Right now i use a rough prototype (one of my friend told me that i'm 
crazy, when i show him what i did :))
Anyway it's just a prototype(with terrible performance) :).

I use eXist XML database with XPath support and objects-tree to XML 
mapping.

put: objects-tree => XML => eXist
get: XPath => eXist => XML => objects-tree

Code for previous example with this scenario looks like:

db.get "//[@class = 'Topic' and @name = 'first']"
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