The DataTypeDefinition attribute was introduced in OPC UA 1.04 and provides a simplified option to get access to the meta-data of a structure DataType.
The older and deprecated way to expose the description of structure DataTypes in an OPC UA server address space is a DataTypeDictionary.
At this point, the OPC UA Device Support only uses a DataTypeDictionary. But newer servers have stopped providing this deprecated option by default and might at some point not support it anymore.
The Device Support should be able to use both options, preferring the newer standard.
The DataTypeDefinition attribute was introduced in OPC UA 1.04 and provides a simplified option to get access to the meta-data of a structure DataType.
The older and deprecated way to expose the description of structure DataTypes in an OPC UA server address space is a DataTypeDictionary.
At this point, the OPC UA Device Support only uses a DataTypeDictionary. But newer servers have stopped providing this deprecated option by default and might at some point not support it anymore.
The Device Support should be able to use both options, preferring the newer standard.