Managing Information Technology 6 Edition METHODOLOGIES FOR

Transcription

Managing Information Technology
6th Edition
CHAPTER 10
METHODOLOGIES FOR
CUSTOM SOFTWARE DEVELOPMENT
Copyright © 2009 Pearson Education, Inc. Publishing as Prentice Hall
1
Methodologies for Custom Software
Development
• Although firms are likely to purchase software
packages whenever they can, the development of
custom software is still highly important and in
demand
• Different approaches to developing customized
applications
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–
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Traditional Systems Development Life Cycle (SDLC)
Evolutionary Prototyping
Rapid Application Development (RAD)
Agile Development
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SYSTEMS DEVELOPMENT LIFE CYCLE
The SDLC steps
• Highly structured process for developing
customized applications
• Most often requires a lot of documentation
• Outputs from one step inputs to next
• Often referred to as the “waterfall” model
• Key characteristic is extensive formal reviews
at the end of each major step
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The SDLC Waterfall
Definition
• Feasibility Analysis
• Requirements Definition
Construction
• System Design
• System Building
• System Testing
Implementation
• Installation
• Operations
• Maintenance
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The SDLC steps
• Extensive up-front time spent determining
requirements to avoid expensive changes later
5
Definition phase
• The first phase of the SDLC is the definition
phase
• This phase contains two steps:
– Feasibility analysis
– Requirements definition
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Definition phase – Feasibility analysis
• Three types of feasibility are assessed
1. Technical
• Primary responsibility of the IS analyst
• Based on
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Knowledge of current and emerging technological solutions
IT expertise of in-house personnel
Anticipated infrastructure needed to both develop and
support the proposed system
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• Three types of feasibility are assessed (cont’d)
2. Operational
• Primary responsibility of the business manager
• Entails assessing the degree to which a proposed
system addresses the business issues that gave rise to
the idea for a new information system
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• Three types of feasibility are assessed (cont’d)
3. Economic
•
•
Business managers and IS analysts work together to
prepare a cost/benefit analysis
IS analyst responsible for establishing the
developmental costs for the project
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• Deliverable is a 10-20 page document:
– Executive overview and recommendations
– Description of what system would do and how it
would operate
– Analysis of costs and benefits
– Development plan
10
Definition phase – Requirements Definition
• Focuses on processes, data flows, and data
interrelationships rather than a specific
physical implementation
• Requirements are gathered by:
– Interviewing individuals or groups
– Reviewing documents
– Observing employees doing their jobs
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Definition phase – Requirements Definition
• Deliverable is a system requirements
document:
– Detailed descriptions of inputs and outputs,
processes used to convert input data to outputs
– Formal diagrams and output layouts
– Revised cost/benefit analysis
– Revised plan for remainder of project
12
Construction phase
• The second major phase of the SDLC is the
construction phase
• This starts after the systems requirements
document from the definition phase is approved
• The phase contains three steps:
– System design
– System building
– System testing
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Construction phase – System design
• Includes:
– Deciding what hardware and software to use
– Designing structure and content of databases
– Defining programs and their interrelationships
• Good design is critical for the quality of the
system
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Construction phase – System design
• Deliverable is a detailed design document:
– Models, such as diagrams of system’s physical
structure
– Descriptions of databases
– Detailed specification for each program in the
system
– Plan for the remaining steps of the Construction
phase
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Construction phase – System building
• Includes:
– Producing the computer programs
– Developing or enhancing the databases and files
to be used by the system
– Procuring new hardware and support software
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Construction phase – System testing
• Might require as much time as writing the code
for the system
• Involves testing by IS specialists, then user testing
• Multiple steps:
– Each module of code is tested
– Modules are assembled into subsystems and tested
– Subsystems are combined and entire system is
integration tested
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Construction phase – System testing
User acceptance testing
• Ensures that the system performs reliably and does
what it is supposed to do in the user environment
Documentation
• Major mechanism of communication among
members of the project team
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Implementation phase
• The final phase of the SDLC is the
implementation phase
• The success of this phase is dependent upon
business managers
• The three steps in this phase are:
– Installation
– Operations
– Maintenance
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Implementation phase – Installation
• Includes:
– Building files and databases
– Converting relevant data from one or more old
systems to the new system
– Training system’s end users
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• Conversion from an old system to a new
system can be difficult
• Several transitioning strategies are commonly
used to assist in this change:
– Parallel: organization operates old system in
parallel with new system until new system is
working sufficiently
– Pilot: new system is introduced to only one part of
the organization first
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• Transitioning strategies (cont’d)
– Phased: new system is implemented one
component at a time
– Cutover: old system is totally abandoned as soon
as the new system is implemented
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Implementation phase – Operations
• New application begins operation in
“production mode”
• Project team is usually disbanded
• Requires adequate documentation
– System documentation for IS specialists who
operate and maintain the system
