提出TriShGAN模型,生成更稀疏且鲁棒的多变量时间序列反事实解释。
TriShGAN: Enhancing Sparsity and Robustness in Multivariate Time Series Counterfactuals Explanation
- 引入三元组损失与形态提取器,提升反事实解释的稀疏性与稳定性。
- 在保持低修改成本的同时,确保解释远离决策边界,增强鲁棒性。
- 适合需要可解释性与可靠性并重的工业级决策系统使用。
在决策过程中,利益相关者常依赖反事实解释,即说明如何改变查询实例以改变AI系统的输出。然而,针对多变量时间序列的反事实解释面临复杂高维结构的挑战。传统基于最近不像邻居的方法通常直接替换查询序列中的子序列,这种刚性替换在真实场景中不够合理。基于残差生成对抗网络的反事实方法虽能学习数据分布生成合成解释,但主要关注最小化从查询序列到反事实解释的成本,忽视了使解释远离决策边界的必要性,导致微小模型变化即可能使解释失效。为此,本文在CounteRGAN框架基础上引入三元组损失,提出无监督的TriShGAN方法。该方法通过距离度量学习,促使反事实解释既贴近原查询序列,又符合目标结果实例的特征分布,实现低代价与高鲁棒性的平衡。此外,集成形态提取器,有策略地选取高维查询序列中最具判别性的部分,进一步提升解释的稀疏性与训练效率。
原文摘要 · Abstract (English)
In decision-making processes, stakeholders often rely on counterfactual explanations, which provide suggestions about what should be changed in the queried instance to alter the outcome of an AI system. However, generating these explanations for multivariate time series presents challenges due to their complex, multi-dimensional nature. Traditional Nearest Unlike Neighbor-based methods typically substitute subsequences in a queried time series with influential subsequences from an NUN, which is not always realistic in real-world scenarios due to the rigid direct substitution. Counterfactual with Residual Generative Adversarial Networks-based methods aim to address this by learning from the distribution of observed data to generate synthetic counterfactual explanations. However, these methods primarily focus on minimizing the cost from the queried time series to the counterfactual explanations and often neglect the importance of distancing the counterfactual explanation from the decision boundary. This oversight can result in explanations that no longer qualify as counterfactual if minor changes occur within the model. To generate a more robust counterfactual explanation, we introduce TriShGAN, under the CounteRGAN framework enhanced by the incorporation of triplet loss. This unsupervised learning approach uses distance metric learning to encourage the counterfactual explanations not only to remain close to the queried time series but also to capture the feature distribution of the instance with the desired outcome, thereby achieving a better balance between minimal cost and robustness. Additionally, we integrate a Shapelet Extractor that strategically selects the most discriminative parts of the high-dimensional queried time series to enhance the sparsity of counterfactual explanation and efficiency of the training process.
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