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LESSON 18
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 provides
- Structure
- Methods
- Controls
- 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.
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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 rules. 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
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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
- Savings
- 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
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• Program Development – this includes
• Application software acquisition & development
• Hardware/system software acquisition
• Procedures development
• Testing
• Conversion
• Operating & maintenance
1
Waterfall Model
Need Assessment
Entry & Feasibility Study
System Analysis
System Design
Next
15
Waterfall Model
Procedures Development
Program Development
Testing
Operations & Maintenance
Changeover
Previous
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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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