Extracting Pre-ordering Rules from Predicate-Argument Structures

Abstract

Word ordering remains as an essential problem for translating between languages with substantial structural differences, such as SOV and SVO languages. In this paper, we propose to automatically extract pre-ordering rules from predicateargument structures. A pre-ordering rule records the relative position mapping of a predicate word and its argument phrases from the source language side to the target language side. We propose 1) a lineartime algorithm to extract the pre-ordering rules from word-aligned HPSG-tree-tostring pairs and 2) a bottom-up algorithm to apply the extracted rules to HPSG trees to yield target language style source sentences. Experimental results are reported for large-scale English-to-Japanese translation, showing significant improvements of BLEU score compared with the baseline SMT systems. 1