Memory-Based Resolution of In-Sentence Scopes of Hedge Cues
Summary
The paper describes the system that CLiPS (University of Antwerp) submitted for the closed-track competition of the CoNLL-2010 Shared Task on hedge detection. The task has two parts: deciding whether a sentence carries uncertain information (Task 1), and identifying hedge cues and the words each cue governs in biomedical text (Task 2).
For Wikipedia data, an SVM labels every token using a hand-picked set of frequent weasel cues, and the sentence label is derived from those token decisions. For the biological data (BIO-ABS, BIO-ART), the authors chain two memory-based classifiers. The first tags cue tokens in a begin/inside/outside scheme, so multiword cues can be found. The second runs once per cue and marks the first and last tokens of its scope. It draws on shallow syntax and dependency syntax from the GDep parser, plus a cue lexicon built from the training data. Postprocessing then handles references to bibliography, tables and figures.
The scope resolver obtained the top F1 in Task 2 (57.32). Even so, the score shows that hedge scope resolution in full biomedical articles remains hard. The main error sources are mistakes in cue detection, flawed dependency parses and metalinguistic sentences.
Key points
- Task 2 result: best F1 among participants, 57.32. Without the reference and scope postprocessing steps, F1 falls to 50.02 and 46.52 respectively.
- Preprocessing tools:
- WIKI data was parsed with MBSP (lemmas, PoS, chunks) and MaltParser (dependencies).
- BIO data was parsed with GDep, which was trained on abstracts and is therefore weaker on full articles.
- Converting the gold xml to CoNLL format kept scorer F1 between 99.10 and 100.00.
- WIKI training data: it contains 3133 weasels across 1984 types, and 63% of the types are unique. For this reason the authors selected 42 frequent weasel cue tokens by hand rather than trying to detect weasels directly.
- Differences from Morante and Daelemans (2009):
- one classifier replaces three classifiers plus a metalearner;
- dependency features are added to shallow ones;
- a cue lexicon built from the training data is added.
- Difficult inputs: ambiguous cues such as "or", subordinate clauses that wrongly end up inside a scope, and a test article about hedge annotation itself, whose metalanguage produced false positives.
Cited by
Cite
@inproceedings{morante2010memory,
title = {{Memory-Based Resolution of In-Sentence Scopes of Hedge Cues}},
author = {Morante, Roser and Asch, Vincent Van and Daelemans, Walter},
booktitle = {Proceedings of the Fourteenth Conference on Computational Natural Language Learning – Shared Task},
year = {2010},
url = {https://aclanthology.org/W10-3006/}
}References
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