Expressive power and consistency properties of state-of-the-art natural language parsers

Abstract

We define Probabilistic Constrained W-grammars (PCW-grammars), a two-level formalism capable of capturing grammatical frameworks used in two state of the art parsers, namely bilexical grammars and stochastic tree substitution grammars. We provide embeddings of these parser formalisms into PCW-grammars, which allows us to derive properties about their expressive power and consistency, and relations between the formalisms studied.