Holistic model building
As we have discussed above, a system is something that has no beginning and end, unless we want to extend our system from the currently known smallest particles to the assumed boundaries of all assumed universes.
The main point of system modelling is that it reasonably but arbitrarily defines the boundaries of the examinable entities according to its current knowledge and current purposes, and fitting these boundaries to construct the model following a bottom-up or top-down approach. This construction process may follow a logical process order or the already mentioned directions of fitting. As an example, we can take the logical process of making food, or the fitting of the food-making process into the larger system of agriculture and the system of digestion.
A system builder thinks holistically, taking into account the whole context and examining the independent behaviour of subsystems within this context. The latter is important when more details are needed, the former when details can be ignored and relations are important. The system builder decides whether something is important and requires attention or insignificant and can be ignored, according to the task and options.
The responsibility and the beauty of building systems lies precisely in this modelling process which departs from reality into certain directions.
The two resulting views—micro and macro—clearly show the approach.