There's plenty of information on the Web about the confluence (or not, depending on your view) of s-expressions and XML. What's harder to find is anyone using an XML database as a persistence engine for s-expressions. I contacted the folks at SleepyCat to see if they knew of any Scheme (or Lisp) connectors to their XML database and they don't. If you're aware of any, let me know.
XML Databases and Scheme (or Lisp)
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