Machine Translation Evaluation Metrics Research Articles

A comparative analysis of lexical-based automatic evaluation metrics for different Indic language pairs

<p>With the rise of machine translation systems, it has become essential to evaluate the quality of translations produced by these systems. However, the existing evaluation metrics designed for English and other European languages may not always be suitable or apply to other Indic languages due to their complex morphology and syntax. Machine translation evaluation (MTE) is a process of assessing the quality and accuracy of the machine-translated text. MTE involves comparing the machine-translated output with the reference translation to calculate the level of similarity and correctness. Therefore, this study evaluates different metrics, namely, BLEU, METEOR, and TER to identify the most suitable evaluation metric for Indic languages. The study uses datasets for Indic languages and evaluates the metrics on various translation systems. The study contributes to the field of MT by providing insights into suitable evaluation metrics for Indic languages. This research paper aims to study and compare several lexical automatic machine translation evaluation metrics for Indic languages. For this research analysis, we have selected five language pairs of parallel corpora from the low-resource domain, such as English–Hindi, English-Punjabi, English-Gujarati, English-Marathi, and English-Bengali. All these languages belong to the Indo-Aryan language family and are resource-poor. A comparison of the state of art MT is presented and shows which translator works better on these language pairs. For this research work, the natural language toolkit tokenizers are used to assess the analysis of the experimental results. These results have been performed by taking two different datasets for all these language pairs using fully automatic MT evaluation metrics. The research study explores the effectiveness of these metrics in assessing the quality of machine translations between various Indic languages. Additionally, this dataset and analysis will make it easier to do future research in Indian MT evaluation.</p>

A review of existing Machine Translation Approaches, their Challenges and Evaluation Metrics

Machine translation is the process of translating a natural language into another. The primary goal of machine translation is to bridge the linguistic gap between languages. A significant job that may be utilized is to extract information from texts written in different languages through machine translation (MT). Due to the remarkable developments in Machine Translation over the past several years, we have entered the era of Neural Machine Translation (NMT). A review of MT is essential for better understanding of MT in the domain of Natural Language Processing. This paper focuses on Statistical, Corpus, Example, Rule based, Transfer based, direct based and Nural Machine Translation approach, their challenges, and existing evaluation metrics such as BLEU score and Human evaluation metrics.

Does a Formal Post-editing Training Affect the Performance of Novice Post-editors? An Experimental Study

Machine translation systems led to the creation of a new role for translators: the post-editor. With the birth of neural machine translation systems, the demand for post-editing has been increasing in the recent years, and it has now become a common service given by language service providers and professional translators. Such a change in the landscape of the translation industry might evolve the translation training programs worldwide. It is still heavily discussed whether post-editing and translation skills overlap, and post-editing courses are now included into the curriculum by several translation departments. We set out to investigate whether post-editing training influences the performance of student post-editors in order to explore the necessary background and skills in post-editing tasks. We measured productivity parameters and quality of the final outputs produced by two groups of participants, one of which was previously trained on post-editing. Our results show that, the experimental and control groups did not differ significantly from each other in terms of productivity. There was also little to no difference when we evaluated the post-edited outputs produced by both groups against a reference text using automatic machine translation evaluation metrics. However, we detected a statistical significance between the groups when we analyzed the number of errors in the final output. The post-editors in the experimental group were more aware of the typical errors of machine translation engines.

Evaluation of Semantic Answer Similarity Metrics

There are several issues with the existing general machine translation or natural language generation evaluation metrics, and question-answering (QA) systems are indifferent in that context. To build robust QA systems, we need the ability to have equivalently robust evaluation systems to verify whether model predictions to questions are similar to ground-truth annotations. The ability to compare similarity based on semantics as opposed to pure string overlap is important to compare models fairly and to indicate more realistic acceptance criteria in real-life applications. We build upon the first to our knowledge paper that uses transformer-based model metrics to assess semantic answer similarity and achieve higher correlations to human judgement in the case of no lexical overlap. We propose cross-encoder augmented bi-encoder and BERTScore models for semantic answer similarity, trained on a new dataset consisting of name pairs of US-American public figures. As far as we are concerned, we provide the first dataset of co-referent name string pairs along with their similarities, which can be used for training.

