If a DataType Nodeis exposed in the AddressSpace, it shall provide its DataTypeEncodingsusing HasEncoding References. These Referencesshall be bi-directional. Figure 12provides an example how DataTypesare modelled in the AddressSpace.
The information on how to encode the DataTypeis provided in the Attribute DataTypeDefinitionof the DataType Node. The content of this Attributeshall not be changed once it had been provided to Clientssince Clientsmight persistently cache this information. If the encoding of a DataTypeneeds to be changed conceptually a new DataTypeneeds to be provided, meaning that a new NodeIdshall be used for the DataType. Since Clientsidentify the DataTypevia the DataTypeEncodings, also the NodeIdsfor the DataTypeEncodingsof the DataTypeshall be changed, when the encoding changes.