Figure 2

Scheme of the tree with arrows labelled by operators. Arrows are interpreted as operators ‘R_(j→k)’s that could be regarded as ordinal elements ‘R_j’s belonging to a single set R. Each operator that changes ‘R_j to R_k’ can be traced and its degree for each session identified from initial and final states. The final states (R₆, R₉, R₁₆ and R₁₇) can be traced back to any initiating state ‘R₁’ by performing an appropriate sequence of ‘R_(j→k)’s.