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Extending Feature Decay Algorithms Using Alignment Entropy

Part of the Lecture Notes in Computer Science book series (LNAI,volume 10341)


In machine-learning applications, data selection is of crucial importance if good runtime performance is to be achieved. Feature Decay Algorithms (FDA) have demonstrated excellent performance in a number of tasks. While the decay function is at the heart of the success of FDA, its parameters are initialised with the same weights. In this paper, we investigate the effect on Machine Translation of assigning more appropriate weights to words using word-alignment entropy. In experiments on German to English, we show the effect of calculating these weights using two popular alignment methods, GIZA++ and FastAlign, using both automatic and human evaluations. We demonstrate that our novel FDA model is a promising research direction.


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  1. 1.

    Note that we were unable to calculate statistical significance for the CHRF metric. Note too that prior to tuning, statistically significant improvements were seen for GIZA++ over FastAlign for BLEU, NIST, TER and METEOR.

  2. 2.

    In experiments before tuning (excluded here for reasons of space), the METEOR and CHRF scores of the output of the system executed with GIZA++ did outperform the baseline system before tuning.

  3. 3.

    Why is it the case that better scores are more likely with the METEOR evaluation metric? This measure evaluates a hypothesis against a reference calculating sentence-level similarity scores. In so doing it searches for all the possible matches of the words between the two sentences. The words can match (i) if they are the same, (ii) if they have the same stem, (iii) if they are synonyms, or (iv) if they are found as a match in a paraphrase table. Therefore, this metric takes into consideration not only the n-grams, but also the semantic of the words. As the human evaluation shows, many semantically equivalent translations are output by our GIZA++ system, which are penalised by most automatic metrics, but not by METEOR.


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This research is supported by the ADAPT Centre for Digital Content Technology, funded under the SFI Research Centres Programme (Grant 13/RC/2106) and co-funded under the European Regional Development Fund, and the European Union Seventh Framework Programme FP7/2007-2013 under grant agreement PIAP-GA-2012-324414 (AbuMaTran).

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Correspondence to Alberto Poncelas .

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Poncelas, A., Way, A., Toral, A. (2017). Extending Feature Decay Algorithms Using Alignment Entropy. In: Quesada, J., Martín Mateos , FJ., López Soto, T. (eds) Future and Emerging Trends in Language Technology. Machine Learning and Big Data. FETLT 2016. Lecture Notes in Computer Science(), vol 10341. Springer, Cham.

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