Automatic assessment of spoken-language interpreting based on machine-translation evaluation metrics

Abstract Automated metrics for machine translation (MT) such as BLEU are customarily used because they are quick to compute and sufficiently valid to be useful in MT assessment. Whereas the instantaneity and reliability of such metrics are made possible by automatic computation based on predetermined algorithms, their validity is primarily dependent on a strong correlation with human assessments. Despite the popularity of such metrics in MT, little research has been conducted to explore their usefulness in the automatic assessment of human translation or interpreting. In the present study, we therefore seek to provide an initial insight into the way MT metrics would function in assessing spoken-language interpreting by human interpreters. Specifically, we selected five representative metrics – BLEU, NIST, METEOR, TER and BERT – to evaluate 56 bidirectional consecutive English–Chinese interpretations produced by 28 student interpreters of varying abilities. We correlated the automated metric scores with the scores assigned by different types of raters using different scoring methods (i.e., multiple assessment scenarios). The major finding is that BLEU, NIST, and METEOR had moderate-to-strong correlations with the human-assigned scores across the assessment scenarios, especially for the English-to-Chinese direction. Finally, we discuss the possibility and caveats of using MT metrics in assessing human interpreting.

A comprehensive understanding of popular machine translation evaluation metrics

A comprehensive understanding of popular machine translation evaluation metrics

AdaBLEU: A Modified BLEU Score for Morphologically Rich Languages

Machine Translation (MT) depends upon the MT evaluation for comparing several MT systems and gives a measure of their efficiency in terms of translation sentences. Consequently, MT evaluation has become an integral part of the MT procedure and it has led to the development of several MT evaluation metrics which can automatically assess the MT systems. Lexical metrics like BLEU have been mostly used in MT evaluation. However, these metrics poorly represent lexical relationships and impose strict identity matching, leading to less correlation with human evaluation for morphologically rich languages. To overcome the limitations posed by the BLEU evaluation metric for morphologically rich languages, we propose a MT evaluation score called AdaBLEU that is a modified BLEU evaluation score. The proposed score considers the lexical and syntactical properties for any language including the morphologically rich languages. It considers the Parts-of-Speech tags and Dependency Parsing tags along with the BLEU score of sentences. Our modification to the BLEU score does not require multiple reference sentences for evaluation. The evaluation of the performance of AdaBLEU has been conducted by comparing our proposed metric’s performance with several other evaluation metrices on different test datasets for different morphological languages. Experimental results show an improved performance in the case of the proposed score.

Can automated machine translation evaluation metrics be used to assess students’ interpretation in the language learning classroom?

The use of translation and interpreting (T&I) in the language learning classroom is commonplace, serving various pedagogical and assessment purposes. Previous utilization of T&I exercises is driven largely by their potential to enhance language learning, whereas the latest trend has begun to underscore T&I as a crucial skill to be acquired as part of transcultural competence for language learners and future language users. Despite their growing popularity and utility in the language learning classroom, assessing T&I is time-consuming, labor-intensive and cognitively taxing for human raters (e.g., language teachers), primarily because T&I assessment entails meticulous evaluation of informational equivalence between the source-language message and target-language renditions. One possible solution is to rely on automated quality metrics that are originally developed to evaluate machine translation (MT). In the current study, we investigated the viability of using four automated MT evaluation metrics, BLEU, NIST, METEOR and TER, to assess human interpretation. Essentially, we correlated the automated metric scores with the human-assigned scores (i.e., the criterion measure) from multiple assessment scenarios to examine the degree of machine-human parity. Overall, we observed fairly strong metric-human correlations for BLEU (Pearson’s r = 0.670), NIST (r = 0.673) and METEOR (r = 0.882), especially when the metric computation was conducted on the sentence level rather than the text level. We discussed these emerging findings and others in relation to the feasibility of operationalizing MT metrics to evaluate students’ interpretation in the language learning classroom. Supplemental data for this article is available online at https://doi.org/10.1080/09588221.2021.1968915 .

