# Unsupervised Morphological Tree Tokenizer

arXiv: https://arxiv.org/abs/2406.15245 · HTML: https://mlsanity.com/paper/2406.15245/

## Key facts

- No citing papers in the map yet (data through 14 Oct 2026).
- Builds on 23 of its 52 references that are in the map.
- First posted on arXiv 21 Jun 2024.

## Builds on (most cited first, 23 of 23)

- [BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding](https://mlsanity.com/paper/1810.04805/) (2018)
- [Pointer Sentinel Mixture Models](https://mlsanity.com/paper/1609.07843/) (2016)
- [Neural Machine Translation of Rare Words with Subword Units](https://mlsanity.com/paper/1508.07909/) (2015)
- [Subword Regularization: Improving Neural Network Translation Models with Multiple Subword Candidates](https://mlsanity.com/paper/1804.10959/) (2018)
- [Byte Pair Encoding is Suboptimal for Language Model Pretraining](https://mlsanity.com/paper/2004.03720/) (2020)
- [Between words and characters: A Brief History of Open-Vocabulary Modeling and Tokenization in NLP](https://mlsanity.com/paper/2112.10508/) (2021)
- [Superbizarre Is Not Superb: Derivational Morphology Improves BERT's Interpretation of Complex Words](https://mlsanity.com/paper/2101.00403/) (2021)
- [Unsupervised Latent Tree Induction with Deep Inside-Outside Recursive Autoencoders](https://mlsanity.com/paper/1904.02142/) (2019)
- [How Much Does Tokenization Affect Neural Machine Translation?](https://mlsanity.com/paper/1812.08621/) (2018)
- [Jointly Learning Sentence Embeddings and Syntax with Unsupervised Tree-LSTMs](https://mlsanity.com/paper/1705.09189/) (2017)
- [R2D2: Recursive Transformer based on Differentiable Tree for Interpretable Hierarchical Language Modeling](https://mlsanity.com/paper/2107.00967/) (2021)
- [Morphological and Language-Agnostic Word Segmentation for NMT](https://mlsanity.com/paper/1806.05482/) (2018)
- [The Effectiveness of Morphology-aware Segmentation in Low-Resource Neural Machine Translation](https://mlsanity.com/paper/2103.11189/) (2021)
- [Fast-R2D2: A Pretrained Recursive Neural Network based on Pruned CKY for Grammar Induction and Text Representation](https://mlsanity.com/paper/2203.00281/) (2022)
- [Effects of sub-word segmentation on performance of transformer language models](https://mlsanity.com/paper/2305.05480/) (2023)
- [Morfessor EM+Prune: Improved Subword Segmentation with Expectation Maximization and Pruning](https://mlsanity.com/paper/2003.03131/) (2020)
- [Dynamic Programming in Rank Space: Scaling Structured Inference with Low-Rank HMMs and PCFGs](https://mlsanity.com/paper/2205.00484/) (2022)
- [Generative Pretrained Structured Transformers: Unsupervised Syntactic Language Models at Scale](https://mlsanity.com/paper/2403.08293/) (2024)
- [Morphological Word Embeddings](https://mlsanity.com/paper/1907.02423/) (2019)
- [CompoundPiece: Evaluating and Improving Decompounding Performance of Language Models](https://mlsanity.com/paper/2305.14214/) (2023)
- [Augmenting Transformers with Recursively Composed Multi-grained Representations](https://mlsanity.com/paper/2309.16319/) (2023)
- [Weakly Supervised Domain Detection](https://mlsanity.com/paper/1907.11499/) (2019)
- [A Multi-Grained Self-Interpretable Symbolic-Neural Model For Single/Multi-Labeled Text Classification](https://mlsanity.com/paper/2303.02860/) (2023)

## Abstract (arXiv)

As a cornerstone in language modeling, tokenization involves segmenting text inputs into pre-defined atomic units. Conventional statistical tokenizers often disrupt constituent boundaries within words, thereby corrupting semantic information. To address this drawback, we introduce morphological structure guidance to tokenization and propose a deep model to induce character-level structures of words. Specifically, the deep model jointly encodes internal structures and representations of words with a mechanism named textitMorphOverriding to ensure the indecomposability of morphemes. By training the model with self-supervised objectives, our method is capable of inducing character-level structures that align with morphological rules without annotated training data. Based on the induced structures, our algorithm tokenizes words through vocabulary matching in a top-down manner. Empirical results indicate that the proposed method effectively retains complete morphemes and outperforms widely adopted methods such as BPE and WordPiece on both morphological segmentation tasks and language modeling tasks. Code is available at https://github.com/martianmartina/TreeTokenizer.