The notion of computer systems as finished products that operate in a stable environment leads to viewing system enhancement as an error correcting activity. However computer systems change due to new requirements stemming from organisational changes and the users' experience with the system. Because of this, it is more fruitful to view system enhancement as an evolving activity. This is a better basis for balancing the technical and functional quality of a computer system during its working life.

On this basis we suggest that system enhancement should be planned, and that techniques known from system development should be applied also during enhancement. Both development and enhancement aim at adjusting computer systems to changes in usage. By means of a case study we show how our proposals for changes in the organisation of enhancement tasks in the computer department may be realized.