Within the scope of this book, an interactive user interface (GUI) to the process--metallurgic reactor model (PRM) is to be developed. The PRM was developed and implemented by the Institute of Metallurgy at Clausthal University of Technology and is available as a C-source code. The principal purpose of this user interface is to give an understanding of the different steps of the steel production process and the "driving" of a specific virtual plant by the user. The second task is to support interactive case studies for the optimization of the model parameters and finally the overall operation of the plant. The PRM treats a specific way of steelmaking, separating this process into two steps. First, the production of raw steel in an electric arc furnace (EAF) which is implemented in the PRM as EAF07 module. Second, the alloying and transportation of the raw steel which takes place in a ladle furnace (LF) and is implemented in the PRM as LF07 module likewise.