A method includes an algorithm that is adapted for resorting sorted data items in accordance with levels and the ordering of the nodes within each level of a tree data structure, each data item corresponding to a node of the tree data. The items are received at a client computer, and to be stored on the tree data structure. The received data items are sorted in accordance with a predefined sorting order. The algorithm is processed at the client computer for resorting the sorted received data items. A data table is generated for representing the tree data structure in a tabular form having columns and rows, wherein in accordance with the resorting order each row of the data table represents a respective resorted data item, wherein values in the columns are determined in accordance with the order of the rows. The data table is stored as the tree data structure.