Morphology-aware Word-Segmentation in Dialectal Arabic Adaptation of Neural Machine Translation (original) (raw)
Related papers
Unsupervised Word Segmentation Improves Dialectal Arabic to English Machine Translation
Proceedings of the EMNLP 2014 Workshop on Arabic Natural Language Processing (ANLP), 2014
We demonstrate the feasibility of using unsupervised morphological segmentation for dialects of Arabic, which are poor in linguistics resources. Our experiments using a Qatari Arabic to English machine translation system show that unsupervised segmentation helps to improve the translation quality as compared to using no segmentation or to using ATB segmentation, which was especially designed for Modern Standard Arabic (MSA). We use MSA and other dialects to improve Qatari Arabic to English machine translation, and we show that a uniform segmentation scheme across them yields an improvement of 1.5 BLEU points over using no segmentation.
Morphologically rich languages pose a challenge for statistical machine translation (SMT). This challenge is magnified when translating into a morphologically rich language. In this work we address this challenge in the framework of a broad-coverage English-to-Arabic phrase based statistical machine translation (PBSMT). We explore the full spectrum of Arabic segmentation schemes ranging from full word form to fully segmented forms and examine the effects on system performance. Our results show a difference of 2.61 BLEU points between the best and worst segmentation schemes indicating that the choice of the segmentation scheme has a significant effect on the performance of a PBSMT system in a large data scenario. We also show that a simple segmentation scheme can perform as good as the best and more complicated segmentation scheme. We also report results on a wide set of techniques for recombining the segmented Arabic output.
IEEE Access
Morphologically rich and complex languages such as Arabic, pose a major challenge to neural machine translation (NMT) due to the large number of rare words and the inability of NMT to translate them. Unknown word (UNK) symbols are used to represent out-of-vocabulary words because NMT typically operates with a fixed vocabulary size. These rare words can be effectively encoded as sequences of subword units by using algorithms, such as byte pair encoding (BPE), to tackle the UNK problem. However, for languages with highly inflected and morphological variations, such as Arabic, the aforementioned method has its own limitations that make it not effective enough for translation quality. To alleviate the UNK problem and address the inconvenient behavior of BPE when translating the Arabic language, we propose to utilize a romanization system that converts Arabic scripts to subword units. We investigate the effect of our approach on NMT performance under various segmentation scenarios and compare the results with systems trained on original Arabic form. In addition, we integrate Romanized Arabic as an input factor for Arabic-sourced NMT compared with well-known factors, namely, lemma, part-of-speech tags, and morph features. Extensive experiments on Arabic-Chinese translation demonstrate that the proposed approaches can effectively tackle the UNK problem and significantly improve the translation quality for Arabic-sourced translation. Additional experiments in this study focus on developing the NMT system on Chinese-Arabic translation. Before implementing our experiments, we first propose standard criteria for the data filtering of a parallel corpus, which helps in filtering out its noise.
Machine Translation of Arabic Dialects
2018
Machine Translation of Arabic Dialects Wael Salloum This thesis discusses different approaches to machine translation (MT) from Dialectal Arabic (DA) to English. These approaches handle the varying stages of Arabic dialects in terms of types of available resources and amounts of training data. The overall theme of this work revolves around building dialectal resources and MT systems or enriching existing ones using the currently available resources (dialectal or standard) in order to quickly and cheaply scale to more dialects without the need to spend years and millions of dollars to create such resources for every dialect. Unlike Modern Standard Arabic (MSA), DA-English parallel corpora is scarcely available for few dialects only. Dialects differ from each other and from MSA in orthography, morphology, phonology, and to some lesser degree syntax. This means that combining all available parallel data, from dialects and MSA, to train DA-to-English statistical machine translation (SMT) systems might not provide the desired results. Similarly, translating dialectal sentences with an SMT system trained on that dialect only is also challenging due to different factors that affect the sentence word choices against that of the SMT training data. Such factors include the level of dialectness (e.g., code switching to MSA versus dialectal training data), topic (sports versus politics), genre (tweets versus newspaper), script (Arabizi versus Arabic), and timespan of test against training. The work we present utilizes any available Arabic resource such as a preprocessing tool or a parallel corpus, whether MSA or DA, to improve DA-to-English translation and expand to more dialects and sub-dialects. The majority of Arabic dialects have no parallel data to English or to any other foreign language. They also have no preprocessing tools such as normalizers, morphological analyzers, or tokenizers. For such