Incremental/Iterative model

Incremental/Iterative model

This model does not attempt to start with full specification of requirements. Multiple development cycles take place here, making the life cycle a “multi-waterfall”

cycle. Cycles are divided up into smaller, more easily managed iterations. Each iteration passes through the requirements, design, implementation and testing phases.
A working version of software is produced during the first iteration, so you have working software early on during the software life cycle. Subsequent iterations build

on the initial software produced during the first iteration.

Key Points
§ Development and delivery is broken down into increments
§ Each increment delivers part of the required functionality
§ Requirements are prioritised and the highest priority requirements are included in early increments
§ Once the development of an increment is started, the requirements are frozen
§ Requirements for later increments can continue to evolve


Advantages
§ System functionality is available earlier and customer does not have to wait as long.
§ Early increments act as a prototype to help elicit requirements for later increments.
§ The highest priority functionalities tend to receive more testing.
§ More flexible – less costly to change scope and requirements.
§ Easier to test and debug during a smaller iteration.
§ Easier to manage risk because risky pieces are identified and handled during its iteration.
§ Each iteration is an easily managed milestone.

Disadvantages
§ Each phase of an iteration is rigid and do not overlap each other.
§ Problems may arise pertaining to system architecture because not all requirements are gathered up front for the entire software life cycle.