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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. Demonstration of prior experience to lead a complete research project (e.g., publication in NLP or other fields) is required. Motivation to apply for a PhD program at the end of 2026 is strongly 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.

Area Chair of ACL Rolling Review (ACL, NAACL, EMNLP, EACL, AACL) since Feb 2024, COLING 2025
Session Chair of ACL 2024, AACL-IJCNLP 2020
Program Chair of MASC-SLL 2023, MASC-SLL 2021
Reviewer of LREC-COLING 2024, EMNLP 2023, ACL 2023, ARR Mar 2022, DaSH Workshop @ EMNLP 2022, COLING 2022, LREC 2022, ARR Nov 2021, COLING 2020, Computer Speech and Language 2018


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.


[40] Language Model Planners do not Scale, but do Formalizers? Owen Jiang, Cassie Huang, Ashish Sabharwal and Li Zhang; preprint.Paper BibTeX Code

[39] Language Model as Planner and Formalizer under Constraints Cassie Huang, Stuti Mohan, Ziyi Yang, Stefanie Tellex and Li Zhang; in ACL 2026.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; in Findings of ACL 2026.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; in Findings of ACL 2026.Paper BibTeX Code

[33] A Reality Check of Language Models as Formalizers on Constraint Satisfaction Problems; Rikhil Amonkar*Equal contribution, Ceyhun Efe Kayan*Equal contribution, Qimei 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


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