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Computing Essentials 1999 - 2000
Systems Analysis and Design
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
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”
Computing Essentials 1999 - 2000
The Traditional Systems Development Life Cycle
(SDLC)
The SDLC is a structured framework that consists of sequential processes by which information systems are developed.
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
Systems Analysis and Design
Computing Essentials 1999 - 2000
Phase 1: Preliminary Investigation
In the preliminary investigation phase, the problems are briefly identified and a few solutions are suggested
Computing Essentials 1999 - 2000
Phase 1: Preliminary Investigation
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
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
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 1: Preliminary Investigation
Computing Essentials 1999 - 2000
Phase 2: Analysis
In the systems analysis phase, the present system is studied in depth, and new requirements are specified.
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
System System FlowchartFlowchart
System System FlowchartFlowchart
Computing Essentials 1999 - 2000
System System Flowchart Flowchart SymbolsSymbols
System System Flowchart Flowchart SymbolsSymbols
decision
Computing Essentials 1999 - 2000
Analyzing the Data
Automated design tools
Help systems analyst evaluate hardware and software alternatives
Often called computer-aided software engineering tools or CASE tools
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
Documenting the Systems Analysis Stage
In report to higher managementCurrent system describedRequirements for new system specifiedPossible development schedule proposed
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
Phase 4:Development
In the systems development phase, new hardware and software are developed, acquired and tested.
Computing Essentials 1999 - 2000
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
Computing Essentials 1999 - 2000
Phase 5: Implementation
In the systems implementation phase, the new information system is installed, and people are trained to use it.
Computing Essentials 1999 - 2000
Phase 5: Implementation
Types of conversion
Direct approach - old system abandoned, new one adopted
Parallel approach - both systems operated side by side until new system proves itself
Computing Essentials 1999 - 2000
Phase 5: Implementation
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
Computing Essentials 1999 - 2000
Phase 5: Implementation
Pilot and phased approach most favored
Training
Most commonly overlooked
Can be commenced before equipment delivery
Outside trainers sometimes used
Computing Essentials 1999 - 2000
Phase 6: Maintenance
Systems maintenance is first a systems audit and then an ongoing evaluation to see whether a system is performing productively.
Computing Essentials 1999 - 2000
Phase 6: Maintenance
Systems audit - performance compared to original specifications
Periodic evaluation - “checkups” from time to time, modifications if necessary