As illustrated here, one can convert between directed and undirected graph models by the method of moralization, where one corrects for directed relationships between disconnected parent nodes and their children by connection the parent nodes directly with an undirected path. For example, consider the middle case in the illustration. In the top row, a and b are connected to c with a directed relationship, but not to each other. In the bottom row, this has been converted into an undirected graph by removing the dependency arrows and connecting a and b to each other. This graph is the simplest case (a single "immorality") where the directed version cannot be converted into an undirected version without losing some independencies.