针对罕见逻辑异常检测难题,提出特征级反事实训练方法。
When Rule Violations Are Rare: Chimera Training for Logical Anomaly Detection

- 用神经网络编译逻辑规则为有向无环图,学习带特征的子树门控机制。
- 在多个数据集上显著提升组合与关系规则的异常检测准确率。
- 适合需要逻辑一致性验证的视觉系统,如视频理解与场景推理。
许多实际异常并非仅仅是稀有输入,而是语义约束的违反:物体以结构化方式共现,动作隐含前提条件,事件满足时间或关系规律。本文研究此类场景下的异常检测,其中约束以学习到的视觉概念上的逻辑规则形式给出,但真实规则违反在训练中极为罕见或完全缺失。我们提出一种神经规则评估器,将每条约束编译为有向无环图,并为内部逻辑算子学习特征感知的子树多层感知机门控。每个门控将子节点特征与边级否定映射为父节点表示和规则满足概率,中间监督来自真值概念标签的精确布尔传播。主要挑战在于同图像训练数据难以覆盖有意义的真值配置,且易导致捷径解。为此,我们引入奇美拉训练:在特征层面进行操作数级反事实构造。不混合输入图像,而是拼接来自不同样本的子树特征;每个操作数保留原样本的硬真值标签,奇美拉目标通过应用节点逻辑算子继承标签得到。该方法在无需真实异常图像的情况下提供受监督的逻辑反例。在CLEVRER、OpenImages和VidOR上,所得评估器在规则级别异常检测的AUROC优于独立事件和同图像语义训练基线,尤其在组合与关系规则上表现更优。该方法同时输出标量异常分数与规则级归因。
原文摘要 · Abstract (English)
Many practical anomalies are not merely rare inputs, but violations of semantic constraints: objects co-occur in structured ways, actions imply preconditions, and events satisfy temporal or relational regularities. We study anomaly detection in this setting, where constraints are given as logical rules over learned visual concepts, but real rule violations are rare or absent during training. We propose a neural rule evaluator that compiles each constraint into a directed acyclic graph and learns feature-aware subtree MLP gates for its internal logical operators. Each gate maps child features and edge-level negations to a parent representation and a rule-satisfaction probability, with intermediate supervision obtained from exact Boolean propagation over ground-truth concept labels. The key difficulty is that same-image training data often provide insufficient coverage of informative truth configurations and also allow shortcut solutions. To address this, we introduce chimera training: an operand-level counterfactual construction at the feature level. Instead of mixing input images, we concatenate subtree features from different samples; each operand keeps the hard truth label of the sample it came from, and the chimera target is obtained by applying the node's logical operator to those inherited labels. This supplies supervised logical counterexamples without requiring real anomalous images. Across CLEVRER, OpenImages, and VidOR, the resulting evaluator improves rule-level anomaly AUROC over independent-events and same-image semantic-training baselines, especially for compositional and relational rules. The method yields both scalar anomaly scores and rule-level attributions.
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