Chapter 10 Systems Planning, Analysis, and Design.

Chapter 10Systems Planning, Analysis, and

Design

Presentation Summary

I. The Steps of Systems Analysis

II. Fact-Gathering Techniques

III. Techniques for Organizing Facts

IV. Structured Systems Analysis

V. The Steps of Systems Design

I. The Steps of Systems Analysis

A. Survey the Present SystemB. Identify Information Needs

C. Identify System RequirementsD. Develop a Systems Analysis Report

A. Survey the Present System

Four objectives of the system survey are concerned with:

1. Understanding the Operational Aspects of the Current System

2. Establishing a Working Relationship with System Users

3. Collection of Data for Systems Design4. Identification of Specific System Problems

1. Understanding the Operational Aspects of the Current System

It is dangerous to try to modify an existing

system that you do not thoroughly understand.

The strengths and weaknesses of the

current system must be identified before

modifying the system.

2. Establishing a Working Relationship with System Users

Get to know the people involved in the system as soon as possible.

Communicate the benefits of the new system.Provide assurance, when possible, of job security and

no changes in job responsibilities.Project a genuine concern for making the life of the

system user better.

The success or failure of a systems project largely depends on the relationship between the development

team and the people who use the system.

3. Collection of Data for Systems Design

Internal data may be collected from sources

like interviews, questionnaires,

observations, and policy manuals.

Outside data may be collected from industry

publications, professional journals, and customers.

4. Identification of Specific System Problems

Effectiveness considers whether the system meets

its objectives.Efficiency determines

whether objectives are met at the lowest possible cost.Evaluation of the system

should also consider bottlenecks. These are

areas where small changes could result in major

improvements.

B. Identify Information NeedsIdentify the managers primary job responsibility.

Identify the means by which the manager is evaluated.

Identify some major problems the manager faces.

Identify the way the manager evaluates personal output.

Managers often have difficulty in expressing just how they make decisions. Identification of the above areas can

be helpful in pinpointing a manager’s decision process. Identification of problems may be best done by simply

getting the manager talking while you listen.

C. Identify the System Requirements

Requirements can be specified in terms of inputs and outputs.First determine the

required outputs that a manager needs to make

a decision.Then determine the

inputs and processing needed to generate the

outputs.

D. The Systems Analysis Report

Description of the overall problems in subsystem

being studiedRecommendations for

improving existing system or design of new system.Overall cost budget and timetable for project to

date.

The report should organize and document the first three phases of analysis. Some key elements of the

report include:

II. Fact-Gathering Techniques

A. Fact Gathering Through Interviews

B. Fact Gathering Through Questionnaires

A. Fact Gathering Through Interviews

1. Depth Interviews - Conversation is guided largely by

feelings and interest of the person being interviewed.

2. Structured Interviews - Useful after a depth interview for obtaining answers to a specific set of questions.

B. Fact Gathering Through Questionnaires

1. Open-Ended Questionnaires - Persons provide written

answers to general rather than specific questions.

2. Closed-End Questionnaires - Use for routine situations or

when a large number of similar individuals would be

questioned.

What types of information

do you use to make decisions?

III. Structured Systems Analysis

A. Structured Systems Analysis Defined

B. The Development of Logical Data Flow Diagrams

C. Defining Data Dictionaries

D. Defining Access Methods

E. Defining Process Logic

A. Structured Systems Analysis Defined

Structured systems analysis is a system of

documentation.

An approach to systems analysis that begins with a very general description of

a particular system, and then moves to ever

increasing detail ending with computer program code and other details.

B. The Development of Logical Data Flow Diagrams

1. Data Flow Diagram Levels

2. Data Flow Diagram Symbols

3. Data Flow Diagram Conventions

1. Data-Flow Diagram LevelsContext Diagrams represent the highest level of data-flow diagrams. More detail is provided in subsequent diagrams beginning at level zero.

0Purchasing

System

StoresStores Requisition

Purchase Order

Purchase Details PurchaseFile

PurchaseFile

Context Diagram

VendorsVendors

1. Data-Flow Diagram Levels

1.0Validate

Requisition

StoresStores Requisition

Details

Purchase Details PurchaseFile

PurchaseFile

VendorsVendors

2.0Prepare

PurchaseOrder

Purchase Order

(Continued)

2. Data-Flow Diagram Symbols

Sources and destinations of data and information are shown in rectangular symbols around the process

symbol.

Process symbol(s) in center of diagram identify system(s) under investigation.

Data flow lines describe the input data to the system and the output reports from the system.

3. Data Flow Diagram Conventions

Each process must have at least one input data flow and one output data flow.

A data flow has at least one end connected to a process

A diagram should not contain more than seven processes before being leveled into

more detailed diagrams.

C. Defining Data Dictionaries

The data dictionary corresponds to the data stores referenced in the logical data flow

diagrams. This involves giving a description of the data structure and data

elements involved.

D. Defining Access MethodsIt is necessary to specify how data stores will be accessed.

This typically involves defining primary and secondary access keys. For example, in the purchase file the “account-no-1” may serve as the primary key and

“person responsible” as the secondary key.

Purchase File DescriptionAccount – Identifiers account-no-1 … primary account number account-no-2 … secondary account number person-responsible … person in charge of account

Financial-Information account-balance … current balance last – purchase … most recent transaction

E. Defining Process Logic

There are a number of different approaches to documenting the process logic, including decision trees

and structured English.

Structured English is a special language for describing process logic that uses several key words, including IF,

THEN, ELSE IF, and SO.

Structured English does not include provisions for error conditions and data file access. If these are added, the

resulting documentation is pseudocode. See pseudocode for a C++ program on the following slide.

Pseudocode for A C++ ProgramII. Design (Continued)

B. Level 2

1.1 Open “P4outJSZ.txt” for writing as outfile 1.2 Open “P4test.txt” for reading as infile 8.1 If ch is an operand 8.2 postfix = postfix + ch 8.3 else 8.4 current = ch 8.5 If current = = opening parenthesis ‘( ‘ or S1 stack is empty 8.6 Process current using Rule 4 or Rule 3b 8.7 else if current = = closing parenthesis ‘)’ 8.8 Process current using Rule 5 8.9 else 8.10 Process current using Rule 3

V. Steps in Systems Design

A. Evaluation of Design AlternativesB. Preparation of Detailed Design

SpecificationsC. Preparation of Systems Design Report

A. Evaluation of Design Alternatives

There are usually a number of attractive solutions that could be chosen.

Completely new systems may be designed from scratch or a pre-made system could be

recommended.Alternative systems should be documented with

information concerning advantages/disadvantages and cost information.

A given system must be feasible from both an operational and technical perspective.

B. Preparation of Detailed Design SpecificationsReports and

Other OutputsReports and

Other Outputs

DatabaseDesignDatabaseDesign

SpecifyProcessing

SpecifyProcessing

SpecifyInputsSpecifyInputs

ControlConsiderations

ControlConsiderations

3. Once these decisions have been made, the designer then builds in

the appropriate controls.

2. Once all the outputs are specified, the data inputs and processing steps

are automatically determined.

1. Working with system objectives, the designer should design all management reports

and operational output documents.

C. Preparation of Systems Design Report

The completed design specifications should

take the form of a proposal.

Contents include timetables for

completion, a budget, personnel requirements,

and diagrams of the system to be implemented.

Summary

Four Steps of Systems Analysis

Gathering Information Through Interviews and Questionnaires

Structured Systems Analysis as a Form of Documentation

Detailed Design Specifications