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Proposed Bigram model and PHMM
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model
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Generic in the
forms
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Systematic
parameter estimation by EM
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algorithm
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These two models
can be applied to other
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applications
using surface text patterns
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Soft patterns
have been applied to information
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extraction (Xiao et
al., 2004)
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PHMM is more
flexible in dealing with gaps,
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but requires more
training data to converge
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