arXiv:2510.20084cs.LGcs.AI2025-10NeurIPS被引 8

用形状片段提升时序分类解释力,更准更可信。

ShapeX: Shapelet-Driven Post Hoc Explanations for Time Series Classification Models

  • 基于形状片段检测框架,自动提取关键子序列。
  • 在真实与合成数据上,精准识别核心片段,优于现有方法。
  • 适合医疗、金融等需高可信解释的场景。

时序分类模型的可解释性至关重要,尤其在医疗、金融等高风险领域,透明度与信任度尤为关键。尽管众多时序分类方法已证明形状片段(shapelets)是实现顶尖性能的核心特征,并在分类结果中起决定性作用,但现有事后解释(PHTSE)方法主要聚焦于时间步级特征归因,忽视了分类结果主要由关键形状片段驱动这一基本先验。为此,我们提出 ShapeX,一种创新框架:将时序数据分割为有意义的形状片段驱动段,并利用 Shapley 值评估其重要性。ShapeX 的核心是形状片段描述与检测(SDD)框架,能有效学习多样化的分类关键形状片段。我们进一步证明,由于形状片段的原子性特性,ShapeX 所产生的解释揭示的是因果关系而非仅相关性。在合成与真实数据集上的实验表明,ShapeX 在识别最相关子序列方面显著优于现有方法,提升了解释的精确性与因果真实性。

原文摘要 · Abstract (English)

Explaining time series classification models is crucial, particularly in high-stakes applications such as healthcare and finance, where transparency and trust play a critical role. Although numerous time series classification methods have identified key subsequences, known as shapelets, as core features for achieving state-of-the-art performance and validating their pivotal role in classification outcomes, existing post-hoc time series explanation (PHTSE) methods primarily focus on timestep-level feature attribution. These explanation methods overlook the fundamental prior that classification outcomes are predominantly driven by key shapelets. To bridge this gap, we present ShapeX, an innovative framework that segments time series into meaningful shapelet-driven segments and employs Shapley values to assess their saliency. At the core of ShapeX lies the Shapelet Describe-and-Detect (SDD) framework, which effectively learns a diverse set of shapelets essential for classification. We further demonstrate that ShapeX produces explanations which reveal causal relationships instead of just correlations, owing to the atomicity properties of shapelets. Experimental results on both synthetic and real-world datasets demonstrate that ShapeX outperforms existing methods in identifying the most relevant subsequences, enhancing both the precision and causal fidelity of time series explanations.

时序解释形状片段因果解释

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