L-nodes arising from P-nodes of the PIM depicted in Figure4. Binding process 1 and 4 give rise to the L-node pairs (A_b1, R_b1) and (R_p1, B_b1); modification process 2 and 3 give rise to the unique L-nodes R_p1 and R_p2. One can clearly distinguish three types of L-nodes: those arising from a P-node corresponding to a binding process (green), those arising from a P-node corresponding to a modification process (blue) and those arising from both a binding and a modification process (blue and green). The construction of the interaction graph is based on a one-to-one correspondence between P-nodes and a subset of the L-nodes (see main text). To this end, observe that as the L-node R_p1 arises from two processes (binding process 4 and modification process 2), the L-node pair (R_p1, B_b1) can be brought into a one-to-one connection with the P-nodes 2 and 4, while the L-node pair (A_b1, R_b1) cannot be brought into a one-to-one connection with two P-nodes.