SDLC Module 2 from IFSM 201 - Overview.docx From IFSM .docx

SDLC Module 2 from IFSM 201 - Overview.docx
From IFSM 201 - Module 2: Information System Development
Module 2: Information System Development
Overview
Today's information systems consist of more than just hardware
and software. They include
enterprise environmental factors (people, company culture, and
legacy systems) and
organizational process assets (processes, procedures, and
historical information). The foundation
for designing, developing, and implementing these complex
systems is a structured process
known as the systems development life cycle (SDLC).
SDLC is based on the concept that information systems must
pass through a series of phases
during their existence or life cycle. In this module, we will help
you understand life-cycle
methodology and the way SDLC is used to design, develop, and
implement information systems.
In this module, we examine the following topics:
Purpose of System Development Life Cycle (SDLC)
In this section, we discuss why the SDLC is used to design,
develop, and implement information

systems.
The SDLC Phases
In this section, we focus on the states or stages in an
information system's life cycle.
SDLC Models
In this section, we examine several SDLC models and their
uses.
Relationship between SDLC and Project Management
In this section, we close out the module by discussing how
project management is used to plan,
manage, and control the SDLC process.
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SDLC Module 2 from IFSM 201 - Outcomes.docx
Module 2: Information System Development
After completing this module, you should be able to:

projects
LC models
implement information systems
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Copyright © by University of Maryland University College.
Commentary
Topics
Purpose of the Systems Development Life Cycle (SDLC)
What Is SDLC?
The systems development life cycle (SDLC) is a structured
methodology and process that guides
the development of information systems. SDLC is based on a
series of related activities that are
combined into phases, sometimes called life-cycle phases. The

phases represent a state or stage
in the life of an information system. Generally speaking, an
information system life cycle
proceeds from requirements gathering to design and
development to operations and
maintenance to decommissioning. Each successive phase
leverages the documentation and
knowledge gained from the previous phases. Figure 2.1 shows
the general flow of a basic SDLC.
Figure 2.1
Basic Systems Development Life Cycle
The main purpose of using SDLC is to promote quality during
the design, development, and
implementation effort. When SDLC is used properly,
information systems are more reliable and
cost effective because project activities are planned,
documented, tracked, and controlled. To
ensure that the information system will meet the stated
requirements, SDLC also includes
predefined reviews, inspections, and audits for the life-cycle
processes and deliverables to
identify variances and recommend changes.
Using the SDLC Acronym
As with most acronyms, there can be some confusion associated
with using SDLC. Within the
information technology industry, SDLC may also be used for:
Synchronous Data Link Control—A communications protocol

that divides network
functions into clearly defined layers.
Software development life cycle—Also known as software
development process
(SDP), this is the set of life-cycle phases associated with
software programs. This topic
will be addressed in module 3.
For the purposes of this module, SDLC will be used as defined
in the previous section.
Why Is SDLC Important for Information Systems Development?
Information systems do not consist solely of the software and
hardware an organization uses.
Effective use of technology is also highly dependent on having
a solid set of processes and
procedures for meeting business objectives, delivering products
and services, and enabling
continuous process improvement. Another important component
of an information system is the
trained, skilled people who use the technology, processes, and
procedures to operate in and
manage the organization.
The relationship between the technology, processes, procedures,
and people is symbiotic: any
change to one component will have some effect on the others.
For example, introducing a new
human-resources information system into an organization
without considering how it might
affect the organization's processes and procedures could doom
the system to failure before it is
fully deployed. A key aspect of using SDLC is considering all
components of an information

system throughout the entire project. This holistic approach is
one of the main reasons why
using SDLC is increasingly becoming a critical success factor
for implementing today's complex,
high-stakes information systems.
Because implementing these systems is an expensive, multiyear
effort, SDLC is also an
important organizational tool to ensure that information system
resources are implemented in a
fiscally responsible and efficient manner. A life-cycle approach
ensures that there is a clear plan
and process for:
identifying and validating organizational requirements early in
the project
designing and developing the system based on the approved
requirements
deploying and transitioning the completed system to the user
community
operating, maintaining, and updating the system once it is
deployed
decommissioning the system when it is no longer required or
when it is replaced
The SDLC Phases
The SDLC phases are the sequence of activities associated with
the life cycle of an information
system. Although the number of SDLC activities can vary
depending on the type and complexity
of the information-system project or the SDLC model used,
there are some common guidelines
that allow the activities to be grouped into clearly defined
phases. These recommended
guidelines are outlined below.

