Vision Language Models Cannot Plan, but Can They Formalize?

Fuente: arXiv
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Hauptverfasser: He, Muyu, Zheng, Yuxi, Liu, Yuchen, An, Zijian, Cai, Bill, Huang, Jiani, Zhou, Lifeng, Liu, Feng, Li, Ziyang, Zhang, Li
Format: Preprint
Veröffentlicht: 2025
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author He, Muyu
Zheng, Yuxi
Liu, Yuchen
An, Zijian
Cai, Bill
Huang, Jiani
Zhou, Lifeng
Liu, Feng
Li, Ziyang
Zhang, Li
author_facet He, Muyu
Zheng, Yuxi
Liu, Yuchen
An, Zijian
Cai, Bill
Huang, Jiani
Zhou, Lifeng
Liu, Feng
Li, Ziyang
Zhang, Li
contents The advancement of vision language models (VLMs) has empowered embodied agents to accomplish simple multimodal planning tasks, but not long-horizon ones requiring long sequences of actions. In text-only simulations, long-horizon planning has seen significant improvement brought by repositioning the role of LLMs. Instead of directly generating action sequences, LLMs translate the planning domain and problem into a formal planning language like the Planning Domain Definition Language (PDDL), which can call a formal solver to derive the plan in a verifiable manner. In multimodal environments, research on VLM-as-formalizer remains scarce, usually involving gross simplifications such as predefined object vocabulary or overly similar few-shot examples. In this work, we present a suite of five VLM-as-formalizer pipelines that tackle one-shot, open-vocabulary, and multimodal PDDL formalization. We evaluate those on an existing benchmark while presenting another two that for the first time account for planning with authentic, multi-view, and low-quality images. We conclude that VLM-as-formalizer greatly outperforms end-to-end plan generation. We reveal the bottleneck to be vision rather than language, as VLMs often fail to capture an exhaustive set of necessary object relations. While generating intermediate, textual representations such as captions or scene graphs partially compensate for the performance, their inconsistent gain leaves headroom for future research directions on multimodal planning formalization.
format Preprint
id arxiv_https___arxiv_org_abs_2509_21576
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Vision Language Models Cannot Plan, but Can They Formalize?
He, Muyu
Zheng, Yuxi
Liu, Yuchen
An, Zijian
Cai, Bill
Huang, Jiani
Zhou, Lifeng
Liu, Feng
Li, Ziyang
Zhang, Li
Computation and Language
The advancement of vision language models (VLMs) has empowered embodied agents to accomplish simple multimodal planning tasks, but not long-horizon ones requiring long sequences of actions. In text-only simulations, long-horizon planning has seen significant improvement brought by repositioning the role of LLMs. Instead of directly generating action sequences, LLMs translate the planning domain and problem into a formal planning language like the Planning Domain Definition Language (PDDL), which can call a formal solver to derive the plan in a verifiable manner. In multimodal environments, research on VLM-as-formalizer remains scarce, usually involving gross simplifications such as predefined object vocabulary or overly similar few-shot examples. In this work, we present a suite of five VLM-as-formalizer pipelines that tackle one-shot, open-vocabulary, and multimodal PDDL formalization. We evaluate those on an existing benchmark while presenting another two that for the first time account for planning with authentic, multi-view, and low-quality images. We conclude that VLM-as-formalizer greatly outperforms end-to-end plan generation. We reveal the bottleneck to be vision rather than language, as VLMs often fail to capture an exhaustive set of necessary object relations. While generating intermediate, textual representations such as captions or scene graphs partially compensate for the performance, their inconsistent gain leaves headroom for future research directions on multimodal planning formalization.
title Vision Language Models Cannot Plan, but Can They Formalize?
topic Computation and Language
url https://arxiv.org/abs/2509.21576