The Cost of Change

In general the further a project is through its lifecycle the great the cost it is to introduce a change. The change could be a actual change in requirements due to changes in business or technical need, or a defect found during the testing phases at the end.

• A change required in analysis, requires a change in design
• A change required in design, requires a change in development
• A change required in development, requires a change in testing

The further we have to go back in the process the greater the impact on everything has come after it, and therefore the greater the overall cost to the project. If sufficiently large, the change could be rejected leaving the customer having paid for something they now no longer need.

Iterative, increment delivery and the fact that each release could potentially provide a usable product that releases value signficantly reduces the cost of change. By only focusing on those requirements that are required for the next release, less effort is consumed up front on analysis and design that has the potential to change in the future.

Even if a delivered piece of functionality is then subsequently changed, by the fact that it has been delivered and used, it has been releasing value to the customer. Therefore the overall cost of change is offset by the value it has already released.