TPLinker: Single-stage Joint Extraction of Entities and Relations Through Token Pair Linking
Summary
The paper addresses joint extraction of entities and relational triplets from text, focusing on overlapping cases where triplets share one entity (SEO) or both entities (EPO). Earlier joint models either generate triplets step by step with a decoder or first find subjects and then their objects. Both approaches train on gold context but must rely on their own predictions at test time, so errors accumulate (exposure bias). The authors propose TPLinker, a single-stage model that treats extraction as linking pairs of tokens. Its handshaking tagging scheme uses three kinds of links: entity head to entity tail, subject head to object head, and subject tail to object tail. The two subject–object link types are tagged separately for each relation. No step depends on an earlier prediction, so training and inference behave the same way. On the NYT and WebNLG benchmarks, TPLinker reports state-of-the-art results. Its largest gains are on sentences with overlapping relations or many triplets, and it also decodes faster than the CasRel baseline. This matters for building knowledge bases from realistic, densely related text.
Key points
- The task is split into 2N+1 sequence-labeling subtasks, where N is the number of relation types. The entity-boundary matrix is shared across relations. Each tag sequence covers the upper triangle of the token-pair matrix, with length (n²+n)/2.
- The scheme handles nested entities and both SEO and EPO overlaps by design, for example "New York" and "New York City" sharing the object "De Blasio".
- TPLinker outperforms CasRel by 6.3 F1 points on sentences containing 5 or more triplets.
- TPLinker_BERT decodes about 3.6× faster than CasRel_BERT because it supports batched inference:
- NYT: 15.2 ms vs 54.0 ms per sample.
- WebNLG: 25.6 ms vs 76.8 ms per sample.
- On WebNLG (171 relations, 5,019 training sentences), TPLinker roughly matches CasRel. The authors attribute this to near-saturated scores and to near-synonymous relation labels in the annotation. Code is published on GitHub.
Cited by
Cite
@inproceedings{wang2020tplinker,
title = {{TPLinker: Single-stage Joint Extraction of Entities and Relations Through Token Pair Linking}},
author = {Wang, Yucheng and Yu, Bowen and Zhang, Yueyang and Liu, Tingwen and Zhu, Hongsong and Sun, Limin},
booktitle = {Proceedings of the 28th International Conference on Computational Linguistics},
year = {2020},
doi = {10.18653/v1/2020.coling-main.138},
url = {https://doi.org/10.18653/v1/2020.coling-main.138}
}References
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