A comprehensive understanding of popular machine translation evaluation metrics

A comprehensive understanding of popular machine translation evaluation metrics

Statistical Analysis of Machine Translation Evaluation Systems for English- Hindi Language Pair

Background: Automatic Machine Translation (AMT) Evaluation Metrics have become popular in the Machine Translation Community in recent times. This is because of the popularity of Machine Translation engines and Machine Translation as a field itself. Translator is a very important tool to break barriers between communities especially in countries like India, where people speak 22 different languages and their many variations. With the onset of Machine Translation engines, there is a need for a system that evaluates how well these are performing. This is where machine translation evaluation enters. Objective: This paper discusses the importance of Automatic Machine Translation Evaluation and compares various Machine Translation Evaluation metrics by performing Statistical Analysis on various metrics and human evaluations to find out which metric has the highest correlation with human scores. Methods: The correlation between the Automatic and Human Evaluation Scores and the correlation between the five Automatic evaluation scores are examined at the sentence level. Moreover, a hypothesis is set up and p-values are calculated to find out how significant these correlations are. Results: The results of the statistical analysis of the scores of various metrics and human scores are shown in the form of graphs to see the trend of the correlation between the scores of Automatic Machine Translation Evaluation metrics and human scores. Conclusion: Out of the five metrics considered for the study, METEOR shows the highest correlation with human scores as compared to the other metrics.

Taking MT Evaluation Metrics to Extremes: Beyond Correlation with Human Judgments

Automatic Machine Translation (MT) evaluation is an active field of research, with a handful of new metrics devised every year. Evaluation metrics are generally benchmarked against manual assessment of translation quality, with performance measured in terms of overall correlation with human scores. Much work has been dedicated to the improvement of evaluation metrics to achieve a higher correlation with human judgments. However, little insight has been provided regarding the weaknesses and strengths of existing approaches and their behavior in different settings. In this work we conduct a broad meta-evaluation study of the performance of a wide range of evaluation metrics focusing on three major aspects. First, we analyze the performance of the metrics when faced with different levels of translation quality, proposing a local dependency measure as an alternative to the standard, global correlation coefficient. We show that metric performance varies significantly across different levels of MT quality: Metrics perform poorly when faced with low-quality translations and are not able to capture nuanced quality distinctions. Interestingly, we show that evaluating low-quality translations is also more challenging for humans. Second, we show that metrics are more reliable when evaluating neural MT than the traditional statistical MT systems. Finally, we show that the difference in the evaluation accuracy for different metrics is maintained even if the gold standard scores are based on different criteria.

Machine Translation Evaluation Metric Based on Dependency Parsing Model

Most of the syntax-based metrics obtain the similarity by comparing the sub-structures extracted from the trees of hypothesis and reference. These sub-structures cannot represent all the information in the trees because their lengths are limited. To sufficiently use the reference syntax information, a new automatic evaluation metric is proposed based on the dependency parsing model. First, a dependency parsing model is trained using the reference dependency tree for each sentence. Then, the hypothesis is parsed by this dependency parsing model and the corresponding hypothesis dependency tree is generated. The quality of hypothesis can be judged by the quality of the hypothesis dependency tree. Unigram F-score is included in the new metric so that lexicon similarity is obtained. According to experimental results, the proposed metric can perform better than METEOR and BLEU on system level and get comparable results with METEOR on sentence level. To further improve the performance, we also propose a combined metric which gets the best performance on the sentence level and on the system level.

