Subject: Software Engineering

Topic: Process Models

Difficulty: High

Incremental Model is combination of one or more Waterfall Models. In Incremental Model, Project requirements are divided into multiple modules and each module is developed separately. During development of each module, waterfall model is followed for each module development separately.

Each developed module in Incremental Model is standalone feature and could be delivered to the end users to use it. On incremental basis other modules are integrated as additional features one after another and finally delivered to the client. In Incremental Model no need to wait for all the modules to be developed and integrated.

As each module is standalone application and there is no dependencies on other modules so we can deliver the project with initial developed feature and other features could be added on incremental basis with new releases.In incremental model the whole requirement is divided into various builds. Multiple development cycles take place here, making the life cycle a “multi -waterfall” cycle.

Cycles are divided up into smaller, more easily managed modules. Incremental model is a type of software development model like V-model, Agile model etc.In this model, each module passes through the requirements, design, implementation and testing phases. A working version of software is produced during the first module, so you have working software early on during the software life cycle. Each subsequent release of the module adds function to the previous release. The process continues till the complete system is achieved. For example:

In the diagram above when we work incrementally we are adding piece by piece but expect that each piece is fully finished. Thus keep on adding the pieces until it’s complete. As in the image above a person has thought of the application. Then he started building it and in the first iteration the first module of the application or product is totally ready and can be demoed to the customers. Likewise in the second iteration the other module is ready and integrated with the first module. Similarly, in the third iteration the whole product is ready and integrated. Hence, the product got ready step by step.

Diagram of Incremental model:

Advantages of Incremental model:

i ) Generates working software quickly and early during the software life cycle.

ii ) This model is more flexible – less costly to change scope and requirements.

iii ) It is easier to test and debug during a smaller iteration.

iv ) In this model customer can respond to each built.

v ) Lowers initial delivery cost.

Disadvantages of Incremental model:

i ) Needs good planning and design.

ii ) Needs a clear and complete definition of the whole system before it can be broken down and built incrementally.

iii ) Total cost is higher than other traditional model..