Statistical NLP: Lecture 12

3/13/00


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Table of Contents

Statistical NLP: Lecture 12

Motivation

Formal Definition of PCFGs

Assumptions of the Model

Some Features of PCFGs

Questions fo PCFGs

Restriction

From HMMs to Probabilistic Regular Grammars (PRG)

From PRGs to PCFGs

The Probability of a String I: Using Inside Probabilities

The Probability of a String II: Using Outside Probabilities

Finding the Most Likely Parse for a Sentence

Training a PCFG

Problems with the Inside-Outside Algorithm

 Author: N & N

Email: nat@cs.dal.ca

Home Page: http://borg.cs.dal.ca/~nat