Figure 1.8: The Markov blanket of a node in an undirected graph. The statistics of the node s4 in the middle are only dependent on those nodes which are neighbours in the graph. (a) shows the interactions associated with the shaded node and its co-parents. (b) shows the conditional distribution of s4 given all the other nodes in the graph. Now there is no dependence on the nodes s3 and s5.