44,191 research outputs found
A Survey of Word Reordering in Statistical Machine Translation: Computational Models and Language Phenomena
Word reordering is one of the most difficult aspects of statistical machine
translation (SMT), and an important factor of its quality and efficiency.
Despite the vast amount of research published to date, the interest of the
community in this problem has not decreased, and no single method appears to be
strongly dominant across language pairs. Instead, the choice of the optimal
approach for a new translation task still seems to be mostly driven by
empirical trials. To orientate the reader in this vast and complex research
area, we present a comprehensive survey of word reordering viewed as a
statistical modeling challenge and as a natural language phenomenon. The survey
describes in detail how word reordering is modeled within different
string-based and tree-based SMT frameworks and as a stand-alone task, including
systematic overviews of the literature in advanced reordering modeling. We then
question why some approaches are more successful than others in different
language pairs. We argue that, besides measuring the amount of reordering, it
is important to understand which kinds of reordering occur in a given language
pair. To this end, we conduct a qualitative analysis of word reordering
phenomena in a diverse sample of language pairs, based on a large collection of
linguistic knowledge. Empirical results in the SMT literature are shown to
support the hypothesis that a few linguistic facts can be very useful to
anticipate the reordering characteristics of a language pair and to select the
SMT framework that best suits them.Comment: 44 pages, to appear in Computational Linguistic
A discriminative latent variable-based "DE" classifier for ChineseâEnglish SMT
Syntactic reordering on the source-side
is an effective way of handling word order
differences. The (DE) construction
is a flexible and ubiquitous syntactic
structure in Chinese which is a major
source of error in translation quality.
In this paper, we propose a new classifier
model â discriminative latent variable
model (DPLVM) â to classify the
DE construction to improve the accuracy
of the classification and hence the translation
quality. We also propose a new feature
which can automatically learn the reordering
rules to a certain extent. The experimental
results show that the MT systems
using the data reordered by our proposed
model outperform the baseline systems
by 6.42% and 3.08% relative points
in terms of the BLEU score on PB-SMT
and hierarchical phrase-based MT respectively.
In addition, we analyse the impact
of DE annotation on word alignment and
on the SMT phrase table
Fine-grained human evaluation of neural versus phrase-based machine translation
We compare three approaches to statistical machine translation (pure
phrase-based, factored phrase-based and neural) by performing a fine-grained
manual evaluation via error annotation of the systems' outputs. The error types
in our annotation are compliant with the multidimensional quality metrics
(MQM), and the annotation is performed by two annotators. Inter-annotator
agreement is high for such a task, and results show that the best performing
system (neural) reduces the errors produced by the worst system (phrase-based)
by 54%.Comment: 12 pages, 2 figures, The Prague Bulletin of Mathematical Linguistic
Addressing the Rare Word Problem in Neural Machine Translation
Neural Machine Translation (NMT) is a new approach to machine translation
that has shown promising results that are comparable to traditional approaches.
A significant weakness in conventional NMT systems is their inability to
correctly translate very rare words: end-to-end NMTs tend to have relatively
small vocabularies with a single unk symbol that represents every possible
out-of-vocabulary (OOV) word. In this paper, we propose and implement an
effective technique to address this problem. We train an NMT system on data
that is augmented by the output of a word alignment algorithm, allowing the NMT
system to emit, for each OOV word in the target sentence, the position of its
corresponding word in the source sentence. This information is later utilized
in a post-processing step that translates every OOV word using a dictionary.
Our experiments on the WMT14 English to French translation task show that this
method provides a substantial improvement of up to 2.8 BLEU points over an
equivalent NMT system that does not use this technique. With 37.5 BLEU points,
our NMT system is the first to surpass the best result achieved on a WMT14
contest task.Comment: ACL 2015 camera-ready versio
Attention Focusing for Neural Machine Translation by Bridging Source and Target Embeddings
In neural machine translation, a source sequence of words is encoded into a
vector from which a target sequence is generated in the decoding phase.
Differently from statistical machine translation, the associations between
source words and their possible target counterparts are not explicitly stored.
Source and target words are at the two ends of a long information processing
procedure, mediated by hidden states at both the source encoding and the target
decoding phases. This makes it possible that a source word is incorrectly
translated into a target word that is not any of its admissible equivalent
counterparts in the target language.
In this paper, we seek to somewhat shorten the distance between source and
target words in that procedure, and thus strengthen their association, by means
of a method we term bridging source and target word embeddings. We experiment
with three strategies: (1) a source-side bridging model, where source word
embeddings are moved one step closer to the output target sequence; (2) a
target-side bridging model, which explores the more relevant source word
embeddings for the prediction of the target sequence; and (3) a direct bridging
model, which directly connects source and target word embeddings seeking to
minimize errors in the translation of ones by the others.
Experiments and analysis presented in this paper demonstrate that the
proposed bridging models are able to significantly improve quality of both
sentence translation, in general, and alignment and translation of individual
source words with target words, in particular.Comment: 9 pages, 6 figures. Accepted by ACL201
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