Auxiliary coordinate variables (spatial and time) must contain missing values to indicate a void in data storage in the file but must not have missing data for any other reason. This situation may arise for unused elements in the incomplete multidimensional array representation, and in any representation if the instance dimension is set to a larger size than the number of features currently stored.   It is not permitted for auxiliary coordinate variables to have missing values for elements where there is non-missing data. Where any auxiliary coordinate variable contains a missing value, all other coordinate, auxiliary coordinate and data values corresponding to that element should also contain missing values. Data variables should (as usual) also contain missing values to indicate when there is no valid data available for the element, although the coordinates are valid.

Similarly, for indices where the instance variable identified by cf_role contains a missing value indicator, all other instance variable should also contain missing values.