Service-oriented architectures (SOA) and web service technologies have been proposed to respond to some central interoperability challenges of heterogeneous health information systems (HIS). We propose a model, which we are using to define services and solutions for healthcare applications from the requirements in the healthcare processes. Focusing on the transition from the process level of the model to the application level, we also present some central design considerations, which can be used to guide the design of service-based interoperability and illustrate these aspects with examples from our current work in service-enabled HIS.