A model is a representation of the reality, a simplified abstraction for a dedicated usage. Models not only contribute to a better under-standing of structure and behavior, but also help to understand the system more clearly earlier on in the development phase. To ease the understanding of the purpose, models rely on graphical notations, e.g. a physical equation, a 3D mechanical drawing, an electronic scheme, or a behavioral description.
From a structural point of view, three pillars are essential for modeling: