Graph Classification via Deep Learning with Virtual Nodes
This work addresses graph classification problems in domains like chemistry and software engineering, but it is incremental as it builds on existing node representation methods.
The paper tackles graph classification by introducing a virtual node method to augment graphs, using Column Networks to create an end-to-end model called Virtual Column Network (VCN), which shows competitive performance on bio-activity prediction and software vulnerability detection tasks.
Learning representation for graph classification turns a variable-size graph into a fixed-size vector (or matrix). Such a representation works nicely with algebraic manipulations. Here we introduce a simple method to augment an attributed graph with a virtual node that is bidirectionally connected to all existing nodes. The virtual node represents the latent aspects of the graph, which are not immediately available from the attributes and local connectivity structures. The expanded graph is then put through any node representation method. The representation of the virtual node is then the representation of the entire graph. In this paper, we use the recently introduced Column Network for the expanded graph, resulting in a new end-to-end graph classification model dubbed Virtual Column Network (VCN). The model is validated on two tasks: (i) predicting bio-activity of chemical compounds, and (ii) finding software vulnerability from source code. Results demonstrate that VCN is competitive against well-established rivals.