1999 | OriginalPaper | Buchkapitel
A Graphical Method for Parameter Learning of Symbolic-Statistical Models
verfasst von : Yoshitaka Kameya, Nobuhisa Ueda, Taisuke Sato
Erschienen in: Discovery Science
Verlag: Springer Berlin Heidelberg
Enthalten in: Professional Book Archive
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We present an efficient method for statistical parameter learning of a certain class of symbolic-statistical models (called PRISM programs) including hidden Markov models (HMMs). To learn the parameters, we adopt the EM algorithm, an iterative method for maximum likelihood estimation. For the efficient parameter learning, we first introduce a specialized data structure for explanations for each observation, and then apply a graph-based EM algorithm. The algorithm can be seen as a generalization of Baum-Welch algorithm, an EM algorithm specialized for HMMs. We show that, given appropriate data structure, Baum-Welch algorithm can be simulated by our graph-based EM algorithm.