A Review of Stochastic Block Models and Extensions for Graph Clustering.

There have been rapid developments in model-based clustering of graphs, also known as block modelling, over the last ten years or so. We review different approaches and extensions proposed for different aspects in this area, such as the type of the graph, the clustering approach, the inference approach, and whether the number of groups is selected or estimated. We then review unsupervised learning of texts, also known as topic modelling, as the two areas are closely related. Also reviewed are the models that combine block modelling with topic modelling, as such incorporations are natural because both areas have the same goal of model-based clustering. How different approaches cope with various issues will be summarised and compared, to facilitate the demand of practitioners for a concise overview of the current status of these two areas of literature.