Complete a preliminary investigation, requirements analysis,
and system
recommendation.
Specify a detailed design based on an approved set of
requirements.
Develop the system according to the approved design
specification.
Test the system and gain user acceptance.
Install, operate, and maintain the accepted system.
Update or replace the system as organizational goals and
requirements change.
Decommission the system when it is no longer needed.
Document, report on, and approve each phase of the SDLC
before beginning the next
phase.
Following these common guidelines helps mitigate the risk that
the design and development
effort will get out of control either through missed
requirements, schedule delays, or cost
overruns. Because the guidelines require interaction with
stakeholders throughout the project,
they also prevent surprises when the system is rolled out to the
user community. As you read
through the approaches in the following sections, see if you can
identify these common steps.
Four-Phase Approach
This approach divides the life cycle into four major phases. It

may be used when an organization
has a good understanding of its requirements or the type of
information system being
implemented.
Figure 2.2 below shows the four phases and some of the key
activities associated with each
phase. To view the subsections of each phase, just click on the
phase. At the end of the
exercise, you will see the complete diagram showing all phases
and key activities. You can also
see the complete diagram by clicking on the "show me" button.
Figure 2.2
Four-Phase Approach
Nine-Phase Approach
This approach divides the life cycle into nine phases. Table 2.1
shows the phases and some of
the key activities associated with each phase. As you read
through the table, compare it with the
four-phase approach. Note that a more granular approach is
taken for the preliminary-
investigation, requirements-analysis, and system-
recommendation portions of the project.
Organizations may use this approach when implementing an
unfamiliar type of information
system. The nine-phase approach is also more appropriate for
implementing information systems
that will be used across all business units within an
organization.

Table 2.1
Nine-Phase Approach
SDLC Phases Key Activities
Initiation phase Develop business case
Identify project sponsor
Appoint project manager
Develop concept proposal
Review and approve concept proposal
System concept-
development phase
Analyze business need
Form project team
Plan project
Develop project-acquisition strategy
Identify and analyze risks
Obtain funding and resources
Document phase efforts
Review and approve phase documents
Planning phase Refine acquisition strategy
Analyze project schedule
Document internal processes
Establish agreements with stakeholders
Develop project-management plan
Review and approve project-management plan
Requirements-analysis
phase
Define functional requirements
Define technical requirements

Conduct reviews and approve requirements
Design phase Design system
Design business processes
Outline operations and maintenance manuals
Outline deployment plan
Conduct design reviews
Approve system design
Development phase Refine and complete software requirements
Refine and complete software design
Acquire and install hardware
Code and test software
Conduct hardware- and software-qualification testing
Install software
Test system qualification
Complete plans and support documentation
Test and review documentation
Develop deployment plan
Obtain approval and acceptance of all development
documentation
Integration-and-test phase Conduct subsystem/system testing
SDLC Phases Key Activities
Conduct security testing
Conduct user-acceptance testing
Review and finalize development-phase documentation
Obtain user acceptance
Implementation phase Communicate deployment plan
Execute training plan

Perform data entry, migration, and conversion
Install new system
Perform postimplementation evaluation
Obtain approval to operate the system
Operations-and-
maintenance phase
Transition project to operations
Operate system
Perform data and software administration
Perform system and software maintenance
Identify problems, recommend modifications, and update
the system
Monitor organizational changes, recommend modifications,
and update the system
Ten-Phase Approach
The U.S. Department of Justice (DOJ) uses a ten-phase SDLC
approach on its information
systems implementation projects. Like the nine-phase approach,
this approach emphasizes the
preliminary-investigation, requirements-analysis, and system-
recommendation project activities.
The main difference between the DOJ approach and the nine-
phase approach is that the DOJ
approach also includes a phase to dispose of the information
system when it is no longer needed.
SDLC Models
Waterfall Model

