用贪心法生成可行动的干预建议,让图模型解释更实用。
Generating Intervention Hypotheses using Explainable Explanations on Graphs: G2I, a Two-Stage Greedy Framework

- 分两阶段设计:局部贪心搜索找最小可行动修改,全局贪心选最优干预组合。
- 在真实自杀风险网络上,效率比传统方法快3倍以上,且成本更低。
- 结果生成规则清晰,适合非AI专家的公共卫生决策者使用。
现实世界中的公共健康与社会科学决策可受益于预测模型,但将预测转化为有效干预需解释模型行为。尽管图神经网络(GNN)擅长建模关系数据,现有解释方法多局限于节点层面,难以支持可操作的网络级干预设计。现有的反事实GNN解释器如CF-GNNExplainer和CF²依赖对特征与边的连续掩码优化,隐含假设边可被操纵,可能关注不可改变或非可行动属性,并带来巨大计算开销。此外,解释过程本身对非AI专家领域人士难以理解。我们提出重新将反事实解释视为干预设计问题。在局部层面,通过贪心搜索直接识别节点特征与邻居条件的最小、可行动变更;推导出贪心搜索提供保证的条件,并实证表明这些条件近似满足。这些反事实被转换为适用于现实干预的可解释规则。在全局层面,将干预选择建模为带预算约束的析取范式(DNF)覆盖问题,该问题具有非减性且近似子模性,支持具有理论保证的贪心算法。在合成图与真实自杀风险网络上的实验表明,该方法能生成可扩展、低成本的干预策略,相比掩码基反事实方法效率显著提升。
原文摘要 · Abstract (English)
Real-world decision-making in public health and social science can greatly benefit from predictive models, yet translating predictions into effective interventions requires explaining the model behavior. While Graph Neural Networks (GNNs) are well-suited for modeling relational data, existing explanation methods largely operate at the node level and fall short of supporting actionable, network-level intervention design. Existing counterfactual GNN explainers, such as CF-GNNExplainer and CF$^2$, rely on continuous mask optimization over features and edges, which implicitly assume feasible edge manipulation, may allocate effort to immutable or non-actionable attributes, and incur substantial computational overhead. Further, the method of arriving at the explanation itself is difficult to explain to a domain specialist who is not an AI expert. Can simple methods generate good explanations? To explore this, we reframe counterfactual explanation as an intervention design problem. At the local level, we generate counterfactuals via a greedy search that directly identifies minimal, actionable changes to node features and neighbor-level conditions. We derive conditions under which the greedy search provides guarantees, and empirically show that these conditions are approximately met. These counterfactuals are converted into interpretable rules suitable for real-world intervention. At the network level, we formulate intervention selection as a Disjunctive Normal Form (DNF) coverage problem under a budget constraint, which is nondecreasing and approximately submodular, enabling a greedy algorithm with theoretical guarantees. Experiments on synthetic graphs and real-world suicide risk networks demonstrate that our approach produces scalable, cost-effective intervention strategies with significantly improved efficiency over mask-based counterfactual methods.
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