The Manufacturing Message Specification is an application layer standard designed to support messaging communications to and from programmable devices in a Computer Integrated Manufacturing (CIM) environment. This environment is referred to in ISO 9506 as the manufacturing environment. This part of ISO 9506 does not specify a complete set of services for remote programming of devices, although provision of such a set of services may be the subject of future standardization efforts. This part of ISO 9506 defines the Manufacturing Message Specification within the OSI application layer in terms of: a) an abstract model defining the interaction between users of the service; b) the externally visible functionality of implementations conforming to ISO 9506, in the form of procedural requirements associated with the execution of service requests; c) the primitive actions and events of the service; d) the parameter data associated with each primitive action and event; e) the relationship between, and the valid sequences of, these actions and events. The service defined in this part of ISO 9506 is that which is provided by the Manufacturing Message Specification protocol. The service may be used by other application layer service elements or by other elements of the application process. This part of ISO 9506 does not specify individual implementations or products, nor does it constrain the implementation of entities and interfaces within a computer system. This part of ISO 9506 specifies the externally visible functionality of implementations together with conformance requirements for such functionality.