In‐Young Ko

Eunho Cho, Donghwan Shin, In-Young Ko

The machine learning(ML) component of an ML-enabled system evolves through retraining, fine-tuning, and optimization, so previously valid test results may no longer hold. A single evolution step can worsen performance on some test cases while improving others, making regression test prioritization inherently directional. We present Gradient-based Behavior Vector-Parameter Delta(GBV-PD), the first approach to operationalize the behavior vector space for evolution-aware regression test prioritization. GBV-PD represents each test case as a gradient-based vector(GBV), a low-dimensional projection of its loss gradient under the original model. It then projects the observed parameter update of the evolved model onto the same PCA basis and uses the resulting alignment to estimate whether each test case's loss is likely to increase or decrease, without running the evolved model on test cases during prioritization. In an empirical study across classification and regression tasks, GBV-PD consistently outperformed non-directional baselines and remained competitive with a full-gradient reference, while offering better time and storage profiles for repeated updates via reusable GBV caching. These results show that behavior-space ideas can be operationalized into a practical and efficient mechanism for repeated-update regression testing of evolving ML-enabled systems.

Zhaoyan Wang, Zheng Gao, Arogya Kharel et al.

Graph Neural Networks (GNNs) are widely adopted in Web-related applications, serving as a core technique for learning from graph-structured data, such as text-attributed graphs. Yet in real-world scenarios, such graphs exhibit deficiencies that substantially undermine GNN performance. While prior GNN-based augmentation studies have explored robustness against individual imperfections, a systematic understanding of how graph-native and Large Language Models (LLMs) enhanced methods behave under compound deficiencies is still missing. Specifically, there has been no comprehensive investigation comparing conventional approaches and recent LLM-on-graph frameworks, leaving their merits unclear. To fill this gap, we conduct the first empirical study that benchmarks these two lines of methods across diverse graph deficiencies, revealing overlooked vulnerabilities and challenging the assumption that LLM augmentation is consistently superior. Building on empirical findings, we propose Robust Graph Learning via Retrieval-Augmented Contrastive Refinement (RoGRAD) framework. Unlike prior one-shot LLM-as-Enhancer designs, RoGRAD is the first iterative paradigm that leverages Retrieval-Augmented Generation (RAG) to inject retrieval-grounded augmentations by supplying class-consistent, diverse augmentations and enforcing discriminative representations through iterative graph contrastive learning. It transforms LLM augmentation for graphs from static signal injection into dynamic refinement. Extensive experiments demonstrate RoGRAD's superiority over both conventional GNN- and LLM-enhanced baselines, achieving up to 82.43% average improvement.

Zhaoyan Wang, Xiangchi Song, In-Young Ko

Notably, current intelligent transportation systems rely heavily on accurate traffic forecasting and swift inference provision to make timely decisions. While Graph Convolutional Networks (GCNs) have shown benefits in modeling complex traffic dependencies, the existing GCN-based approaches cannot fully extract and fuse multi-granular spatiotemporal features across various spatial and temporal scales sufficiently in a complete manner, proven to yield less accurate results. Besides, as extracting multi-granular features across scales has been a promising strategy across domains such as computer vision, natural language processing, and time-series forecasting, pioneering studies have attempted to leverage a similar mechanism for spatiotemporal traffic data mining. However, additional feature extraction branches introduced in prior studies critically increased model complexity and extended inference time, making it challenging to provide fast forecasts. In this paper, we propose MultiGran-STGCNFog, an efficient fog distributed inference system with a novel traffic forecasting model that employs multi-granular spatiotemporal feature fusion on generated dynamic traffic graphs to fully capture interdependent traffic dynamics. The proposed scheduling algorithm GA-DPHDS, optimizing layer execution order and layer-device scheduling scheme simultaneously, contributes to considerable inference throughput improvement by coordinating heterogeneous fog devices in a pipelined manner. Extensive experiments on real-world datasets demonstrate the superiority of the proposed method over selected GCN baselines.