sad sabitha 2012students

Systems Analysis and

Design

Sabitha S.

1

Systems Analysis

Systems analysis is the application

of the systems approach to

problem solving using computers.

The ingredients are systems

elements, processes and

technology.2

System

The term system is derived from

the Greek word systema, which

means an organized relationship

among functioning units or

components.

3

System

System is an orderly grouping of interdependent components linked together according to a

plan to achieve a specific objective.

4

Systems concept has three basic

implications:

1. A system must be designed to achieve a predetermined objective.

2. Interrelationships and interdependence must exist among the components.

3. The objectives of the organization as a whole have a higher priority than the objectives of its subsystems.

5

Information System

An information system can be any

organized combination of people,

hardware, software, communications

networks, and data resources that

stores and retrieves, transforms and

disseminates information in an

organization.

6

Characteristics of a System

1. Organization (Grouping)

2. Interaction

3. Interdependence

4. Integration

5. Central Objective

7

Elements of a System

1. Outputs

2. Inputs

3. Processor

4. Control

5. Feedback

6. Environment

7. Boundaries and interface

8

The Components of an

Information System

All information systems use people, hardware,

software, data and network resources to

perform input, processing, output, storage

and control activities that transform data

resources into information products.

9

The Components of an Information System

Network Resources

Control of System Performance

Storage of data Resources

Input

of

Data

Resources

Processing

Data

into

information

Output

of

information

Products

Network Resources

System Activities

10

The Components of an

Information System

All information systems use people, hardware,

software, data and network resources to

perform input, processing, output, storage

and control activities that transform data

resources into information products.

11

People Resources

People are the essential ingredient for the

successful operation of all information

systems. These people resources include

end users and IS specialists.

12

End users

End users also called users or clients are

people who use an information system or

the information it produces. They can be

customers, sales persons, engineers,

clerks, accountants or managers.

13

IS specialists

IS specialists are people who develop and operate

information systems. They include system

analysts, software developers, system operators

and other managerial, technical and clerical IS

personnel. System analysts design information

systems based on the information requirements

of end users, software developers create

computer programs based on the specifications of

system analysts, and system operators help to

monitor and operate large computer systems and

networks.

14

Hardware Resources

The concept of hardware resources includes all

physical devices and materials used in

information processing. It includes not only

machines such as computers and other

equipments, but also all the data media,

that is tangible objects on which data are

recorded, from sheets of paper to magnetic

disks.

15

Software Resources

The concept of software resources

includes all sets of information

processing instructions. It includes

programs and procedures (operating

instructions for the people who will use

an information system).

16

Data Resources

Data resources include text, image, video,

audio and other forms of data.

17

Network Resources

Telecommunications technologies and networks like the internet, intranets and extranets are

essential to the successful electronic business and commerce operations of all types of organizations and their computer-

based information systems. Telecommunications network consist of

computers, communications processors and other devices interconnected by

communications media and controlled by communications software.

18

Information System

Activities

1. Input data resources

2. Processing of data into information

3. Output of information products

4. Storage of data resources

5. Control of system performance

19

System Development Life Cycle

(SDLC)Recognition

of need

Feasibility

Study

Analysis

Design

Implementation

Post-implementation

& Maintenance20

Recognition of need/Requirement

determination

Preliminary Survey/ Initial

Investigation

21

Recognition of need/Requirement

determination

It involves studying the current business

system to find out how it works and

where improvements should be made.

System studies result in an evaluation of

how current methods are working and

whether adjustments are necessary or

possible.

22

Activities in Requirement

determination

1. Requirements anticipation

2. Requirements investigation

3. Requirements specification

23

Requirements anticipation

Foreseeing systems characteristics

based on previous experience.24

24

Requirements investigation

Study and documentation of the current

system using fact finding

techniques, data flow analysis, etc.

Using a variety of tools and

skills, analysts study the current

system and document its features for

further analysis.

25

Requirements specifications

The data produced during the fact-finding

investigation are analyzed to

determine requirements

specifications, the description of

features for a new system.

26

Requirements specifications

This activity has three inter related parts:

a. Analysis of factual data

b. Identification of essential requirements

c. Selection of requirements fulfillment

strategies.

27

Basic Requirements

Analysts structure their investigation by

seeking answers to four major

questions:

1. What is the basic business process?

2. What data are used or produced during

that process?

28

Basic Requirements

Analysts structure their investigation by

seeking answers to four major

questions:

3. What are the limits forced by time and

the volume of work?

4. What performance controls are used?

29

1. Understand the process

Analysts must raise questions like:

• What is the purpose of this business activity?

• What steps are performed?

• Where are they performed?

• Who performs them?

• How long does this take?

• How often it is done?

