Example of a processing node that is part of a multistep architecture with $N=5$⁠, visualized as a directed graph. Here, $X3$ processes the output of $X2$ by transforming a prior policy $p(x3|x1)$ to a posterior policy $P(x3|x2,x1)$⁠. The prior of $X3$ being conditioned on the output of $X1$ (indicated by the dashed arrow) means that $X1$ determines which of the prior policies ${p(·|x1)}x1∈X1$ is used by $X3$ to process a given output of $X2$⁠.