Whilst spectral Graph Neural Networks (GNNs) are theoretically well-founded in the spectral domain, their practical reliance on polynomial approximation implies a profound linkage to the spatial domain. As previous studies rarely examine spectral GNNs from the spatial perspective, their spatial-domain interpretability remains elusive, e.g., what information is essentially encoded by spectral GNNs in the spatial domain? In this paper, to answer this question, we establish a theoretical connection between spectral filtering and spatial aggregation, unveiling an intrinsic interaction that spectral filtering implicitly leads the original graph to an adapted new graph, explicitly computed for spatial aggregation. Both theoretical and empirical investigations reveal that the adapted new graph not only exhibits non-locality but also accommodates signed edge weights to reflect label consistency between nodes. These findings thus highlight the interpretable role of spectral GNNs in the spatial domain and inspire us to rethink graph spectral filters beyond the fixed-order polynomials, which neglect global information. Built upon the theoretical findings, we revisit the state-of-the-art spectral GNNs and propose a novel Spatially Adaptive Filtering (SAF) framework, which leverages the adapted new graph by spectral filtering for an auxiliary non-local aggregation. Notably, our proposed SAF comprehensively models both node similarity and dissimilarity from a global perspective, therefore alleviating persistent deficiencies of GNNs related to long-range dependencies and graph heterophily. Extensive experiments over 13 node classification benchmarks demonstrate the superiority of our proposed framework to the state-of-the-art models.

光谱图神经网络在空间域具有可解释性，通过建立光谱滤波和空间聚合的理论联系，揭示了光谱滤波将原始图形隐式导向适应的新图形，以进行空间聚合和反映节点之间的标签一致性，进而提出了一种新颖的空间自适应滤波(SAF)框架，通过光谱滤波和辅助的非局部聚合综合建模节点的相似性和差异性，在全局角度缓解了图神经网络与长距离依赖和图形异质性相关的不足，并在13个节点分类基准上进行了广泛实验，证明了该框架相较于现有模型的优越性。

空间自适应滤波下的频谱图神经网络再思考