A device is required to provide mandatory functionality. Optional functionality is not required, but if it is provided, it shall be supported as defined.
The IEC 61987 CDD is the source for the definition of properties according to IEC 61987 specification, which have an IRDI dictionary entry. These definitions include a version at the end after the “#” (e.g. #001). For easier readability, some IRDI dictionary definitions have been copied and added to this specification. Although highly unlikely, the IRDI definitions in this specification may deviate from IEC definitions as the IEC specification may change. In such cases the IEC 61987 CDD specification has precedence over the definitions in this specification.
The IRDI dictionary entries are referenced from the TypeDefinitions in this specification. When instantiating the TypeDefinitions, the instances shall have the same IRDI dictionary entries as defined for the TypeDefinitions in this specification. If an instance is based on a subtype, it shall have all IRDI dictionary entries of the subtype, and of the supertypes, as defined in this specification. The same applies for InstanceDeclarations. All instances based on InstanceDeclarations shall have the same IRDI dictionary entries as their InstanceDeclaration. If the InstanceDeclaration is overridden, also the InstanceDeclarations of the supertypes shall be provided. Note: As HasDictionaryEntry Reference is a non-hierarchical Reference and the IRDI Objects do not have ModellingRules, the OPC UA Information Model does not force this automatically.
The primary unit according CDD should be used as default unit and may be modified if applicable.