Waterfall Methodology - What is it?
The Waterfall model is a software development process, that was first introduced by Dr. Winston W. Royce in 1970. It is a linear sequential flow, which means that any phase in the development process begins when the previous phase is completed, the phases do not overlap. The outcome of one phase acts as the input for the next phase sequentially.
Waterfall approach was the first SDLC Model to be used widely in Software Engineering to ensure success of the project. In "The Waterfall" approach, the whole process of software development is divided into separate phases as following.
Requirement Gathering and analysis − All requirements of the system to be developed are documented in a requirement specification document (PRD).
System Design − The requirement specifications from first phase are studied in this phase and the system design is prepared. This system design helps in specifying hardware and system requirements and helps in defining the overall system architecture (SRS).
Implementation − With inputs from the 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.
All these phases are cascaded to each other in which progress is seen as flowing steadily downwards (like a waterfall) through the phases. The next phase is started only after the defined set of goals are achieved for previous phase and it is signed off.
Waterfall Model - Advantages
Some of the major advantages of the Waterfall Model are as follows −
Each development phase is clearly defined and proceeds in strict order one at a time. Development moves from requirements, through design, implementation, testing, installation, troubleshooting, and ends up at operation and maintenance.
A schedule can be set with deadlines for each stage of development, milestones and tasks are well understood and easy to arrange. Waterfall model allows departmentalization and control.
Development is easy to manage as each phase has specific outputs and review process.
Works well for smaller projects where requirements are clear and understood.Process and results are well documented.
Waterfall Model - Disadvantages
The major disadvantages of the Waterfall Model are as follows −
Not advisable for complex and object-oriented projects. It does not allow much reflection or revision. Changing requirements can’t be accommodated in any phase.Once an application is in the testing stage, it is very difficult to go back and change something that was not well-documented or thought upon in the concept stage.When the product is in testing phase, it is very difficult to go back and change something which is left during the requirement analysis phase.
High amounts of risk and uncertainty.
Not suitable for the projects where requirements are at a moderate to high risk of changing.
As testing is done at a later phase, there is a chance that challenges and risks at earlier phases will not be identified.
Integration is done as a "big-bang. at the very end, which doesn't allow identifying any technological or business bottleneck or challenges early.
No working software is produced until late during the life cycle.
Poor model for long and ongoing projects.It is difficult to measure progress within stages.
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