8. The method of claim 7 , wherein the selectivity factor decreases as the number of referenced structured documents increases.
8. The method of claim 7 , wherein the selectivity factor decreases as the number of referenced structured documents increases. 9. The method of claim 8 wherein when the selectivity factor of the first path-value pair is less than the selectivity factor of the second path-value pair, intersecting the structured documents includes comparing the at least one structured documents referenced by the second path-value pair to the at least one structured documents referenced by the first path-value pair, thereby allowing the indexing engine to skip non-matching structured documents referenced by the first path-value pair.