meljun cortes - system life cycle methodologies

8/9/2019 MELJUN CORTES - System Life Cycle Methodologies

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System Life Cycle

Methodologies

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The Systems Life Cycle (SLC)

Methodology

Recommended way of doing something

An application of the systems approachto the task of developing and using a

computer-based system

Often called waterfall approach

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Phases in the SDLC

1) Planning

2) Analysis

3) Design4) Implementation

5) Use

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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

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Life Cycle Management

An upward migration

Executive responsibility

MIS steering committee

Functions

Set policy

Control the purse strings Resolve conflicts

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Executives

MIS Steering

Committee

Project leader -Warehouse

location model team

Project leader

MRP 11 team

Project leader

ISDN

system team

Project leader

HRIS team

Marketing

Manufacturing

Finance

Human

Resources

Project leader

Credit approval

system team

Managers of Systems Life Cycles are Arranged in a Hierarchy

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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.

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Planning Phase

Benefits

Define scope of the project

Spot potential problems

Arrange tasks in sequence

Provide basis for control

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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.

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Steps (cont.)

5.Conduct feasibility study (TENLOS)

Technical

Economic return

Noneconomic return

Legal and ethical

Operational

Schedule

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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?

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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

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Define theproblem

Consult

Prepare a system

study proposal

Establish a control mechanism

Approve or disapprove the study project

Recognize theproblem

Set systemobjectives

Identify systemconstraints

The Planning PhaseMIS Steering Comm Manager Systems Analyst

1.

2.

3.

4.

5.

6.

7.

8.

Conduct afeasibility study

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Outline of a System Study Proposal1. Executive summary

2. Introduction3. System objectives and constraints4. Possible system alternatives5. The recommended system study project

5.1 Tasks to be performed5.2 Human resource requirements5.3 Schedule of work5.4 Estimated cost

6. Expected impact of the system

6.1 Impact on the firms organization structure6.2 Impact on the firms operations

6.3 Impact on the firms resources7. General development plan (analysis, design, and implementation

phase)

8. Summary7-14


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Project Schedule (cont.)

3. Identify input data Systems analyst 0.50

requirements DBA

4. Prepare new system Systems analyst 2.00

documentation

5. Design network Network specialist 1.50

6. Design database DBA 0.50

7. Review design Product manager 0.25

Systems analyst8. Prepare program Programmer 1.00

documentation

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Project Schedule (cont.)

9. Code program Programmer 1.25

10. Test program Programmer 0.75

Operations staff

11. Approve program Product manager 0.50VP of marketing

12. Prepare database DBA 2.00

13. Educate users Systems analyst 0.50

14. Cutover to model Operations staff 0.75

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Analysis Phase

Steps

1.Announce

Reasons for project Purpose: inform and counteract fear

2.Organize project team

User(s)

Specialists

Define roles

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Analysis Phase (cont.)

3. Define information needs

Methods

Personal interview (the preferred method)

Observation Record search (includes review of existing

documentation)

Surveys

Aproject directory can be

maintained as an encompassing set

of documentation to describe the

system7-19


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Analysis Phase (cont.)

4. Define system performance criteria

5. Prepare design proposal

(Compare to system study proposal)

6. Approve or disapprove the design

project

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Announce the system study

Organize the project team

Define information needs

Define system performance criteria

Prepare

design

proposal

Approve or disapprove the design project

1.

2.

3.

4.

5.

6.

The Analysis PhaseMIS Steering

CommitteeManager Systems Analyst

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Outline of a Design Proposal1. Executive summary

2. Introduction3. Problem definition4. System objectives and constraints5. Performance criteria6. Possible system alternatives7. The recommended design project

7.1 Tasks to be performed7.2 Human resource requirements7.3 Schedule of work7.4 Estimated cost

8. Expected impact of the system

8.1 Impact on the firms organization structure8.2 Impact on the firms operations

8.3 Impact on the firms resources9. General development plan (analysis, design, and implementation)10. Summary

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Approve or disapprove the systemimplementation

Prepare the

detaileddesignsystem

Identifyalternatesystem

configurations

Evaluatesystem

configurations

Select thebest

configuration

Prepare theimplementation

proposal

1.

