Systems Analysis & Design Sixth Edition Systems Analysis & Design Sixth Edition Chapter 6.
Systems Analysis And Design 2
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Transcript of Systems Analysis And Design 2
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Systems Analysis and Design:The Big Picture
Computers:Tools for an Information Age
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ObjectivesDefine the terms “system,” “analysis,” and “design”Describe the principal functions of the systems analystList and describe the phases of the systems development life cycleDescribe the various data-gathering and analysis toolsDescribe a selection of systems design toolsExplain the concept of prototypingExplain the role of the maintenance task in the systems development life cycle
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Systems Analysis DesignSystem – an organized set of related components established to accomplish a certain task Computer system – a system that has a computer as one of
its components
Analysis - Studying an existing system to determine how it works and how it meets users’ needs Typically happens as a result of some impetus for change,
combined with the authority to make the change
Design - The process of developing a plan for an improved system, based on the result of the systems analysis
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Who Participates?
ProjectTeam
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Key Individuals Involved in Systems Analysis
Systems analyst – performs analysis and designMay perform some programming as well
Client – the person or organization contracting to have the work done
User – the people who will have contact with the system
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Systems Analyst: A Change AgentThe catalyst or persuader who overcomes the reluctance to change within an organizationSystems analyst can function as change agent, but it works best if it is someone inside the organization What it takes: Coordination of many people, tasks, and schedules Communication skills, both oral and written Planning and design (an analytical mind)
Self-discipline and self-direction Good organizational skills Creativity The ability to work without tangible results
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System Development Life Cycle (SDLC)
Organized set of activities that guides those involved through the development
of an information system.
Phases Preliminary Investigation Analysis Design Development (Documentation) Implementation
Ongoing activities Project management Overall
Documentation Information gathering
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Preliminary InvestigationOr feasability study•Problem Definition
Development and testing.•Scheduling•Programming
Implementation•Training•Conversion•Evaluation•Maintenance
Analysis•Gather data•Analyze data•Develop requirements
Design•Preliminary design•Detail design
Ongoing Activities•Project Management•Documentation•Information Gathering.
Systems Development Life Cycle
•Documentation
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System Development Guidelines
Use a structured approach
Involve the Users
Develop Standards
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Ongoing Activity: Project Management
The process of planning, scheduling, and controlling activities during the SDLC
Scope (goal, objectives, expectations)
Activities and Deliverables to be completed
Time estimates
Cost estimates
Order activities occur
Activities performed concurrentlyGantt Chart
Project Plan
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Ongoing Activity: Feasibility AssessmentMeasure of how suitable the development of a system will be in the
organization. (Initially occurs in the Preliminary Investigation phase but needs to be continuously reevaluated)
Operational feasibility
Schedule feasibility
Technical feasibility
Economic or cost/benefit feasibility
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Ongoing Activity: Documentation
Compilation and summarization of data and informationReports
DiagramsProgramsOther deliverables generated during SDLC
Project NotebookProject Dictionary/Repository
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Ongoing Activity: Data & Info Gathering
Review current system documentation
Observe
Send Questionnaires
Interview Structured/Unstructured
Conduct JAD (joint application design) sessions
Research
Begins in Analysis Phase, but is continually updated
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Phase 1: Preliminary Investigation
A brief study of the problem to determine A brief study of the problem to determine whether the project should be pursuedwhether the project should be pursued
•Also called the feasibility study or system Also called the feasibility study or system surveysurvey
•Involves working with the usersInvolves working with the users
•Organization chart – a hierarchical drawing Organization chart – a hierarchical drawing showing the organization’s managementshowing the organization’s management
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Feasibility StudyTechnical feasibility
Economic feasibility
Operational feasibility are the current work practices and procedures
adequate to support the new system? Legal feasibility
Schedule feasibility how long will the system take to develop, or can it
be done in a desired time-frame?
