Meaningful XML Keyword Search is a hot topic in academic research now. This is because XML is hierarchical and hierarchical structures are not linear they are nonlinear with multiple pathways and hierarchies with multiple families of structures. This presents a problem if you are searching for keywords that are on multiple paths. Your query could match both keywords but each match could be from a different family or occurrence of the structure. This is not a valid match up of keywords and is an unmeaning matchup and is not correct. The solution to this problem is to use lowest common ancestor (LCA) logic to detect correct matches and process correct processing across pathways.
It just so happens that SQL, not XQuery, handles LCA logic automatically. This is good because LCA logic can be quite complex and error prone. With SQL performing hierarchical processing automatically, the LCA processing is always correct. With SQL performing hierarchical processing, XML integration at a hierarchical processing level is also possible. Now with SQL hierarchical processing, LCA processing and XML integration is supported, the XML Keyword Search is automatically performed correctly.