Example mixture model structures. a) Model structure for a conventional mixture with 5 components and four RVs. Each cell of the matrix represents a set of parameters θ
in the mixture and every RV has an unique distribution in each component. b) CSI model structure. Multiple components may share the same set of parameters for a RV as indicated by the matrix cells spanning multiple rows. In example C2, C3 and C4 share the same set of parameters for X2.