Summary
Graph Neural Networks (GNNs) are effective for representation learning of graphs, with a focus on neighborhood aggregation. This paper presents a theoretical framework analyzing the expressive power of GNNs, comparing them to the Weisfeiler-Lehman (WL) graph isomorphism test. It introduces Graph Isomorphism Network (GIN) as a powerful GNN model that can distinguish different graph structures efficiently. The study explores the conditions for GNNs to be as powerful as the WL test, emphasizing the importance of injective aggregation functions. GIN utilizes deep multisets and universal functions for neighbor aggregation, achieving high discriminative power among GNN architectures.