ISO/IEC 19793:2015 defines use of the unified modelling language (UML 2.4.1 superstructure specification, ISO/IEC 19505-2, for expressing system specifications in terms of the viewpoint specifications defined by the reference model of open distributed processing (RM-ODP, Rec. ITU-T X.901 to X.904 | ISO/IEC 10746 Parts 1 to 4) and the Enterprise Language (Rec. ITU-T X.911 | ISO/IEC 15414). It covers: a) the expression of a system specification in terms of RM-ODP viewpoint specifications using defined UML concepts and extensions (e.g., structuring rules, technology mappings, etc.); b) relationships between the resultant RM-ODP viewpoint specifications. ISO/IEC 19793:2015 is intended for the following audiences: - ODP modellers who want to use the UML notation for expressing their ODP specifications in a graphical and standard way; - UML modellers who want to use the RM-ODP concepts and mechanisms to structure their UML system specifications; - modelling tool suppliers, who wish to develop UML-based tools that are capable of expressing RM-ODP viewpoint specifications.