The Hierarchy of Block Models
This provides a unified framework for network analysis, addressing a methodological gap for researchers in statistical modeling and machine learning, though it is incremental in building on existing models.
The paper tackles the lack of a nested structure and parameter jumps in existing network block models by proposing a Nested Block Model (NBM) that includes SBM, DCBM, and PABM as special cases, enabling clustering and estimation without preliminary testing.
There exist various types of network block models such as the Stochastic Block Model (SBM), the Degree Corrected Block Model (DCBM), and the Popularity Adjusted Block Model (PABM). While this leads to a variety of choices, the block models do not have a nested structure. In addition, there is a substantial jump in the number of parameters from the DCBM to the PABM. The objective of this paper is formulation of a hierarchy of block model which does not rely on arbitrary identifiability conditions. We propose a Nested Block Model (NBM) that treats the SBM, the DCBM and the PABM as its particular cases with specific parameter values, and, in addition, allows a multitude of versions that are more complicated than DCBM but have fewer unknown parameters than the PABM. The latter allows one to carry out clustering and estimation without preliminary testing, to see which block model is really true.