Patent ID: 7882109

Claim:
A method comprising: constructing a table representing a directed tree of data entries in a set of data, each data entry of said set being associated with a particular node of said tree, wherein constructing comprises: assigning, in a processor arrangement, a first index to each node of said tree, the first index representing the node rank according to a first bijective order relation ordering all the nodes of the tree according to a combination of (a) a descending order relation ordering a node relative to its descendants and (b) a primogeniture order relation of the nodes which are the offspring of one of said nodes; assigning, in the processor arrangement, a second index to each node of said tree, the second index representing a node rank according to a second bijective order relation ordering all the nodes of the tree according to a combination of (a) the inverse order relation of said descending order relation and (b) said primogeniture order relation, wherein a given node s 2 of the directed tree depends on another node s 1 of the directed tree if and only if the node rank of s 2 according to the first order relation is greater than the node rank of s 1 according to the first order relation and the node rank of s 2 according to the second order relation is less than the node rank of s 1 according to the second order relation and; and storing, in the table with the processor arrangement, values representing the first index of nodes in the tree at addresses representing the second index of nodes in the tree.