Coreference for Discourse Parsing: A Neural Approach
Summary
The authors examine whether coreference information helps neural parsing of documents into Rhetorical Structure Theory (RST) trees. Their motivation comes from discourse theory, notably Veins theory, which holds that tree structure limits where antecedents of anaphors may appear, so coreference links could in turn narrow the parser's search space. They build a greedy shift-reduce parser with two MLP classifiers, one for action and nuclearity and one for relation, on top of SpanBERT-Base. Three levels of coupling are compared. The first is a baseline with no coreference input. The second injects clusters predicted by a pretrained SpanBERT coreference resolver into the input embeddings through attention and gating. The third is a multitask model in which a shared SpanBERT encoder is trained jointly on discourse parsing (RST-DT) and coreference (OntoNotes 5.0). Even the baseline exceeds earlier systems and comes close to human agreement. However, neither coreference-aware variant yields a statistically significant gain, and both show greater variance. The study is a useful negative result for discourse–coreference integration, though it covers only one dataset.
Key points
- Evaluation uses RST-DT with RST-Parseval micro precision. Reported scores are the mean of five single-model runs.
- SpanBERT-NoCoref reaches 87.8 / 75.8 / 63.4 (structure / nuclearity / relation). SpanBERT-CorefFeats gets 88.1 / 76.1 / 63.6, and SpanBERT-MultiTask gets 87.9 / 75.9 / 63.3. Human agreement is 88.3 / 77.3 / 65.4.
- The baseline beats the previous best system, the D2P2S2E ensemble (87.0 / 74.6 / 60.0), especially on relation labels. The relation classifier covers 18 coarse-grained RST relations.
- The authors offer several possible reasons for the null result:
- SpanBERT may already encode the relevant coreference signal.
- Coreference may be only a weak cue for discourse structure.
- Predicted coreference clusters may be too noisy.
- The ways of fusing the two tasks may be inadequate.
- A case study (wsj_0631) shows the baseline producing a subtree that strict Veins theory would forbid when gold coreference is available.
Cited by
- A Simple and Strong Baseline for End-to-End Neural RST-style Discourse Parsing
- Why Can't Discourse Parsing Generalize? A Thorough Investigation of the Impact of Data Diversity
- Can we obtain significant success in RST discourse parsing by using Large Language Models?
- GENTLE: A Genre-Diverse Multilayer Challenge Set for English NLP and Linguistic Evaluation
- RST Discourse Parsing with Second-Stage EDU-Level Pre-training
- The DISRPT 2021 Shared Task on Elementary Discourse Unit Segmentation, Connective Detection, and Relation Classification
- eRST: A Signaled Graph Theory of Discourse Relations and Organization
Cite
@inproceedings{guz2020coreference,
title = {{Coreference for Discourse Parsing: A Neural Approach}},
author = {Guz, Grigorii and Carenini, Giuseppe},
booktitle = {Proceedings of the First Workshop on Computational Approaches to Discourse},
year = {2020},
doi = {10.18653/v1/2020.codi-1.17},
url = {https://doi.org/10.18653/v1/2020.codi-1.17}
}References
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