Annotation-Inspired Implicit Discourse Relation Classification with Auxiliary Discourse Connective Generation
Summary
Implicit discourse relations are hard to classify because no connective (such as "but" or "because") signals the link between two arguments. Earlier work used annotated implicit connectives only as an extra training signal, which gave little benefit. Liu and Strube instead mimic how PDTB annotators work: they first insert a suitable connective and then choose a relation label. Their end-to-end model is built on RoBERTa. It predicts a connective at a [MASK] position between Arg1 and Arg2, then feeds the arguments together with that connective into a relation classifier. Both modules share the embeddings and Transformer layers. Connectives generated early in training are unreliable, and gold connectives are unavailable at test time. To handle both issues, the authors apply Scheduled Sampling, which moves the classifier gradually from annotated to generated connectives. On PDTB 2.0, PDTB 3.0 and the German PCC, the model beats other connective-enhanced baselines and comes close to state-of-the-art systems. The work shows that placing connectives directly in the input is more effective than using them only as auxiliary targets.
Key points
- Level-1 results (Ji split): On PDTB 2.0 the model reaches 74.59 accuracy and 68.64 F1, against 68.61 and 60.89 for plain RoBERTa. On PDTB 3.0 it scores 76.23 and 71.15, against 73.51 and 67.98.
- Ablation: Removing Scheduled Sampling lowers PDTB 2.0 F1 to 66.68. Also dropping the connective-generation loss lowers it further to 63.43, which still beats RoBERTa. This suggests the annotation-inspired architecture helps on its own.
- Per-relation results: Contingency.Cause improves most (F1 66.35 vs. 60.03). However, all models fail on rare senses such as Temporal.Synchrony, Contingency.Pragmatic cause and Comparison.Concession.
- Analysis findings:
- End-to-end training makes the model more robust to wrongly generated connectives.
- Incorrect connectives remain the main bottleneck.
- The model balances evidence from the arguments and the connective better than the baselines do.
- Practical notes: Parameter count and memory use are close to RoBERTa, but training is slower because each input passes through the encoder twice. Multi-label instances (3.45% in PDTB 2.0, 5% in PDTB 3.0) are reduced to their first label. The code is released as ConnRel on GitHub.
Cited by
- Mapping Explicit and Implicit Discourse Relations between the RST-DT and the PDTB 3.0
- What Causes the Failure of Explicit to Implicit Discourse Relation Recognition?
- Discursive Socratic Questioning: Evaluating the Faithfulness of Language Models' Understanding of Discourse Relations
- An Empirical Study of Synthetic Data Generation for Implicit Discourse Relation Recognition
Cite
@inproceedings{liu2023annotation,
title = {{Annotation-Inspired Implicit Discourse Relation Classification with Auxiliary Discourse Connective Generation}},
author = {Liu, Wei and Strube, Michael},
booktitle = {Proceedings of the 61st Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)},
year = {2023},
doi = {10.18653/v1/2023.acl-long.874},
eprint = {2306.06480},
archivePrefix = {arXiv},
url = {https://doi.org/10.18653/v1/2023.acl-long.874}
}References
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- L1 L2 PDTB 2.0 Comparison Contingency Expansion Temporal Comparison.Concession Comparison.Contrast Contingency.Cause Contingency.Pragmatic cause Expansion.Conjunction Expansion.Instantiation Expansion.Alternative Expansion.List Expansion.Restatement Temporal.Asynchronous Temporal.Synchrony PDTB 3.0… find