work with a noncontextual hidden-variable theory where the measurements are determined locally, “so the first thing we need to do is momentarily forget all our knowledge of quantum mechanics,” [@NC page 148]. But we do use the data obtained in three optical experiments of the kind depicted in Figure 1.

1.  Experiment $AB$ involves orientations $\vec A$ and $\vec B$,

2.  Experiment $BC$ involves orientations $\vec B$ and $\vec C$,

3.  Experiment $AC$ involves orientations $\vec A$ and $\vec C$.

This gives rise to the following observation space $T = (\Omega,{\ensuremath{\mathrm{CO}}},{\mathcal P})$.

[Sample space.]{} The sample space $\Omega$ consists of eight sample points $$\begin{aligned}
&1, a.k.a.\quad +++, && 2, a.k.a.\quad ++-, &&3, a.k.a.\quad +-+, &&4,\quad a.k.a. +--,\\
&5, a.k.a.\quad -++, && 6, a.k.a.\quad -+-, &&7, a.k.a.\quad --+, &&8,\quad a.k.a. ---.\end{aligned}$$ In the three-letter words $abc$ in alphabet $\{+,-\}$, the first letter $a$ is the result of measuring the spin in the $\vec A$ direction. Similarly for the second letter $b$ and the third letter $c$ using the $\vec B$ and $\vec C$ directions.

[Coobservation.]{} The first two letters $a,b$ of outcomes $abc$ give rise to an equivalence relation $ abc\equiv a'b'c'\iff (a=a'\land b=b')$ whose four equivalence classes $ \{1,2\}, \{3,4\}, 