olson and J. M. Brady. 
IEEE Systems, Man and Cybernetics, 24(11):1593-1610, 1994. 
</ul>
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<h2><a name="hmm">Hidden Markov Models (HMMs)</h2>

The simplest kind of DBN is a Hidden Markov Model (HMM), which has
one discrete hidden node and one discrete or continuous
observed node per slice. We illustrate this below.
As before, circles denote continuous nodes, squares denote
discrete nodes, clear means hidden, shaded means observed.
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(The observed nodes can be
discrete or continuous; the crucial thin