Babel
http://service.simile-widgets.org/babel/
can convert from RDF/XML to Exhibit/JSON. It only processes resources
that have rdf:type's.
You can even feed Exhibit an RDF/XML URL directly, and Exhibit will
route it through Babel, e.g.,
http://people.csail.mit.edu/dfhuynh/projects/data-theft/data-theft.html
David
Backstage's code is here
http://simile.mit.edu/repository/backstage/trunk/
It might not work out of the box but you could get some hints for how to
architecture the faceted browsing engine.
David