Incremental Model

´  Incremental Model is a process of software development where requirements are broken down into multiple standalone modules of SDLC

´  Incremental development is done in steps from analysis design, implementation, testing/verification, maintenance.

´  Each iteration passes through the requirements, design, coding and testing phases.

´  Each subsequent release of the system adds function to the previous release until all designed functionality has been implemented.

´  Prioritizes the services to be provided by the system.

´  Maps these requirements to Increment based on priority.

´  Freezes requirement for the current Increment.

´  Requirements for the later increments can evolve concurrently.

´  Each Increment release is a working system:

´  Allows user to experiment.

´  Can be put into service right away.

Why incremental model is used

´  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.

Characteristics of an Incremental module includes:

´  System development is broken down into many mini development projects

´  Partial systems are successively built to produce a final total system

´  Highest priority requirement is tackled first

Once the requirement is developed, requirement for that increment are frozen

´  Requirements of the system are clearly understood

´  When demand for an early release of a product arises

´  When software engineering team are not very well skilled or trained

´  When high-risk features and goals are involved

´  Such methodology is more in use for web application and product based companies

Advantages:

´  Early utilization:

´  the 1^st increment satisfies the most critical requirement.

´  Early increments can serves as prototypes.

´  Lower risk of overall project failure.

´  Most crucial and basic services are implemented first.

´  It is flexible and less expensive to change requirements and scope

´  This model is less costly compared to others.

Problems:

´  Hard to map requirement into small increments (< 20,000 lines of code).

´  Becomes invalid when there is time constraint on the project schedule or when the users cannot accept the phased deliverables.

´  Contractual problems

´  Requires good planning and design.

´  Budget may over runs.