These specific rules are essential to characterize a «flexible» inflation target regime and they may consist either in a principle, announced by several Central Banks, that the interest rate should be adjusted such that the resulting inflation forecast at an appropriate horizon (usually about two-years ahead) is on target, or they may specify operational Euler conditions for monetary policy.
«In particular, an optimal targeting rule expresses the equality of the marginal rates of transformation and the marginal rates of substitution between the target variables in an operational way» (Svensson, 2003). It is the important role attached to inflation forecasts and the commitment to move rates in reaction to them, that really differentiates the ITF from other monetary strategies.