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Systems Development Life Cycle

Systems Development Life Cycle

System Development Life Cycle (SDLC) is the overall process of developing information systems through a
multi-step process from investigation of initial requirements through analysis, design, implementation and
maintenance. SDLC is also known as information systems development or application development. SDLC
is a systems approach to problem solving and is made up of several phases, each comprised of multiple
steps. It describes the stages a system passes through from inception until it is discarded or replaced. SDLC
1. Structure
2. Methods
3. Controls
4. Checklist

18.1 Project lifecycle vs. SDLC
The systems development life cycle is a project management technique that divides complex projects into
smaller, more easily managed segments or phases. Segmenting projects allows managers to verify the
successful completion of project phases before allocating resources to subsequent phases. Although System
development can be seen as a project in itself, but the attribute that makes system development different
from regular projects is that a project has a definite end and it is unlikely that ongoing maintenance will be
included in the scope of the project but this falls in the definition of SDLC.

18.2 Types of System Development Life-Cycle Model
The concept of system development lifecycle model has been explained in various shapes and forms. The
concluding form follows the same spirit except for minor differences.

Waterfall model / Classic lifecycle/ Linear Sequential Model
The waterfall model is a software development model (a process for the creation of software) in which
development is seen as flowing steadily downwards (like a waterfall) through the various phases

Incremental Models
In incremental models, software is built not written. Software is constructed step by step in the same way a
building is constructed. The products is designed, implemented, integrated and tested as a series of
incremental builds, where a build consists of code pieces from various modules interacting together to
provide a specific functional capability and testable as a whole.

Iterative Models
In these models customer feed back is taken at each phase and project is modified accordingly – if need be.
Prototypes are used in these models.

Need Assessment
Information systems are usually developed on need-basis, that is, problems and opportunities arise and
render system development necessary. In this phase the stakeholders must attempt to come to some
understanding of the nature of the problem or opportunity they are addressing. Issues which can be
considered in this phase are. Is the problem
Well structured/Structured -- constrained problems with convergent solutions, limited number of rules
and principles within well-defined parameters.
Unstructured -- multiple solutions, fewer parameters, and contain uncertainty about which concepts and
Should formal terms of reference be prepared and approved by the steering committee or project
committee? This depends on the size, impact and cost of the system being prepared. The TOR usually
covers following aspects.
Investigation on existing system
Definition of system requirements
Specifying performance criteria for the system
Detailed cost budget
Draft plan for implementation
If the problem is decided to be addressed, the level of acceptance that exists among the stakeholders on the
need of change. The level of technological uncertainty the proposed solution to the problem/opportunity
has. The most critical phase is the agreement of the stakeholders on the definition of problem and
parameters of solution.

Entry and Feasibility Study
The purpose of this phase is to obtain a commitment to change and to evaluate whether cost effective
solutions are available to address the problem or opportunity that has been identified. Following examples
can be considered to explain this situation.
Say a problem has been recognized by a group of users. They believe they can design and implement a
solution themselves using a high level language. Their proposed system will have little impact on others
within the organization, nor will it be material from the viewpoint of the overall organization. In this
situation, the users are already motivated to bring about change. Thus activities to accomplish successful
entry are minor or unnecessary.
On the other hand, consider a solution where potential solutions will have a widespread impact on the
overall organization. Activities to accomplish successful entry are now critical. Information systems
professionals must seek to establish themselves as legitimate change agents among the stake holders.
Moreover they must seek to foster among the stakeholders a commitment to change. If potential
solutions will have a significant impact on task and social systems, a spirit of collaborative analysis and
evaluation among stakeholders must be developed.
Once the entry is successful, a preliminary study can be carried out to evaluate the feasibility of the new
system. A Feasibility study team should be constituted
Draw representatives from the departments affected by the project
At least one person must have a detailed knowledge of computers and systems design (called system
At least one person should have a detailed knowledge of
The organization
How current system operates
Information needs of the system
Defects in the existing system
Consultants from the outside

Key Areas of Feasibility
Following aspects/criteria can be covered in a feasibility study.
Technical Feasibility – is the available technology sufficient to support the proposed project? Can the
technology be acquired or developed?
Response times – time between request and execution
Volume of transactions which can processed within the given time
Capacity to hold files or records of a certain size
Number of users supported without execution

Operational Feasibility – compliance and adjustability with the way organization works with attitude to
change or chains of command.
Can the input data be collected for the system?
Is the output usable?

