Discriminative Latent Variable Grammars

As we saw in the previous chapter, learning a refined latent variable grammar involves the estimation of a set of grammar parameters θ on latent annotations despite the fact that the original trees lack the latent annotations. In the previous chapter, we considered generative grammars, where the parameters θ are set to maximize the joint likelihood of the training sentences and their parse trees. In this section we will consider discriminative grammars, where the parameters θ are set to maximize the likelihood of the correct parse tree (vs. all possible trees) given a sentence.