" What the investigator I does in modeling is formulating a problem P in terms of the original O, translate that problem into a problem P' in terms of M, obtain a solution S' of P' and translate S' into a solution candidate S of P in terms of O. If S is actually a solution of P then the modeling process was successful and can be terminated . If, however, that is not the case then the investigator I can start over with a different problem, model, means of investigation, or relation between model and original. It is worth noting that the concept of solution to a problem depends on the investigator, its purpose, intended means of investigation, time-horizon of that investigation and so forth. What has been presented here so far essentially is due to Stachowiak, [1]. To understand how then models are used in more detail one needs to distinguish from each other the various reference modes in which the investigator puts the model with respect to the original. The reference modes that perhaps are most important in computing are: (1) descriptive, i. Male Model Photographye. , the model describes the original. "

", the model prescribes the original. If the deviation from model to original cannot be tolerated then the original has to be changed. Design models are in a prescriptive reference mode to their originals, i. e. , the implementation. (3) idealizing, i. e. Male Model Photographer, the model is supposed to deviate from the original and as long as there is a good reason for that one doesn't worry. Software process models are in an idealizing reference mode to the actually realized software process. "