This abstract DataType defines a value that can have any valid DataType.
It defines a special value null indicating that a value is not present. This abstract DataType does not have an encoding defined in OPC 10000-6. Any direct subtype shall only be defined in NameSpaceIndex 0.
A BaseDataType is an abstract DataType which represents any possible value including arrays of values. When an array of BaseDataTypes is specified each element of the array can be a scalar or array of any DataType.
When a BaseDataType is used in conjunction with a ValueRank then the ValueRank specifies whether there is an array of BaseDataType values. The ValueRank does not restrict the content of each element.