Erect means build or upright. If you erect a house, you build it. If you stand erect, you hold your body as tall as possible.
A mathematical model is a description of a system using mathematical concepts and language.The process of building a mathematical model is termed mathematical modeling.Mathematical models are used in the natural sciences (such as physics, biology, earth science, meteorology) and engineering disciplines (e.g. computer science, artificial intelligence). mathematical model is a description of a system using mathematical concepts and language.
Universal Systems Model. A systematic approach implies that the designer has a conceptual model of the process. Models are abstractions of reality. Physical models (model cars, airplanes, dolls, etc) are the closest visual representation while mathematical models (formulas) dont look anything like the real object or process.