For instance, if an asset has occupancy for period="day" and "night" we take the mean of the two values?
If an asset has occupancy for period="day", "night", "transit" we take the mean of the three values?
If it has occupancy only for "day" we take that value? And if in the same file another asset has occupancy only for night we take that value too, i.e. we do not distinguish "night" and "day"? And if there exists an asset without any occupancy value it is an error invalidating the whole computation?