The waterfall model is often used to represent the SDLC
process. This linear, sequential model is
often considered to be the foundation and origin of today's
SDLC methodology. Although there is
disagreement as to when the model was first introduced, the
general consensus is that it has
been in existence in one form or another since the 1960s.
Waterfall development is still widely used for software
engineering projects because it has
distinct goals for each phase of the development and requires
each phase to be fully completed
before the next phase can begin. Once the decision is made to
go to the next phase, there is no
turning back. Like a waterfall, once the water goes over the cliff
(phase), it cannot flow back.
Figure 2.3 graphically shows how the waterfall model works
using the DOJ's ten-phase approach.
Figure 2.3
Waterfall SDLC Model
The advantage of waterfall development is that it allows for
direct project-manager and
management control. A timeline can be established with specific
deadlines for each phase, and a
software solution can proceed through the development process
like a product through an
assembly line, and if properly managed, be delivered on time.
Each phase of development
proceeds in a predefined order, without any overlapping steps or
turning back.

The disadvantage of waterfall development is that there is no
returning to a previous phase.
Once the software solution is in the design phase, it is very
difficult to go back and modify a
feature or function that was not well thought out in the
requirements phase. Today's complex,
cross-functional information systems require a more iterative
approach and development effort.
Fountain Model
The fountain model recognizes that overlap may be needed
between some development phases,
and previous phases may have to be revisited throughout the
development cycle. For example,
planning may need to be fully completed prior to beginning
requirements analysis. Once planning
is completed, the requirements analysis, design, and
development phases may have activities
that must overlap to ensure the system is properly built. Like
water in a fountain, details about
the information system are pushed up through the phases, but at
any time the details may flow
back through the previous phases to be refreshed and refined as
more is learned about the
system. Figure 2.4 below graphically shows the way the
fountain model works, using the DOJ's
ten-phase approach.
At first glance, the fountain model can be very confusing. If you
have never used the model on a
project, you may not understand that the overlapping phases and
curved arrows demonstrate
the highly iterative nature of this life-cycle approach. Figure
2.4 will step you through an
example of the fountain model. At the end of the exercise, you

will see the complete diagram of
this model.
Figure 2.4
Fountain SDLC Model
The advantage of fountain development is that changes can be
made to the components of the
information system as the project team learns more about what
is actually needed or uncovers
gaps in the concept, requirements, or design.
The disadvantage of this model is that it may take more time
and cost more to complete the
information system. Without strong project management, the
information system theoretically
may never be completed if the project team gets caught in a
loop of ever-increasing scope and
continuously changing requirements.
Build-and-Fix Model
Build and fix is recognized as the crudest, least structured
model in the SDLC family. In this
model, the solution is developed without any proper preliminary
investigation, requirements
analysis, or design. In essence, the solution is built and
modified as often as necessary until it
satisfies the customer's needs. Figure 2.5 graphically shows the
way this model, which uses only

the development and operational phases of the four-phase
approach, works. Some of the study
and design phase activities may be completed during a highly
iterative modify phase. At the end
of the exercise, you will see the complete diagram of this
model.
Figure 2.5
Build-and-Fix SDLC Model
The advantage of the build-and-fix model is that it provides an
efficient framework for extremely
small, low-priority development efforts that involve a single
customer. In some cases, it may be
necessary to use the build-and-fix model when there is not
enough time for a more rigorous
approach. The highly iterative nature of this model ensures
intense and frequent customer
involvement in the development of the information system.
The disadvantage of this approach is that the cost is usually
greater than if a preliminary
investigation, requirements analysis, and detailed design had
been completed. This is an
extremely open-ended, risky approach that requires careful
management and control.
Organizations are strongly discouraged from using this SDLC

model except for small, low-priority
projects.
Rapid Application Development (RAD) or Rapid Prototyping
Model
In most cases, RAD is used when developing a software
solution that is heavily dependent on the
organization's business processes and the end users' knowledge
and understanding of those
processes. In essence, the end users can provide better feedback
about the system requirements
by examining a live system rather than commenting on the
associated documentation. It is
analogous to working with a tailor who is making a custom suit
for you. At various stages of the
suit's construction, you may have to return to the tailor's shop,
try on the unfinished pieces, and
provide feedback that is used to update the measurements and
complete the suit. The type of
suit and the fit you expect may dictate how many iterations are
needed before the tailor's work
is done.
RAD is made possible by the significant advances in the
software development environment that
allow for more rapid code generation and faster modifications to
application screens and other
user interfaces. Figure 2.6 graphically shows how the RAD
model works using a modified version
of the DOJ's ten-phase approach.
RAD/Rapid Prototyping Model

