The success of Graph Neural Networks (GNNs) has led to a need for
understanding their decision-making process and providing explanations for
their predictions, which has given rise to explainable AI (XAI) that offers
transparent explanations for black-box models. Recently, the use of prototypes
has successfully improved the explainability of models by learning prototypes
to imply training graphs that affect the prediction. However, these approaches
tend to provide prototypes with excessive information from the entire graph,
leading to the exclusion of key substructures or the inclusion of irrelevant
substructures, which can limit both the interpretability and the performance of
the model in downstream tasks. In this work, we propose a novel framework of
explainable GNNs, called interpretable Prototype-based Graph Information
Bottleneck (PGIB) that incorporates prototype learning within the information
bottleneck framework to provide prototypes with the key subgraph from the input
graph that is important for the model prediction. This is the first work that
incorporates prototype learning into the process of identifying the key
subgraphs that have a critical impact on the prediction performance. Extensive
experiments, including qualitative analysis, demonstrate that PGIB outperforms
state-of-the-art methods in terms of both prediction performance and
explainability.

在这项研究中，我们提出了一种新颖的解释性图神经网络框架（PGIB），将原型学习与信息瓶颈框架相结合，为模型预测提供关键子图的原型。通过广泛的实验和定性分析，证明了 PGIB 在预测性能和可解释性方面优于最先进的方法。