“…In metric spaces, a natural approach to solve this problem consists in indexing one or both sets independently (by using any from the plethora of metric indices [3,4,7,8,[10][11][12]14,15,17,21,27,[36][37][38]40,41,44,[47][48][49][50], most of them compiled in [13,26,46,51]), and then solving range queries for all the involved elements over the indexed sets. In fact, this is the strategy proposed in [19], where the authors use the D-index [18] in order to solve similarity self joins.…”