The lack of adequate support for the development of mathematical process models confines the application of model-based techniques in the design and operation of complex chemical processes. To overcome this problem considerable effort has to be put into the development of knowledge-based software tools. The development of such tools requires a proper structuring of process models followed by a formalization of their representation. In this contribution, elementary modeling objects for the representation of the behavioral aspects of chemical processes are defined. The introduced methodology is based on ontological principles and general systems theory. Its formalization in terms of the object-oriented data model VeDa allows the formal representation of the mixed types of equations and formalisms arising in mathematical process models. It provides generality and extensibility since new types of equations or formalisms can be incorporated easily.