
 hidden Markov model (Site not responding. Last check: 20071107) 
  Definition: A variant of a finite state machine having a set of states, Q, an output alphabet, O, transition probabilities, A, output probabilities, B, and initial state probabilities, Π. 
  Usually the states, Q, and outputs, O, are understood, so an HMM is said to be a triple, (A, B, Π). 
  Although the states cannot, by definition, be directly observed, the most likely sequence of sets for a given sequence of observed outputs can be computed in O(nt), where n is the number of states and t is the length of the sequence. 
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