2.

3.

4.

5.

6.

MIS Steering Committee Manager Systems Analyst

The Design Phase

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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

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Popular Documentation Tools

Data Modeling Entity-relationship diagram

Data dictionaryScreen/printer layout form

Process Modeling System flowchartProgram flowchartData flow diagramStructured English

Object Modeling Object relationship modelClass specification

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Data Flow Diagram of Four Data Processing Subsystems

Customers

1.4Accounts

Receivable

1.1OrderEntry

1.3Billing

1.2Inventory

Sales orders

Rejected salesorder notices

Accepted orders

Paymentsby

customers

Invoices

Billed orders

Receivables ledger data

Order logremovals file

Filled items

Inventory

ledger data

Received items

Purchasingdata

3

3 2

2

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D Fl Di f O d E S


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Data Flow Diagram of Order Entry SystemSales orderedit rejects

Order log

Sales ordercredit rejects

Customercredit file

Customer

1.1.1Edit

orderdata

1.1.2Compute

creditcheck

1.1.3Log inorders

1.1.4Markfilled

orders

1.2

1.3

Sales orders Edit rejects

Rejectedsales ordernotices

Edited orders

Credit data

Edited and checked orders

Credit rejects

Acceptedorders

Completed orders Date filled

Order data

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Hardware Choices Make Possible

Multiple System Configurations

System Elements AlternativesCRT terminalHardcopy terminalOCR

Input

Order log

Customer credit file

Rejected orders file

Accepted orders file

Completed orders file

Rejected orders notice

Processing

Magnetic tapeDASD

Magnetic tapeDASD

Magnetic tapeDASD

Magnetic tapeDASD

Magnetic tapeDASD

PrinterCRT terminalHardcopy terminalBatch

Online

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Alternatives Selected for Detailed Study

AlternativeInput

OrderLog

CustomerCredit File

Accepted &Rejected

Orders File

CompletedOrders File

RejectedOrdersNotice

1.

2.

3.

Scanner

Keyboardterminal

Magnetictape

Keyboardterminal

Magnetictape

Magnetictape

Magnetictape

Magnetictape

Magnetictape

Magnetictape

Magnetictape

Magnetictape

Magnetictape

Magnetictape

Magnetictape

Printer

Printer

Hardcopyterminal

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Design Phase (cont.)

3. Evaluate configurations

4. Select best configuration

5. Prepare implementation proposal

6. Approve or disapprove the system

implementation

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1. Executive summary2. Introduction

3. Problem definition4. System objectives and constraints5. Performance criteria

6. System design6.1 Summary description

6.2 Equipment configuration7. The recommended implementation project7.1 Tasks to be performed7.2 Human resource requirements7.3 Schedule of work7.4 Estimated cost

8. Expected impact of the system8.1 Impact on the firms organization structure

8.2 Impact on the firms operations

8.3 Impact on the firms resources9. General implementation plan

10. Summary

Outline of an Implementation Proposal

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Implementation Phase

Acquire and integrate the physical and

conceptual resources to produce a

working system

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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

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Plan the implementation

Announce the implementation

Control

Cutover the new system

Obtain thehardware resources

Obtain the softwareresources

Prepare the database

Educate theparticipants and users

Prepare thephysical facilities

Control

1.

2.

3

4

5

6

7

8.

The Implementation PhaseMIS Steering Committee Manager Information Specialists

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Outline of a Request for Proposal

1. Letter of transmittal2. System objective and applicable constraints3. System design

3.1 Summary description3.2 Performance criteria3.3 Equipment configuration3.4 Summary system documentation

3.5 Estimated transaction volume3.6 Estimated file size4. Installation schedule

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Outline of Supplier Proposal

1. Letter of transmittal2. Summary of recommendations3. Advantages

4. Equipment configuration5. Equipment specifications

5.1 Performance data5.2 Prices

6. Satisfaction and performance criteria7. Delivery schedule

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C


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Cutover Approaches

OldSystem

Old System New System

Immediate cutover

Phased cutover

Parallel cutover

Pilot

System

Immediate

Old SystemNew SystemPhased

New system

Old System

Parallel

Time

Pilot

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Use Phase

1.Use2.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 reengineering7-38

The Use Phase


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The Use Phase

ControlUse thesystem

Audit thesystem

Maintainthe

system

Prepare

re-engineering

proposal

Approve or disapprove thereengineering proposal

MIS Steering Committee Manager Information Specialists

12

3

4

5

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Prototyping

Type I -- Becomes operational system

Type II -- Serves as a blueprint

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Development of a Type I Prototype

1.

