Application Development by Information Systems Professionals

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CHAPTER 9

• Application Development by Information Systems
  Professionals

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SYSTEMS DEVELOPMENT LIFE CYCLE (SDLC)

• DEFINITION PHASE
• Feasibility analysis
• Requirement definition
• CONSTRUCTION PHASE
• System design
• System building
• System testing
• IMPLEMENTATION PHASE
• Installation
• Operations
• Maintenance

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DEFINITION PHASE

• FEASIBILITY ANALYSIS Thorough analysis by team
  (leader, systems analysts, end-users). Economic,
  operational, technical
• REQUIREMENTS DEFINITION If feasibility report
  approved, team develops logical design
  processes, data flow relationships. Result is
  system requirements document

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CONSTRUCTION PHASE

• SYSTEM DESIGN Detailed design of physical system
  based on requirements document. Details of
  hardware, software, databases, modules,
  interrelationships for quality system (accurate,
  reliable, auditable, robust, changeable, secure,
  efficient, user friendly, flexible, well
  documented)

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CONSTRUCTION PHASE

• SYSTEM BUILDING IS specialists produce programs,
  databases. End-users answer questions, interpret
  requirements, help design documents
• SYSTEM TESTING By module, subsystem, entire
  system to find correct problems. Users
  acceptance test
• DOCUMENTATION

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IMPLEMENTATION PHASE

• INSTALLATION Four strategies
• Parallel Run old new systems for awhile to
  check validity. Safe
• Pilot Install in one part of organization at a
  time. Learn and adapt
• Phased In large system change one function at a
  time (e.g., order entry)
• Cutover Start using entire system. Can be
  dangerous if errors exist

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IMPLEMENTATION PHASE

• OPERATIONS Training, documentation, people and
  computers must work well together. Project team
  disbanded
• MAINTENANCE Operations stage of life cycle.
  Correct errors as discovered, update as needed,
  monitor activities and output. Be aware of gap
  between organizations needs and systems
  performance

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COST OF ERROR CORRECTION
1. REQUIREMENTS 4. DEVELOPMENT TEST 2. DESIGN 5.
ACCEPTANCE TEST 3. CODE 6. OPERATION
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SDLC ROLES

• PROJECT MANAGER Must have IS skills, plans
  project, uses project management tools, builds
  project team
• SYSTEMS ANALYST IS professional changes business
  problem into IS solution
• END-USER Functional representative provides
  needs, judges results
• SPONSORS, CHAMPIONS Will be addressed in Chapter
  12

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SDLC CHARACTERISTICS

• MANAGEABLE PROJECT SIZE Break into independent
  pieces. Stay within budget other constraints
• ACCURATE REQUIREMENTS DEFINITION Extraneous
  specifications lead to added expense, extends
  completion
• EXECUTIVE SPONSORSHIP Sponsor with
  responsibility and resources critical to success

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SDLC ADVANTAGES

• HIGHLY STRUCTURED, SYSTEMATIC PROCESS
• THOROUGH DEFINITION REQUIREMENTS
• CLEAR MILESTONES WITH MANAGEMENT SIGN-OFFS

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SDLC DISADVANTAGES

• MAY IGNORE EVOLVING REQUIREMENTS DURING PROJECT
• TIME-CONSUMING, COSTLY PROCESS
• TOP-DOWN COMMITMENT REQUIRED

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PROTOTYPING LIFE CYCLE

• 1. IDENTIFY REQUIREMENTS
• 2. DEVELOP INITIAL PROTOTYPE
• 3. USE PROTOTYPE, NOTE CHANGES
• 4. REVISE, ENHANCE PROTOTYPE Return to Step 3 as
  needed
• 5. EVALUATE OPERATIONAL SYSTEM
• 6. MAKE CHANGES OR ABANDON
• 7. INSTALL, OPERATE, MAINTAIN

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COMBINING PROTOTYPING SDLC

• PROTOTYPING/PILOTING PHASE
• DETERMINE BASIC REQUIREMENTS
• PROTOTYPE SYSTEM
• PILOT PROTOTYPE
• SDLC CONSTRUCTION PHASE
• SYSTEM BUILDING
• SYSTEM TESTING
• SDLC IMPLEMENTATION PHASE
• INSTALLATION
• OPERATIONS
• MAINTENANCE

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JOINT APPLICATION DESIGN (JAD)

• TECHNIQUE INVOLVING TEAM OF USERS, IS SPECIALISTS
• INTENSE, STRUCTURED PROCESS
• DEVELOP REQUIREMENTS OR REVIEW DESIGN PROPOSAL
• CAN LAST HOURS, DAYS, OFTEN AT LOCATION REMOVED
  FROM WORKPLACE

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COMPUTER-AIDED SOFTWARE ENGINEERING (CASE)

• COLLECTION OF SOFTWARE TOOLS TO AUTOMATE SDLC
  PROCESSES
• DIAGRAMMING TOOLS
• COMPUTER DISPLAY, REPORT GENERATORS
• ANALYSIS TOOLS
• CENTRAL REPOSITORY
• DOCUMENTATION GENERATORS
• CODE GENERATORS

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RAPID APPLICATION DEVELOPMENT (RAD)

• HYBRID OF SDLC, PROTOTYPING, JAD, CASE
• PRODUCE SYSTEM IN 6 MONTHS OR LESS
• STEPS
• PLANNING
• USER DESIGN
• CONSTRUCTION
• IMPLEMENTATION (CUTOVER)

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RAD ADVANTAGES

• DRAMATIC SAVING IN TIME
• FOCUSES ON ESSENTIAL SYSTEM REQUIREMENTS
• ABILITY RAPIDLY TO CHANGE SYSTEM DESIGN AT USERS
  REQUEST

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RAD DISADVANTAGES

• QUALITY MAY BE SACRIFICED FOR SPEED
• TIME CONSUMING FOR KEY PERSONNEL
• POSSIBLE SHORTCUTS ON INTERNAL STANDARDS, MODULE
  REUSABILITY

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OBJECT-ORIENTED METHODS (O-O)

• HOLD GREAT PROMISE TO PRODUCE BETTER SYSTEMS AT
  LESS COST
• OBJECTS HIGHLY COHESIVE, LOOSELY COUPLED,
  REUSABLE
• CAN REDUCE ERRORS, IMPROVE MAINTENANCE

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CHAPTER 9

• Application Development by Information Systems
  Professionals