Review of Bidirected Graph Neural Networks and Multidirected Graph Neural Networks
Takaaki Fujita
Graph theory offers a versatile language for modeling relationships by representing entities as vertices interconnected by edges [1]. While undirected graphs assume symmetric connections, directed, bidirected, and multidirected variants capture richer orientation and multiplicity semantics. Graph Neural Networks (GNNs) have rapidly advanced the field of learning on graphs, with recent extensions addressing directed edges [2–4]. In this paper, we introduce two novel GNN architectures—Bidirected GNNs and Multidirected GNNs—which inherently respect endpoint-specific directions and parallel-edge counts [5–8]. We demonstrate how these models naturally encode complex orientation patterns and provide illustrative examples to highlight their expressiveness. We anticipate that our contributions will spur further advances in graph representation learning for complex network structures.