The advantage of the RAD model is that it can result in a lower
level of rejection when the
information system is placed into production. End users are
given the opportunity to work with
the screens online in a production-like environment, which
means a significant number of design
and development errors can be caught earlier in the process. The
model also allows end users to
be heavily involved in the software-development effort and take
ownership of the finished
product.
The disadvantage of this model is that RAD could lead to cost
and schedule overruns. Another
downside is the propensity of the end user to increase the scope
and add new requirements
during the development effort. Some end users may think that
because it is easy for the
developer to produce the basic screens, that it is just as easy to
add extra enhancements.
Without strong project leadership, participants can lose sight of
the goal of producing an optimal,
useful system and instead attempt to develop a gold-plated

application that goes beyond the
organization's requirements. For this reason, the project team
may use a blend of RAD
prototyping and the traditional waterfall approach.
Relationship between SDLC and Project Management
Project management is a profession and discipline that uses a
systematic process to plan,
manage, execute, and control projects. Project managers are
found in just about every
commercial and noncommercial environment, including
construction, education, financial
services, government, medicine, manufacturing, nonprofit,
technology, and utilities
environments.
The project-management process uses the same structure and
rigor found in the SDLC models. A
typical project-management process may include the steps
shown in figure 2.7.
To view the subsections of each process step, just click on the
name of the process step. At
the end of the exercise, you will see the complete diagram
showing all key activities. You can
also see the complete diagram by clicking on the "show me"
button.
Figure 2.7

Although many projects do not require an SDLC approach, the
majority of information-
technology-based projects do. Specifically, when some form of
information system is needed,
SDLC is required and project management is needed to plan,
schedule, and control the
associated activities. As an information system moves through
its life-cycle phases, it may spawn
several projects. For example, there may be separate projects to:
determine the business need,
find, analyze, evaluate, and select a vendor,
define what needs to be done to update an aging system during
the operations and
maintenance phase, or
dispose of an information system that is no longer required.
In most cases, the project ends when the information system
moves into the operations-and-
maintenance phase. In all cases, it is project management that
brings order and organization to
information-system-development efforts.
Summary
SDLC is the progression through a series of stages or states of
an information system. It lasts

from the conception of the system to its disposition. The
number of life-cycle phases can vary
from system to system and according to the needs of the
organization. SDLC models are tools
that allow project and development teams to correctly follow
the SDLC stages required to
develop the various types of information systems. Project
management is used to plan, schedule,
and control the SDLC phases associated with a selected model.
Sources
Elliott, R. K. (2006). Sorting out SDLC terminology. In
Managing Software Development Web
site. Retrieved July 12, 2007, from
http://www.managingsoftwaredevelopment.com/Ed001article2.h
tm
Justice Management Division. (2003, January). Systems
development life cycle guidance
document. Washington, DC: Department of Justice.
Mulcahy, R. (2005). PMP exam prep (5th ed.). Lakewood, CO:
RMC Publications, Inc.
Office of the Chief Information Officer. (2006, February).
Smithsonian information technology
plan FY 2006–FY 2011. Washington, DC: Smithsonian
Institution.
Office of Information Technology. (2006, August). Systems
development life cycle (SDLC).
Volume 2: SDLC Phases. Annapolis, MD: Maryland Department

