1. CHAPTER 6 DATA DESIGN

2. 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 3

3. 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

4. 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

5. 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 4

6. Data Design Concepts
Before constructing an information system, a systems analyst must understand basic design concepts, including data structures and the characteristics of file processing and database systems, including Web-based database design

7. 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

8. Data Design Concepts Overview of File Processing
Some companies still use file processing to handle large volumes of structured data on a regular basis
Although much less common today, file processing can be efficient and cost-effective in certain situations

9. Data Design Concepts Overview of File Processing Potential problems
Data redundancy
Data integrity
Rigid data structure

10. Data Design Concepts Overview of File Processing
Various types of files
Master file
Table file
Transaction file
Work file
Security file
History file

11. Data Design Concepts
The Evolution from File Systems to Database Systems
A properly designed database system offers a solution to the problems of file processing
Provides an overall framework that avoids data redundancy and supports a real-time, dynamic environment

12. 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

13. Data Design Concepts
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)
Stronger standards

14. Data Design Concepts
The Evolution from File Systems to Database Systems
Advantages
Controlled redundancy
Better security
Increased programmer productivity
Data independence

15. Data Design Concepts
The Evolution from File Systems to Database Systems
Although the trend is toward enterprise-wide database design, many companies still use a combination of centralized DBMSs and smaller, department-level database systems
The compromise, in many cases, is a client/server design, where processing is shared among several computers

16. DBMS Components
A DBMS provides an interface between a database and users who need to access the data
In addition to interfaces for users, database administrators, and related systems, a DBMS also has a data manipulation language, a schema and subschemas, and a physical data repository

17. 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

18. 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

19. DBMS Components Data Manipulation Language
A data manipulation language (DML) controls database operations, including storing, retrieving, updating, and deleting data
Some database products also provide an easy-to-use graphical environment that enables users to control operations with menu-driven commands.

20. DBMS Components 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
For example, specific users, systems, or locations might be permitted to create, retrieve, update, or delete data, depending on their needs and the company’s security policies

21. 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

22. Web-Based Database Design
The following sections discuss the characteristics of Web-based design, Internet terminology, connecting a database to the Web, and data security on the Web

23. Web-Based Database Design
Characteristics of Web-Based Design
In a Web-based design, the Internet serves as the front end, or interface for the database management system. Internet technology provides enormous power and flexibility
Web-based systems are popular because they offer ease of access, cost-effectiveness, and worldwide connectivity

24. Web-Based Database Design
Internet Terminology
Web browser
Web page
HTML (Hypertext Markup Language)
Tags
Web server
Web site

25. Web-Based Database Design
Internet Terminology
Intranet
Extranet
Protocols
Web-centric
Clients
Servers

26. Web-Based Database Design
Connecting a Database to the Web
Database must be connected to the Internet or intranet
The database and the Internet speak two different languages
Middleware
Adobe ColdFusion

27. Web-Based Database Design
Data Security
Web-based data must be 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

28. Data Design Terminology
Definitions
Entity
Table or file
Field
Attribute
Common field
Record
Tuple

29. Data Design Terminology
Key Fields
Primary key
Combination key
Composite key
Concatenated key
Multi-valued key

30. Data Design Terminology
Key Fields
Candidate key
Nonkey field
Foreign key
Secondary key

31. 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

32. Entity-Relationship Diagrams
An entity is a person, place, thing, or event for which data is collected and maintained
Entity-relationship diagram (ERD)
An ERD provides an overall view of the system, and a blueprint for creating the physical data structures

33. 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

34. 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)
Associative entity

35. 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

36. Normalization Normalization Table design
Involves four stages: unnormalized design, first normal form, second normal form, and third normal form
Most business-related databases must be designed in third normal form

37. 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)

38. Normalization Repeating Groups and Unnormalized Design Repeating group
Often occur in manual documents prepared by users
Unnormalized
Enclose the repeating group of fields within a second set of parentheses

39. 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

40. Normalization Second Normal Form
To understand second normal form (2NF), you must understand the concept of functional dependence
Field X is functionally dependent on field Y if the value of field X depends on the value of field Y

