An IODD variable having the IODD data type ArrayT is mapped to an OPC UA Variable with ValueRank OneDimensionalArray.
The data type used in the array of the IODD is the base for the mapping of the data type to OPC UA (see 12.2). That does include the VariableType to use and what Properties on the Variable shall exist.
The ValueRank Attribute of the OPC UA Variable shall be OneDimensionalArray.
The ArrayDimensions Attribute of the OPC UA Variable shall be an array with exactly one entry. The value of that entry shall be the size element of the IODD Variable.