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Structured Mean-Field Variational Inference for Higher-Order Span-Based Semantic Role Labeling

Wei Liu, Songlin Yang, Kewei Tu


Abstract
In this work, we enhance higher-order graph-based approaches for span-based semantic role labeling (SRL) by means of structured modeling. To decrease the complexity of higher-order modeling, we decompose the edge from predicate word to argument span into three different edges, predicate-to-head (P2H), predicate-to-tail (P2T), and head-to-tail (H2T), where head/tail means the first/last word of the semantic argument span. As such, we use a CRF-based higher-order dependency parser and leverage Mean-Field Variational Inference (MFVI) for higher-order inference. Moreover, since semantic arguments of predicates are often constituents within a constituency parse tree, we can leverage such nice structural property by defining a TreeCRF distribution over all H2T edges, using the idea of partial marginalization to define structural training loss. We further leverage structured MFVI to enhance inference. We experiment on span-based SRL benchmarks, showing the effectiveness of both higher-order and structured modeling and the combination thereof. In addition, we show superior performance of structured MFVI against vanilla MFVI.
Anthology ID:
2023.findings-acl.58
Volume:
Findings of the Association for Computational Linguistics: ACL 2023
Month:
July
Year:
2023
Address:
Toronto, Canada
Editors:
Anna Rogers, Jordan Boyd-Graber, Naoaki Okazaki
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
918–931
Language:
URL:
https://aclanthology.org/2023.findings-acl.58
DOI:
10.18653/v1/2023.findings-acl.58
Bibkey:
Cite (ACL):
Wei Liu, Songlin Yang, and Kewei Tu. 2023. Structured Mean-Field Variational Inference for Higher-Order Span-Based Semantic Role Labeling. In Findings of the Association for Computational Linguistics: ACL 2023, pages 918–931, Toronto, Canada. Association for Computational Linguistics.
Cite (Informal):
Structured Mean-Field Variational Inference for Higher-Order Span-Based Semantic Role Labeling (Liu et al., Findings 2023)
Copy Citation:
PDF:
https://aclanthology.org/2023.findings-acl.58.pdf
Video:
 https://aclanthology.org/2023.findings-acl.58.mp4