4. The method of claim 3 , further comprising: packing the plurality of elements of the tree-structured data, including the first set of elements and the second set of elements and the meta-data levels associated therewith, into a plurality of leaf nodes of the index structure; merging the plurality of leaf nodes of the index structure into a plurality of non-leaf nodes of the index structure until a root non-leaf node is generated; and associating the plurality of non-leaf nodes of the index structure with the explicit meta-data levels of the packed first set of elements.
4. The method of claim 3 , further comprising: packing the plurality of elements of the tree-structured data, including the first set of elements and the second set of elements and the meta-data levels associated therewith, into a plurality of leaf nodes of the index structure; merging the plurality of leaf nodes of the index structure into a plurality of non-leaf nodes of the index structure until a root non-leaf node is generated; and associating the plurality of non-leaf nodes of the index structure with the explicit meta-data levels of the packed first set of elements. 8. The method of claim 4 , further comprising associating the plurality of non-leaf nodes of the index structure with the inherited meta-data levels of the packed second set of elements.