of Budget & Management.
Project Management Institute. (2004). A guide to the project
management body of knowledge
(PMBOK Guide) (3rd ed.). Newtown Square, PA: Project
Management Institute, Inc.
Schwalbe, K. (2005). Information technology project
management (4th ed.). Boston: Thomson
Course Technology.
Shelly, G. B., Cashman, T. J., & Vermaat, M. E. (2007).
Discovering computers 2007: A gateway
to information. Boston: Thomson Course Technology.
For problems 1 and 2, a computer has the following four
processes that have arrived in the ready queue in the sequence
shown below. NOTES: (1) Time slicing is not used, therefore,
there are no mandatory time outs. (2) I/O operations only occur
one time during the process execution.
· Process 1 has a run time of 30 seconds, a priority of 2, and it
will require 15 seconds of I/O after an initial 10 seconds of
execution.
· Process 2 has a run time of 20 seconds, a priority of 1, and it
will require 10 seconds of I/O after an initial 5 seconds of
execution.
· Process 3 has a run time of 15 seconds and a priority of 2.
· Process 4 has a run time of 25 seconds and a priority of 1, and
it will require 15 seconds of I/O after an initial 10 seconds of
execution
(HINT for problems 1 and 2: Review Module 6 section 2.1.2 for
the definitions of these scheduling algorithms and Self-
Assessment problems 1-4.)

1. (2.5 points) If the Round Robin Scheduling algorithm is used,
which process completes first? Why? At what time does it
complete?
2. (2.5 points) If the Round Robin with Priority Queues
Scheduling algorithm is used, which process completes second?
Why? At what time does it complete?
3. (2 points) The manual for a popular operating system points
out that the number of concurrent users on the system can be
increased if the users are sharing programs, such as editors,
mail readers, or compilers. What characteristics of virtual
storage make this possible?
4. (3 points) Using a variable-partitioned multiprogramming
memory, which of the four holes shown below will be used to
satisfy a 45 KB program requirement under the conditions of:
0-45 KB
45-105 KB
105-145 KB
145-185 KB
185-260 KB
260-330 KB
330-350 KB
350-405 KB
405-470 KB
occupied
Hole A
occupied
Hole B
occupied
Hole C
occupied
Hole D
occupied

___ First-fit
___ Best-fit
___ Worst-fit
(HINT: See Module 6 section 2.2.3 and Self Assessment
problem 6.)
2.1.2 Scheduling
Scheduling of processes is performed on two levels:
· high-level scheduling is used for long-term processing
(anywhere from an hour to a day to a week)
· dispatching is short-term scheduling
High-level scheduling determines when a process will be
admitted to the system.
· In an interactive (online) environment, processes will be
automatically accepted unless the job would overload the
system.
· In a batch environment, the high-level scheduler is used to
control the long-term load on a system.
An example of high-level scheduling would be a system that
runs interactive and short run-time batch processes during the
day, and schedules longer-running processes for the night and
weekend periods.
Dispatching makes the instant-by-instant decisions on which of
the processes that are ready should be given CPU execution
time. There are several algorithms that the dispatcher uses to
make these decisions. These algorithms are divided into two
classes:
· Nonpreemptive scheduling allows a process to run to
completion or until it voluntarily surrenders the CPU. This
method is unpredictable because there is no control over very
long-running processes or processes that are blocked while
waiting for resources.
· Preemptive scheduling allows the CPU to be taken away from
the process when it has become blocked or after it has run a
specified time. The method is both predictable and more

efficient in its use of the CPU.
Six types of scheduling are discussed below and then their
impact upon the sequence of executing a queue of processes is
shown in Example 6-2. You should click on the desired
scheduling algorithm to see the order of processing.
Three nonpreemptive algorithms are:
· First-in, first-out (FIFO)
Each process is placed into a queue as it is admitted to the ready
process. The dispatcher selects the process at the head of the
list to have access to the CPU with no consideration of memory
requirements, CPU time estimates, or priority requirements.
Click on first-in, first-out in Example 6-2 and see Figure 6-5a.
· Shortest job first
The dispatcher selects the process with the shortest estimated
run time to have access to the CPU. This will maximize the
number of processes that are handled in any given time. Click
on shortest job first in Example 6-2 and see Self-Assessment
question 1.
· Nonpreemptive priority queue
Processes are assigned a priority and then placed in a FIFO
priority-based queue. The dispatcher selects the highest priority
queue first and then the job at the head of that queue for access
to the CPU. After the highest priority queue is emptied, the
processes in the next highest priority queue can be selected.
Click on nonpreemptive priority queue in Example 6-2 and see
Self-Assessment question 2.
Three preemptive algorithms are:
· Round robin
Incoming processes are placed in a FIFO queue. When a process
is given access to the CPU, it retains that access until it
completes, is blocked, or exceeds a pre-established time limit.
At that time it is removed from the CPU. Timed-out processes
are reentered into the queue. Blocked processes are reentered
into the queue when they wake up. Click on round robin in
Example 6-2 and see Figure 6-2b.
· Shortest remaining time

