This part of ISO/IEC 9506 defines the Manufacturing Message Specification within the OSI application layer in terms of an abstract model defining the interaction between users of the service; the externally visible functionality of implementations confirming to ISO/IEC 9506, in the form of procedural requirements associated with the execution of service requests; the primitive actions and events of the service; the parameter data associated with each primitive action and event; the relationship between, and the valid sequences of, these actions and events. The service defined in this part is that which is provided by the Manufacturing Message Specification protocol.