generative model和discriminative model的区别是什么？

Training classifiers involves estimating f: X -> Y, or P(Y|X) Discriminative classifiers (also called ‘informative’ by Rubinstein&Hastie): Assume some functional form for P(Y|X) Estimate parameters of P(Y|X) directly from training data Generative classifiers Assume some functional form for P(X|Y), P(X) Estimate parameters of P(X|Y), P(X) directly from training data Use Bayes rule to calculate P(Y|X= xi)

参见 machine learning(new edition) Tom M. Mitchell Chapter 1 generative and discriminative classifier: naive bayes and logistic regression

俺的理解是这样滴：generative model是给定条件，怎样建立合适的模型，使其在此模型下能够最大可能性地得到观察序列，discrimitive model是给定条件，建立模型，在此模型下分别计算各种输出的可能性，取最大可能的序列。