Papers with unsupervised grammar induction

7 papers
The Return of Lexical Dependencies: Neural Lexicalized PCFGs (2020.tacl-1)

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Challenge: Existing approaches to grammar induction focus on discovering constituents or dependencies.
Approach: They propose to model lexical dependencies using context free grammars instead of lexicals . they show that this unified framework induces both constituents and dependencies .
Outcome: The proposed model overcomes sparsity problems and induces constituents and dependencies better than the current methods.
Video-aided Unsupervised Grammar Induction (2021.naacl-main)

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Challenge: Existing methods of multi-modal grammar induction focus on grammar inducing from text-image pairs, but videos provide even richer information, such as static objects and actions.
Approach: They propose a video-aided grammar induction model which learns a constituency parser from unlabeled text and its corresponding video.
Outcome: The proposed model outperforms existing systems on three benchmarks.
Fast-R2D2: A Pretrained Recursive Neural Network based on Pruned CKY for Grammar Induction and Text Representation (2022.emnlp-main)

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Challenge: Chart-based models have shown great potential in unsupervised grammar induction, running recursively and hierarchically, but requiring O(n3) time-complexity.
Approach: They propose a model-guided pruning method that scales to large language model pretraining by introducing a heuristic pruning method.
Outcome: The proposed method significantly improves grammar induction quality and achieves competitive results in downstream tasks.
Variance of Average Surprisal: A Better Predictor for Quality of Grammar from Unsupervised PCFG Induction (P19-1)

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Challenge: In unsupervised grammar induction, data likelihood is only weakly correlated with parsing accuracy, especially at convergence after multiple runs.
Approach: They propose to use VAS instead of data likelihood to find better grammars by examining linguistically-motivated constraints related to syntax.
Outcome: The proposed model is better suited for word order typology classification than data likelihood.
The Grammar of Emergent Languages (2020.emnlp-main)

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Challenge: Existing studies on emergent languages focus on semantics, but lack tools to analyse their properties.
Approach: They propose to use unsupervised grammar induction techniques to analyse emergent languages and to examine their syntactic properties.
Outcome: The proposed techniques are appropriate to analyse emergent languages and show that they exhibit syntactic properties similar to those observed in human language.
Phrase-aware Unsupervised Constituency Parsing (2022.acl-long)

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Challenge: Recent studies have achieved inspiring success in unsupervised grammar induction using masked language modeling (MLM) as the proxy task.
Approach: They propose to regularize the parser with phrases extracted by an unsupervised phrase tagger to help the LM model quickly manage low-level structures.
Outcome: The proposed method improves the identification of high-level structures using phrase-guided masking.
Structural Optimization Ambiguity and Simplicity Bias in Unsupervised Neural Grammar Induction (2024.findings-acl)

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Challenge: Unsupervised grammar induction models lack analysis of traditional challenges, especially regarding the training loss.
Approach: They propose a method to reduce the parse pool per sentence for loss evaluation using structural bias from pre-trained parsers.
Outcome: The proposed method significantly improves performance while reducing variance and bias toward overly simplistic parses.

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