{"type":"ScholarlyArticle","title":"Computational Complexity of Planning for Recursive Primitive Task Networks: Selective Action Nullification with State Preservation","authors":[{"name":"Yifan Zhang","slug":"yifan-zhang","given":"Yifan","family":"Zhang","affiliation":""},{"name":"Pascal Bercher","slug":"pascal-bercher","given":"Pascal","family":"Bercher","affiliation":""}],"abstract":"This paper investigates fundamental aspects of Hierarchical Task Network (HTN) planning by systematically exploring recursive arrangements of primitive task networks. Working within a general framework that aligns with recently identified ACKERMANN-complete HTN problems, we map the computational complexity across various recursive configurations, revealing a rich complexity landscape. Through a novel proof technique that we call selective action nullification with state preservation, we demonstrate that even a highly restricted class of regular HTN problems remains PSPACE-complete, establishing a profound connection to classical planning. We hope these findings contribute to a deeper and broader understanding of the theoretical foundations of HTN planning.","doi":"10.24963/ijcai.2025/967","url":"https://ijcai.org/proceedings/2025/967","pdf":"https://ijcai.org/proceedings/2025/0967.pdf","markdown":"https://ijcai.org/proceedings/2025/967.md","bibtex":"https://ijcai.org/proceedings/2025/bibtex/967","volume":{"slug":"2025","title":"Proceedings of the Thirty-Fourth International Joint Conference on Artificial Intelligence","short_title":"IJCAI 2025","url":"https://ijcai.org/proceedings/2025/","year":2025,"location":"Montreal, Canada","dates":"16-22 August 2025","editors":"James Kwok","isbn":"978-1-956792-06-5","publisher":"International Joint Conferences on Artificial Intelligence Organization","doi_prefix":"10.24963/ijcai.2025"},"section":"Planning and Scheduling","track":"Main Track","number":967,"pages":{"first":8696,"last":8704},"keywords":["Planning and Scheduling: PS: Theoretical foundations of planning","Planning and Scheduling: PS: Hierarchical planning"],"videos":[],"references":[],"license_note":"Copyright International Joint Conferences on Artificial Intelligence."}