Gen-GraphEx: Generative In-Distribution Graph Explanations for Time-Efficient Model-Level Interpretability of GNNs

Graph neural networks (GNNs) have become the prevailing methodology for addressing graph data-related tasks, permeating critical domains like recommendation systems and drug development. The necessity for trustworthiness and interpretability of GNNs has risen to the forefront, especially given their direct impact on end users' lives. To address this need, we present Gen-GraphEx, a model-agnostic, model-level explanation method that prioritizes user centricness by eliminating the need for having access to the hidden layers of the GNN model it seeks to explain. Given a particular class label, Gen-GraphEx learns a graph generative model (GGM) that produces explanation graphs that not only contain discriminative patterns that the GNN has learned for that class but also lie in distribution with real graphs that belong to that class according to the GNN. Unlike existing state-of-the-art models, Gen-GraphEx also has the unique ability to interpolate the GGMs of two target classes to generate instances that lie near the decision boundary of the two classes giving a deeper insight into the model's decision-making. Its advantages over existing methods in the literature also include nonreliance on another subsequent deep learning module for explanation generation, ability to generate graphs with various node and edge features, and being more computationally efficient. Extensive validation and thorough comparative analysis of the proposed approach is carried out across an array of real and synthetic datasets that consistently demonstrate its exceptional performance and competitiveness ranking alongside state-of-the-art model-level explainers. Our code is available at https://github.com/amisayan/Gen-GraphEx.