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Chapter 7

IntégréTéléchargement
MANAGEMENT INFORMATION SYSTEMS 8/E
Raymond McLeod, Jr. and George Schell
Chapter 7
System Life Cycle
Methodologies
Copyright 2001 Prentice-Hall, Inc.
7-1
The Systems Life Cycle (SLC)

Methodology
– Recommended way of doing something
An application of the systems approach
to the task of developing and using a
computer-based system
 Often called waterfall approach

7-2
Phases in the SDLC
1) Planning
2) Analysis
3) Design
4) Implementation
5) Use
7-3
The System Development Life
Cycle (SDLC)


SDLC is the phrase that encompasses the planning,
analysis, design, and implementation phases of the system
life cycle
Who participates
– IS personnel
– User
– Information specialists can consult

Traditional
– Information specialists working with users.
– A new strategy: Outsourcing
7-4
Life Cycle Management
An upward migration
 Executive responsibility
 MIS steering committee

– Functions
» Set policy
» Control the purse strings
» Resolve conflicts
7-5
Managers of Systems Life Cycles are Arranged in a Hierarchy
Executives
MIS Steering
Committee
Marketing
Manufacturing
Finance
Human
Resources
Project leader -Warehouse
location model team
Project leader
MRP 11 team
Project leader
ISDN
system team
Project leader
Credit approval
system team
Project leader
HRIS team
7-6
Main Advantages of
the Steering Committee
Total firm support
 Projects will be characterized by good
planning and control
 Establishes policies, provides fiscal control,
and resolves conflicts

Since the steering committee will probably not get
involved with the details of the work, a project
team is usually appointed.
7-7
Planning Phase

Benefits
– Define scope of the project
– Spot potential problems
– Arrange tasks in sequence
– Provide basis for control
7-8
Steps
1. Recognize problem (the trigger)
2. Define problem
3. Set objectives
4. Identify constraints
Recall that objectives, standards,
and constraints are problem-solving
elements.
7-9
Steps (cont.)
5.Conduct feasibility study (TENLOS)
–
–
–
–
–
–
Technical
Economic return
Noneconomic return
Legal and ethical
Operational
Schedule
7-10
Steps (cont.)
6.Prepare study project proposal
– Goes to MIS steering committee
7.Approve or disapprove (go/no go)
– Key questions?
1.Will the system accomplish its goals?
2.Is this the best way to go about it?
7-11
Steps (cont.)
8.Establish a control mechanism
– Think in terms of:
» 1. What
» 2. Who
» 3. When (Person-months versus calendar months)
– PERT and CPM network diagrams
7-12
The Planning Phase
MIS Steering Comm
Manager
1.
Systems Analyst
Recognize the
problem
Define the
problem
2.
3.
4.
Set system
objectives
Consult
Identify system
constraints
5.
6.
7.
8.
Conduct a
feasibility study
Prepare a system
study proposal
Approve or disapprove the study project
Establish a control mechanism
7-13
Outline of a System Study Proposal
1. Executive summary
2. Introduction
3. System objectives and constraints
4. Possible system alternatives
5. The recommended system study project
5.1 Tasks to be performed
5.2 Human resource requirements
5.3 Schedule of work
5.4 Estimated cost
6. Expected impact of the system
6.1 Impact on the firm’s organization structure
6.2 Impact on the firm’s operations
6.3 Impact on the firms resources
7. General development plan (analysis, design, and implementation
phase)
8. Summary
7-14
A Project Schedule
Functional System:
Subsystem:
Model:
Subtask
Marketing
Product
Product Deletion
Responsibility
Time
Estimate
(Person Months)
1. Identify
Systems analyst
deletion criteria Product manager
0.75
2. Identify output
information
requirements
0.25
Systems analyst
Network specialist
Product manager
7-15
Project Schedule (cont.)
3.
4.
5.
6.
7.
8.
Identify input data
requirements
Prepare new system
documentation
Design network
Design database
Review design
Prepare program
documentation
Systems analyst
DBA
Systems analyst
0.50
Network specialist
DBA
Product manager
Systems analyst
Programmer
1.50
0.50
0.25
2.00
1.00
7-16
Project Schedule (cont.)
9. Code program
10. Test program
11. Approve program
12. Prepare database
13. Educate users
14. Cutover to model
Programmer
Programmer
Operations staff
Product manager
VP of marketing
DBA
Systems analyst
Operations staff
1.25
0.75
0.50
2.00
0.50
0.75
7-17
Analysis Phase

