tailieunhanh - Báo cáo khoa học: "Dynamic Strategy Selection in Flexible Parsing"

Robust natural language interpretation requires strong semantic domain models, "fall-soff" recovery heuristics, and very flexible control structures. Although single-strategy parsers have met with a measure of success, a approach is shown to provide a much higher degree of flexibility, redundancy, and ability to bring task-specific domain knowledge (in addition to general linguistic knowledge) to bear on both grammatical and ungrammatical input. A parsing algorithm is presented that integrates several different parsing strategies, with case-frame instantiation dominating. . | Dynamic strategy Selection in Flexible Parsing Jaime G. Carbonell and Philip J. Hayes Carnegie-Mellon University Pittsburgh PA 15213 Abstract Robust natural language interpretation requires strong semantic domain models fail-soft recovery heuristics and very flexible control structures. Although single-strategy parsers have met with a measure of success a multi-strategy approach is shown to provide a much higher degree of flexibility redundancy and ability to bring task-specific domain knowledge in addition to general linguistic knowledge to bear on both grammatical and ungrammatical input. A parsing algorithm is presented that integrates several different parsing strategies with case-frame instantiation dominating. Each of these parsing strategies exploits different types of knowledge and their combination provides a strong framework in which to process conjunctions fragmentary input and ungrammatical structures as well as less exotic grammatically correct input. Several specific heuristics for handling ungrammatical input are presented within this multi-strategy framework. 1. Introduction When people use language spontaneously they often do not respect grammatical niceties. Instead of producing sequences of grammatically well-formed and complete sentences they often miss out or repeat words or phrases break off what they are saying and rephrase or replace it speak in fragments or use otherwise incorrect grammar. While other people generally have little trouble comprehending ungrammatical utterances most natural language computer systems are unable to process errorful input at all. Such inflexibility In parsing is a serious impediment to the use of natural language in interactive computer systems. Accordingly we 6 and other researchers Including Weischedel and Black 14 and Kwasny and Sondheimer 9 have attempted to produce flexible parsers . parsers that can accept ungrammatical Input correcting the errors when possible and generating several alternative .