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A Simple yet Effective Layout Token in Large Language Models for Document Understanding
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Proposes LayTokenLLM, which compresses each OCR text segment's bounding box into a single learnable-query layout token, shares position IDs between text and layout tokens, and pretrains with a next-interleaved text-and-layout token prediction objective for document understanding.
Problem
Layout-as-token methods for LLM document understanding allocate extra position IDs to layout tokens, which reduces the position range available for text and causes untrained position IDs in long multi-page contexts.
Approach
Represent each text segment's layout as one layout token (attention pooling over a projected bounding box with a learnable query), assign it the position ID of the segment's first text token so no extra position IDs are needed, and train with a next-token objective that predicts both text tokens (CE) and layout coordinates (MSE).
Key results
- LayTokenLLM-8B reaches 74.31 ANLS on MP-DocVQA and 52.00 on DUDE, versus 69.42 and 46.77 for MPLUG-DocOwl2-8B among compared MLLMs.
- LayTokenLLM-7B scores 92.03 on SIBR vs 68.39 for InternVL2-8B, while LayTokenLLM-8B achieves 85.11 on DocVQA.
- Ablation: layout tokenizer plus shared position IDs (LayPosID) yields +2.3% on multi-page tasks; NTLP adds 2.2% single-page and 0.8% multi-page ANLS average.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Add the layout tokenizer to compress layout information (ablation) | LayTokenLLM · Single-page document tasks | ANLS average: 80.07 -> 78.89 | Hurt |
| Add the layout tokenizer to compress layout information (ablation) | LayTokenLLM · Multi-page document tasks | ANLS average: 50.09 -> 58.22 | Helped |
| Add LayPosID positional encoding (ablation) | LayTokenLLM with layout tokenizer · Single-page document tasks | ANLS average: 78.89 -> 79.27 | Helped |
| Add LayPosID positional encoding (ablation) | LayTokenLLM with layout tokenizer · Multi-page document tasks | ANLS average: 58.22 -> 60.50 | Helped |
| Add NTLP pre-training objective (ablation) | LayTokenLLM with LayPosID · Single-page document tasks | ANLS average: 79.27 -> 81.51 | Helped |
| Add NTLP pre-training objective (ablation) | LayTokenLLM with LayPosID · Multi-page document tasks | ANLS average: 60.50 -> 61.27 | Helped |
Surprising findings
- Explicit text-with-layout inputs (e.g., '{text, Box}' format) underperform the compressed layout token on multi-page DocVQA, with ANLS gaps of over 10 points among layout-as-token baselines.
Limitations
- May overlook graphical elements such as charts and icons.
- Single layout token compression loses some information (single-page performance slightly degrades without shared position IDs).
- Only fine-grained layout relationship prediction left for future work.
Experimental setup
Datasets: LayoutLLM layout-aware SFT data DocVQA SIBR MP-DocVQA DUDE FUNSD CORD
Benchmarks: DocVQA SIBR FUNSD CORD MP-DocVQA DUDE
Metrics: ANLS F1 FLOPs/MACs
Baselines: Qwen1.5-7B-Chat Llama3-8B-Instruct DocLLM LayoutLLM LayTextLLM InternVL2-8B TextMonkey QwenVL Idefics3-8B MPLUG-DocOwl2-8B LongVA-7B LLaVA-next-interleave-7B
Builds on: LayoutLLM LayTextLLM RoPE LoRA
Closest papers by meaning
- LayoutLLM: Layout Instruction Tuning with Large Language Models for Document Understanding (CVPR 2024 · similarity 0.92)
- DocLayLLM: An Efficient Multi-modal Extension of Large Language Models for Text-rich Document Understanding (CVPR 2025 · similarity 0.91)
- MMLONGBENCH-DOC: Benchmarking Long-context Document Understanding with Visualizations (NeurIPS 2024 · similarity 0.88)
- In-Context Pretraining: Language Modeling Beyond Document Boundaries (ICLR 2024 · similarity 0.87)
- Read, Parse, Describe: Unified Document Parsing with Visual Element Description Generation (NeurIPS 2026 · similarity 0.86)
- Graph-based Document Structure Analysis (ICLR 2025 · similarity 0.86)
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