Steps
1.Announce
» Reasons for project
» Purpose: inform and counteract fear
2.Organize project team
» User(s)
» Specialists
» Define roles
7-18
Analysis Phase (cont.)
3. Define information needs
» Methods
Personal interview (the preferred method)
 Observation
 Record search (includes review of existing
documentation)
 Surveys

A project directory can be
maintained as an encompassing set
of documentation to describe the
system
7-19
Analysis Phase (cont.)
4. Define system performance criteria
5. Prepare design proposal
(Compare to system study proposal)
6. Approve or disapprove the design
project
7-20
The Analysis Phase
MIS Steering
Committee
1.
Manager
Systems Analyst
Announce the system study
2.
Organize the project team
3.
Define information needs
4.
Define system performance criteria
5.
6.
Approve or disapprove the design project
Prepare
design
proposal
7-21
Outline of a Design Proposal
1. Executive summary
2. Introduction
3. Problem definition
4. System objectives and constraints
5. Performance criteria
6. Possible system alternatives
7. The recommended design project
7.1 Tasks to be performed
7.2 Human resource requirements
7.3 Schedule of work
7.4 Estimated cost
8. Expected impact of the system
8.1 Impact on the firm’s organization structure
8.2 Impact on the firm’s operations
8.3 Impact on the firms resources
9. General development plan (analysis, design, and implementation)
10. Summary
7-22
MIS Steering Committee
Manager
Systems Analyst
1.
The Design Phase
2.
3.
4.
5.
6.
Approve or disapprove the system
implementation
Prepare the
detailed
design
system
Identify
alternate
system
configurations
Evaluate
system
configurations
Select the
best
configuration
Prepare the
implementation
proposal
7-23
Design Phase
1.Prepare detailed design
– Structured design (top down)
» System level
» Subsystem level
– Documentation tools
2. Identify alternate system configurations
– Refine to a manageable set
7-24
Popular Documentation Tools
Data Modeling
Entity-relationship diagram
Data dictionary
Screen/printer layout form
Process Modeling
System flowchart
Program flowchart
Data flow diagram
Structured English
Object Modeling
Object relationship model
Class specification
7-25
Data Flow Diagram of Four Data Processing Subsystems
Sales orders
Customers
Rejected sales
order notices
Payments
by
customers
Accepted orders
1.1
Order
Entry
Filled items
Order log
removals file
1.2
Inventory
Invoices
1.4
Accounts
Receivable
1.3
Billing
Billed orders
Inventory
ledger data
Purchasing
data
2
Received items
Receivables ledger data
3
2
7-26
3
Data Flow Diagram of Order Entry System
Edit rejects
Sales orders
Sales order
edit rejects
Customer
1.1.1
Edit
order
data
Rejected
sales order
notices
Accepted
orders
1.2
1.1.3
Log in
orders
Edited orders
Customer
credit file
Edited and checked orders
1.1.2
Compute
credit
check
Credit data
Credit rejects
Sales order
credit rejects
Order data
1.3
Completed orders
1.1.4
Mark
filled
orders
Date filled
Order log
7-27
Hardware Choices Make Possible
Multiple System Configurations
System Elements
Input
Order log
Customer credit file
Rejected orders file
Accepted orders file
Completed orders file
Alternatives
•CRT terminal
•Hardcopy terminal
•OCR
•Magnetic tape
•DASD
•Magnetic tape
•DASD
•Magnetic tape
•DASD
•Magnetic tape
•DASD
•Magnetic tape
•DASD
Rejected orders notice
•Printer
