Systems Analysis

Systems Analysis & Design 7th Edition

2008 Truman College

Chapter-08Data Design

Mohammad Moizuddin

© 2 0 08 Truman College. Slide 2

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Chapter Objectives

Explain data design concepts and data structures

Describe file processing systems

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

Describe Web-based data design


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


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


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


Data Design Concepts

Data Structures A file or table contains data about people, places or

events that interact with the system File-oriented system File processing Database system



Overview of File Processing Can be more efficient and

cost-effective in certain situations

Potential problems Data redundancy Data integrity Rigid data structure



Overview of File Processing Various types of files

Master file Table file Transaction file Work file Security file History file



The Evolution from File Systems to Database Systems Advantages

Scalability Better support for client/server systems Economy of scale Flexible data sharing Enterprise-wide application – database administrator

(DBA)



The Evolution from File Systems to Database Systems Advantages

Stronger standards Controlled redundancy Better security Increased programmer productivity Data independence



Database Tradeoffs Because DBMSs are powerful, they require more

expensive hardware, software, and data networks capable of supporting a multi-user environment

More complex than a file processing system Procedures for security, backup, and recovery are more

complicated and critical


DBMS Components

Interfaces for Users, Database Administrators, and Related Systems Users Database Administrators Related information systems

A DBMS can support several related information systems that provide input to, and require specific data from, the DBMS


DBMS Components

Data Manipulation Language A data manipulation language (DML) controls database

operations

Schema The complete definition of a database, including

descriptions of all fields, tables, and relationships You also can define one or more subschemas


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


Web-Based Database Design

Characteristics of Web-Based Design



Internet Terminology Web browser Web page HTML (Hypertext Markup Language) Tags Web server Web site



Internet Terminology Intranet Extranet Protocols Web-centric Clients Servers



Connecting a Database to the Web Database must be connected to the

Internet or intranet Middleware Adobe

ColdFusion



Data Security Web-based data must be totally secure, yet easily

accessible to authorized users To achieve this goal, 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


Data Design Terminology

Definitions Entity Table or file Field

Attribute Common field

Record Tuple



Key Fields Primary key

Combination key Composite key Concatenated key Multi-valued key



Key Fields Candidate key

Nonkey field Foreign key Secondary key



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


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



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)

Associative entity



Cardinality Cardinality notation Crow’s foot notation Unified Modeling

Language (UML)


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)


Normalization

Repeating Groups and Unnormalized Design Repeating group

Often occur in manual documents prepared by users Unnormalized


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


Normalization

Second Normal Form A standard process exists for converting a table from

1NF to 2NF

1. First, create and name a separate table for each field in the existing primary key

2. Next, create a new table for each possible combination of the original primary key fields

3. Finally, study the three tables and place each field with its appropriate primary key


Normalization

Second Normal Form Four kinds of problems are found with 1NF description

that do not exist with 2NF Consider the work necessary to change a particular

product’s design 1NF tables can contain inconsistent data Adding a new product is a problem Deleting a product is a problem


Normalization

Third Normal Form 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


Normalization

A Normalization Example


Using Codes During System 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

transmission time, and decrease data entry time Can reduce data input errors



Types of Codes

1. Sequence codes

2. Block sequence codes

3. Alphabetic codes

a. Category codes

b. Abbreviation codes – mnemonic codes



Types of codes

4. Significant digit codes

5. Derivation codes

6. Cipher codes

7. Action codes



Developing a Code

1. Keep codes concise

2. Allow for expansion

3. Keep codes stable

4. Make codes unique

5. Use sortable codes



Developing a Code

6. Avoid confusing codes

7. Make codes meaningful

8. Use a code for a single purpose

9. Keep codes consistent


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


Database Models

Relational Databases The relational model was introduced during the 1970s

and became popular because it was flexible and powerful

Object-Oriented Databases Many systems developers are using object-oriented

database (OODB) design as a natural extension of the object-oriented analysis process


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



Logical and Physical Storage Logical storage

Characters Date element or data item Logical record

Physical storage Physical record or block Buffer Blocking factor



Data Storage Formats Binary digits Bit Byte EBCDIC and ASCII Unicode - internationalize



Data Storage Formats Binary

Binary storage format Integer format Long integer format Other binary formats exist for efficient storage of

exceedingly long numbers



Selecting a Data Storage Format In many cases, a user can select a specific data storage

format For example, when using Microsoft Office, you can store

documents, spreadsheets, and databases in Unicode-compatible form by using the font called Arial Unicode MS

Best answer is it depends on the situation


Data Storage and Access Date Fields

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

Can be sorted easily and used in comparisons Absolute date Best method depends on how the specific date will be

printed, displayed or used in a calculation


Data Control

User ID

Password

Permissions

Encryption

Backup

Recovery procedures

Audit log files

Audit fields


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


Chapter Summary

Data design tasks include creating an initial ERD; assigning data elements to an entity; normalizing all table designs; and completing the data dictionary entries for files, records, and data elements

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


Chapter Summary File and database control measures include limiting access to

the data, data encryption, backup/recovery procedures, audit-trail files, and internal audit fields

Chapter 8 complete


Next Week


Next Week Quiz-8 from Chapter 8

Practice for next week Quiz Multiple Choice True-False Short Answer Practice Test

Chapter-9: Phase-3 (System Architecture) Phase-3 ends at System Architecture

Home Work Due: North Shore Boat Sales

Class Work from Chapter 9


Home Work North Shore Boat Sales


Class Work scsite.com/sad7e/learn

Class Work: Flash Card

– Number of Playing Cards (Type-25)– Type your name: __________– After you done answering 25 question, print the page.

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Systems Analysis