computing essentials 1999 - 2000 systems analysis and design

Computing Essentials 1999 - 2000

Systems Analysis and Design


OverviewEffective information systems don’t

happen by accident, they are the result of considerable thought and effort

A six step problem-solving process called systems analysis and design underpins the development of effective information systems


System Analysis and Design

System - “collection of activities and elements organized to accomplish a goal”

Information system - “collection of hardware, software, people, procedures and data”


The Traditional Systems Development Life Cycle

(SDLC)

The SDLC is a structured framework that consists of sequential processes by which information systems are developed.


System Analysis and Design Steps

1. Preliminary investigation – overview of problems and solutions, feasibility considered, report prepared

2. Systems analysis - system studied, new requirements specified

3. Systems design - new or alternative system design to solve problem


System Analysis and Design Steps

4. Systems development - new hardware and software acquired, developed and system tested (not live)

5. Systems implementation – conversion to new live system with training

6. Systems maintenance - periodic evaluation and updating


Systems Analysis and Design


Phase 1: Preliminary Investigation

In the preliminary investigation phase, the problems are briefly identified and a few solutions are suggested



To determine if a new system is needed, problems are briefly identified and a few solutions are suggested

Systems analysts here are concerned with three tasks:Briefly defining the problemSuggesting alternative solutionsPreparing a short report


Phase 1:Preliminary Investigation

Defining the problem Examining current systemBy observation and interview, determining what

information is needed by whom, when, where and why

Suggesting alternative systems

Short report summarizing investigation results


Alternative systems are designed and evaluated for Economic feasibility - do benefits justify costs?Technical feasibility - is reliable technology and

training available?Operational feasibility - will the employees,

managers or clients support it?Time feasibility – can the project be competed

within a suitable time frame?



Phase 2: Analysis

In the systems analysis phase, the present system is studied in depth, and new requirements are specified.


Gathering Data

Expanding on data gathered in Phase 1

In addition to observation and interviews, formal lines of authority and standard operating procedures investigated

Organization chart excellent source document during this phase


Workers

SupervisorsControl

Middle ManagerControl & Planning

Top Managers

Long-Range Planning

… etc

Organisation chart and management

pyramid

CEO

VP Accounting

VP Marketing

VP Production

VPHR

VP Research


Analyzing the Data

How information flows, and reasons for any inefficiencies

Checklists - list of questions

Top-down analysis methodology - start with top level components, break down through each successive level


Analyzing the Data

Grid charts - to show relationship between inputs and outputs

System flowcharts - charts flow of input data to processing and finally to output

Data flow diagrams - displays data or information flow within an information system


System System FlowchartFlowchart

System System FlowchartFlowchart


System System Flowchart Flowchart SymbolsSymbols

System System Flowchart Flowchart SymbolsSymbols

decision


Analyzing the Data

Automated design tools

Help systems analyst evaluate hardware and software alternatives

Often called computer-aided software engineering tools or CASE tools


Client Database

Time & Billing DatabaseClient

Client Information

Request Service

Request Denied

Update if necessary

Request Accepted

Completed Service

Database UpdatedBill Mailed

Data Flow Data Flow DiagramDiagram

Data Flow Data Flow DiagramDiagram

Verify Account

Perform Service

Entity Process File Data Flow

Data Flow Diagram (DFD) Symbols

Prepare Client Bill


Documenting the Systems Analysis Stage

In report to higher managementCurrent system describedRequirements for new system specifiedPossible development schedule proposed


Phase 3: Design

Systems analysis describes what a system must do to solve the business problem, and systems design describes how the system will accomplish this task


Phase 3:Design

In selecting the best system, questions that must be answered:Will new system fit into overall system?Will it be flexible for the future?Can it be secured against unauthorized use?Are the costs worth the benefits?

Writing the systems design report - alternatives described, one recommended


The deliverable of the systems design phase is the technical design --that specifies the following:

• System outputs, inputs, and user interfaces

• Hardware, software, databases, telecommunications, personnel, and procedures

• How these components are integrated


Two Major Aspects of the New System

Logical systems designStates what the system will do

Physical systems designStates how the system will perform its functions


Phase 4:Development

In the systems development phase, new hardware and software are developed, acquired and tested.


Phase 4:Development

Developing software - two optionsOff-the-shelfCustom designed

Acquiring hardware - what kinds needed and where to install

Testing the new system Sample data fed into systemResults evaluated


Phase 5: Implementation

In the systems implementation phase, the new information system is installed, and people are trained to use it.



Types of conversion

Direct approach - old system abandoned, new one adopted

Parallel approach - both systems operated side by side until new system proves itself



Types of conversion (cont.)Pilot approach - new system launched in only

one area of the business, once system operating smoothly implementation goes company-wide

Phased approach - gradual implementation over time



Pilot and phased approach most favored

Training

Most commonly overlooked

Can be commenced before equipment delivery

Outside trainers sometimes used


Phase 6: Maintenance

Systems maintenance is first a systems audit and then an ongoing evaluation to see whether a system is performing productively.


Phase 6: Maintenance

Systems audit - performance compared to original specifications

Periodic evaluation - “checkups” from time to time, modifications if necessary

computing essentials 1999 - 2000 systems analysis and design

Documents

designcomputing essentials

updatingcomputing essentials

datacomputing essentials

problemcomputing essentials

suggestedcomputing essentials

system analysis

systems analysis phase

new system