systems analysis and design: the big picture chapter 15
TRANSCRIPT
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Systems Analysis and Design:
The Big Picture
Chapter 15
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Objectives• Define the terms system, analysis, and design
• Describe the principal functions of the systems analyst
• List and describe the phases of the systems development life cycle
• Describe the various data gathering and analysis tools
• Describe a selection of systems design tools
• Explain the concept of prototyping
• Explain the role of the maintenance task in the systems development life cycle
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Contents
• What is Systems Analysis and Design?
• Systems Analyst
• Systems Development Life Cycle
• Preliminary Investigation
• Analysis
• Design
• Development
• Implementation
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Systems Analysis and Design What is it?
• System– organized set of related components established
to accomplish certain task– Natural– Planned and placed by people
• Computer system– A system that has computers as one of its
components
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Systems Analysis and Design What is it?
• Systems analysisProcess of studying an existing system to determine how it works and how it meets user needs
• Systems designProcess of developing a plan for an improved system, based upon the results of the systems analysis
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Systems Analysis and Design Why do it?
• Impetus for change– Internal force– External force
• Authority for change– Approval of higher management
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Systems Analyst
• Professional computer employee who performs analysis and design
• Change agent – Overcome reluctance of users to change
• Typical career path– Programmer– Programmer / Analyst– Systems Analyst
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Systems AnalystFunctions
Coordination• Schedules and system-related tasks
• Personnel– Manager– Programmers– Users– Vendors of computer equipment– Mail room employees– Contractors
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Systems AnalystFunctions
Communication– Oral presentations– Written documentation
Planning and design– Plans and designs new system– Involved from beginning of project through
final implementation of the system
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Systems AnalystPersonal Qualities
• Analytical mind
• Good communication skills
• Self-discipline
• Self-direction
• Organizational skills
• Creativity
• Ability to work without tangible results
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SDLCSystems Development Life Cycle
• Preliminary investigation
• Analysis
• Design
• Development
• Implementation
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SDLCPreliminary Investigation
• Feasibility study / System survey
• Determine the problem
• Describe the problem
• Understand management decisions– Organizational chart– Informal hierarchy
• Produces rough plan and what to do
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SDLCPreliminary Investigation
Problem Definition• Nature of the problem
Separate problem from symptoms of problem
• Scope of the projectBudget and schedule
• Objectives of the projectWhat user thinks system should do
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SDLCPreliminary Investigation
ReportWhat you have found
Recommendations
Financially feasible
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SDLCPreliminary Investigation
Resulting Management Decision• Drop
• Fix a simple problem
• Authorize the analysis phase
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SDLCAnalysis
• Understand the existing system– Gather data– Analyze data
• Establish system requirements
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SDLCAnalysis – Data Gathering
• Written documents
• Interviews– Structured– Unstructured
• Questionnaires
• Observation– Visits by appointment– Participant observation
• Sampling
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SDLCAnalysis – Analyze Data
• How the current system works
• Determine system requirements
• Basis for documentation
• Tools– Data flow diagram (DFD)– Decision tables
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SDLCAnalysis – Data Flow Diagram
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SDLCAnalysis –Decision Tables
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SDLCAnalysis – System Requirements
• Detailed list of things the system must be able to do
• Design is based upon system requirements
• Agreement upon requirements is needed before proceeding
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SDLCAnalysis – Report to Management
• Summarize problems
• Describe requirements
• Cost analysis
• Recommendations for next step
• Obtain authorization to proceed
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SDLCDesign
• Planning the new system
• Two phases– Preliminary design– Detail design
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SDLCPreliminary Design
Major system aspects• Centralized or distributed
• Online or batch
• PC-based?
• How will input be captured?
• Necessary reports
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SDLCPreliminary Design
• Make or buy decision
• Packaged software– Meet at least 75% of requirements?– Change business procedures for part or all of
remainder?– Customize for part of all of remainder?
• Custom software– Programmers write code
• Outsourcing– System is developed by external organization
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SDLCPreliminary Design
• Create an overall plan
• Offer alternatives that meet requirements
• Explain differences
• Evaluate costs
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SDLCPreliminary Design
• Build a prototype– Limited working system of subset
• Does not need true functionality– Output looks like anticipated system output
• Working model that can be modified and fine-tuned– Uses high-level software tools – CASE– Best for small-scale systems
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SDLCPreliminary Design
CASE toolsComputer-Aided Software Engineering
• Supports specific analysis and design tasks
• Integrated environment that supports the entire systems development process
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SDLCPreliminary Design
Presentation
• All alternatives
• Selected plan
• Prototype of the system
• Obtain authorization to proceed
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SDLCDetail Design
Parts of detail design phase• Output requirements
• Input requirements
• Files and databases
• Systems processing
• Systems controls and backup
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SDLCDetail Design
Output requirements
• Medium
• Type of reports
• Contents
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SDLCDetail Design
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SDLCDetail Design
Input requirements
• Medium
• Content
• Input forms
• Validation
• Volume
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SDLCDetail Design
Files and Databases
• Organization
• Access
• Format of records
• Coordinate with database administrator regarding external databases and updating
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SDLCDetail Design
Flowchart Symbols
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SDLCDetail Design
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SDLCDetail Design
Systems Controls and Backup• Insure that input is processed correctly
• Prevent fraud and tampering
• System journals
• Backup of system files
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SDLCDetail Design
Report to Management
• Detailed design specifications report
• Presentation
• Obtain authorization to proceed
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SDLCDevelopment
• Doing the work to bring the new system into being
• Scheduling
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SDLCDevelopment
• Programming– Refine the design– Detailed logic flowcharts and pseudocode
• Testing– Unit testing– System testing– Volume testing
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SDLCImplementation
• Converting to the new system
• Training
• Equipment conversion
• File conversion
• System conversion
• Auditing
• Evaluation
• Maintenance
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SDLCImplementation – Training
• Begin during testing
• User’s manual (Technical Writers)
• Hands-on
• Training consideration– Space– Equipment– Data– User’s schedules
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SDLCImplementation – Conversion
• Equipment– Planning– Installation of new equipment
• File– Manual to electronic– Special programs to convert old format to
new
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SDLCImplementation – Conversion
• System– Direct conversion– Phased conversion– Pilot conversion– Parallel conversion
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SDLCImplementation –Auditing
• Audit trail
• Trace output back to source
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SDLCImplementation – Evaluation
• Working
• Meets original requirements
• Benefits
• Meets budget
• Improvements
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SDLCImplementation – Maintenance
Ongoing activity for life of system
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