Glad you like the links, but I disagree with your disagreement =P You can use factor graphs for either directed or undirected models. See this paper: Extendi

Glad you like the links, but I disagree with your disagreement =P You can use factor graphs for either directed or undirected models. See this paper: Extending factor graphs so as to unify directed and undirected graphical models B. J. Frey Proceedings of the 19th Conference on Uncertainty in Artificial Intelligence, 257-264, Morgan Kaufmann, San Francisco, CA, August 2003.