2.

3.

4.

N

Identify user needs

Develop a prototype

Prototypeacceptable?

Y

Use the prototype

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Id if


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Development

of a Type IIPrototype N

N

Identify userneeds

Develop aprototype

Code theoperational system

Test theoperational system

Use the

operational system

Prototypeacceptable?

Systemacceptable?

Y

Y

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The Attraction of Prototyping

Communications between the systemsanalyst and user are improved.

The analyst can do a better job of

determining the users needs.

The user plays a more active role in system

development.

The information specialists and the user

spend less time and effort in developing thesystem.

Implementation is much easier because the

user knows what to expect.7-43


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Potential Pitfalls of Prototyping

The haste to deliver the prototype mayproduce shortcuts in problem definition,

alternative evaluation, and documentation.

The users may get so exited about the

prototype that they have unrealisticexpectations of the operational system.

Type I prototypes might not be as efficient

as systems coded in a programminglanguage.

The computer-human interface provided by

certain prototyping tools may not reflect

good design techniques.7-44

Applications That Are Good


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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 behavior7-45


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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 thesystems approach

Tools are mainly 4th generation languages and

CASE tools 7-46


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Information

strategyplanning

(ISP)

Business area

analysis

(BAA)

Rapid application development

(RAD).

Strategic overview of the

information needed to run

an enterprise as efficiently

as possible

Data model

Design of

records usedby specific

procedures

Strategic overview of the

functions and goals of

an enterprise

The process needed to

operate the enterprise

and how they interrelate

Design ofprocedures for

specific

applications

Rapid Application Development is an

Integral Part of Information Engineering7-47

Business Process Redesign


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Business Process Redesign

(BPR)

Often used to react to systems that can no

longer function adequately in the current

business environment of the firm (legacysystems fall into this category)

Three techniques for business process

redesign are

1) reverse engineering

2) restructuring

3) reengineering7-48


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Reverse EngineeringReverse Engineering Produces Documentation on

Successively Higher Levels but Leaves the SystemUnchanged

Reverse

Engineering Engineering

Reverse

Engineering

Reverse

Engineering

Reverse

PlanningPhase

AnalysisPhase

DesignPhase

ImplementationPhase

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Restructuring

Planning

Phase

Restructuring Restructuring Restructuring Restructuring

AnalysisPhase DesignPhase ImplementationPhase

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R i i


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Reengineering

Reverse

Engineering

Reverse

Engineering ReverseEngineering ReverseEngineering

Forward

Engineering

Forward

Engineering

Forward

Engineering

Forward

Engineering

Planning

Phase

Analysis

Phase

Design

Phase

Implementation

Phase

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Selection of BPR Components

Based upon functional quality

What the system does

Based upon technical qualityHow the system does its job

The relationship between these two

characteristics suggest which BPRtechnique would be appropriate

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Selection of BPR Components


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Functional

Quality

(What?)

Good

Technical Quality

(How?)

Poor

Poor

Good

p

ReverseEngineer

Restructure

Do Nothing

Forward

EngineerReengineer

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SLC Prototyping RAD and BPR in


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SLC, Prototyping, RAD, and BPR in

Perspective

SLC, prototyping, and RAD are all

methodologies

Recommended ways of implementing acomputer-based system

BPR revamps systems that were

implemented with computer technology that

has become obsolete

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Summary

System Life Cycle

Planning

AnalysisDesign

Implementation

Use

Cycle management responsibility

Other methodologies7 55

meljun cortes - system life cycle methodologies

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