  KS themselves, in the abstract, proceed in exactly the same way, but they illustrate with an example that does establish a direct connection with physical space. It is important to see this connection, but also to be clear that it is produced by KS’s example and is not inherent in their mathematical result. KS propose to consider a one-particle spin-1 system and the measurement of the squared components of orthogonal directions of spin in physical space Sx2, Sy2, Sz2, which are compatible (while Sx,  Sy, Sz themselves are  not).[7]  Measurement of a squared component of spin determines only its absolute value. Here, they derive a slightly different constraint on value assignments, again using the Sum Rule and the Product Rule  (Proof):