关键词: Viterbi路径，句法分析，概率Earley算法

Abstract: Probabilistic Earlcy algorithm applies Viterbi path to construct parse trees for input sequences, but the grammar limits often result in many empty trees.This paper exploited optional start states, new sequential beginnings and more subtrees to extend the traditional Viterbi path, removed almost all empty trees, and improved the general parsing performance of Earley algorithm.

Key words: Viterbi path, Parsing, Probabilistic earley algorithm