The waterfall model is a step by step process of activities performed to develop software. Waterfall model is the most common model of software development life cycle. It is a sequential process which performs requirement, analysis, design and implementation phases to develop a complete software product.
The risk inherent in waterfall model is:
• The product gets ready only when all the stages are completed which results in high risk and uncertainty at the end stage.
• In waterfall model it is difficult to determine the progress of the stages while development.
• It is a non-flexible model in which changes and adjustments are difficult and expensive to be done.
• Waterfall model can be used only when you have detailed planning and specification documentation. It requires lots of documentation work.
Waterfall model is the most common model of software development life cycle. It is a sequential process which performs requirement, analysis, design and implementation phases to develop a complete software product. If any changes or update are required at any phase then feedback loops are followed. This can be termed as iteration (maintenance) is being done.
When software product is developed using iterative and incremental model, the software is broken into set of increments. For each increment all the phases of waterfall model (requirement, analysis, design and implementation) are performed. That means that the software product is divided into a series of mini waterfall models and during each mini waterfall model iteration is performed.
Thus, iteration and incremental model is very much related to waterfall model. In iterative and incremental model the software is developed as a series of small phases using waterfall model.
In Spiral life cycle model risk analysis is done at each phase of software development.
Spiral model will be inappropriate in the following situations:
• As the spiral model concentrates much on the risk analysis so it is not appropriate for those projects in which risk assessment is not critical.
• Spiral model is not suitable for small projects which have low budget because cost of risk identification is high.
• Spiral model needs lot of time so is not suitable for the products which have time constraints and need to be completed as per schedule.
• If the project have well defined specification and clearly defined requirements then spiral model is not required.