Data dependence as "constrained discretion"

Ben Bernanke and Rick Mishkin called the use of data dependence in monetary policy "constrained discretion". We are in another of those periods of constrained discretion regarding inflation and monetary policy. 

Robert Hetzel, a former Fed economist, said that policymaking has a flavor of "guess and correct." There are forecasts and guesses of what should be the key target variables, inflation and growth, and then policy is corrected to move toward the target. 

The data dependence is an important part of the guess-and-correct view. There is no set rule, but a set of adjustments toward the expected target.