Machine Translation Evaluation: Unveiling the Role of Dense Sentence Vector Embedding for Morphologically Rich Language

Machine Translation (MT) evaluation metrics like BiLingual Evaluation Understudy (BLEU) and Metric for Evaluation of Translation with Explicit Ordering (METEOR) are known to have poor performance for word-order and morphologically rich languages. Application of linguistic knowledge to evaluate MTs for morphologically rich language like Hindi as a target language, is shown to be more effective and accurate [S. Tripathi and V. Kansal, Using linguistic knowledge for machine translation evaluation with Hindi as a target language, Comput. Sist.21(4) (2017) 717–724]. Leveraging the recent progress made in the domain of word vector and sentence vector embedding [T. Mikolov and J. Dean, Distributed representations of words and phrases and their compositionality, Adv. Neural Inf. Process. Syst. 2 (2013) 3111–3119], authors have trained a large corpus of pre-processed Hindi text ([Formula: see text] million tokens) for obtaining the word vectors and sentence vector embedding for Hindi. The training has been performed on high end system configuration utilizing Google Cloud platform resources. This sentence vector embedding is further used to corroborate the findings through linguistic knowledge in evaluation metric. For morphologically rich language as target, evaluation metric of MT systems is considered as an optimal solution. In this paper, authors have demonstrated that MT evaluation using sentence embedding-based approach closely mirrors linguistic evaluation technique. The relevant codes used to generate the vector embedding for Hindi have been uploaded on code sharing platform Github. a

VERTa: a linguistic approach to automatic machine translation evaluation

Machine translation (MT) is directly linked to its evaluation in order to both compare different MT system outputs and analyse system errors so that they can be addressed and corrected. As a consequence, MT evaluation has become increasingly important and popular in the last decade, leading to the development of MT evaluation metrics aiming at automatically assessing MT output. Most of these metrics use reference translations in order to compare system output, and the most well-known and widely spread work at lexical level. In this study we describe and present a linguistically-motivated metric, VERTa, which aims at using and combining a wide variety of linguistic features at lexical, morphological, syntactic and semantic level. Before designing and developing VERTa a qualitative linguistic analysis of data was performed so as to identify the linguistic phenomena that an MT metric must consider (Comelles et al. 2017). In the present study we introduce VERTa’s design and architecture and we report the experiments performed in order to develop the metric and to check the suitability and interaction of the linguistic information used. The experiments carried out go beyond traditional correlation scores and step towards a more qualitative approach based on linguistic analysis. Finally, in order to check the validity of the metric, an evaluation has been conducted comparing the metric’s performance to that of other well-known state-of-the-art MT metrics.

Discourse Structure in Machine Translation Evaluation

In this article, we explore the potential of using sentence-level discourse structure for machine translation evaluation. We first design discourse-aware similarity measures, which use all-subtree kernels to compare discourse parse trees in accordance with the Rhetorical Structure Theory (RST). Then, we show that a simple linear combination with these measures can help improve various existing machine translation evaluation metrics regarding correlation with human judgments both at the segment level and at the system level. This suggests that discourse information is complementary to the information used by many of the existing evaluation metrics, and thus it could be taken into account when developing richer evaluation metrics, such as the WMT-14 winning combined metric DiscoTKparty. We also provide a detailed analysis of the relevance of various discourse elements and relations from the RST parse trees for machine translation evaluation. In particular, we show that (i) all aspects of the RST tree are relevant, (ii) nuclearity is more useful than relation type, and (iii) the similarity of the translation RST tree to the reference RST tree is positively correlated with translation quality.

Guiding automatic MT evaluation by means of linguistic features

Machine translation (MT) has become increasingly important and popular in the past decade, leading to the development of MT evaluation metrics aiming at automatically assessing MT output. Most of these metrics use reference translations to compare systems output, therefore, they should not only detect MT errors but also be able to identify correct equivalent expressions so as not to penalize them when those are not displayed in the reference translations. With the aim of improving MT evaluation metrics a study has been carried out of a wide panorama of linguistic features and their implications. For that purpose a Spanish and an English corpora containing hypothesis and reference translations have been analysed from a linguistic point of view, so that common errors can be detected and positive equivalencies highlighted. This article focuses on this qualitative analysis describing the linguistic phenomena that should be considered when developing an automatic MT evaluation metric. The results of this analysis have been used to develop an automatic MT evaluation metric that takes into account different dimensions of language. A brief review of the metric and its evaluation are also provided.

