LIFE CYCLE

1. WELCOME
• OBJECTIVE
Students will be able to explain the various
stages of the system development life
cycle (SDLC) and software engineering

2. Starting the SystemStarting the System
Development ProcessDevelopment Process
The process of development can be costly, theThe process of development can be costly, the
systems investigation stage may require asystems investigation stage may require a
preliminary study called a feasibility study.preliminary study called a feasibility study.
A feasibility studyA feasibility study is a preliminary study whereis a preliminary study where
the information needs of prospective users andthe information needs of prospective users and
the resource requirements, costs, benefits,the resource requirements, costs, benefits,
and feasibility of a project are determinedand feasibility of a project are determined

3. The goal of Feasibility Studies is
to evaluate alternative system
solutions and to propose the most
feasible and desirable e-business
application for development.

4. Four major categories ofFour major categories of
feasibility studyfeasibility study
1. Organizational feasibility
How well a proposes system supports the
strategic e-business priorities of the
organization.
2. Economic feasibility
Is concerned with whether expected cost
savings, increased revenue, increase profits,
reductions in required investment, and other
types of benefits will exceed the costs of
developing and operating the proposed
system.

5. 3. Technical feasibility
Can be demonstrated if reliable
hardware and software capable
meeting the needs a proposed system
can be acquire or developed by the
business in the required time.
4. Operational feasibility
Is the willingness and ability of the
management, employees, customers,
suppliers, and others to operate, use,
and support a proposed system

6. System Development
Life Cycle (SDLC)
• To help create successful
information systems, the System
Development Life Cycle was
developed. SDLC is an organized way
to build an information system.

7. Phase 1
System Analysis
During this phase the development team
focuses on completing three tasks:
1. Defining the problem and deciding
whether to proceed
2. Analyzing the current system in depth
and developing possible solutions to the
problem
3. Selecting the best solution and defining
its function

8. Analysts can document a problem or an
entire system in several different ways.
1. Data Flow diagrams
Shows the flow of data through a system
(Allow students find diagrams online)
2. Structured English
Uses English terms and phases to describe
events, actions and alternative actions that
can occur within the system
3. Decision Tree
Graphically illustrates the event and actions
that can occur in the system.

9. Phase 2
Systems Design
• During this phase the project team tackles
the “how” of the selected solution.
• The different elements of the solution are
designed in line with the requirements set
out in the systems analysis. This will
involve creating design specifications for
hardware, software, databases,
telecommunication/network links,
personnel and procedures.

10. • Discuss diagram found on page 160 in
AS&A Level ICT Through Diagrams
Text Book.

11. Phase 3
Development
• During this phase programmers
create or customize the software
for the various parts of the system.
• They are two alternative paths:
1. Acquisition
2. Local Development

12. Acquisition
• The team may decide that some or all of
the necessary system components are
available as off-the-shelf hardware or
software and may decide to acquire,
rather than develop, these components.
• Advantages
1. System will be built faster and cheaper
2. Components are already tested proven
reliable although they may need to be
customized to fit into the overall
information system

13. Local Development
• When an off-the-shelf solution is not
available or will not work with other parts
of the system, the project team may need
to develop a solution themselves.
• This means writing program code from
scratch or making changes to existing
software in the system.

14. • In many cases, project teams buy some
components and develop others. Thus the follow
both acquisition and local paths at the same time.
• During this phase, technical writers and/or online
help authors work with the project team to
produce the technical documentation and online
help for the system.

15. • Testing is also an integral of Phases 3 & 4.
• After the software and equipment have
been installed, the system should be
tested.
• The typical approach to testing is to move
from an individual component to (Unit
testing) and then tests the components of
the system with each other (system
testing)
• Sample data is fed into the system. The
processed information is then evaluated to
see whether the results are correct.
Errors are corrected, the necessary
changes are made, and the tests are then
run again.

16. • The next step is installation testing,
when the system is installed in a test
environment and tested with other
applications used by the business.
• Finally, acceptance testing is done;
the end users test the installed
system to make sure that it meets
their criteria.

17. Phase 4
Implementation
• In the systems implementation phase, the new
information system is installed, and people are
trained to use it.
• Another name for this phase is Conversion. It is
the process of changing – converting-from the old
system to the new and training people to use the
new system.
• IS professionals must handle this process
carefully to avoid losing or corrupting data or
frustrating users trying to perform their work.

18. Types of Conversion
There are four approaches to
conversion:
• Direct Conversion
• Parallel Conversion
• Pilot Conversion
• Phased Conversion

19. 1. Direct Conversion
All users stop using the old system at the
same time and then begin using the new.
This option is fast, but it can be
disruptive and pressure on support
personnel can be excessive.
This approach is not recommended
precisely because it is so risky. If
anything is still wrong with the new
system, the old system is not around to
fall back on.

20. 2. Parallel Conversion
Old and new systems are operated
side by side until the new one has
proved to be reliable. However,
keeping enough equipment and
people active to manage two
systems at the same time can be
very expensive. Thus, the parallel
approach is used only in cases in
which the cost of failure or of
interrupted operation is great.

21. 3. Pilot Conversion
• The new system is tried out in only one
part of the organisation. Once the system
is working smoothly in that part, it is
implemented throughout the rest of the
organisation.
• This approach is certainly less expensive
than the parallel approach. It also is
somewhat riskier. However, the risks can
be controlled because problems will be
confined to only certain areas of the
organisation. Difficulties will not affect
the entire organisation.

22. Phased Conversion
• Users start using the new system,
component by component by
component. This option works only
for systems that can be
compartmentalized.
• This is an expensive proposition,
because the implementation is done
slowly. However, it is certainly one of
the least risky approaches.

23. • Trainers and support personnel play
a significant role during the
conversion. Training courses usually
involve classroom-style lectures,
hand-on sessions with sample data,
and computer-based training that
users can work with on their own
time.

24. Phase 5
Maintenance
• Systems maintenance first a systems
audit and then an ongoing evaluation
to see whether a system is
performing productively.
• Maintenance has two main parts
» A systems audit
» Periodic evaluation

25. • In the systems audit, the system’s
performance is compared to the original
design specifications. This is to determine
whether the new procedures are actually
furthering productivity. If they are not,
some redesign may b necessary.
• After the systems audit, the new
information system is further modified, if
necessary. All systems should be
evaluated from time to time to determine
whether they are meeting the goals and
providing the service they are supposed to.