For example, as Woodford suggests in his 2012 Kansas City Fed paper, A more useful form of forward guidance, I believe, would be one that emphasizes the target criterion that will be used to determine when it is appropriate to raise the federal funds rate target above its current level, rather than estimates of the “lift-off” date.
Jean-Claude Trichet: The role of research in central banks and at the ECB Speech by Mr Jean-Claude Trichet, President of the European Central Bank, at the ceremony for the Award of the Germán Bernácer Prize, Madrid, 21 May 2007.