NEST_250323_250411

NEST (Novel Emerging Segmentation Task) is a benchmark dataset for segmenting (i) novel entities that MLLMs fail to recognize due to their absence from training data, and (ii) emerging entities that exist within the model’s knowledge but demand up-to-date external information for accurate recognition, introduced in the CVPR 2026 Findings paper ROSE: Retrieval-Oriented Segmentation Enhancement.

Dataset Description

NEST targets two categories of challenging entities that MLLM-based segmentation models struggle with:

• Novel entities: objects entirely absent from MLLMs' training data (e.g., newly released products)
• Emerging entities: objects within the model's prior knowledge but requiring up-to-date context for accurate segmentation (e.g., current officeholders, recent event participants)

This dataset contains 1,548 image-question-answer-mask samples built from news articles published between March 23, 2025 and April 11, 2025, covering diverse domains including economics, technology, politics, entertainment, sports, and society.

Each sample includes:

• A natural language question about a named entity depicted in the image
• The ground-truth answer (entity name)
• One or more images containing the target entity alongside other entities
• Segmentation mask annotations for the target entity

Dataset Statistics

Statistic	Value
Total QA pairs	1,548
Average entities per image	~2.7
Average questions per image	~1.6
Date range	Mar 23 – Apr 11, 2025
Domains	Economics, Technology, Politics, Entertainment, Sports, Society
Entity types	People, Products
Image format	JPEG (images), PNG (annotations/masks)

Usage

from datasets import load_dataset

ds = load_dataset("SongTang/NEST_250323_250411")

# Access a sample
sample = ds["train"][0]
print(sample["question"])    # Question about the target entity
print(sample["answer"])      # Ground-truth entity name
print(sample["images"])      # List of PIL images (multi-entity scenes)
print(sample["annotations"]) # List of segmentation mask PIL images

Data Fields

Field	Type	Description
id	string	Unique identifier for each sample
question	string	Natural language question about a novel or emerging named entity
answer	string	Ground-truth entity name
images	list of images	Scene images containing the target and other entities
annotations	list of images	Binary segmentation masks for the target entity

Automated Data Collection & Annotation

To reflect the dynamic nature of the NEST task — where evaluation data must be continuously refreshed to prevent leakage into future model training — this dataset is collected and annotated via a fully automated pipeline requiring no human intervention. For the complete implementation and usage instructions, please refer to:

👉 https://github.com/FudanCVL/ROSE

The pipeline continuously retrieves up-to-date image–news pairs from the web, constructs VQA samples, and generates segmentation mask annotations, enabling scalable and timely evaluation of models' novel emerging segmentation capabilities.

Citation

If you use this dataset, please cite:

@inproceedings{tang2026rose,
    title={{ROSE}: Retrieval-Oriented Segmentation Enhancement},
    author={Tang, Song and Jie, Guangquan and Ding, Henghui and Jiang, Yu-Gang},
    booktitle={CVPR 2026 Findings},
    year={2026}
}