•CRT terminal
•Hardcopy terminal
•Batch
Processing
•Online
7-28
Alternatives Selected for Detailed Study
Alternative
Input
1.
2.
3.
Order
Log
Customer
Credit File
Scanner
Magnetic
tape
Magnetic
tape
Keyboard
terminal
Magnetic
tape
Magnetic
tape
Keyboard
terminal
Magnetic
tape
Magnetic
tape
Accepted &
Rejected
Orders File
Magnetic
tape
Magnetic
tape
Magnetic
tape
Completed
Orders File
Rejected
Orders
Notice
Magnetic
tape
Printer
Magnetic
tape
Magnetic
tape
Printer
Hardcopy
terminal
7-29
Design Phase (cont.)
3. Evaluate configurations
4. Select best configuration
5. Prepare implementation proposal
6. Approve or disapprove the system
implementation
7-30
Outline of an Implementation Proposal
1. Executive summary
2. Introduction
3. Problem definition
4. System objectives and constraints
5. Performance criteria
6. System design
6.1 Summary description
6.2 Equipment configuration
7. The recommended implementation project
7.1 Tasks to be performed
7.2 Human resource requirements
7.3 Schedule of work
7.4 Estimated cost
8. Expected impact of the system
8.1 Impact on the firm’s organization structure
8.2 Impact on the firm’s operations
8.3 Impact on the firms resources
9. General implementation plan
10. Summary
7-31
Implementation Phase
 Acquire
and integrate the physical and
conceptual resources to produce a
working system
7-32
Steps for the Implementation Phase
1. Plan implementation
2. Announce
3. Obtain hardware resources
RFP
/ Written Proposals
4. Obtain software resources
"Make or buy"
5. Prepare database
6. Prepare physical facilities
7. Educate participants and users
8. Prepare cutover proposal
9. Approve or disapprove cutover to new systsem
10. Cutover to new system
7-33
The Implementation Phase
MIS Steering Committee
Information Specialists
Plan the implementation
1.
2.
Manager
Announce the implementation
3
Obtain the
hardware resources
4
Obtain the software
resources
5
Control
Control
6
7
8.
Prepare the database
Prepare the
physical facilities
Educate the
participants and users
Cutover the new system
7-34
Outline of a Request for Proposal
1. Letter of transmittal
2. System objective and applicable constraints
3. System design
3.1 Summary description
3.2 Performance criteria
3.3 Equipment configuration
3.4 Summary system documentation
3.5 Estimated transaction volume
3.6 Estimated file size
4. Installation schedule
7-35
Outline of Supplier Proposal
1. Letter of transmittal
2. Summary of recommendations
3. Advantages
4. Equipment configuration
5. Equipment specifications
5.1 Performance data
5.2 Prices
6. Satisfaction and performance criteria
7. Delivery schedule
7-36
Cutover Approaches
Pilot
Old
System
Pilot
System
Immediate cutover
Phased cutover
Parallel cutover
Immediate
New System
Old System
Phased
Old System
New System
Old System
Parallel
New system
Time
7-37
Use Phase
1.Use
2.Audit (post implementation review)
» By information specialist(s)
» By internal auditor (a different one from the
project team member)
3. Maintain the system
» Correct errors
» Keep current
» Improve
4. Prepare reengineering proposal
5. Approve or disapprove reengineering
7-38
The Use Phase
MIS Steering Committee
Manager
2
1
Control
5
Information Specialists
Use the
system
Audit the
system
3
Maintain
the
system
4
Prepare
reengineering
proposal
Approve or disapprove the
reengineering proposal
7-39
Prototyping

