Annual Report 2010 - Fachgruppe Informatik an der RWTH Aachen ...

• The phrase-based translation system was improved with a focus on search organization,
including new knowledge source and better coupling with automatic speech recognition
systems.
• Additionally to the phrase-based translation system, a hierarchical translation system was
implemented using the cube growing and cube pruning algorithms in decoding. It
performs similar to the phrase-based system and thus has been extensively used in
evaluations. Further extensions to this are being investigated.
• Two extensions of standard word lexicons in machine translation have been implemented:
A discriminative word lexicon that uses sentence-level source information to predict the
target words and a trigger-based lexicon model that extends IBM model 1 with a second
trigger, allowing for a more fine-grained lexical choice of target words.
• A consistent phrase model training using a forced alignment procedure has been
implemented. This novel method utilizes phrase-alignment data in order to make training
consistent with the translation decoder.
• Different possibilities for handling large language models in the translation process have
been investigated. These approaches allow the usage of large language models with a
relatively small memory footprint and have been successfully applied in the systems used
in evaluations.
• Our method for system combination for statistical machine translation, inspired from
methods in speech recognitions, was improved.
• Research efforts were continued in the area of automatic translation between German
written text and German Sign Language. In April 2009 the SignSpeak project started.
Speech Recognition
Architecture of an automatic speech recognition system
Today, state-of-the-art systems for automatic speech recognition are based on the statistical
approach of Bayes decision rule. The implementation of Bayes decision rule for automatic
speech recognition is based on two kinds of stochastic models: the acoustic model and the
language model which together are the basis for the decision process itself, i.e. the search for
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