This document specifies messaging among user, interface and service objects in the HES gateway to enable interworking among home cluster systems and interoperability among the applications supported by these cluster systems, as well as a common user interface to these cluster-system applications. This common user interface provides input and output methods for user information exchange to access, monitor and control applications running on home cluster systems. This document specifies messaging among the required service and interface modules from the interoperability standard necessary for interworking and incorporation of these modules in the HES gateway (ISO/IEC 15045 series).