Program evolution

摘要

Following a brief review of the development of the concept of program evolution, the paper identifies some of the program attributes that are changed over system life-time in response to evolutionary pressures. It recognises that their evolution may, in part, be due to inadequate specification, design and implementation technologies; the processes by which a system is conceived and implemented, and the primitives in terms of which this is done. Basically, however, evolution is recognised as intrinsic to the very nature of computer application, of computing systems, and, most significantly, of programs.All systems evolve. The peculiar feature of computing systems is their rate of evolution. Analysis of this phenomenon leads to the identification of levels of evolutionary development; thence to the concept of a continuous programming process supported by an integrated support environment. One model of such a process is outlined and then decomposed into a sequence of orthogonal elements or steps that can all be described by a common paradigm. The former provides a conceptual framework for the design of integrated support environments, the latter its core concept.