Learning sign language machine translation based on elastic net regularization and latent semantic analysis

In this paper, we present a new sign language machine translation approach based on regression method. The aim of this work is to improve the translation quality and accuracy of existing regularized regression methods. Our approach represents a methodological foundation for small-scale corpus domains such as the Sign Language Machine Translation field. Our method is based on the Elastic net regularization using linear combination of the L1 and L2 penalties of the lasso and ridge methods. We show that using both the de-bruijn graph with the Latent Semantic Analysis technique in the decoding process improves the translation results. The system is experimented on American Sign Language parallel corpora containing 300 sentences and assessed by BLEU, METEOR, NIST and F1-MESURE machine translation evaluation metrics. We obtained good experimental results compared to classical phrase based approach i.e MOSES framework. Also our approach improved the translation results compared to LASSO and RIDGE regression approaches.

Paraphrase Identification by Using Clause-Based Similarity Features and Machine Translation Metrics

Paraphrase identification is a semantic text similarity task which is an important part of many natural language processing applications. Existing methods use vector space models, word co-occurrence information, lexical databases, parsers and machine translation (MT) evaluation metrics to find text similarity. However, other aspects such as negations, inverse relations and semantic roles of the sentences are also very much important in identifying paraphrases. Furthermore, the semantics of the sentences are hidden when the sentences are complex. We propose an approach to find similarity between pair of texts by considering all these factors. We have used an approach to determine set of clauses present in the texts by resolving conjunctions in complex sentences that identify hidden triples from the text. The approach extracts clause-based similarity features namely concept score, relation score, proposition score and word score from the texts. We have combined these similarity features along with MT metrics features to identify whether the texts are paraphrases or not using Support Vector Machine model. We have evaluated our methodology to measure the paraphrase similarity for Microsoft Research corpus. The statistical tests namely |$k$|-fold paired |$t$|-test and McNemar's test show that including clause-based features significantly improved the performance. Also, our approach outperforms state-of-the-art methods in terms of accuracy, |$F$|1-measure and |$f$|1-measure.

Evaluating MT systems with BEER

Abstract We present BEER, an open source implementation of a machine translation evaluation metric. BEER is a metric trained for high correlation with human ranking by using learning-to-rank training methods. For evaluation of lexical accuracy it uses sub-word units (character n-grams) while for measuring word order it uses hierarchical representations based on PETs (permutation trees). During the last WMT metrics tasks, BEER has shown high correlation with human judgments both on the sentence and the corpus levels. In this paper we will show how BEER can be used for (i) full evaluation of MT output, (ii) isolated evaluation of word order and (iii) tuning MT systems.

Neural-based Machine Translation for Medical Text Domain. Based on European Medicines Agency Leaflet Texts

The quality of machine translation is rapidly evolving. Today one can find several machine translation systems on the web that provide reasonable translations, although the systems are not perfect. In some specific domains, the quality may decrease. A recently proposed approach to this domain is neural machine translation. It aims at building a jointly-tuned single neural network that maximizes translation performance, a very different approach from traditional statistical machine translation. Recently proposed neural machine translation models often belong to the encoder-decoder family in which a source sentence is encoded into a fixed length vector that is, in turn, decoded to generate a translation. The present research examines the effects of different training methods on a Polish-English Machine Translation system used for medical data. The European Medicines Agency parallel text corpus was used as the basis for training of neural and statistical network-based translation systems. The main machine translation evaluation metrics have also been used in analysis of the systems. A comparison and implementation of a real-time medical translator is the main focus of our experiments.