Hi @Kimcha, there is an interesting article from Roleant Vos on the subject (in the data vault realm) : unknown-keys-zero-keys-or-ghost-keys-in-hubs-for-dv2-0, with a taxonomy on missing values. In my case, we use two distinct missing key values : one when the key is missing but mandatory (problem in the loading or in source data), and another when the key is missing but optional (loading and data ok but data is missing for ‘business’ reason).
Best,
Fabrice