Inter-organizational systems have significantly been affected by Service-oriented Architectures (SOA) andWeb Services - the state-of-the-art technology to implement SOA. SOA is said to enable quick and inexpensive changes of the IT in order to establish new business partnerships or to reflect changes in existing partnerships. However, current approaches to inter-organizational systems focus too much on existing Web Services standards and, thus, on the technology layer. In such an approach the technology drives the business. In this paper we analyze the shortcomings of this bottom-up approach. As an alternative we suggest a top-down methodology where the business requirements drive the technology. This methodology starts off with the business value perspective, leading to a business process perspective and resulting in an IT execution perspective. We do not invent any new approaches on each of these layers, rather we outline how existing approaches are used and combined into a business requirements driven approach to inter-organizational systems.