@inproceedings{xu-etal-2026-synapsehsg,
title = "{S}ynapse{HSG}: One-Shot Hyper-Semantic Grounding for Long-Context Multimodal Question Answering",
author = "Xu, Sherricane Jiayu and
Shen, Zhijie and
Liu, Yongqiang and
Jing, Xiaojun and
Li, Shuangyin",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Findings of the {A}ssociation for {C}omputational {L}inguistics: {EMNLP} 2026",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.findings-emnlp.206/",
pages = "4326--4344",
ISBN = "979-8-89176-462-0",
abstract = "Answering complex queries over long-context multimodal streams requires dynamically synthesizing asynchronous and heterogeneous evidence across extended temporal and logical spans. Existing approaches often rely on iterative Multimodal Retrieval-Augmented Generation (RAG), facing structural challenges from semantic and modality gaps as well as context bloat induced by multi-step retrieval. To address these challenges, we propose SynapseHSG, a decoupled one-shot grounding framework for long-context multimodal Question Answering. SynapseHSG introduces a hyper-semantic evidence organization method (named M2HSG) that constructs an offline graph index to align cross-modal evidence. During inference, we design a Semantic Decomposer to convert natural-language queries into graph-operable constraints. Guided by these constraints, SynapseHSG retrieves a compact query-anchored subgraph in one shot and linearizes it as structured evidence for a frozen generator. This avoids repeated LLM-driven retrieval while restricting trainable components to graph construction and query parsing. To support systematic evaluation, we introduce MM-ConfQA, a new long-context multimodal QA benchmark built from academic conference presentations. Experimental results on MM-ConfQA show that SynapseHSG improves grounded answer generation over strong multimodal and retrieval baselines, especially on dispersed-evidence questions, highlighting the value of pre-organized multimodal evidence over repeated search in raw heterogeneous contexts. We release the code and data to public."
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<abstract>Answering complex queries over long-context multimodal streams requires dynamically synthesizing asynchronous and heterogeneous evidence across extended temporal and logical spans. Existing approaches often rely on iterative Multimodal Retrieval-Augmented Generation (RAG), facing structural challenges from semantic and modality gaps as well as context bloat induced by multi-step retrieval. To address these challenges, we propose SynapseHSG, a decoupled one-shot grounding framework for long-context multimodal Question Answering. SynapseHSG introduces a hyper-semantic evidence organization method (named M2HSG) that constructs an offline graph index to align cross-modal evidence. During inference, we design a Semantic Decomposer to convert natural-language queries into graph-operable constraints. Guided by these constraints, SynapseHSG retrieves a compact query-anchored subgraph in one shot and linearizes it as structured evidence for a frozen generator. This avoids repeated LLM-driven retrieval while restricting trainable components to graph construction and query parsing. To support systematic evaluation, we introduce MM-ConfQA, a new long-context multimodal QA benchmark built from academic conference presentations. Experimental results on MM-ConfQA show that SynapseHSG improves grounded answer generation over strong multimodal and retrieval baselines, especially on dispersed-evidence questions, highlighting the value of pre-organized multimodal evidence over repeated search in raw heterogeneous contexts. We release the code and data to public.</abstract>
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%0 Conference Proceedings
%T SynapseHSG: One-Shot Hyper-Semantic Grounding for Long-Context Multimodal Question Answering
%A Xu, Sherricane Jiayu
%A Shen, Zhijie
%A Liu, Yongqiang
%A Jing, Xiaojun
%A Li, Shuangyin
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Findings of the Association for Computational Linguistics: EMNLP 2026
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-462-0
%F xu-etal-2026-synapsehsg
%X Answering complex queries over long-context multimodal streams requires dynamically synthesizing asynchronous and heterogeneous evidence across extended temporal and logical spans. Existing approaches often rely on iterative Multimodal Retrieval-Augmented Generation (RAG), facing structural challenges from semantic and modality gaps as well as context bloat induced by multi-step retrieval. To address these challenges, we propose SynapseHSG, a decoupled one-shot grounding framework for long-context multimodal Question Answering. SynapseHSG introduces a hyper-semantic evidence organization method (named M2HSG) that constructs an offline graph index to align cross-modal evidence. During inference, we design a Semantic Decomposer to convert natural-language queries into graph-operable constraints. Guided by these constraints, SynapseHSG retrieves a compact query-anchored subgraph in one shot and linearizes it as structured evidence for a frozen generator. This avoids repeated LLM-driven retrieval while restricting trainable components to graph construction and query parsing. To support systematic evaluation, we introduce MM-ConfQA, a new long-context multimodal QA benchmark built from academic conference presentations. Experimental results on MM-ConfQA show that SynapseHSG improves grounded answer generation over strong multimodal and retrieval baselines, especially on dispersed-evidence questions, highlighting the value of pre-organized multimodal evidence over repeated search in raw heterogeneous contexts. We release the code and data to public.
%U https://aclanthology.org/2026.findings-emnlp.206/
%P 4326-4344
Markdown (Informal)
[SynapseHSG: One-Shot Hyper-Semantic Grounding for Long-Context Multimodal Question Answering](https://aclanthology.org/2026.findings-emnlp.206/) (Xu et al., Findings 2026)
ACL