13,130 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 syntactic skeleton for statistical machine translation
We present a method for improving statistical machine translation performance by using linguistically motivated syntactic information. Our algorithm recursively decomposes source language sentences into syntactically simpler and shorter chunks, and recomposes their translation to form target language sentences. This improves both the word order and lexical selection of the translation. We report statistically significant relative improvementsof 3.3% BLEU score in an experiment (English!Spanish) carried out on
an 800-sentence test set extracted from the Europarl corpus
Using percolated dependencies for phrase extraction in SMT
Statistical Machine Translation (SMT) systems rely heavily on the quality of the phrase pairs induced from large amounts of training data. Apart from the widely used method of heuristic learning of n-gram phrase translations from word alignments, there are numerous methods for extracting these phrase pairs. One such class of approaches uses translation information encoded in parallel treebanks to extract phrase pairs. Work to date has demonstrated the usefulness of translation models induced from both constituency structure trees and dependency structure trees. Both syntactic annotations rely on the existence of natural language parsers for both the source and target languages. We depart from the norm by directly obtaining dependency parses from constituency structures using head percolation tables. The paper investigates the use of aligned chunks induced from percolated dependencies in French–English SMT and contrasts it with the aforementioned extracted phrases.
We observe that adding phrase pairs from any other method improves translation performance over the baseline n-gram-based system, percolated dependencies are a good substitute for parsed dependencies, and that supplementing with our novel head percolation-induced chunks shows a general trend toward improving all system types across two data sets up to a 5.26% relative increase in BLEU
A discriminative latent variable-based "DE" classifier for Chinese–English 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 — discriminative latent variable
model (DPLVM) — 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
Dutch hypernym detection : does decompounding help?
This research presents experiments carried out to improve the precision and recall of Dutch hypernym detection. To do so, we applied a data-driven semantic relation finder that starts from a list of automatically extracted domain-specific terms from technical corpora, and generates a list of hypernym relations between these terms. As Dutch technical terms often consist of compounds written in one orthographic unit, we investigated the impact of a decompounding module on the performance of the hypernym detection system.
In addition, we also improved the precision of the system by designing filters taking into account statistical and linguistic information.
The experimental results show that both the precision and recall of the hypernym detection system improved, and that the decompounding module is especially effective for hypernym detection in Dutch
Capturing translational divergences with a statistical tree-to-tree aligner
Parallel treebanks, which comprise paired source-target parse trees aligned at sub-sentential level, could be useful
for many applications, particularly data-driven machine translation. In this paper, we focus on how translational
divergences are captured within a parallel treebank using a fully automatic statistical tree-to-tree aligner. We
observe that while the algorithm performs well at the phrase level, performance on lexical-level alignments
is compromised by an inappropriate bias towards coverage rather than precision. This preference for high precision
rather than broad coverage in terms of expressing translational divergences through tree-alignment stands in
direct opposition to the situation for SMT word-alignment models. We suggest that this has implications not only
for tree-alignment itself but also for the broader area of induction of syntaxaware models for SMT
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