---
title: "Are White Knights Worth the Trouble? Reconciling POCL and Partial-Order Plans for Plan Optimization"
authors:
  - "Harrison Oates"
  - "Pascal Bercher"
doi: "10.24963/ijcai.2026/688"
url: "https://ijcai.org/proceedings/2026/688"
pdf: "https://ijcai.org/proceedings/2026/0688.pdf"
venue: "Proceedings of the Thirty-Fifth International Joint Conference on Artificial Intelligence"
year: 2026
pages: "6183-6190"
track: "Main Track"
keywords:
  - "Planning and Scheduling: Theoretical foundations of planning"
---

# Are White Knights Worth the Trouble? Reconciling POCL and Partial-Order Plans for Plan Optimization

Harrison Oates, Pascal Bercher

*Proceedings of the Thirty-Fifth International Joint Conference on Artificial Intelligence*, pages 6183-6190. DOI: [10.24963/ijcai.2026/688](https://doi.org/10.24963/ijcai.2026/688)

## Abstract

Partial order causal link (POCL) planning offers rich structural representations for plan optimization. However, under the classical threat definition, POCL plans form a strict subset of valid partial-order (PO) plans. This gap limits existing POCL optimization techniques to a restricted subspace of PO solutions. We revisit 'white knight' threat semantics, which permit a causal link to persist across a threat provided the deleted condition is re-established by an intermediate producer.  We prove that under this definition, the POCL and PO solution spaces become equivalent. By extending a MaxSAT-based optimization framework, we demonstrate that white knights are theoretically necessary for completeness and practically advantageous: they yield plans with significantly fewer ordering constraints in domains with complex causal interference while maintaining computational tractability on standard benchmarks.