41. Normalization Second Normal Form
A standard process exists for converting a table from 1NF to 2NF
First, create and name a separate table for each field in the existing primary key
Next, create a new table for each possible combination of the original primary key fields
Finally, study the three tables and place each field with its appropriate primary key

42. 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 description
1NF tables can contain inconsistent data
Adding a new product is a problem
Deleting a product is a problem

43. 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

44. Normalization Third Normal Form
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

45. Normalization A Normalization Example
To show the normalization process, consider the familiar situation in Figure 9-27 which might depict several entities in a school advising system: ADVISOR, COURSE, and STUDENT

46. Using Codes During System Design
Overview of Codes
A code is a set of letters or numbers that represents a data item. Codes can be used to simplify output, input, and data formats.
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

47. Using Codes During System Design
Types of Codes
[1] Sequence codes
Numbers/letters assigned in a specific order
E.g. UiTM student matric number
[2] Block sequence codes
Block sequence codes use blocks of numbers for different classifications.
E.g. course codes
1xx – 3xx : diploma courses
4xx – 6xx : bachelor courses
7xx – 8xx : master courses

48. Using Codes During System Design
Types of Codes
[3] Alphabetic codes
[a] Category codes – identify related items using numbers/letters
E.g. ITS – system science courses, ITT – data comm. & networking courses, ITC – comp. science courses, ACC – accounting courses
[b] Abbreviation codes – mnemonic codes/abbreviations
E.g MY = Malaysia, SG = Singapore, NZ = New Zealand

49. Using Codes During System Design
Types of codes
[4] Significant digit codes - Distinguish items by using a series of subgroups of digits
E.g. Classroom number in UiTM Pahang: J1-01, J1-02, A1- 01, A2-01
[5] Derivation codes - Combine data from different item attributes/characteristics to build the code
E.g. Magazine release num: Vol.18 (Vol. 18, Released on September 2011)
Cipher codes
Action codes

50. Using Codes During System Design
Types of codes
[6] Cipher codes: use a keyword to encode a number
E.g. E.g. IASETTO =
[7] Action codes - Indicate action to be executed associated with item
E.g. X – exit program, F – File menu

51. Using Codes During System Design
Developing a Code
Keep codes concise
Allow for expansion
Keep codes stable
Make codes unique
Use sortable codes

52. Using Codes During System Design
Developing a Code
Avoid confusing codes
Make codes meaningful
Use a code for a single purpose
Keep codes consistent

53. Steps in Database Design
Create the initial ERD
Assign all data elements to entities
Create 3NF designs for all tables
Verify all data dictionary entries
After creating your final ERD and normalized table designs, you can transform them into a database

54. 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

55. Database Models Object-Oriented Databases
Many systems developers are using object-oriented database (OODB) design as a natural extension of the object-oriented analysis process
Object Management Group (OMG)
Each object has a unique object identifier

56. Data Storage and Access
Data storage and access involve strategic business tools
Strategic tools for data storage and access
Data warehouse – dimensions
Data mart

57. Data Storage and Access
Strategic tools for data storage and access
Data Mining
Increase average pages viewed per session.
Increase number of referred customers
Reduce clicks to close
Increase checkouts per visit
Increase average profit per checkout
Clickstream storage – market basket analysis

58. Data Storage and Access
Logical and Physical Storage
Logical storage
Characters
Date element or data item
Logical record
Physical storage
Physical record or block
Buffer
Blocking factor

59. Data Storage and Access
Data Coding and Storage
Binary digits
Bit
Byte
EBCDIC, ASCII, and Binary
EBCDIC and ASCII

60. Data Storage and Access
Data Coding and Storage
EBCDIC, ASCII, and Binary
Binary storage format
Integer format
Long integer format
Unicode

61. 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

62. Data Control
File and database control must include all measures necessary to ensure that data storage is correct, complete, and secure
A well-designed DBMS must provide built-in control and security features, including subschemas, passwords, encryption, audit trail files, and backup and recovery procedures to maintain data

63. Data Control User ID Password Permissions Encryption Backup
Recovery procedures
Audit log files
Audit fields

64. 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 49

65. 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 49

66. Chapter Summary
Logical storage is information seen through a user’s eyes, regardless of how or where that information actually is organized or stored
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 49