Service-oriented architectures are the upcoming business standard for realizing enterprise information systems, thus creating a need for analysis and design methods that are truly service-oriented. Most research on this topic so far takes a software engineering perspective. For a proper alignment between business and IT, a service perspective at the business level is needed as well. In this paper, a unified view of services is introduced by means of a service ontology, service classification and service layer architecture. On the basis of these service models, a service design method is proposed and applied to a case from the literature. The design method capitalizes on existing value modeling approaches.