The HasFieldDescription is a concrete ReferenceType and can be used directly. It is a subtype of HierarchicalReferences.

The semantic of this ReferenceType is to link from a DataTypeRefinement Object refining a Structured DataType to a Variable representing a field of that Structured DataType, containing additional metadata, that may potentially restrict the usage of the field.

The SourceNode of References of this type shall be an Object of DataTypeRefinementType or a subtype.

The TargetNode of this ReferenceType shall be a Variable of BaseDataVariableType or a subtype. The BrowseName of the Variable shall have the same name as the field of the Structured DataType that it refines, and the same NamespaceIndex as the DataType, where the field of the Structure is defined. The DataType of the Variable shall follow the rules defined in 5.8.5.2, i.e., it can only be further restricted.

It is not allowed to reference two Variables with the same BrowseName using the HasFieldDescription ReferenceType or a subtype from the same SourceNode.