implementation. [MCF2003]
Modeling, in the broadest sense, is the cost-effective use of something in place of something else for some cognitive purpose. It allows us to use something that is simpler, safer, or cheaper than reality instead of reality for some purpose.
A model represents reality for the given purpose; the model is an abstraction of reality in the sense that it cannot represent all aspects or reality. This allows us to deal with the world in a simplified manner, avoiding the complexity, danger and irreversibility of reality.
Jeff Rothenberg