Completing the Development Cycle

The last three phases of the development cycle close the cycle's loop and bring what has been learned in development and the marketplace back to the "drawing board" for the next version. Successful software may enjoy many cycles of revision and regeneration over its total life-cycle design lifetime. For business enterprise application software, seven or eight versions of a fundamentally good design over 20 years is not unknown. Although software is not manufactured like hard goods, it is designed, redesigned, and redesigned again, many times. This holds true not only for applications software sold by third-party vendors, but also for software developed by management information system (MIS) organizations for use by a single company. The two rules of thumb from the earliest days of business software development were as follows:

• A new application must be developed three times to get it right.

• An application's maintenance cost over five years is equal to the package's initial development cost.

The first may not be so different from the situation with hardware engineering and development, but the second is very different indeed.