Software Design 2e - DIM

198Design processes and design strategiesFigure 9.4A Potts and Bruns model of the processes involved in design steps.(After Potts (1989) © 1989 IEEE)supplement to our basic process model, since it can be used to elaborate on the formof specific components from the process model.The design transformation and elaboration steps in a method can be considered asembodying local tactical decisions, which are in turn guided by the strategy that isadopted by a particular method. Strategic issues, for their part, are generally concernedwith large-scale factors such as the domain of a particular problem, specific constructionaland behavioural characteristics and likely forms of implementation.Where strategy does play a particularly important part is in determining the formof the initial model that a designer will create in order to describe the problem. Whilealmost all design methods claim to begin by modelling the ‘real world’, the form of theDesign Virtual Machine (DVM) that is used for this description can vary very widely,and can make use of a wide variety of viewpoints.There is also a historical perspective to this issue of how the design process isperformed. David J. Koepke (1990) has recorded his research into the evolution of