It might seem very difficult to use Lemma 6.6 in practice, because the equality of local and cumulative constraints is an assumed condition that has to be verified (Equation ). But it is very useful not so much to convert between constraints that are known to be equivalent, but to prove that a given type of constraint has no equivalent. We could have proven example 6.5 by directly applying the conversion formulas (Equation 4) to the cumulative constraints Ñ min , Ñ max . The obtained local constraints N min , N max and the original cumulative constraints fulfill the conditions 39 -43, but as in the original proof of example 6.5 the obtained local constraints have different supergroups S l (N, n GAS , N min , N max ) = S c (N, n GAS , Ñ min , Ñ max ). With Lemma 6.6 we conclude that there are no local constraints that are equivalent to the cumulative constraints from