956 research outputs found
Conditional Random Field Autoencoders for Unsupervised Structured Prediction
We introduce a framework for unsupervised learning of structured predictors
with overlapping, global features. Each input's latent representation is
predicted conditional on the observable data using a feature-rich conditional
random field. Then a reconstruction of the input is (re)generated, conditional
on the latent structure, using models for which maximum likelihood estimation
has a closed-form. Our autoencoder formulation enables efficient learning
without making unrealistic independence assumptions or restricting the kinds of
features that can be used. We illustrate insightful connections to traditional
autoencoders, posterior regularization and multi-view learning. We show
competitive results with instantiations of the model for two canonical NLP
tasks: part-of-speech induction and bitext word alignment, and show that
training our model can be substantially more efficient than comparable
feature-rich baselines
Models of Co-occurrence
A model of co-occurrence in bitext is a boolean predicate that indicates
whether a given pair of word tokens co-occur in corresponding regions of the
bitext space. Co-occurrence is a precondition for the possibility that two
tokens might be mutual translations. Models of co-occurrence are the glue that
binds methods for mapping bitext correspondence with methods for estimating
translation models into an integrated system for exploiting parallel texts.
Different models of co-occurrence are possible, depending on the kind of bitext
map that is available, the language-specific information that is available, and
the assumptions made about the nature of translational equivalence. Although
most statistical translation models are based on models of co-occurrence,
modeling co-occurrence correctly is more difficult than it may at first appear
Word-to-Word Models of Translational Equivalence
Parallel texts (bitexts) have properties that distinguish them from other
kinds of parallel data. First, most words translate to only one other word.
Second, bitext correspondence is noisy. This article presents methods for
biasing statistical translation models to reflect these properties. Analysis of
the expected behavior of these biases in the presence of sparse data predicts
that they will result in more accurate models. The prediction is confirmed by
evaluation with respect to a gold standard -- translation models that are
biased in this fashion are significantly more accurate than a baseline
knowledge-poor model. This article also shows how a statistical translation
model can take advantage of various kinds of pre-existing knowledge that might
be available about particular language pairs. Even the simplest kinds of
language-specific knowledge, such as the distinction between content words and
function words, is shown to reliably boost translation model performance on
some tasks. Statistical models that are informed by pre-existing knowledge
about the model domain combine the best of both the rationalist and empiricist
traditions
Sentence alignment in DPC: maximizing precision, minimizing human effort
A wide spectrum of multilingual applications have aligned parallel corpora as their prerequisite. The aim of the project described in this paper is to build a multilingual corpus where all sentences are aligned at very high precision with a minimal human effort involved. The experiments on a combination of sentence aligners with different underlying algorithms described in this paper showed that by verifying only those links which were not recognized by at least two aligners, an error rate can be reduced by 93.76% as compared to the performance of the best aligner. Such manual involvement concerned only a small portion of all data (6%). This significantly reduces a load of manual work necessary to achieve nearly 100% accuracy of alignment
F-structure transfer-based statistical machine translation
In this paper, we describe a statistical deep syntactic transfer decoder that is trained fully automatically on parsed bilingual corpora. Deep syntactic transfer rules are induced automatically from the f-structures of a LFG parsed bitext corpus by automatically aligning local f-structures, and inducing all rules consistent with the node alignment. The transfer decoder outputs the n-best TL f-structures given a SL f-structure as input by applying large numbers of transfer rules and searching for the best output using a
log-linear model to combine feature scores. The decoder includes a fully integrated dependency-based tri-gram language model. We include an experimental evaluation of the decoder using different parsing disambiguation
resources for the German data to provide a comparison of how the system performs with different German training and test parses
Contextual bitext-derived paraphrases in automatic MT evaluation
In this paper we present a novel method for deriving paraphrases during automatic MT evaluation using only the source and reference texts, which are necessary for
the evaluation, and word and phrase alignment software. Using target language paraphrases produced through word and
phrase alignment a number of alternative reference sentences are constructed automatically for each candidate translation. The method produces lexical and lowlevel
syntactic paraphrases that are relevant to the domain in hand, does not use external knowledge resources, and can be
combined with a variety of automatic MT evaluation system
Dilemma - An Instant Lexicographer
Dilemma is intended to enhance quality and increase productivity of expert
human translators by presenting to the writer relevant lexical information
mechanically extracted from comparable existing translations, thus replacing -
or compensating for the absence of - a lexicographer and stand-by terminologist
rather than the translator. Using statistics and crude surface analysis and a
minimum of prior information, Dilemma identifies instances and suggests their
counterparts in parallel source and target texts, on all levels down to
individual words. Dilemma forms part of a tool kit for translation where focus
is on text structure and over-all consistency in large text volumes rather than
on framing sentences, on interaction between many actors in a large project
rather than on retrieval of machine-stored data and on decision making rather
than on application of given rules. In particular, the system has been tuned to
the needs of the ongoing translation of European Community legislation into the
languages of candidate member countries. The system has been demonstrated to
and used by professional translators with promising results.Comment: 3 pages, LaTeX, in proceedings of COLING 9
Token and Type Constraints for Cross-Lingual Part-of-Speech Tagging
We consider the construction of part-of-speech taggers for resource-poor languages. Recently, manually constructed tag dictionaries from Wiktionary and dictionaries projected via bitext have been used as type constraints to overcome the scarcity of annotated data in this setting. In this paper, we show that additional token constraints can be projected from a resource-rich source language to a resource-poor target language via word-aligned bitext. We present several models to this end; in particular a partially observed conditional random ïŹeld model, where coupled token and type constraints provide a partial signal for training. Averaged across eight previously studied Indo-European languages, our model achieves a 25% relative error reduction over the prior state of the art. We further present successful results on seven additional languages from different families, empirically demonstrating the applicability of coupled token and type constraints across a diverse set of languages
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