– User documentation for those who use the system
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Implementation phase – Maintenance
• The process of making changes to a system
after it has been put into production mode
• Reasons for maintenance
– Correct errors in the system
– Adapt the system to changes in the environment
– Enhance or improve the system
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• Maintenance makes up about 80% of total
costs over a system’s life
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• Problems with maintenance:
– Documentation may not be updated when changes to
the system are made, causing problems for future
maintenance
– Changes to one part of the system may have an
unanticipated effect on other parts of the system (i.e.,
ripple effect )
– Maintenance is considered low-status work by
programmers, so typically only new programmers are
assigned the job
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• Problems with maintenance (cont’d):
– Maintenance may introduce new errors into the
system
– If resources are not
available, business
managers may suffer
long delays before
needed changes are
made
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The SDLC project team
• Usually temporary
• Includes personnel from IS and business units
• Has a project manager
– Traditionally from IS
– Can be from business unit
– May be one from each
– Responsible for success of project – delivering
quality system on time and within budget
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Managing an SDLC project
• Critical success factors:
– Manageable project size
– Accurate requirements definition
– Executive sponsorship
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SDLC advantages and disadvantages
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PROTOTYPING METHODOLOGY
• Takes advantage of fourth generation procedural
languages and relational database management
systems
• Enables creation of system (or part of system) more
quickly, then revise after users have tried it
• Is a type of evolutionary development process
• Can be used as a complete alternative to the SDLC or
within an SDLC process
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• Prototype examples:
– Input and output screens developed for users to
test as part of requirements definition
– “First-of-a-series” – a completely operational
prototype used as a pilot
– “Selected features” – only some essential features
included in prototype, more added later
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The prototyping steps
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The prototyping project team
• Representatives from IS and user
management necessary
• Need team members who can quickly build
systems using advanced tools
• Requires dedicated business user roles
34
Prototyping advantages and disadvantages
• Advantages:
– Only basic requirements needed at front end
– Used to develop systems that radically change how work is
done, so users can evaluate
– Allows firms to explore use of new technology
– Working system available for testing more quickly
– Less strong top-down commitment needed at front end
– Costs and benefits can be derived after experience with
initial prototype
– Initial user acceptance likely higher
35
Prototyping advantages and disadvantages
• Disadvantages:
– End prototype often lacks security and control
features
– May not undergo as rigorous testing
– Final documentation may be less complete
– More difficult to manage user expectations
36
Prototyping within an SDLC process
• Two ways in which prototyping is usually
incorporated into an SDLC process:
1. Used in the
Definition phase
to help users
define system
requirements
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Prototyping within an SDLC process
• Two ways in which prototyping is usually
incorporated into an SDLC process:
2. Includes a pilot
implementation
of a working
prototype
38
NEWER APPROACHES
Rapid applications development (RAD)
• Hybrid methodology
combines aspects of
SDLC and prototyping
• Goal is to produce a
system in less than a
year
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NEWER APPROACHES
Rapid applications development (RAD)
• Advantages and disadvantages
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NEWER APPROACHES
Agile methodologies
• Alternative methodology for smaller projects
• Objective is to deliver software with very low
defect rates
• Based on four key values:
– Simplicity
– Communication
– Feedback
– Courage
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NEWER APPROACHES
Agile methodologies
• eXtreme programming (XP)
– Programmers write code in pairs
– Use simple design and frequent testing
– Three traits characterize the program design
1. System must communicate everything you want to
communicate
2. System must contain no duplicate code
3. System should have the fewest number of
components as possible
42
NEWER APPROACHES
Agile methodologies
• Scrum
– Based on well-orchestrated movement between
team members
• Similar to the coordination in a rugby scrum
– Emphasizes:
• Independent project teams
• Coordination and communication between and within
teams
• Iterative and continuous monitoring of work
• Highly efficient work methods
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MANAGING SOFTWARE PROJECTS
USING OUTSOURCED STAFF
• Advantages of outsourcing:
– Helps keep software development costs down
– Make use of technical expertise not available inhouse
– Can hire capacity above baseline for current
amount of development work
– Frees up internal resources to work on more
strategic or proprietary projects
– Can often complete projects more quickly
44
• Onshore outsourcing: contracting with
companies within the same country or region
• Offshore outsourcing: contracting with
companies not within the same country or
region
– Driven by price because labor costs are typically
much lower
– Risks include loss of some control, language and
cultural barriers, and threats of piracy of
intellectual property
45
• Offshore outsourcing is a good alternative
when:
– System requirements well-defined and remain
stable
– Time is of essence and 7x24 hour availability of
resources a good idea
– Cost of project important
46
• Guidelines for managing offsite outsourcer:
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Manage expectations, not staff
Take explicit actions to integrate the offsite workers
Communicate frequently
Abandoning informal ways may result in increased
rigor
Create a centralized project management office
Begin with pilot projects
Hire offshore legal expertise
Use secure and redundant communication links
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Managing Information Technology 6 Edition METHODOLOGIES FOR

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