CHAPTER 9
Application Development
by Information Systems
Professionals
9.1
© Prentice Hall 2002
SYSTEMS DEVELOPMENT
LIFE CYCLE (SDLC)
• DEFINITION PHASE:
– Feasibility analysis
– Requirement definition
• CONSTRUCTION PHASE:
– System design
– System building
– System testing
• IMPLEMENTATION PHASE:
– Installation
– Operations
– Maintenance
9.2
*
© Prentice Hall 2002
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
*
9.3
© Prentice Hall 2002
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)
*
9.4
© Prentice Hall 2002
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
*
9.5
© Prentice Hall 2002
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
*
9.6
© Prentice Hall 2002
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 organization’s needs
and system’s performance
*
9.7
© Prentice Hall 2002
RELATIVE COST TO
FIX ERROR
COST OF ERROR CORRECTION
200
150
150
100
50
50
1
3.5
10
20
2
3
4
0
1
5
6
PHASE IN WHICH ERROR DETECTED
1. REQUIREMENTS
4. DEVELOPMENT TEST
2. DESIGN
5. ACCEPTANCE TEST
3. CODE
9.8
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
9.9
*
© Prentice Hall 2002
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
*
9.10
© Prentice Hall 2002
SDLC ADVANTAGES
• HIGHLY STRUCTURED, SYSTEMATIC
PROCESS
• THOROUGH DEFINITION
REQUIREMENTS
• CLEAR MILESTONES WITH
MANAGEMENT SIGN-OFFS
*
9.11
© Prentice Hall 2002
SDLC DISADVANTAGES
• MAY IGNORE EVOLVING
REQUIREMENTS DURING PROJECT
• TIME-CONSUMING, COSTLY
PROCESS
• TOP-DOWN COMMITMENT
REQUIRED
*
9.12
© Prentice Hall 2002
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
*
9.13
© Prentice Hall 2002
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
*
9.14
© Prentice Hall 2002
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
9.15
© Prentice Hall 2002
*
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
*
9.16
© Prentice Hall 2002
RAPID APPLICATION
DEVELOPMENT (RAD)
• HYBRID OF SDLC, PROTOTYPING,
JAD, CASE
• PRODUCE SYSTEM IN 6 MONTHS
OR LESS
• STEPS:
–
–
–
–
9.17
PLANNING
USER DESIGN
CONSTRUCTION
IMPLEMENTATION (CUTOVER)
*
© Prentice Hall 2002
RAD ADVANTAGES
• DRAMATIC SAVING IN TIME
• FOCUSES ON ESSENTIAL SYSTEM
REQUIREMENTS
• ABILITY RAPIDLY TO CHANGE
SYSTEM DESIGN AT USER’S
REQUEST
*
9.18
© Prentice Hall 2002
RAD DISADVANTAGES
• QUALITY MAY BE SACRIFICED FOR
SPEED
• TIME CONSUMING FOR KEY
PERSONNEL
• POSSIBLE SHORTCUTS ON
INTERNAL STANDARDS, MODULE
REUSABILITY
*
9.19
© Prentice Hall 2002
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
*
9.20
© Prentice Hall 2002
CHAPTER 9
Application Development
by Information Systems
Professionals
9.21
© Prentice Hall 2002