• Who uses the resulting information?

30

2. Identify data used and

information produced.

Analysts need to find out what data are

used to perform each activity.

31

3. Determine process timing and

volume

• Analysts should learn how often the

activities are repeated.

• Time required for performing an

activity also has to be considered.

32

4. Identify controls

The analysts can examine whether weak or

missing controls are there.

• Are there specific performance

standards?

• Who compares performance against

standards?

• How are mistakes caught?

• How are errors handled?33

Questions to answer in developing

a system profile

Volume

• What volume of activity occurs?

• How frequently does the activity occur?

• Does the activity occur according to any

cycle?

34


a system profile

Control

• What areas need specific control?

• What control methods are currently used?

• What yardsticks are used to measure and

assess performance?

• Are specific security precautions taken to

safeguard against improper activity?

35


a system profile

Processes

• What separate processes, steps or

functions make up the activity?

• What triggers (generate) the activity?

• How long does each activity take? What

factors govern the amount of time taken?

• What delays can occur?

36


a system profile

Processes

• How does interaction with elements

occur?

• What is the cost of system operation?

• Are there specific management

objectives to be satisfied?

37


a system profile

Data

• What data enter the system and what is

the origin of the data?

• In what form are the system data

received? Stored?

• Which data items are stored in the

system or as part of the activities of the

system?38


a system profile

Data

• Who uses the information produced by

the system? What is it used for?

• What is not used? (irrelevant parts)

• What data are often missing?

• Are any data developed or used in an ad

hoc basis?

39

Strategies for determining

Information Requirements

1. Asking

2. Getting information from the

existing information system

3. Prototyping

40

Information Gathering Tools

1. Review of literature, procedures

and forms

2. Onsite observation

3. Interviews

4. Questionnaires

41

Structured Analysis

Structured Analysis is a set of techniques and graphical tools that allow the analyst to develop a new kind of system specifications that are easily understandable to the user.

42

Tools of Structured Analysis

1. Data Flow Diagram

2. Data Dictionary

3. Decision Tree

4. Structured English

5. Decision Tables

43

Data Flow Diagram (DFD)

A DFD is the graphic representation of data

movement, processes, and files (data

stores) used in support of an information

system.

It has the purpose of clarifying system

requirements and identifying major

transformations.44

Example

Draw the DFD for a system which takes

orders from the customer (book store,

library, etc.), checks them against an

index the books available, verifies

customer credit through a credit

information file, and authorizes

shipment with an invoice.

45

DFD

CUSTOMER Process OrderCUSTOMER

INFORMATION FILE

BOOK

INFORMATION FILE

Orders

Invoice

Credit

check

46

Data Dictionary

A Data Dictionary is a structured

repository of data about data such

as meaning, relationships to other

data, origin, usage, and format.

47

Decision Tree

It is a graphic representation of conditions

and outcomes resembling the

branches of a tree. It is easy to

construct, understand and interpret.

It simply sketches the logical structure

based on the stated policy.

48

Example

Consider the discount policy of the publisher.

For any purchase of 5 or fewer copies per book title, no discount is allowed.

Otherwise,

Bookstores get a trade discount of 25%; for orders from libraries and individuals, 5%

allowed on orders of 6-19 copies per book title; 10% on orders for 20-49 copies per book title; 15% on orders for 50 copies or

more per book title.

49

Decision Tree for Discount Policy

Discount

Policy

Bookstore

Individual

6 or more

Less than 6

50 or more

20-49

6-19

Less than 6

25%

Nil

15%

10%

5%

Nil

Discount

Policy

Bookstore

Individual

6 or more

Less than 6

50 or more

20-49

6-19

Less than 6

25%

Nil

15%

10%

5%

Nil

50

Structured English

Structured English is strongly worded formal English statements used for

communicating processing rules or describing the structure of a system.

Structured English borrows heavily from structured programming. Thus structured

English aims at getting the benefits of both the programming logic and natural

language. 51

Structured English

Structured English consists of the following elements:

1. Operation statements written as English phrases executed from the top down

2. Conditional blocks indicated by keywords such as IF, THEN, and ELSE

3. Repetition blocks indicated by keywords such as DO, WHILE, and UNTIL

52

Example

IF customer has a Bank Account THEN

IF Customer has no dues from previous account THEN

Allow loan facility

ELSE

IF Management Approval is obtained THEN

Allow loan facility

ELSE

Reject

ENDIF

ENDIF

ELSE

Reject

ENDIF 53

Decision Table

A decision table is a table of

contingencies for defining a problem

and the actions to be taken. It is a

single representation of the

relationships between conditions and

actions.

54

Decision Table

A Decision Table consists of two parts: stub and entry.

