The IODD data type OctetStringT is mapped to an array of the OPC UA DataType Byte. This mapping, instead of using the OPC UA DataType ByteString, allows to always provide the length of the array. The OctetStringT provides the mandatory element fixedLength which is directly mapped to the ArrayDimensions Attribute. If the value can directly be mapped to a Variable (see section 12.3), the VariableType BaseDataVariableType is used with no additional Properties.