Editing Graphical model (section)

===Cyclic Directed Graphical Models===

[[File:Graph model.svg|thumb|right|alt=An example of a directed graphical model.| An example of a directed, cyclic graphical model. Each arrow indicates a dependency. In this example: D depends on A, B, and C; and C depends on B and D; whereas A and B are each independent.]]

The next figure depicts a graphical model with a cycle.  This may be interpreted in terms of each variable 'depending' on the values of its parents in some manner.  
The particular graph shown suggests a joint probability density that factors as
:<math>P[A,B,C,D] = P[A]\cdot P[B]\cdot P[C,D|A,B]</math>,
but other interpretations are possible.
<ref name=richardson95causal>{{cite book
 |first=Thomas |last=Richardson
 |chapter=A discovery algorithm for directed cyclic graphs
 |title=Proceedings of the Twelfth Conference on Uncertainty in Artificial Intelligence
 |year=1996
 |publisher=Morgan Kaufmann Pub.
 |isbn=978-1-55860-412-4
}}
</ref>