Vviewpoints
DOI: 10.1145/1409360.1409371
The profession of iT
evolutionary system
Development

Large systems projects are failing at an alarming rate. It’s time to take evolutionary design methods off the shelf.

MaNy criTical large systems are failing. The replacement FAA air traffic control system, the FBI virtual case file, and the Navy Marine Corps Internet (NMCI), are a few of the many billion-dollar systems that could not deliver the functions needed. In stark contrast, the Boeing 777 aircraft, the Global Positioning System (GPS), and the U.S. Census database system have been outstanding successes. Why do some systems fail and others succeed?

Development time is the critical factor. This is the time to deliver a system that meets the requirements set at the beginning of the development process. If development time is shorter than the environment change time, the delivered system is likely to satisfy its customers. If, however, the development time is long compared to the environment change time, the delivered system becomes obsolete, and perhaps unusable, before it is finished. In government and large organizations, the bureaucratic acquisition process for large systems can often take a decade or more, whereas the using environments often change significantly in as little as 18 months (Moore’s Law).

The Boeing 777, GPS, and U.S. Census data systems were developed for stable environments—they were completed before any significant changes occurred in their requirements. In contrast, the FAA replacement system, FBI Virtual Case File (see www.spectrum.ieee.org/

sep05/1455), NMCI (GAO⁴, www.nm- cistinks.com) all faced dynamic environments that changed faster than their development processes could. Predecessors of these systems were successful because their environments were stable, but the current generations en-

 

countered trouble because their environments had become too dynamic.

The traditional acquisition process tries to avoid risk and control costs by careful preplanning, anticipation, and analysis. For complex systems, this process usually takes a decade or more. Are there any alternatives that would take much less time and still be fit for use?

Yes. Evolutionary system development produces large systems within dynamic social networks. The Internet, World Wide Web, and Linux are prominent examples. These successes had no central, preplanning process, only a general notion of the system’s architecture, which provided a framework for cooperative innovation. Individuals in the network banded into small groups to quickly produce or modify modules in the architecture. They tested their modules by asking other users to try them. The systems evolved rapidly

in many small increments that aligned with current perceptions of the using environment.

Moreover, the evolutionary process embraces risk, and the patience to see what emerges. It works with nature’s principle of fitness in the environment:

 

components that work well survive, and those that do not are abandoned.

The astonishing success of evolutionary development challenges our common sense about developing large systems. We need to learn from these systems, because evolutionary development may be the only way to achieve satisfactory replacements for aging large systems and to create new, unprecedented systems.

Evolutionary development is a mature idea that has languished away from mainstream practice. In this column, we will analyze why evolutionary development does not fit the current common sense and why we need to work to change that.

 

our current common sense From its founding in 1968, the software engineering field set out to address the “software crisis,” a persistent inabil-