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Talk: Going to the Roots of Dependency Parsing (Miguel Ballesteros, 2014/12/16)

Speaker:  Miguel Ballesteros (Universitat Pompeu Fabra)

Miguel is a Visiting lecturer – Postdoc in Pompeu Fabra University, Barcelona. He works on natural language processing and machine learning with a special interest on linguistic structure prediction problems, such as dependency parsing and phrase structure parsing.  He completed his BsC,  MsC and PhD at the Universidad Complutense de Madrid. During the last years, he was a Visiting Researcher in Uppsala University, Singapore University of Technology and Design and Carnegie Mellon University.

Data: December 16th 2014, Tuesday
Time: 15:30-16:30
Room: 3.2 room. Faculty of Informatics (UPV/EHU)

Title: “Going to the Roots of Dependency Parsing.”


I will first introduce transition-based dependency parsing and present the conclusions extracted from a set of experiments on the root node of dependency analysis,
besides I’m going to sum up my current, past and future research collaboration projects with some new results and developments.

Dependency trees used in syntactic parsing often include a root node representing a dummy
word prefixed or suffixed to the sentence, a device that is generally considered a mere technical
convenience and is tacitly assumed to have no impact on empirical results. We demonstrate that
this assumption is false and that the accuracy of data-driven dependency parsers can in fact be
sensitive to the existence and placement of the dummy root node. In particular, we show that
a greedy, left-to-right, arc-eager transition-based parser consistently performs worse when the
dummy root node is placed at the beginning of the sentence (following the current convention
in data-driven dependency parsing) than when it is placed at the end or omitted completely.
Control experiments with an arc-standard transition-based parser and an arc-factored graph-
based parser reveal no consistent preferences but nevertheless exhibit considerable variation in
results depending on root placement. We conclude that the treatment of dummy root nodes in
data-driven dependency parsing is an underestimated source of variation in experiments and
may also be a parameter worth tuning for some parsers.


Miguel Ballesteros and Joakim Nivre.  2013. Going to the Roots of Dependency Parsing. Computational Linguistics 39:1

Miguel Ballesteros
and Bernd Bohnet   2014.  Automatic Feature Selection for Agenda-Based Dependency Parsing . 25th International Conference on Computational Linguistics (COLING 2014) Dublin, Ireland

Isabel Ortiz, Miguel Ballesteros and Yue Zhang  2014.  ViZPar: A GUI for ZPar with Manual Feature Selection . Demonstrations of the 30th Spanish Conference on Natural Language Processing (SEPLN 2014) Girona, Spain

Miguel Ballesteros and Joakim Nivre.  2014.  MaltOptimizer: Fast and Effective Parser Optimization. Natural Language Engineering.

Miguel Ballesteros, Bernd Bohnet, Simon Mille and Leo Wanner  2014. Deep-Syntactic Parsing. 25th International Conference on Computational Linguistics (COLING 2014) Dublin, Ireland

1 comment to Talk: Going to the Roots of Dependency Parsing (Miguel Ballesteros, 2014/12/16)

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