dialects, we present an MSA-pivoting approach where DA sentences are translated to MSA first, then the MSA output is translated to English using the wealth of MSA-English parallel data. Since there is virtually no DA-MSA parallel data to train an SMT system, we build a rule-based DA-to-MSA MT system, ELISSA, that uses morpho-syntactic translation rules along with dialect identification and language modeling components. We also present a rule-based approach to quickly and cheaply build a dialectal morphological analyzer, ADAM, which provides ELISSA with dialectal word analyses. Other Arabic dialects have a relatively small-sized DA-English parallel data amounting to a few million words on the DA side. Some of these dialects have dialect-dependent preprocessing tools that can be used to prepare the DA data for SMT systems. We present techniques to generate synthetic parallel data from the available DA-English and MSA-English data. We use this synthetic data to build statistical and hybrid versions of ELISSA as well as improve our rule-based ELISSA-based MSA-pivoting approach. We evaluate our best MSA-pivoting MT pipeline against three direct SMT baselines trained on these three parallel corpora: DA-English data only, MSA-English data only, and the combination of DA-English and MSA-English data. Furthermore, we leverage the use of these four MT systems (the three baselines along with our MSA-pivoting system) in two system combination approaches that benefit from their strengths while avoiding their weaknesses. Finally, we propose an approach to model dialects from monolingual data and limited DA-English parallel data without the need for any language-dependent preprocessing tools. We learn DA preprocessing rules using word embedding and expectation maximization. We test this approach by building a morphological segmentation system and we evaluate its performance on MT against the state-of-the-art dialectal tokenization tool.
A Neural Architecture for Dialectal Arabic Segmentation
Proceedings of the Third Arabic Natural Language Processing Workshop
The automated processing of Arabic dialects is challenging due to the lack of spelling standards and the scarcity of annotated data and resources in general. Segmentation of words into their constituent tokens is an important processing step for natural language processing. In this paper, we show how a segmenter can be trained on only 350 annotated tweets using neural networks without any normalization or reliance on lexical features or linguistic resources. We deal with segmentation as a sequence labeling problem at the character level. We show experimentally that our model can rival state-of-the-art methods that heavily depend on additional resources.
Context-based Arabic morphological analysis for machine translation
Proceedings of the Twelfth Conference on …, 2008
In this paper, we present a novel morphology preprocessing technique for Arabic-English translation. We exploit the Arabic morphology-English alignment to learn a model removing nonaligned Arabic morphemes. The model is an instance of the Conditional Random Field (Lafferty et al., 2001) model; it deletes a morpheme based on the morpheme's context. We achieved around two BLEU points improvement over the original Arabic translation for both a travel-domain system trained on 20K sentence pairs and a news domain system trained on 177K sentence pairs, and showed a potential improvement for a large-scale SMT system trained on 5 million sentence pairs.
Segmentation for English-to-Arabic statistical machine translation
Proceedings of the 46th Annual Meeting of the Association for Computational Linguistics on Human Language Technologies Short Papers - HLT '08, 2008
In this paper, we report on a set of initial results for English-to-Arabic Statistical Machine Translation (SMT). We show that morphological decomposition of the Arabic source is beneficial, especially for smaller-size corpora, and investigate different recombination techniques. We also report on the use of Factored Translation Models for Englishto-Arabic translation.
Bridging the inflection morphology gap for Arabic statistical machine translation
2006
Abstract Statistical machine translation (SMT) is based on the ability to effectively learn word and phrase relationships from parallel corpora, a process which is considerably more difficult when the extent of morphological expression differs significantly across the source and target languages. We present techniques that select appropriate word segmentations in the morphologically rich source language based on contextual relationships in the target language.
Word Segmentation of Informal Arabic with Domain Adaptation
Proceedings of the 52nd Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers), 2014
Segmentation of clitics has been shown to improve accuracy on a variety of Arabic NLP tasks. However, state-of-the-art Arabic word segmenters are either limited to formal Modern Standard Arabic, performing poorly on Arabic text featuring dialectal vocabulary and grammar, or rely on linguistic knowledge that is hand-tuned for each dialect. We extend an existing MSA segmenter with a simple domain adaptation technique and new features in order to segment informal and dialectal Arabic text. Experiments show that our system outperforms existing systems on newswire, broadcast news and Egyptian dialect, improving segmentation F 1 score on a recently released Egyptian Arabic corpus to 95.1%, compared to 90.8% for another segmenter designed specifically for Egyptian Arabic.