The evolution of wireless network technology has led to an increasing number of applications for mobile use. In addition, the paradigm of service-oriented architectures allows a composition of applications based on distributed web services. By using registries it becomes possible to choose the appropriate services at runtime. It needs to be considered that services for mobile use may have different scopes. For instance, routing or weather services may be dedicated to a specific region so that they may be useless if a user?s area of interest does not match the service?s scope. It is hence necessary to identify and use those services with a scope that corresponds to the relevant context such as a user?s location. Moreover, if the context changes, it is desirable to automatically switch between different equivalent service instances to provide a user with a continuous connection to a desired service. We denote this mechanism as service roaming. This paper presents the major concepts needed for service roaming as well as a roaming model based on n-dimensional context spaces.