On the Classification and Aggregation of Hierarchies with Different Constitutive Elements

In this paper we present an aggregation method which can be applied to classifications having different vocabularies. The method uses the rank distance (Dinu, 2003), a metric which measures the similarity between two hierarchies based on the ranks of objects. We define the aggregation of n hierarchies as the classification for which the sum of distances from it to each of the n hierarchies is minimal. We study some of his rationality properties and propose some open problems.