This paper presents a conceptual framework for service modelling. This framework provides a conceptual basis for the modelling and reasoning about services, and the operations, such as composition and discovery, that are performed on them at design and run-time. In particular, the framework should facilitate the use of different service description languages tailored to different service aspects, such as the behaviour of a service and the information it manipulates, or design tasks, such as modelling, analysis and implementation. The idea is that models produced by these languages can be mapped onto a single, common conceptual framework, thereby facilitating one to relate these models, e.g., to verify consistency or conformance. Therefore, a requirement on the framework is to capture all elementary and generic service properties that are relevant during the service development process. We capture these properties by analysing existing service definitions and from earlier experience.