Abstract

This paper studies the compntational complexity of dlsambiguation under probabilistic tree-grammars as in (Bod, 1992; Schabes and Waters, 1993). It presents a proof that the following problems are NP-hard: computing the Most Probable Parse frmn a sentence or from a word-graph, and computing the Most Pro'oable Sentence (MPS) from a word- graph. The NP-hardness of computing the MPS from a word-graph also holds for Stochastic Context-Free Gram- mars (SCFGs).

Citations

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