Update: Perl TM::Virtual::DNS
This package implements a virtual map, i.e. a topic map which is a view on some resource. What makes this case extreme, is the fact that you can actually never materialize the global DNS. Not that it would make sense.
While this package existed for quite some time, it broke due some major changes in the core TM package. Now it is working again, and I have even improved the documentation to such a point that it not any longer is completely misleading. :-)
Amazingly, you can run TMQL queries against this map. Right from the test file:
Work supported by the Austrian Research Centers.