NTH

RAD: Rule-Augmented Relational Anomaly Detection

AuthorsNoah Dahle, Anne Tumlin, Ngoc Tran, Xenofon Koutsoukos, Tyler Derr

August 29, 2026 2 min read
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The one-line take

RAD detects unusual behavior in multi-table databases by combining graph-based learning with human-readable behavioral rules.

Key results

1.65B
LANL records

Scale of the LANL cybersecurity relational database.

15.0M
Amazon records

Scale of the Amazon review-churn relational database.

16.7M
H&M records

Scale of the H&M purchase-churn relational database.

0.996
LANL AUROC

AUROC achieved by RAD without edge reconstruction.

0.659
LANL AUPRC

AUPRC achieved by RAD without edge reconstruction.

1.2
Average AUPRC rank

RAD’s average rank across the three benchmark datasets; lower is better.

What the paper found

RAD, or Rule-Augmented Relational Anomaly Detection, targets anomalies whose meaning depends on linked entities, typed relationships, temporal history, and multi-hop context—signals often lost when relational databases are flattened into one feature matrix. It converts tables into a heterogeneous graph, mines candidate behavioral rules from flattened summaries using random-forest paths, refines and compacts selected predicates with an LLM, then injects binary rule features into target nodes before two-layer GraphSAGE message passing. A heterogeneous graph autoencoder scores anomalies through attribute reconstruction and pairwise ranking supervision, while edge reconstruction is optional. The evaluation benchmark covers LANL cybersecurity authentication events with 1.65B records, Amazon review-churn with 15.0M records, and H&M purchase-churn with 16.7M records. Across these tasks, RAD achieves the strongest average AUPRC rank of 1.2, emphasizing retrieval of rare anomalies under severe class imbalance; on LANL, its no-edge-reconstruction variant reaches 0.996 AUROC and 0.659 AUPRC, substantially exceeding flattened detectors and relational baselines. Ablations show that direct rule injection and ranking supervision are central, whereas edge reconstruction can hurt when sampled graph topology is noisy. LLM refinement contributes mainly through rule filtering, tightening, deduplication, and compaction rather than independent anomaly labeling or scoring.

Original abstract

Anomaly detection is often applied to data stored in relational databases, yet most existing methods require flattening multiple tables into a single feature matrix. This flattening can obscure entity identity, schema structure, and multi-hop dependencies, limiting the detection of anomalies that depend on relational context rather than isolated feature values. Beyond preserving relational structure, relational anomaly detection raises an additional challenge: how to incorporate symbolic behavioral evidence into learned relational representations. To address these challenges, we study relational anomaly detection, where the goal is to identify anomalous entities or events in a multi-table database. We propose RAD, a rule-augmented relational anomaly detector that combines heterogeneous graph representation learning with refined symbolic rule signals. RAD derives candidate rules from random-forest paths over flattened summaries of the entities or events being scored, refines them into compact interpretable predicates, injects the resulting rule features into the graph model, and learns anomaly scores using reconstruction-based and pairwise-ranking supervision. To evaluate this setting, we introduce a relational anomaly detection benchmark spanning three settings: LANL cybersecurity event detection and two unexpected user-churn anomaly tasks derived from Amazon and H&M relational databases. Experiments show that RAD improves anomaly ranking over flattened tabular detectors and relational baselines under natural class imbalance, achieving the best average rank on AUROC and AUPRC across the benchmark. Ablations show that direct rule injection and ranking-based supervision are key contributors to performance, while edge reconstruction is not uniformly beneficial. Our code and data are available at: https://github.com/noahd15/RAD_RelationalAnomalyDetection.

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