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

The semantic of this ReferenceType is, in addition to the semantic of its supertype, to indicate that the field shall not be provided. This indicates to Clients, that the Server will never provide the optional field and that they are not allowed to write a value containing the optional field. For Unions that implies that the DataType of the field shall never be used in the Union.

This ReferenceType shall only be applied to fields declared as optional, i.e., either fields having IsOptional set to true on Structured DataTypes where the StructureType is StructureWithOptionalFields; or fields of Structured DataTypes where the StructureType is Union or UnionWithSubtypedValues.

Note: As the ReferenceType defines that the field shall not be provided, adding additional restrictions or meta data is not helpful and should be avoided.