Context-free parsing with finite-state transducers
Résumé
This article is a study of an algorithm designed and implemented by Emmanuel Roche for parsing natural language sentences according to a context-free grammar. This algorithm is based on the construction and use of a finite-state transducer. Roche successfully applied it to a context-free grammar with very numerous rules. In contrast, the complexity of parsing words according to context-free grammars is usually considered in practice as a function of one parameter: the length of the input sequence; the size of the grammar is generally taken to be a constant of a reasonable value. In this article, we first explain why a context-free grammar with a correct lexical and grammatical coverage is bound to have a very large number of rules and we review work related with this problem. Then we exemplify the principle of Roche's algorithm on a small grammar. We provide formal definitions of the construction of the parser and of the operation of the algorithm and we prove that the parser can be built for a large class of context-free grammars, and that it outputs the set of parsing trees of the input sequence.
Origine : Fichiers produits par l'(les) auteur(s)
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