Modelica is an object-oriented language designed
for modeling and simulation of complex physical
systems. To enable the possibility for an engineer
to discover errors in a model, languages and com-
pilers are making use of the concept of types and
type checking. This paper gives an overview of
the concept of types in the context of the Model-
ica language. Furthermore, a new concrete syntax
for describing Modelica types is given as a starting
point to formalize types in Modelica. Finally, it is
concluded that the current state of the Modelica
language specification is too informal and should
in the long term be augmented by a formal defin-
ition.