Chapter 09x

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Systems Analysis and Design
8
th

Edition

Chapter 9

Data Design

Chapter Objectives


Explain data design concepts and structures


Describe file processing systems


Explain database systems and define the
components of a database management
system (DBMS)


Describe Web
-
based data design

2

Chapter Objectives


Explain data design terminology, including
entities, fields, common fields, records, files,
tables, and key fields


Describe data relationships, draw an entity
relationship diagram, define cardinality, and
use cardinality notation


Explain the concept of normalization


Explain the importance of codes and describe
various coding schemes

3

Chapter Objectives


Describe relational and object
-
oriented
database models


Explain data warehousing and data mining


Differentiate between logical and physical
storage and records


Explain data control measures

4

Introduction


You will develop a physical plan for data
organization, storage, and retrieval


Begins with a review of data design concepts and
terminology, then discusses file
-
based systems
and database systems, including Web
-
based
databases


Concludes with a discussion of data storage and
access, including strategic tools such as data
warehousing and data mining, physical design
issues, logical and physical records, data storage
formats, and data controls

5

Data Design Concepts


Data Structures


Each file or table
contains data about
people, places, things or
events that interact with
the information system


File
-
oriented system


File processing system


Database system

6

Data Design Concepts


Overview of File
Processing


File processing can be
efficient and cost
-
effective in certain
situations


Potential problems


Data redundancy


Data integrity


Rigid data structure


7

Data Design Concepts


Overview of File Processing


Various types of files


Master file


Table file


Transaction file


Work file


Security file


History file

8

Data Design Concepts


The Evolution from File
Systems to Database
Systems


A database management
system (DBMS) is a
collection of tools,
features, and interfaces
that enables users to add,
update, manage, access,
and analyze the contents
of a database


The main advantage of a
DBMS is that it offers
timely, interactive, and
flexible data access

9

Data Design Concepts


The Evolution from File Systems to Database
Systems


Some Advantages


Scalability


Economy of scale


Enterprise
-
wide application


database administrator
(DBA)


Controlled redundancy


Data independence


10

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

11

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

12

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

13

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


ODBC


open database connectivity


JDBC


Java database connectivity

14

Web
-
Based Database Design


Characteristics of Web
-
Based Design

15

Web
-
Based Database Design


Internet Terminology


Web browser


Web page


HTML (Hypertext Markup Language)


Tags


Web server


Web site

16

Web
-
Based Database Design


Internet Terminology


Intranet


Extranet


Protocols


Web
-
centric


Clients


Servers

17

Web
-
Based Database Design


Connecting a Database to the Web


Database must be connected to the Internet or
intranet


Middleware


Adobe ColdFusion


Data Security


Well
-
designed systems provide security at three
levels: the database itself, the Web server, and the
telecommunication links that connect the
components of the system

18

Data Design Terminology


Definitions


Entity


Table or file


Field


Record

19

Data Design Terminology


Key Fields


Primary key


Candidate key


Foreign key


Secondary key

20

Data Design Terminology


Referential Integrity


Validity checks can help
avoid data input errors


In a relational database,
referential integrity
means that a foreign key
value cannot be entered
in one table unless it
matches an existing
primary key in another
table


Orphan

21

Entity
-
Relationship Diagrams


Drawing an ERD


The first step is to list the
entities that you identified
during the fact
-
finding
process and to consider
the nature of the
relationships that link them


A popular method is to
represent entities as
rectangles and
relationships as diamond
shapes

22

Entity
-
Relationship Diagrams


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)

23

Entity
-
Relationship Diagrams


Cardinality


Cardinality notation


Crow’s foot notation


Unified Modeling
Language (UML)


Now that you understand
database elements and
their relationships, you
can start designing tables

24

Normalization


Standard Notation Format


Designing tables is easier if you use a standard
notation format to show a table’s structure, fields,
and primary key



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

25

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

26

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 table’s primary
key to include the primary key of the repeating
group

27

Normalization


Second Normal Form


A table design is in second normal form (2NF) if it is in
1NF and if all fields that are not part of the primary
key are functionally dependent on the entire primary
key


A standard process exists for converting a table from
1NF to 2NF


The objective is to break the original table into two or
more new tables and reassign the fields so that each
nonkey

field will depend on the entire primary key in
its table

28

Normalization


Third Normal Form


3NF design avoids redundancy and data integrity
problems that still can exist in 2NF designs


A table design is in third normal form (3NF) if it is
in 2NF and if no
nonkey

field is dependent on
another
nonkey

field


To convert the table to 3NF, you must remove all
fields from the 2NF table that depend on another
nonkey

field and place them in a new table that
uses the
nonkey

field as a primary key

29

Normalization


A Normalization Example

30

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

31

Using Codes During Data Design


Types of Codes

1.
Sequence codes

2.
Block sequence codes

3.
Alphabetic codes

4.
Significant digit codes

5.
Derivation codes

6.
Cipher codes

7.
Action codes

32

Using Codes During Data Design


Developing a Code

1.
Keep codes concise

2.
Allow for expansion

3.
Keep codes stable

4.
Make codes unique

5.
Use
sortable

codes


33

Using Codes During Data Design


Developing a Code

6.
Avoid confusing codes

7.
Make codes meaningful

8.
Use a code for a single purpose

9.
Keep codes consistent

34

Steps in Database Design

1.
Create the initial ERD

2.
Assign all data elements to entities

3.
Create 3NF designs for all tables

4.
Verify all data dictionary entries


After creating your final ERD and normalized table
designs, you can transform them into a database

35

Database Models


Relational Databases


The relational model was introduced during the
1970s and became popular because it was flexible
and powerful


Because all the tables are linked, a user can
request data that meets specific conditions


New entities and attributes can be added at any
time without restructuring the entire database

36

Database Models


Object
-
Oriented
Databases


Many systems
developers are using
object
-
oriented
database (OODB) design


Object Management
Group (OMG)


Each object has a unique
object identifier

37

Data Storage and Access


Data storage and access
involve strategic
business tools


Strategic tools for data
storage and access


Data warehouse


dimensions


Data mart


Data Mining


38

Data Storage and Access


Logical and Physical Storage


Logical storage


Characters


Data element or data item


Logical record


Physical storage


Physical record or block


Buffer


Blocking factor

39

Data Storage and Access


Data Coding and
Storage


Binary digits


Bit


Byte


EBCDIC, ASCII, and
Binary


Unicode

40

Data Storage and Access


Data Coding and Storage


Storing dates


Y2K Issue


Most date formats now are based on the model
established by the International Organization for
Standardization (ISO)


Absolute date

41

Data Control


User ID


Password


Permissions


Encryption


Backup


Recovery procedures


Audit log files


Audit fields

42

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


An entity
-
relationship diagram (ERD) is a
graphic representation of all system entities
and the relationships among them

43

Chapter Summary


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


Logical storage is information seen through a
user’s eyes, regardless of how or where that
information actually is organized or stored

44

Chapter Summary


Physical storage is hardware
-
related and
involves reading and writing blocks of binary
data to physical media


File and database control measures include
limiting access to the data, data encryption,
backup/recovery procedures, audit
-
trail files,
and internal audit fields



Chapter 9 complete

45