Service-based applications can be built according to multiple technologies. Although there is a clear need for a model integrating them in multiple real-world contexts, no integrated model does (yet) exist. In this paper we introduce a model as a foundation for heterogeneous services, with particularly studying SOAP/WS* and RESTful models. The model completely abstracts away from service implementations, composes them in a truly concurrent manner, and supports asynchronous message passing as well as mobility of typed channels. We consider the application of this model to the problem of type checking messages and communications in presence of channel mobility and malicious agents.