  We address a largely open problem of multilabel classification over graphs.
Unlike traditional vector input, a graph has rich variable-size substructures
which are related to the labels in some ways. We believe that uncovering these
relations might hold the key to classification performance and explainability.
We introduce GAML (Graph Attentional Multi-Label learning), a novel graph
neural network that can handle this problem effectively. GAML regards labels as
auxiliary nodes and models them in conjunction with the input graph. By
applying message passing and attention mechanisms to both the label nodes and
the input nodes iteratively, GAML can capture the relations between the labels
and the input subgraphs at various resolution scales. Moreover, our model can
take advantage of explicit label dependencies. It also scales linearly with the
number of labels and graph size thanks to our proposed hierarchical attention.
We evaluate GAML on an extensive set of experiments with both graph-structured
inputs and classical unstructured inputs. The results show that GAML
significantly outperforms other competing methods. Importantly, GAML enables
intuitive visualizations for better understanding of the label-substructure
relations and explanation of the model behaviors.
