In our project BSopt we have developed a model-driven approach towards inter-organizational systems. During its evaluation phase we recognized that different partner networks operate similar, but still slightly differ in some details. However, our current approach is limited with respect to re-use of models or parts thereof for different partner networks. Thus, we plan to incorporate well established design techniques from reference modeling into our approach leading to inter-organizational reference models. We believe that inter-organizational reference models will speed up the development and will improve the quality of inter-organizational systems. In this position paper we outline our plans of integrating the design techniques of reference modeling into inter-organizational system development even if we do not provide a solution yet.