Comments on "Observability of discrete event dynamic systems" by C. M. Ozveren and A.S. Willsky

It is pointed out that the algorithm introduced in the above-titled work (see ibid., vol.35, no.7, p.797-806, July 1990) to compute the maximal set of indistinguishable state pairs is incorrect under the given definition of the automation O/sub p/. It is suggested that to remove the difficulty, either the definition of O/sub p/ or the algorithm itself should be modified.<>