What is a Model?

Abstract

With the recent trend to model driven development a commonly
agreed notion of \model" becomes a pivotal issue. However, currently
there is little consensus about what exactly a model is and what it is
not. Furthermore, basic terms such as \metamodel" are far from being
understood in the same way by all members of the modeling community.
This article attempts to start establishing a consensus about generally
acceptable terminology. Its main contribution is the distinction between
two fundamentally different kinds of models, i.e. \type model" versus
\token model". The recognition of the fundamental difference in these
two kinds of models is crucial to avoid misunderstandings and unnecessary
disputes among members of the modeling community.