For improving the efficiency and effectiveness of business collaboration, the need emerges to inter-organizationally match e-business services. Recent research activities show heightened attention into that direction with the ecosystems-emergence of service-oriented computing clouds. As this increases the business-, conceptual-, and technical governance complexity, a need exists for using a reference architecture to evaluate and design standard-, and concrete architectures for business-to-business (B2B) collaboration. In this paper, we fill that gap by presenting the eSourcing Reference Architecture eSRA that emerges from B2B-research projects and we check this with a scenario-based validation method. We demonstrate how eSRA enables a quick evaluation of not only research-based B2B-architectures but also of industry application suits. That way, we show the usability and applicability in that with the help of eSRA, system designers directly establish a comprehensive understanding of fundamental B2B concepts and develop higher-quality domain-specific architectures.