Designing electronic markets is still a rather intricate process. eNegotiation - and thereby trading rules - embody the core of the institution ”electronic market”. Although success or failure of electronic markets is strongly influenced by the design of the trading rules the design process currently constitutes a trial-and-error game. It is only partly guided by theory and by all available evidence, but it also uses ad-hoc methods to resolve issues about which theory is silent. Consequently, this paper suggests a conceptual framework for domain-independent eNegotiation design. The core of the framework is described by an expertise model which divides knowledge into three categories: domain, task and inference knowledge. The main contribution of this expertise model is twofold. Firstly, it can guide the further acquisition of knowledge. Secondly, a knowledge based system that could be built upon this model renders reproducible designs. In case the expertise model is sufficiently...