The success of the service-oriented computing (SOC) paradigm considerably depends on the ability of service consumers to distinguish between published services and choose the ones best suited for a development project. Current SOC standards primarily give information about technical service properties such as the programming interface and the binding information. This enables designers to analyze the technical compatibility of services with the rest of the system. On the basis of such technical information, it is difficult to assess which business semantics a service actually implements and whether it is suited to satisfy functional requirements, however. In this paper, we therefore propose the WS-Functionality language which allows providers to specify the business semantics of software services in business terms. In a design science approach, we firstly describe how conceptual models, which contain business terms and relationships between them, can be used to specify the business semantics of services. Building upon this solution concept, we present the language constructs of WS-Functionality and show a prototypic implementation as proof-of-concept. In a controlled experiment, we were able to support our claim that the information provided with WS-Functionality enhances the ability of service consumers to analyze the business semantics of services and judge whether it satisfies existing functional requirements.