Abstract: An apparatus arranged to implement a priority search tree to represent a plurality of data elements, the apparatus comprising: a memory; and a processor comprising: a storage unit for storing in the memory for each of said data elements a corresponding data point for the priority search tree, said the data point having a first component value and a second component value; a tree-processing module for performing at least one function operation on the data points, the at least one function operation involving using a comparison module to perform a comparison operation to determine the relative positions of a first data point and a second data point in an ordering for the data points, the comparison operation comprising one of: determining the relative positions of a first data point and a second data point based on a comparison of the respective first component values of the first and second data points and, if the first component value of the first data point equals the first component value of the second data