Parsing the Voyager Domain Using Pearl.

摘要

This paper describes a natural language parsing algorithm for unrestricted text which uses a probability-based scoring function to select the 'best' parse of a sentence according to a given grammar. The parser, Pearl, is a time-asynchronous bottom-up chart parser with Earley-type lop-down prediction which pursues the highest-scoring theory in the chart, where the score of a theory represents the extent to which the context of the sentence predicts that interpretation. This parser differs from previous attempts at stochastic parsers in that it uses a richer form of conditional probabilities based on context to predict likelihood. Pearl also provides a framework for incorporating the results of previous work in part-of-speech assignment, unknown word models, and other probabilistic models of linguistic features in one parsing tool, interleaving these techniques instead of using the traditional pipeline architecture. In tests performed on the Voyager direction-finding domain, Pearl has been successful at resolving part-of-speech ambiguity, determining categories for unknown words, and selecting correct parses first using a very loosely fitting covering grammar.