BattRAE: Bidimensional Attention-Based Recursive Autoencoders for Learning Bilingual Phrase Embeddings

In this paper, we propose a bidimensional attention based recursive autoencoder (BattRAE) to integrate clues and sourcetarget interactions at multiple levels of granularity into bilingual phrase representations. We employ recursive autoencoders to generate tree structures of phrases with embeddings at different levels of granularity (e.g., words, sub-phrases and phrases). Over these embeddings on the source and target side, we introduce a bidimensional attention network to learn their interactions encoded in a bidimensional attention matrix, from which we extract two soft attention weight distributions simultaneously. These weight distributions enable BattRAE to generate compositive phrase representations via convolution. Based on the learned phrase representations, we further use a bilinear neural model, trained via a max-margin method, to measure bilingual semantic similarity. To evaluate the effectiveness of BattRAE, we incorporate this semantic similarity as an additional feature into a state-of-the-art SMT system. Extensive experiments on NIST Chinese-English test sets show that our model achieves a substantial improvement of up to 1.63 BLEU points on average over the baseline.Comment: 7 pages, accepted by AAAI 201

Dependency-based Bilingual Word Embeddings and Neural Machine Translation

Bilingual word embeddings, which represent lexicons from various languages in a common embedding space, are critical for facilitating semantic and knowledge trans- fers in a wide range of cross-lingual NLP applications. The significance of learning bilingual word embedding representations in many Natural Language Processing (NLP) tasks motivates us to investigate the effect of many factors, including syntac- tical information, on the learning process for different languages with varying levels of structural complexity. By analysing the components that influence the learning process of bilingual word embeddings (BWEs), this thesis examines some factors for learning bilingual word embeddings effectively. Our findings in this thesis demon- strate that increasing the embedding size for language pairs has a positive impact on the learning process for BWEs. While sentence length depends on the language. Short sentences perform better than long ones in the En-ES experiment. However, by increasing the sentence, En-Ar and En-De experiment achieve improved model accuracy. Arabic segmentation, according to En-Ar experiments, is essential to the learning process for BWEs and can boost model accuracy by up to 10%. Incorporating dependency features into the learning process enhances the trained models performance and results in more improved BWEs in all language pairs. Finally, we investigated how the dependancy-based pretrained BWEs affected the neural machine translation (NMT) model. The findings indicate that in various MT evaluation matrices, the trained dependancy-based NMT models outperform the baseline NMT model