" Models are used as substitutes for originals because properties of the latter are of interest and the originals are not going to be investigated themselves. There may be a number of reasons for that such as taboos preventing from studying the original itself, or inability, the involved cost in terms of resources or moral damage being intolerable, or similar . For an investigator I it makes only sense to consider an entity M as a substitute of an entity O, if I can (1) establish an analogy, similarity, or similar relation between M and O that permits the substitution of O by M with respect to purpose and means, time-horizon etc. , and (2) I can actually investigate M in the required way. That implies firstly that M does not have the properties of O that prevent I from investigating O. Also other properties of O may not be properties of M. In that sense a model is more abstract than its original. Boat C Flying Model R Secondly, a model M will in general have properties that O does not have and that actually aid I in investigating M. 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. "

" [2] Wieringa, R. J. ; "Algebraic foundations for dynamic conceptual models"; PhD dissertation Free University of Amsterdam; 17 May 1990. [3] Kaschek, R. ; "Modeling ontology use for information systems"; In: Althoff, K. -D. & Dengel, A. Boat Case Display Model & Bergmann, R. & Nick, M. "