7. The method of claim 1 , wherein each subtree identifier further comprises a relevance score indicative of a relevance of the subtree to a particular target query element.
7. The method of claim 1 , wherein each subtree identifier further comprises a relevance score indicative of a relevance of the subtree to a particular target query element. 8. The method of claim 7 , wherein the relevance score is normalized to the number of step queries contained in the associated subtree fragment.