Paper: Improved Word Alignment Using A Symmetric Lexicon Model

ACL ID C04-1006
Title Improved Word Alignment Using A Symmetric Lexicon Model
Venue International Conference on Computational Linguistics
Session Main Conference
Year 2004

Word-aligned bilingual corpora are an important knowledge source for many tasks in natural language processing. We improve the well-known IBM alignment models, as well as the Hidden-Markov alignment model using a symmetric lex- icon model. This symmetrization takes not only the standard translation direc- tion from source to target into account, but also the inverse translation direction from target to source. We present a the- oretically sound derivation of these tech- niques. In addition to the symmetriza- tion, we introduce a smoothed lexicon model. The standard lexicon model is based on full-form words only. We propose a lexicon smoothing method that takes the word base forms explicitly into ac- count. Therefore, it is especially useful for highly inflected languages such as Ger- man. ...