Information Bottlenecks, Causal States, and Statistical Relevance Bases:   How to Represent Relevant Information in Memoryless Transduction
  Discovering relevant, but possibly hidden, variables is a key step in constructing useful and predictive theories about the natural world. This brief note explains the connections between three approaches to this problem: the recently introduced information-bottleneck method, the computational mechanics approach to inferring optimal models, and Salmon's statistical relevance basis. 
Cosma Rohilla Shalizi and James P. Crutchfield (Santa Fe Institute)