Essential graphs are graphs in which there are directed arcs and edges (not directed arcs). The essential graph corresponding to a given Bayesian network is the graph in which the directed arcs correspond to the arcs of the Bayesian network whose orientation cannot be changed without changing the probabilistic relations encoded. Edges represent the arcs that can be inverted.
- Show Edges: This function, which is directly available via the key < E >, allows changing the arcs whose orientation can be modified while preserving the same probabilistic relations into edges. The example below illustrates a Bayesian network and the corresponding essential graph.
- Global Orientation of Edges: This function allows converting an essential, or semi directed graph, into a Bayesian network graph, by directing all the edges while preserving the same probabilistic relations. This function is directly available via key < I >. It is also possible to direct specific edges by using the contextual menu associated with the arcs. The activation of this on an edge or a previously directed edge allows its orientation/inversion. These arc orientations trigger the propagation of the new information through the network so that the probability law remains identical, namely:
- orientation of the edges that cannot be inverted anymore,
- inversion of previously oriented arcs in order to preserve the probabilistic relations encoded by the initial Bayesian network,
- removing of the orientation of the arcs that have been previously oriented threw propagation,
- changing of the conditional probability tables