To facilitate the planning of product processes, the Formalized Process Description (FPD) model was proposed. It enables users to graphically describe the requirements of a production process. However, the FPD model has limits. To overcome these limits, this paper describes an extension of the FPD model, which is called the Extended FPD model. The objects in the Extended FPD model are assigned types and logical statements to represent their specifications. Hence, the expressive power of the FPD model is enhanced. In this paper, a formal definition of the Extended FPD model is also presented. Based on this definition, a set of rules is defined to detect the contradictions automatically in the Extended FPD model. In addition, the description of requirements by using the Extended FPD model can also enable the integration of more formal verification methods.