According to ongoing scholarly work in the information systems discipline, Business Process Management (BPM) and Service-oriented Architecture (SOA) are top-priorities gaining a great deal of attention in both industry and academia. Both approaches aim at convergence in order to bring business-oriented and technology-oriented stakeholders closer together and enable business system engineering in an increasingly viable manner. In our paper, we claim that only a holistic and complete approach to business system engineering is capable of creating sustainable value by facilitating the emergence of new and innovative electronic business models within and between organisational borders. Therefore, we provide a service-oriented methodology combining two well-established and promising approaches, the Semantic Object Model (SOM) and the Business Process Modelling Notation (BPMN). With this combined methodology, we are able to cover the design of an entire enterprise architecture. By addressing a business system in Home Telecare and deriving a business process model, which can eventually be controlled and executed by machines; in particular by composed web services, the full potential of a process-centric SOA is exploited. The guided design of enterprise architectures is highly relevant for both practitioners and researchers in the field of information systems.