Type I -- Becomes operational system

Type II -- Serves as a blueprint
7-40
Development of a Type I Prototype
1.
Identify user needs
2.
Develop a prototype
N
3.
Prototype
acceptable?
Y
4.
Use the prototype
7-41
Identify user
needs
Development
of a Type II
Prototype
Develop a
prototype
Y
Prototype
acceptable?
N
Code the
operational system
Test the
operational system
Y
System
acceptable?
Use the
operational system
N
7-42
The Attraction of Prototyping





Communications between the systems
analyst and user are improved.
The analyst can do a better job of
determining the user’s needs.
The user plays a more active role in system
development.
The information specialists and the user
spend less time and effort in developing the
system.
Implementation is much easier because the
user knows what to expect.
7-43
Potential Pitfalls of Prototyping




The haste to deliver the prototype may
produce shortcuts in problem definition,
alternative evaluation, and documentation.
The users may get so exited about the
prototype that they have unrealistic
expectations of the operational system.
Type I prototypes might not be as efficient
as systems coded in a programming
language.
The computer-human interface provided by
certain prototyping tools may not reflect
good design techniques.
7-44
Applications That Are Good
Prospects for Prototyping
High risk
 Considerable user interaction
 Large number of users
 A need for quick delivery
 An expected short use phase of the
system
 An innovative system
 Unpredictable user behavior

7-45
Rapid Application Development (RAD)




Information engineering (IE)
Key ingredients
– Management should be experimenters or
early adapters
– Specialized teams
– Methodologies (RAD life cycle)
– Tools (I-CASE, 4GLs)
RAD and the SLC are applications of the
systems approach
Tools are mainly 4th generation languages and
CASE tools
7-46
Strategic overview of the
information needed to run
an enterprise as efficiently
as possible
Data model
Design of
records used
by specific
procedures
.
Information
strategy
planning
(ISP)
Business area
analysis
(BAA)
Rapid application development
(RAD)
Strategic overview of the
functions and goals of
an enterprise
The process needed to
operate the enterprise
and how they interrelate
Design of
procedures for
specific
applications
Rapid Application Development is an
Integral Part of Information Engineering
7-47
Business Process Redesign
(BPR)
Often used to react to systems that can no
longer function adequately in the current
business environment of the firm (legacy
systems fall into this category)
 Three techniques for business process
redesign are

1) reverse engineering
2) restructuring
3) reengineering
7-48
Reverse Engineering
Reverse Engineering Produces Documentation on
Successively Higher Levels but Leaves the System
Unchanged
Planning
Phase
Reverse
Reverse
Reverse
Reverse
Engineering
Engineering
Engineering
Engineering
Analysis
Phase
Design
Phase
Implementation
Phase
7-49
Restructuring
Restructuring
Planning
Phase
Restructuring
Analysis
Phase
Design
Phase
Restructuring
Restructuring
Implementation
Phase
7-50
Reengineering
Reverse
Engineering
Reverse
Engineering
Forward
Engineering
Planning
Phase
Forward
Engineering
Analysis
Phase
Reverse
Engineering
Forward
Engineering
Design
Phase
Reverse
Engineering
Forward
Engineering
Implementation
Phase
7-51
Selection of BPR Components

Based upon functional quality
– What the system does

Based upon technical quality
– How the system does its job

The relationship between these two
characteristics suggest which BPR
technique would be appropriate
7-52
Selection of BPR Components
Good
Functional
Quality
(What?)
Poor
Reverse
Engineer
Restructure
Do Nothing
Forward
Engineer
Reengineer
Poor
Good
Technical Quality
(How?)
7-53
SLC, Prototyping, RAD, and BPR in
Perspective

SLC, prototyping, and RAD are all
methodologies
– Recommended ways of implementing a
computer-based system

BPR revamps systems that were
implemented with computer technology that
has become obsolete
7-54
Summary

System Life Cycle
–
–
–
–
–
Planning
Analysis
Design
Implementation
Use
Cycle management responsibility
 Other methodologies

7-55
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