Fitness for purpose requires the anticipation of change [software development]

All developers of software systems, and many of the customers for such systems, know that their products will undergo considerable changes during their lifetime. These changes are due to inadequate original specifications, changing functional requirements and mistakes of design and construction. It is the authors´ thesis that the anticipation of such change is an intrinsic original requirement of systems, and is therefore an important component of the quality of the systems. This is an internal component of quality that is best assessed by inspecting the production process rather than the product itself. They identify three related properties of methodically constructed software which contribute significantly to the anticipation of change. They concentrate on two methodologies, formal specification and functional programming, where the connection between the methodology and the properties mentioned is more unexpected