electronic

equipment, including

parts and labor

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Database Models

Working with a Relational Database

To understand the power and flexibility of a

relational database, try the following exercise

Suppose you work in IT, and the sales team needsanswers to three specific questions

The data might be stored physically in seven tables

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Data Storage and Access

Data storage and access

involve strategic

business tools

Strategic tools for datastorage and access

Data warehouse

dimensions

Data mart

Data Mining

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Logical and Physical Storage

Logical storage

Characters

Data element or data item

Logical record

Physical storage

Physical record or block

Buffer

Blocking factor

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Data Coding and

Storage

Binary digits

Bit Byte

EBCDIC, ASCII, and

Binary

Unicode

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Data Coding and Storage

Storing dates

Y2K Issue

Most date formats now are based on the modelestablished by the International Organization for

Standardization (ISO)

Absolute date

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Data Control

User ID

Password

Permissions

Encryption

Backup

Recovery procedures

Audit log files

Audit fields

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Chapter Summary

Files and tables contain data about people,

places, things, or events that affect the

information system

DBMS designs are more powerful and flexible

than traditional file-oriented systems

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Chapter Summary

An entity-relationship (ERD) is a graphic

representation of all system entities and the

relationships among them

A code is a set of letters or numbers used to

represent data in a system

The most common database models are

relational and object-oriented

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Chapter Summary

Logical storage is information seen through ausers eyes, regardless of how or where thatinformation actually is organized or stored

Physical storage is hardware-related and involvesreading and writing blocks of binary data tophysical media

File and database control measures include

limiting access to the data, data encryption,backup/recovery procedures, audit-trail files, andinternal audit fields

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Chapter Summary

Chapter 9 complete

Documents

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