An Efficient Augmented-Context-Free Parsing Algorithm (1987)
| Venue: | Computational Linguistics |
| Citations: | 65 - 3 self |
BibTeX
@ARTICLE{Tomita87anefficient,
author = {Masaru Tomita},
title = {An Efficient Augmented-Context-Free Parsing Algorithm},
journal = {Computational Linguistics},
year = {1987},
volume = {13},
pages = {31--46}
}
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Abstract
This paper introduces an efficient on-line parsing algorithm, and focuses on its practical application to natural language interfaces. The algorithm can be viewed as a generalized LR parsing algorithm that can handle arbitrary context-free grammars, including ambiguous grammars. Section 2 describes the algorithm by .extending the standard LR parsing algorithm with the idea of a "graph-structured stack". Section 3 describes how to represent parse trees efficiently, so that all possible parse trees (the parse forest) take at most polynomial space as the ambiguity of a sentence grows exponentially. In section 4, several examples are given. Section 5 presents several empirical results of the algorithm's practical performance, including comparison with Earley's algorithm. In section 6, we discuss how to enhance the algorithm to handle augmented context-free grammars rather than pure context-free grammars. Section 7 describes the concept of on-line parsing, taking advantage of left-to-right operation of our parsing algorithm. The on-line parser parses a sentence strictly from left to right, and starts parsing as soon as the user types in the first word, without waiting for the end of line. Benefits of on-line parsing are then discussed. Finally, several versions of on-line parser have been implemented, and they are mentioned in section 8