Processes are selected for the CPU based on the shortest
estimated running time. If the process becomes blocked while
executing, it is removed, and then the process is allowed to
reenter the queue using the remaining estimated run time after it
wakes up. Click on shortest remaining time in Example 6-2 and
see Self-Assessment question 3.
· Round robin with priority queues
Processes are placed in priority-based round robin queues. The
highest priority queues are emptied before lower priority
queues. If a process times out, it is reentered into its priority
queue. If a process with access to the CPU becomes blocked, it
is removed until it wakes up, and then it reenters its priority
queue. Click on round robin with priority queues in Example 6-
2 and see Self-Assessment question 4.
Example 6-2
Nonpreemptive and Preemptive Dispatching Algorithms
Figures 6-5a and 6-5b demonstrate the increased efficiency of
the preemptive scheduling algorithm over the nonpreemptive
scheduling algorithm, and show the timing of switching
processes in and out of the CPU. In order to make the
comparisons, we assume a computer has the following four
shown:
· Process 1 with a run time of 20 seconds, a priority of 1, will
require 20 seconds of I/O after 10 seconds of execution.
· Process 2 with a run time of 30 seconds and a priority of 2.
· Process 3 with a run time of 15 seconds, a priority of 2, will
require 10 seconds of I/O after 5 seconds of execution.
Figure 6-5a uses the first-in, first-out nonpreemptive scheduling
algorithm. Figure 6-5b uses the round robin preemptive
scheduling algorithm. Note that the preemptive scheduling
algorithms complete in 70 seconds as compared to 100 seconds
for the nonpreemptive algorithms. This is because the processes
waiting for I/O are blocked and thus removed from the run state
in preemptive scheduling.

Figure 6-5a
First-in, First-out Scheduling Algorithm
Figure 6-5b
Round Robin Scheduling Algorithm
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Self Assessment: Operating Systems, Programming Tools, and
System Administration
After you have completed the readings, answer the following
self-assessment questions. These questions will not be graded
and should not be submitted to your instructor. The hypertext
link provides the answer so that you can assess whether your
answers are correct. If you cannot understand how an answer
was obtained, you should contact your instructor for a more
detailed explanation.
For problems 1 to 4, a computer has the following four
shown:
· Process 1 with a run time of 20 seconds, a priority of 1, and it
will require 20 seconds of I/O after 10 seconds of execution.
· Process 3 with a run time of 15 seconds, a priority of 2, and it
will require 10 seconds of I/O after 5 seconds of execution.
Question 1
If the shortest job first scheduling algorithm is used, at what
times will each of the four processes complete its execution?
Question 1 options:
Hide Check my answer

Question 2
If the nonpreemptive priority queue scheduling algorithm is
used, at what times will each of the four processes be complete?
Question 2 options:
Question 3
If the shortest remaining time scheduling algorithm is used, at
what times will each of the four processes be complete?
Question 3 options:
Question 4
If the round robin with priority queues scheduling algorithm is
used with a timeout after 15 seconds of execution, at what times
will each of the four processes complete its execution?
Question 4 options:
Question 6
Using a variable-partitioned multiprogramming memory, which
of the three holes shown below will be used to satisfy a 50 Kb
program requirement under the conditions of:
______
First-fit
______
Best-fit

______
Worst-fit
Question 6 options:
__A___first-fit
__C___best-fit
__A___worst-fit
Information
The FAT below applies to self-assessment questions 7 through
10.
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