RAPO-RL-TAC: Risk-Aware Partial-Order Reinforcement Learning with Timed Automata Completion for the Interval Job Shop Problem

In the Interval Job Shop Problem (IJSP), operation processing times are represented by intervals, making machine-sequencing decisions sensitive to temporal uncertainty. We propose Risk-Aware Partial-Order Reinforcement Learning with Timed Automata Completion (RAPO-RL-TAC), which couples Risk-Aware Partial-Order Reinforcement Learning (RAPO-RL) for machine-order construction with Timed Automata Completion (TAC) for execution-time resolution of deferred sequencing decisions. Risk awareness focuses on preserving temporal flexibility in machine-order relations whose preferred ordering is sensitive to interval uncertainty. RAPO-RL selectively commits comparatively determinate machine conflicts while retaining a bounded set of timing-sensitive relations. TAC completes unresolved relations as execution evolves, while statistical model checking characterises completion-time variability across timed executions. On 14 ORB and LA benchmark instances, RAPO-RL-TAC achieves mean midpoint makespans 2.92% and 1.63% lower than population-based neighbourhood search (PNS) and genetic algorithm (GA), respectively. Compared with reproduced Fast Elitist Artificial Bee Colony (fEABC) variants, RAPO-RL-TAC achieves a lower midpoint than at least one variant on 7 of 14 instances. In the controlled ablation study, RAPO-RL-TAC achieves a 13.85% lower mean midpoint makespan than hard enforcement of the learned relations. These results indicate that risk-aware selective commitment preserves temporal flexibility while maintaining competitive nominal schedule quality under interval uncertainty.