16. The apparatus of claim 12 , wherein at least one ranking criterion of the common ranking criteria comprises a plurality of ranking keys that are combined into a single ranking value.
16. The apparatus of claim 12 , wherein at least one ranking criterion of the common ranking criteria comprises a plurality of ranking keys that are combined into a single ranking value. 17. The apparatus of claim 16 , wherein the at least one ranking criterion of the common ranking criteria further comprises a plurality of weights each assigned to the plurality of ranking keys, wherein the plurality of weights are applied to the respective ones of the plurality of ranking keys before combining the ranking keys into the single ranking value.