The stub part is divided into an upper quadrant called the condition stub and a

lower quadrant called the action stub.

The entry part is also divided into an upper quadrant called the condition entry and a lower quadrant called the action entry.

55

Decision Table for Discount Policy

Customer is bookstore?

Order-size 6 copies or more?

IF Customer Librarian or Individual?

(condition) Order-size 50 copies or more?

Order-size 20-49 copies?

Order-size 6-19 copies?

Allow 25% discount

Allow 15% discount

THEN Allow 10% discount

(action) Allow 5% discount

No discount allowed

Y Y N N N N

Y N N N N N

Y Y Y Y

Y N N N

Y N N

Y N

X

X

X

X

X X

Condition StubCondition Entry

Action Stub Action Entry

1 2 3 4 5 6

56

Feasibility Study

A Feasibility study is to serve as a decision document, it must answer three key questions:

1. Is there a new and better way to do the job that will benefit the user?

2. What are the costs and savings of the alternatives?

3. What is recommended?57

Feasibility Considerations

Three key considerations are involved in the feasibility analysis.

• Economic Feasibility

• Technical Feasibility

• Behavioral Feasibility

58

Economic Feasibility Cost/Benefit Analysis

It is the most frequently used

method for evaluating the

effectiveness of the system.

59

Economic feasibilityCost/Benefit Analysis

Identifying the advantages or benefits

and the disadvantages or costs of a

proposed solution.

60

Economic Feasibility Cost/Benefit Analysis

The procedure is to determine the benefits and savings that are expected from a candidate system and compare them with costs. If benefits outweigh costs, then the decision is made to design and implement the system. Otherwise further justification and alterations in the proposed system will have to be made if it is to have a chance of to be implemented.

61

Cost/Benefit Analysis

Identifying the advantages or benefits

and the disadvantages or costs of a

proposed solution.

62

Technical Feasibility

It centers around the existing

computer system and to what

extent it can support the

proposed addition.

63

Behavioral Feasibility

User friendliness of the

proposed system.

64

Steps in Feasibility Analysis

1. Form a project team and appoint a project leader.

2. Prepare system flowcharts.

3. Enumerate potential candidate systems.

4. Describe and identify characteristics of candidate systems.

65


5. Determine and evaluate

performance and cost

effectiveness of each candidate

system.

66

Performance/Cost factors

Performance CostsSystem accuracy System development

Growth potential User Training

Response time System operations

User-friendly Payback

67


6. Weight system performance and cost data.

7. Select the best candidate system.

8. Prepare and report final project directive to management.

68

System Analysis

Detailed evaluation of present

system.

Data collection

69

System Analysis

Systems Analysis is not a preliminary

study. It is an in-depth study of end

user information needs that produces

functional requirements that are used

as the basis for the design of a new

information system.

70

System Analysis

Systems Analysis traditionally involves a detailed study of:

1. The information needs of a company and end users.

2. The activities, resources and products of one or more of the present information systems being used.

3. The information system capabilities required to meet the information requirements of the organization and those of other business stakeholders that may use the system.

71

Categories of System Analysis

1. Organizational Analysis

2. Analysis of the Present System

3. Functional Requirements Analysis

72

System Design

Output Design

Input Design

File /Database Design

Procedure Design

73

Objectives of Information

System Design

1. Specify logical design elements

2. Support business activities

3. Meet User requirements

4. Easy to use

5. Provide software specifications

6. Conform to design standards

74

1. Specify logical design

elements

System design involves first logical

design and then physical construction

of the system. When analysts

formulate a logical design, they write

the detailed specifications for the new

system. They describe its features

such as the outputs, inputs,

databases, procedures, etc.

contd…75

1. Specify logical design

elements

The statement of these features is

termed as the design specifications of

the system.

76

2. Support Business Activities

The fundamental objective in the design

of an information system is to ensure

that it supports the business activity

for which it is developed.

Contd…

77

2. Support Business Activities

For example, if it is essential for an

organization to move information very

quickly to remain competitive, then

the design specifications of the

information system must be based

around this essential business

objective.

78

3. Ensure that system features

meet user requirements

User requirements are translated into

system characteristics during design. We

say that an information system meets

user needs if it accomplishes the

following:

• Performs the right procedures properly.

• Presents information and instructions in

an acceptable and effective fashion.

Contd…79

3. Ensure that system features

meet user requirements

• Produces accurate results

• Provides an acceptable interface and

method of interaction

• Is perceived by users as a reliable

system.

80

4. Provide a system engineered

for ease of use by people

• Favorable human engineering

• Ergonomic design that is physically

comfortable and contributes to user

effectiveness and efficiency.

81

5. Provide software specifications

System design includes formulating

software specifications.

