This Recommendation / International Standard is based on the framework of abstractions and concepts developed in the Reference Model for Open Distributed Processing (ITU-T Rec. X.902 / ISO/IEC 10746-2 and ITU-T Rec. X.903 / ISO/IEC 10746-3). This Recommendation / International Standard defines how interactions between computational objects in a computational specification of a system relate to protocol support for those interactions in an engineering specification of that system.