This  case can be given a cubical geometric interpretation (or a graph-theoretic interpretation) as follows: when moving along the edge from  to , XOR up the functions of the two end-vertices of the edge in order to obtain the coefficient of .
This case can be viewed as having a cubic geometric interpretation (or a graph-theoretic interpretation), where traversing the edge from  to  entails merging the endpoint functions via an XOR operation to yield the coefficient of .