What Tim said.  Most search engines do not have database storage, they have 
a fairly simple inverted index.  Trying to put all the XML info in there 
would overload them.  The point of having an XML search is to have metadata 
and context, so you probably need to use some of the more sophisticated 
text retrieval and library systems.
BTW, I'm trying to collect information on XML and search, so please keep me 
posted if you are working on something.  I post everything I hear about at 
<http://www.searchtools.com/related/xml.html>
Avi
________________________________________________________________
Avi Rappoport, Web Site Search Tools Maven: <mailto:avirr@lanminds.com>
Guide to Site Indexing and Local Search Engines: <http://www.searchtools.com>