what are the methods to estimate probabilities of production rules?

Question

I know that n-gram is useful for finding the probability of words,I want to know, How to estimate probabilities of production rules? How many methods or rules to calculate probabilities of production rules?

I could not find any good blog or something on this topic.Now I am studying on probabilistic context free grammar & CKY parsing algorithm.

Answer 1

据我所知，你问的是如何根据数据估算PCFG模型的参数。

简而言之，当您在训练数据中进行事实真相解析时，很容易进行经验性生产规则概率估计。如果您想估算S -> NP VP的概率，则类似于Count(S -> NP VP) / Count(S -> *)，其中*是任何可能的子树。

您可以在网上的许多地方找到更正式的声明（搜索“PCFG估算”或“PCFG学习”）。这是迈克尔柯林斯的讲义中的一个很好的一个：http://www.cs.columbia.edu/~mcollins/courses/nlp2011/notes/pcfgs.pdf#page=9