Shallow Discourse Parsing with Conditional Random Fields
Summary
This paper addresses a gap in discourse parsing. Earlier systems either recovered only argument heads or covered only some connectives. Here the task is to find the complete text spans of both arguments (Arg1 and Arg2) of explicit discourse connectives in the Penn Discourse Treebank (PDTB). The authors assume the connectives are already known and make no prior assumptions about span shape. They frame the problem as token-level sequence labeling, solved by a cascade of conditional random fields (CRFs). Arg2, which is syntactically tied to the connective, is labeled first, and that output then feeds the Arg1 model. The features are lexical, syntactic and semantic, drawn from gold PDTB annotation and Penn Treebank parse trees, including the connective's top-level sense class. The best feature combinations include both syntactic and semantic information. Arg1 within the connective's own sentence is found about as reliably as Arg2. Arg1 in an earlier sentence remains the hardest case. The approach yields a flat, non-hierarchical discourse representation that can support applications such as opinion mining, where exact argument spans matter.
Key points
- Data: PDTB, about one million words of Wall Street Journal text with 18,459 explicit connective tokens of 100 types. Arg1 sits in the same sentence as the connective in 60.9% of cases. The test split contains 1028 intra-sentential and 617 inter-sentential relations.
- Arg1 within a sentence (exact match): F1 is about 0.66–0.68, rising to roughly 0.85 under the more lenient overlap metric.
- Arg1 across sentences: this case depends on a "Prev" feature. With it, exact-match F1 rises from 0.02 to 0.36.
- Results by connective type: Arg2 exact-match F1 is fairly uniform at 0.78–0.82. Adverbial connectives are the weakest case for Arg1, reaching 0.44 F1 even with Prev.
- Efficiency and error patterns: pruning the search space by 90% kept training time manageable while dropping only about 5% of Arg1 instances. Recall was consistently below precision. Most errors involved locating exact span boundaries rather than finding the right sentence.
Cited by
- PDTB Discourse Parsing as a Tagging Task: The Two Taggers Approach
- Global Features for Shallow Discourse Parsing
- CODRA: A Novel Discriminative Framework for Rhetorical Analysis
- A Constituent-Based Approach to Argument Labeling with Joint Inference in Discourse Parsing
- Reflections on the Penn Discourse TreeBank, Comparable Corpora, and Complementary Annotation
- Comparative Evaluation of Argument Extraction Algorithms in Discourse Relation Parsing
- Towards Cross-Domain PDTB-Style Discourse Parsing
- The UniTN Discourse Parser in CoNLL 2015 Shared Task: Token-level Sequence Labeling with Argument-specific Models
- The DCU Discourse Parser for Connective, Argument Identification and Explicit Sense Classification
- A Refined End-to-End Discourse Parser
- What excludes an Alternative in Coherence Relations?
Cite
@inproceedings{ghosh2011shallow,
title = {{Shallow Discourse Parsing with Conditional Random Fields}},
author = {Ghosh, Sucheta and Johansson, Richard and Riccardi, Giuseppe and Tonelli, Sara},
booktitle = {Proceedings of 5th International Joint Conference on Natural Language Processing},
year = {2011},
url = {https://aclanthology.org/I11-1120/}
}References
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