SDLC - Waterfall Model

The first introduced Process Model is Waterfall Model hence it is basic mode of SDLC which is also known as mother of all other model.

It is simple to understand and use. It is referred to as a linear-sequential life cycle model where each phase should be executed fully before the next phase can begin. This model is basically used for the project where there are no uncertain requirements and small. Here testing starts only when the development is complete. The phases do not overlap in waterfall model.

The sequential phases in Waterfall model are:

• Requirement Gathering and analysis: All possible requirements of the system to be developed are captured in this phase and documented in a requirement specification doc.
• System Design: The requirement specifications from first phase are studied in this phase and system design is prepared. System Design helps in specifying hardware and system requirements and also helps in defining overall system architecture.
• Implementation: With inputs from system design, the system is first developed in small programs called units, which are integrated in the next phase. Each unit is developed and tested for its functionality which is referred to as Unit Testing.
• Integration and Testing: All the units developed in the implementation phase are integrated into a system after testing of each unit. Post integration the entire system is tested for any faults and failures.
• Deployment of system: Once the functional and non-functional testing is done, the product is deployed in the customer environment or released into the market.
• Maintenance: There are some issues which come up in the client environment. To fix those issues patches are released. Also to enhance the product some better versions are released. Maintenance is done to deliver these changes in the customer environment.

 When to use the waterfall model:

• Application definition is stable.
• The requirements are well known, clear and understood.
• Requirements should not have any ambiguous
• The project is smaller.

Advantages:

• In this model each stage is clearly defined.
• This model is simple and easy to understand and use.
• In this model execution happens sequentially.
• In this model phases are executed and completed one at a time and phases do not overlap.
• Waterfall model suits well for projects where requirements are well understood and for shorter projects.
• In this model each phase process and results are documented well.

Disadvantages:

• This model is not suitable for complex and object-oriented projects.
• In this waterfall-model requirement changes are very difficult once an application is in the testing phase.
• Changes are not allowed hence it is not suitable for moderate to high risk of changing projects.
• After development of the product and if any deviations occur then the cost of fixing those issues are high and time consumption is more, because we need to update from document till the code.
• Time consumption is more because each phase should execute completely.
• Since it is executed in sequential order, the parallel deliverables are not possible.
• There is risk and uncertainty.
• Not suitable for the projects where requirements are at a moderate to high risk of changing.
• There is no customer interaction during the development of the product.