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<Paper uid="P06-2066">
  <Title>Mildly Non-Projective Dependency Structures</Title>
  <Section position="9" start_page="512" end_page="513" type="concl">
    <SectionTitle>
5 Conclusion
</SectionTitle>
    <Paragraph position="0"> In this paper, we have reviewed a number of proposals for the characterization of mildly non-projective dependency structures, motivated by the need to find a better balance between expressivity and complexity than that offered by either strictly projective or unrestricted non-projective structures.</Paragraph>
    <Paragraph position="1"> Experimental evaluation based on data from two treebanks shows, that a combination of the well-nestedness constraint and parametric constraints on discontinuity (formalized either as gap degree or edge degree) gives a very good fit with the empirical linguistic data. Important goals for future work are to widen the empirical basis by investigating more languages, and to perform a more detailed analysis of linguistic phenomena that violate certain constraints. Another important line of research is the integration of these constraints into parsing algorithms for non-projective dependency structures, potentially leading to a better trade-off between accuracy and efficiency than that obtained with existing methods.</Paragraph>
    <Paragraph position="2"> Acknowledgements We thank three anonymous reviewers of this paper for their comments. The work of Marco Kuhlmann is funded by the Collaborative Research Centre 378 'Resource-Adaptive Cognitive Processes' of the Deutsche Forschungsgemeinschaft. The work of Joakim Nivre is partially supported by the Swedish Research Council.</Paragraph>
  </Section>
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