Despite the ubiquity of services, there is still no consensus on their exact nature and structure. This consensus, however, is necessary to unambiguously describe and trade services physically as well as in an Internet of Service. To make some progress towards a shared conceptualization, we present in this paper a general service model based on the DOLCE foundational ontology. In our understanding, a service is essentially composed of a service process whose core actions (delivered by a service producer to a service consumer) comply with the exposed description of a service provider's commitment. Each service belongs to a larger service system process which obeys legal and pricing constraints. We illustrate the model's usefulness and relevance by the means of a continuous example.