82

6. Conform to design standards

System design specifications are

established within the systems

development standards such as data

standards and structural standards.

83

Elements of the Design

Analysts must design the following elements:

• Data flows

• Data stores

• Processes

• Procedures

• Controls

• Roles84

Data Flows

The movement of data into, around

and out of the system.

85

Data Stores

Temporary or permanent collections

of data.

86

Processes

Activities to accept, manipulate and

deliver data and information.

87

Procedures

Methods and routines for using the

information system to achieve the

intended results.

88

Controls

Standards and guidelines for

determining whether activities are

occurring in the anticipated or

accepted manner, that is ‘under

control’. Also specify actions to

take when problems or unexpected

circumstances are detected.

89

Roles

The responsibilities of all persons

involved in the new system

including end users, computer

operators and support personnel.

90

System Design – Features to be

designed

a. Design of output

b. Design of files

c. Design of database interactions

d. Design of input

e. Design of control

f. Design of procedures

g. Design of program specifications

91

Input Design

Systems analysts decide the following

input design details:

1. What data to input

2. What medium to use

3. How the data should be arranged

4. The dialogue to guide users in

providing input

Contd… 92

Input Design

Systems analysts decide the following

input design details:

5. Data items and transactions

needing validation to detect

errors.

6. Methods for performing input

validation and steps to follow

when errors occur.93

Objectives of Input Design

1. Controlling the amount of input

2. Avoiding delay

3. Avoiding errors in data

4. Avoiding extra steps

5. Keeping the process simple

94

Output Design

When designing the output, the system

analysts must accomplish the

following:

1. Determine what information to

present

2. Decide whether to display, print

or speak the information and

select the output medium. Contd…95

Output Design

3. Arrange the presentation of

information in an acceptable

format.

4. Decide how to distribute the

output to intended recipients.

96

Output Objectives

1. Convey information about past

activities, current status or

projections of the future.

2. Signal important

events, opportunities, problems or

warnings.

3. Trigger an action

4. Confirm an action.97

Key Output questions

1. Who will receive the output

2. What is its planned use?

3. How much detail is needed?

4. When and how often the output

needed?

5. By what method? (printed or

displayed)

98

File Design

The decisions to be made during file design are:

1. Which data items to include in a record

format within the file.

2. Length of each record based on the

characteristics of the data items on

which it is based.

3. The sequencing of records within the

file.

99

BASIC FILE TERMINOLOGY

Data Item

Record

Record Key

Entity

File

Databases

100

Entity

An entity is any person, place, thing

or event of interest to the

organization and about which

data are captured, stored or

processed.

101

File Organizations

1. Sequential Organization

2. Indexed-Sequential Organization

3. Inverted List Organization

4. Direct Access Organization

102

System Testing

Unit Testing

Combined Module Testing

User Acceptance Testing

103

System Testing

The first test of a system is to see whether it

produces the correct outputs. Following this

step, a variety of other tests are conducted:

• Online response

• Volume

• Stress testing

• Recovery and security

• Usability 104

System Implementation

User Training

Site Preparation

File / System Conversion

Parallel Run

User-friendly documentation

105

Evaluating Hardware, Software and Services

For evaluating the hardware and

software, large companies may require

suppliers to present bids and proposals

based on system specifications

developed during the design stage of

systems development. Minimum

acceptable physical and performance

characteristics for all hardware and

software requirements are established.

106

Quality Assurance

Methods for ensuring that

information systems are free

from errors and fraud and

provide information products of

high quality.

107

Levels of Quality Assurance

There are three levels of quality assurance:

1. Testing

2. Validation and

3. Certification

108

Documentation

A collection of documents or information

that describes a computer

program, information system or

required data processing operations.

Examples : Sample Data Entry Display

screens, forms and reports.

109

Documentation

Documentation is extremely important in

diagnosing errors and making

changes, especially if the end users or

systems analysts who developed a

system are no longer with the

organization.

110

Documentation

Documentation serves as a method of communication among the people

responsible for developing, implementing and

maintaining a computer based system. Installing and operating a newly

designed system or modifying an established application requires a

detailed record of that system’s design.

111

Training

Training is a vital implementation activity.

Training may involve activities like data

entry, or it may also involve all aspects

of the proper use of a new system.

112

Training

Managers and end users must be educated

in how the new technology impacts the

company’s business operations and

management. This knowledge should

be supplemented by training

programmes for any new hardware

devices, software packages and their

use for specific work activities.

113

Training Aids

1. The user manual

2. Help screens

3. Data dictionary

4. Job performance aids

Eg: Flowcharts to guide the user in

detecting and handling errors, restarting

system, etc.

114

sad sabitha 2012students

Documents