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Defining the Problem
Two points that must be agreed upon The nature of the problem The scope (boundaries) of
the problem
Agreeing on the problem helps define the objectives of the system
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Project Request
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Feasibility Assessment
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Feasibility Assessment
(continued)
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Phase 2: Analysis
Understand the existing system
Two tasks are involvedData gatheringData analysis
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Data Gathering
A number of techniques can be used Interviews with users and managers
Structured interview – includes only questions that have been written out in advance
Unstructured interview – interviewer has a general goal but few, if any questions prepared
Examining current business and systems documents and output
may include current order documents, computer systems procedures and reports used by operations and senior management
Sending out questionnaires Observation of current procedures
by spending time in various departments; a time and motion study can show where procedures could be more efficient, or to detect bottlenecks
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Data Analysis
Typical tools for data analysisEntity Relationship diagramData flow diagramDecision table/Decision TreeWritten report
Report to management/ customer/ client
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Entity-Relationship Diagrams (ERD)
Tool to graphically represent the associations between entities in the project
Noun
Verb
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Data Flow Diagrams (DFD)Tool to graphically represent the
flow of data in a system
Process
Sour
ce
Data Flow
Data Store
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Decision Table
Decision Tree
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System Requirements & recommendations
A detailed list of things the system must be able to do Highlight problems with current system The design of the new system will be based on these
requirements Analyst and management must come to a clear
agreement on requirements List of possible solutions Hardware/software recommendations
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Report to Management
Summarizes the problems found in the current system
Describes the requirements for the new system, including a cost analysis
Makes a recommendation on what course to take next
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Pre-Design considerationsThe hardware platform which type of computer, network
capabilities, input, storage and output devices
The software programming language, package or
database
The outputs report layouts and screen designs
The inputs documents, screen layouts, validation
procedures
The user interface how users will interact with the
computer system
The modular design of each program in the application
The test plan and test dataConversion plan how the new system is to be
implemented
Documentation User Technical
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Phase 3: DesignThe new system is actually planned
Divided into two subphasesPreliminary design
Several key decisions must be madeDetail design specifications
Output requirements Input requirementsFiles and databasesSystem processingSystem controls and backups
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Build or Buy?
Custom Software Developed by user Developed at user
request by outside vendor
Packaged Software Horizontal
Many org types
Vertical Industry specific
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Acquire Hardware/Software
Technical specifications
Solicit vendor proposals
Test & evaluate Benchmark Test
Make a decision
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Input OutputThings to consider The medium (paper,
screen, etc.) of the output
The types of reports needed and what data is needed for the reports
Things to consider The input medium
(captured at the source, keyed from source document)
The fields needed, how they are laid out on the input screen, etc.
Input validation may be necessary
Requirements
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Input/Output Design
Mockup(User)
Layout Chart(Programmer)
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Files and Databases
Things to considerHow files are organized
Sequentially, directly, or by another methodThe format of the records making up the
data files
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Database Design
Table structure definitions & relationships
Security
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Program DesignData Entry
Program
File
Hard copy
Comment
Flow ChartSystem Processing
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Phase 4: Development
Schedule and monitor the two principal activities Programming Testing
There are several project scheduling tools available
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Programming
Prepare program design specifications
Use logic flowcharts and pseudocode to facilitate code development
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Testing
Unit testing – verifies that individual program units workPerform testing with test data
System testing – determines whether all program units work together as plannedVolume testing – uses real data in large amountsDetermines whether the system can handle
a large volume of data
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Phase 5: Implementation
Steps involved in starting the new systemTrainingEquipment conversionFile conversionSystem conversionAuditingEvaluationMaintenance
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Training
Teach users how to use the systemThe system will do no better than the
people using itDevelop user’s manual to aid users who
are not familiar with the systemHands-on training is best
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Equipment Conversion
Items to considerDelivery schedules must be
coordinatedTerminals or personal computers
must be networkedDevices on the system must be
compatible
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File Conversion
If existing files are manual, they must be keyed in or scanned into the systemManual files must be kept current while
data is being input into the new system
If existing files are computer-based, programs must be written to convert the files into the format needed for the new system
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System Conversion
Four approaches Direct conversion – the user simply stops using
the old system and starts using the new one Phased conversion – the system is implemented
one part at a time Pilot conversion – the entire system is used by a
designated set of users Parallel conversion – the old and new systems are
both used until users are satisfied the new system works
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Conversion Options
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Auditing
Systems to trace data in the system back to a source documentVery helpful in tracing security violations
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Evaluation
Determines how well the system is meeting the original requirements, benefits, and budgetsEvaluation can be performed by the
analyst and someone from the organizationEvaluation can also be performed by an
independent third party
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Maintenance
An ongoing activity that lasts the lifetime of the system
Several types of maintenance activitiesEnhancements to the systemFix bugs in the system as they are
identified
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Terms to Know: Chapter 14AnalysisBenchmark testBuild-or-buy decisionCASE Cost/benefit analysisData dictionaryData flow diagramDecision tree/Decision tableDeliverableDesignDevelopmentDirect conversionDocumentationEntity-relationship diagram (ERD)Feasibility Assessment/StudyGantt chartJoint application development (JAD)Layout chartMockup
OutsourcingParallel conversion
Phased conversion
Pilot conversionPost-implementation system reviewPreliminary investigationProject dictionaryProject planPrototypeRFP, RFQ, RFIScopeSystemSystem designSystem development life cycle-SDLCSystem testingSystems analystUnit testingVolume testing
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If asked, can you…Define the terms “system,” “analysis,” and “design”Describe the principal functions of the systems analystList and describe the phases of the systems development life cycleDescribe the various data-gathering and analysis toolsDescribe a selection of systems design toolsExplain the concept of prototypingExplain the role of the maintenance task in the systems development life cycle
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Sources
Capron; Computers: Tools for An Information Age, 8th Ed. 2003
Pfaffenberger; Computers in Your Future 2003
Microsoft Clipart