On the Internal Structure of Finite-State Stochastic Processes

The “Identifiabi1ity problem for functions of finite Markov chains”, which we might now rather call “the finite-state stochastic realization problem”, was stated by BLACKWELL and KOOPMANS [1] in 1957. Even if there exists now a rather abundant literature on this subject, yet, it can safely be asserted that very little progress has been made. This is especially true as for an algorithmic solution is concerned. This actually shows that the problem is a very hard one (though an important one).