Žr. Nulinė veikla, Structure, Heart, SharedUnderstanding, GoingBeyondOneself, Null
NullStructure is important because that's what gets added to Understanding.
An example of a NullStructure to keep in mind is Why in the Representation of the Foursome in terms of situation, and Whether in the Representation of the Foursome in terms of observer. And I think that the null structure also is relevant for the differences among the PrimaryStructures.