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Li "Harry" Zhang  张力


About Me

I am an assistant professor at Drexel University focusing on Natural Language Processing and Artificial Intelligence. I'm interested in planning and reasoning using Large Language Models. I earned my PhD (thesis) from the University of Pennsylvania, having the honor to be mentored by Prof. Chris Callison-Burch, with a thesis committee chaired by Prof. Dan Roth. I earned my BS from the University of Michigan in 2018, mentored by Prof. Rada Mihalcea and Prof. Dragomir Radev.

I offer systematic research mentorship (remote and in-person, undergraduate and graduate, paid and unpaid) to selected interns and volunteers. Past participants implemented existing ideas and published within a few months. The minimal requirement is the ability to answer a complete research question independently. Those looking to apply for a PhD program at the end of 2026 are preferred. Those interested should fill out this form. I cannot respond to emails on this matter. I am currently not hiring PhD students.

CV

Harry.Zhang@drexel.edu


Affiliations

Drexel Universitydrexel logo
Assistant Professor;
Dec 2024 to Present

University of Pennsylvaniaupenn logo
Ph.D.; Aug 2019 to Aug 2024

Allen Institute for Artifical IntelligenceAI2
Research Intern;
April 2023 to Dec 2023

IBM ResearchIBM Research
Research Intern; May 2021 to Aug 2021,
April 2019 to June 2019

University of Michiganumich logo
B.S.E.; Aug 2015 to Dec 2018

Mentorship and Teaching

Haz Lab at DrexelHaz Lab logo
Teaching

Instructor: CS T780-001: Applied NLP (Spring 2025, Spring 2026 at Drexel)

Instructor: CS 614: Applied AI (Spring 2026 at Drexel)

TA: CIS 530: Computational Linguistics (Winter, Fall 2020 at Penn)

TA: EECS 595: Natural Language Processing (Fall 2018 at Michigan)

TA: EECS 280: Programming and Introductory Data Structures (Winter, Fall 2016 at Michigan)


Service

I have reviewed more than 50 papers of and chaired for many NLP conferences and workshops.



Research

LLM-as-Formalizer: Executable and Trustworthy Planning and Problem-Solving

Despite recent efforts in using large language models (LLMs) to plan and solve problems as agents, their hallucinations and lack of verifiability undermine executability and trust, preventing real-world deployment. My work advances an alternative paradigm: LLM-as-formalizer. Instead of relying on LLMs to generate plans directly, we use them as a code generator to translate a user’s environment and goal into formal languages that can be deterministically solved by off-the-shelf solvers.


My primary efforts lie in using LLMs to generate formal language, such as PDDL that describes the planning environment.

[39] Language Model as Planner and Formalizer under Constraints Cassie Huang, Stuti Mohan, Ziyi Yang, Stefanie Tellex and Li Zhang; preprint.Paper BibTeX Code

[37] Vision Language Models Cannot Plan, but Can They Formalize? Muyu He, Yuxi Zheng, Yuchen Liu, Zijian An, Bill Cai, Jiani Huang, Lifeng Zhou, Feng Liu, Ziyang Li and Li Zhang; preprint.Paper BibTeX Code

[36] Documentation Retrieval Improves Planning Language Generation; Renxiang Wang and Li Zhang; in AACL 2025.Paper BibTeX Code

[35] Zero-Shot Iterative Formalization and Planning in Partially Observable Environments; Liancheng Gong, Wang Zhu, Jesse Thomason and Li Zhang; preprint.Paper BibTeX Code

[34] Unifying Inference-Time Planning Language Generation ; Prabhu Prakash Kagitha, Bo Sun, Ishan Desai, Andrew Zhu, Cassie Huang, Manling Li, Ziyang Li and Li Zhang; preprint.Paper BibTeX Code

[33] Are LLMs Better Formalizers than Solvers on Complex Problems; Rikhil Amonkar,May Lai, Ronan Le Bras and Li Zhang; preprint.
Paper BibTeX Code

[30] On the Limit of Language Models as Planning Formalizers; Cassie Huang and Li Zhang; in ACL 2025.
Paper BibTeX Code

[29] PDDLEGO: Iterative Planning in Textual Environments; Li Zhang, Peter Jansen, Peter Clark, Chris Callison-Burch and Niket Tandon; in *SEM 2024.Paper BibTeX Code

[28] PROC2PDDL: Open-Domain Planning Representations from Texts; Tianyi Zhang*Equal contribution^Mentored student, Li Zhang*Equal contribution, Zhaoyi Hou^Mentored student, Ziyu Wang^Mentored student, Yuling Gu, Peter Clark, Chris Callison-Burch and Niket Tandon; in ACL 2024 2st Workshop on Natural Language Reasoning and Structured Explanations.Paper BibTeX Code

[20] Faithful Chain of Thought Reasoning; Qing Lyu*Equal contribution, Shreya Havaldar*Equal contribution, Adam Stein*Equal contribution, Li Zhang, Delip Rao, Eric Wong, Marianna Apidianaki and Chris Callison-Burch; in AACL 2023. Won Area Chair Award.Paper BibTeX Code


My secondary efforts lie in using LLMs to generate solutions directly, using techniques like agents, chain-of-thought, steering...

[38] Prototype-Based Dynamic Steering for Large Language Models; Ceyhun Efe Kayan and Li Zhang; preprint.Paper BibTeX Code

[36] TurnaboutLLM: A Deductive Reasoning Benchmark from Detective Games; Yuan Yuan*Equal contribution, Muyu He*Equal contribution, Adil Shahid, Jiani Huang, Ziyang Li and Li Zhang; in EMNLP 2025.Paper BibTeX Code


Activities


Music

I am a drummer, producer, content creator, and band leader. I run a video channel with over 60,000 subscribers on Bilibili and YouTube, primarily making cover songs from video game and anime soundtracks, in a variety of styles ranging from metal to jazz. I am proudly sponsored by Mackie, NUX, Xvive officially and Chinese retailers of Roland, Alesis, Vater, Tama, etc. I have collaborated with major video games such as Genshin Impact and Azur Lane.
bilibili        
Below are some music videos and drum covers that I played in and produced.

 

Below are recorded live performances of the bands I run locally in Philadelphia.

 

My new album, Megidalon, a collection of reimagined Persona soundracks, is available for streaming on all platforms! My two previous albums Dazzling Tales (reimagined Genshin Impact soundtracks) and A Doll's Lament (reimagined NieR soundtracks) are also available for listening on all major streaming platforms.

Megidalon   Dazzling Tales   A Doll's Lament


I also engage in research of AI music generation, having published a paper on automatic drum composition in an AAAI 2023 workshop.

[32] Not that Groove: Zero-Shot Symbolic Music Editing; Li Zhang; preprint.Paper Code BibTeX

[18] Language Models are Drummers: Drum Composition with Natural Language Pre-Training; Li Zhang and Chris Callison-Burch; in AAAI 2023 Workshop on Creative AI Across Modalities.Paper Code BibTeX


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