Handling of missing values

[dosse]

from @sosna
I could not see a reference to this in the field guide or in the sample, but, my recollection is the same as what you confirmed, i.e., null is used.

The appropriate approach for missing values in SDMX-JSON should be clarified.
The solution should also distinguish between “values to be set to 'missing'” and “values not to be changed when appending”.

Related ticket in SDMX-XML: sdmx-twg/sdmx-ml#32
Related Ticket in SDMX-CSV: sdmx-twg/sdmx-csv#27