时间序列分类的黑盒解释往往只找够用的特征，但可能抓到噪音。这篇论文提出了TimePNS，用反事实推理揪出真正必要的子序列，实验效果比现有方法好。
TimePNS框架解决了现有充分性导向方法可能将无关子序列误判为重要的问题，该框架采用两阶段设计：阶段I学习因果生成过程和充分性掩码；阶段II通过反事实干预评估时间因子的必要性，并以此监督时间门细化解释。在合成和真实时间序列基准上的实验表明，TimePNS能更准确地识别决策关键子序列，并在充分性-必要性权衡上持续优于强基线方法。
Beyond Sufficiency: Time Series Explanation with Counterfactual Necessity
Faithful explanations of time-series classifiers should identify subsequences that are not only sufficient to preserve a black-box model's prediction, but also necessary for maintaining it. However, existing sufficiency-oriented methods can assign high importance to spurious subsequences that support the prediction without being essential to the model's decision. We introduce \textbf{TimePNS}, a necessity-aware framework for time-series explanation. Inspired by Pearl's counterfactual notion of necessity, TimePNS assesses whether a temporal factor is necessary by intervening on it and measuring whether the original prediction is disrupted. The framework adopts a two-stage design. Stage I learns an identifiable causal generative process together with a sufficiency-oriented explanation mask. Stage II performs counterfactual interventions on temporal factors to derive necessity signals, which supervise a temporal gate that refines the initial explanation by suppressing non-essential components and emphasizing counterfactually necessary ones. Experiments on synthetic and real-world time-series benchmarks show that TimePNS more accurately identifies decision-critical subsequences and consistently improves sufficiency-necessity trade-offs over strong baselines.