Economic feasibility – Do the benefits of the system exceed the costs?
It should be the BEST OPTION among those under consideration for the same purpose.
Behavioural feasibility – What impact will the system have on the user’s quality of working life?
Reduction is job stress
Job satisfaction
Quality of output by employees

18.3 Costs of Proposed System

18.4 Benefits from the proposed system
When a system is being introduced, management should consider the impact and amount of proposed
benefits. The purpose of this activity is to consider and
Better decision making
Possible in staff costs through increase of efficiency and not necessarily through redundancies.
In costs of running the department through more organized and efficient computerisation.
More sales revenue
Efficient use of staff time
Customer satisfaction
Better planning of resources required for operations e.g. inventory ordering, fixed asset utilization.

18.5 Classic lifecycle Model / Waterfall Model
Waterfall model is the earliest of software process models. Cascade of phases, the output of one is input to
the next. The waterfall model is a software development model (a process for the creation of software) in
which development is seen as flowing steadily downwards (like a waterfall) through the various phases.
Various phases of waterfall model are
Need Assessment
Entry and feasibility study
Analysis of the existing system
Information processing systems design – This also includes
Formulation of strategic requirements
Organizational & job design
Program Development – this includes
Application software acquisition & development
Hardware/system software acquisition
Procedures development
Operating & maintenance
Waterfall Model
Entry &
Waterfall Model
Operations &
Two phases need assessment and feasibility study, have already been explained in detail. Now let’s take a
look at other phases one by one.

18.6 Analysis of Existing system
Once feasibility has been drawn up, next stage comes for analysis of existing system. Even if the existing
system is to be replaced the designers must study the existing system as this improves the quality of the
work. For example
The new system may change the way employees are rewarded. In such a case the redistribution of rewards
may have to be carefully negotiated. Concerns of employees cannot be ignored. Analysis is a two-part
episode. Studying organization’s history, structure, culture – this would help to understand
The social & task systems
The way systems are coupled
Willingness of stakeholders to change (Change Management to be discussed later)
The greater the impact of the new system, greater time should be spent in understanding the present
organization. Analysis of existing product & information flows. This includes the use of various tools for
documenting the existing system. What these tools are will be discussed in detail in later Lessons.

System Design
System design includes the desired features and operations in detail, including screen layouts, business rules,
process diagrams other documentation. It involves converting the informational, functional, and network
requirements identified during the initiation and planning phases into unified design specifications. This
Formulation of strategic requirements
Organizational & job design
Elicitation of detailed requirements
Design of the information flow
Design of database
Design of user interface
Physical design
Design of hardware & software platform
Formulation of Strategic Requirements
The overall goals and objectives the system must accomplish. Forms can be accomplished in any form, for
A vague goal – increase in the wealth of shareholders
A specific goal – reduce staff turnover by 30%
Strategic requirements for the new system are identified based on perceived deficiencies of existing system.
Trying to fit people and organizations into information systems has been major reason for failure. If
strategic requirements are clear, stakeholders are better placed to consider and evaluate alternative designs.

Organizational & Job Design
Change in the strategic requirements will necessitate the change in the following for the parts of the
organization being affected
Organizational structure
Job descriptions for new or change in existing ones
Trying to fit people and organizations into information systems has been major reason for failure. So
change in both the above is important. If uncertainty surrounds the tasks to be accomplished in the
proposed system, loose organic organizational structures and job designs might be successful. Such promote
creativity and innovations. If organization is dominated by top management and culture is autocratic,
employees might be unwilling to accept the high level of responsibility.

18.7 Elicitation of Detailed Requirements
Designers must understand
What information an IS must provide
The data that must be captured to produce this information
Two approaches can be followed
Ask the stakeholders what they require – helps when they are clear about the requirements on
the basis of past experience or good understanding.
Analysis & experimentation – Where the ones bearing interest are not clear or have no past
experience, onus falls on the designer to work out the requirements.

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