Differential Encoding for Improved Representation Learning over Graphs

Combining the message-passing paradigm with the global attention mechanism has emerged as an effective framework for learning over graphs. The message-passing paradigm and the global attention mechanism basically generate embeddings of nodes by taking the sum of information from a node's local neighbourhood and from the entire graph, respectively. However, this simple summation aggregation approach fails to distinguish between the information from a node itself or from the node's neighbours. Therefore, there exists information lost at each layer of embedding generation, and this information lost could be accumulated and become more serious in deeper model layers. In this paper, we present a differential encoding method to address the issue of information lost. Instead of simply taking the sum to aggregate local or global information, we explicitly encode the difference between the information from a node itself and that from the node's local neighbours (or from the rest of the entire graph nodes). The obtained differential encoding is then combined with the original aggregated representation to generate the updated node embedding. By combining differential encodings, the representational ability of generated node embeddings is improved, and therefore the model performance is improved. The differential encoding method is empirically evaluated on different graph tasks on seven benchmark datasets. The results show that it is a general method that improves the message-passing update and the global attention update, advancing the state-of-the-art performance for graph representation learning on these benchmark datasets.