Improving Word Alignment Using Linguistic Code Switching Data

Linguist Code Switching (LCS) is a situation where two or more languages show up in the context of a single conversation. For example, in EnglishChinese code switching, there might be a sentence like “·‚15© ̈ k ‡meeting (We will have a meeting in 15 minutes)”. Traditional machine translation (MT) systems treat LCS data as noise, or just as regular sentences. However, if LCS data is processed intelligently, it can provide a useful signal for training word alignment and MT models. Moreover, LCS data is from non-news sources which can enhance the diversity of training data for MT. In this paper, we first extract constraints from this code switching data and then incorporate them into a word alignment model training procedure. We also show that by using the code switching data, we can jointly train a word alignment model and a language model using cotraining. Our techniques for incorporating LCS data improve by 2.64 in BLEU score over a baseline MT system trained using only standard sentence-aligned corpora.