Design for changeability (DfC): Principles to enable changes in systems throughout their entire lifecycle

In the past decades the world has been changing in almost every aspect. Systems development is facing rapidly changing and increasingly global environments in markets, competition, technology, regulatory, and societal systems. Systems to be delivered must be designed not only to meet customer or market needs, but also increasingly to meet requirements and constraints of systems sharing its operational context and throughout their entire lifecycle. The design of a system must provide for a continuous evolution of its architecture either by upgrading a system already in service or releasing a new version or derivative. Based on these key challenges imposed on development systems, this paper will evolve the idea of incorporating changeability into a system architecture. Flexibility, agility, robustness, and adaptability as four key aspects of changeability will be defined and described. Design principles to enable flexibility, agility, robustness, and adaptability within systems are proposed and described. A basic approach outlining and guiding an application of the framework described concludes this paper. Examples from varying industries will illustrate the applicability and implementation of selected principles. Thus this paper spans a view from why, when, and how changeability has to be incorporated into a system's architecture. © 2005 Wiley Periodicals, Inc. Syst Eng 8: 342–359, 2005