Distinguishing quantum measurements of observables in terms of state   transformers
  The modern framework of state transformers, i. e., the first Kraus representation of quantum measurement, is introduced and related both to the known textbook concepts and to measurement-interaction evolution (the second Kraus representation). In this framework the known kinds of measurements of ordinary (as distinct from generalized) observables are distinguished by necessary and sufficient conditions. Thus, repeatable,nonrepeatable, and ideal measurements are characterized both algebraically and geometrically in terms of polar factors of state transformers. 
Fedor Herbut