1. A method of using duplicate tree structures for a hierarchical structure data document, comprising the steps of: a) receiving an address and a map pointer associated with an item to be stored; b) determining if the address in the map index is empty; c) when the address in the map index is not empty, determining if a duplicate indicator is set; d) when the duplicate indicator is not set, selecting a duplicate array; e) storing an existing map pointer, at the address in the map index, in a location of the duplicate array; and f) storing the map pointer in a second location of the duplicate array.