A server federation cooperatively interacts to fulfill service requests by communicating using data structures that follow a schema in which the meaning of the communicated data is implied by the schema. Thus, in addition to the data being communicated, the meaning of the data is also communication allowing for intelligent decisions and inferences to be made based on the meaning of the data. Cooperative interaction is facilitated over a wide variety of networks by messaging through a common API that supports multiple transport mechanisms. Also, mid-session transfer between client devices is facilitated by schema and the transport-independent messaging structure. The user interfaces of the client devices will appear consistent even if the client devices have different user interface capabilities.