A maximal set of nodes, connected by undirected edges, is called a chain graph component. Not all graphs are permitted. The following restrictions are imposed on the structure of the network. However, the following specification is legal. Utility nodes may not have any children in the graph.
Undirected edges can only appear between discrete chance nodes.
Continuous nodes can only have continuous nodes as children. If a decision node appears to the left of the vertical bar, it must appear alone. There must be a total ordering of all decisions in the influence diagram, and this ordering must follow from the network structure, i.e., there must be a directed path containing all decisions. Potentials We also need to specify the quantitative part of the model. This part consists of conditional probability functions for random variables and the values a utility function may assume.