提出可生成可执行因果路径的反事实解释框架,让决策建议更真实可行。
P2C: Path to Counterfactuals
- 基于因果关系建模,生成按顺序执行的可行动作路径。
- 确保每一步改变都符合因果逻辑且现实可行,避免不切实际的建议。
- 适合需要透明且可操作建议的高风险场景,如招聘、信贷审批。
机器学习模型在金融、法律和招聘等高风险领域日益重要,亟需透明性与可改进性之间的平衡。反事实解释能说明为何结果不佳,并提供通过特征调整实现改善的路径。现有方法存在两大缺陷:一是忽略特征间的因果依赖,二是假设所有干预可同时发生,这在现实中不成立。为此,本文提出P2C(Path-to-Counterfactuals),一种模型无关的框架,可生成从不利结果到因果一致有利结果的有序行动序列。P2C通过显式建模特征间的因果关系,确保每个中间状态在因果上有效且可行。它利用目标导向的Answer Set Programming系统s(CASP)生成计划,自动处理由因果关系引发的特征变化。此外,仅计算用户主动施加的修改作为成本,使代价估算更真实。实验表明,该因果规划器优于缺乏因果知识的标准规划器,后者常生成非法动作。
原文摘要 · Abstract (English)
Machine-learning models are increasingly driving decisions in high-stakes settings, such as finance, law, and hiring, thus, highlighting the need for transparency. However, the key challenge is to balance transparency -- clarifying `why' a decision was made -- with recourse: providing actionable steps on `how' to achieve a favourable outcome from an unfavourable outcome. Counterfactual explanations reveal `why' an undesired outcome occurred and `how' to reverse it through targeted feature changes (interventions). Current counterfactual approaches have limitations: 1) they often ignore causal dependencies between features, and 2) they typically assume all interventions can happen simultaneously, an unrealistic assumption in practical scenarios where actions are typically taken in a sequence. As a result, these counterfactuals are often not achievable in the real world. We present P2C (Path-to-Counterfactuals), a model-agnostic framework that produces a plan (ordered sequence of actions) converting an unfavourable outcome to a causally consistent favourable outcome. P2C addresses both limitations by 1) Explicitly modelling causal relationships between features and 2) Ensuring that each intermediate state in the plan is feasible and causally valid. P2C uses the goal-directed Answer Set Programming system s(CASP) to generate the plan accounting for feature changes that happen automatically due to causal dependencies. Furthermore, P2C refines cost (effort) computation by only counting changes actively made by the user, resulting in realistic cost estimates. Finally, P2C highlights how its causal planner outperforms standard planners, which lack causal knowledge and thus can generate illegal actions.
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