Papers › Improving Unsupervised Constituency Parsing via Maximizing Semantic Information
Improving Unsupervised Constituency Parsing via Maximizing Semantic Information
Junjie Chen, Xiangheng He, Yusuke Miyao, Danushka Bollegala
Unsupervised constituency parsers organize phrases within a sentence into a tree-shaped syntactic constituent structure that reflects the organization of sentence semantics. However, the traditional objective of maximizing sentence log-likelihood (LL) does not explicitly account for the close relationship between the constituent structure and the semantics, resulting in a weak correlation between LL values and parsing accuracy. In this paper, we introduce a novel objective for training unsupervised parsers: maximizing the information between constituent structures and sentence semantics (SemInfo). We introduce a bag-of-substrings model to represent the semantics and apply the probability-weighted information metric to estimate the SemInfo. Additionally, we develop a Tree Conditional Random Field (TreeCRF)-based model to apply the SemInfo maximization objective to Probabilistic Context-Free Grammar (PCFG) induction, the state-of-the-art method for unsupervised constituency parsing. Experiments demonstrate that SemInfo correlates more strongly with parsing accuracy than LL. Our algorithm significantly enhances parsing accuracy by an average of 7.85 points across five PCFG variants and in four languages, achieving new state-of-the-art results in three of the four languages.
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Tasks
Results from the paper archive 2025-07-28
| Task | Dataset | Model | Metric | Value | Rank at snapshot | Leaderboard | Report |
|---|---|---|---|---|---|---|---|
| Constituency Grammar Induction | CTB | SemInfo-NPCFG (60NT) | Mean F1 | 53.92 | #1 of 1 | Archive leaderboard | report |
| Constituency Grammar Induction | PTB Diagnostic ECG Database | SemInfo-SCPCFG (1024NT) | Mean F1 (WSJ) | 66.92 | #4 of 24 | Archive leaderboard | report |
| Constituency Grammar Induction | SPMRL French | SemInfo-SNPCFG (1024NT) | Mean F1 | 54.37 | #1 of 1 | Archive leaderboard | report |
| Constituency Grammar Induction | SPMRL German | SemInfo-NPCFG (60NT) | Mean F1 | 47.77 | #1 of 1 | Archive leaderboard | report |
Ranks are positions in the archive's leaderboards as they stood at the 2025-07-28 snapshot. Results published since then are not among these rows, so a rank here is not a current standing.
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