Companies model their business processes either for documentation, analysis, re-engineering or automation purposes; usually using normalized business process modeling languages such as EPC or BPMN. Although these models explain how the processes should be performed and by whom, they abstract away their business rationale (i.e. what is offered and why). Business modeling aims to answer the latter and different frameworks have been proposed to express the process in terms of value-chains. Ensuring alignment between both of these views manually is error prone and labor intensive. In this paper, we present a novel approach to derive a value-chain - expressed in REA - from a business process model expressed in BPMN. At the heart of our approach and our main contribution lies a set of nine general business patterns we have defined and classified as structural and behavioral patterns.