Incremental Model

The incremental build model is a method of software development where the product is designed, implemented and tested incrementally (a little more is added each time) until the product is finished. It involves both development and maintenance. The product is defined as finished when it satisfies all of its requirements. This model combines the elements of the waterfall model with the iterative philosophy of prototyping.

The product is decomposed into a number of components, each of which is designed and built separately (termed as builds). Each component is delivered to the client when it is complete. This allows partial utilization of the product and avoids a long development time. It also avoids a large initial capital outlay and subsequent long waiting period. This model of development also helps ease the traumatic effect of introducing a completely new system all at once. There are, however, several problems with this model.

Advantages of Incremental model:

Generates working software quickly and early during the software life cycle.
This model is more flexible – less costly to change scope and requirements.
It is easier to test and debug during a smaller iteration.
In this model customer can respond to each built.
Lowers initial delivery cost.
Easier to manage risk because risky pieces are identified and handled during it’d iteration.
Disadvantages of Incremental model:

Needs good planning and design.
Needs a clear and complete definition of the whole system before it can be broken down and built incrementally.
Total cost is higher than waterfall.
When to use the Incremental model:

This model can be used when the requirements of the complete system are clearly defined and understood.
Major requirements must be defined; however, some details can evolve with time.
There is a need to get a product to the market early.
A new technology is being used
Resources with needed skill set are not available
There are some high risk features and goals.