I have always found them useful and I may be looking to build something similar from another code base.
I am guessing that there is something like a migrate from doxygen. But I would assume that someone has blogged about how it was made at some point.
However Googling for it just returns loads of links to api.drupal.org not about how it was built.
Can anyone point me towards such a blog post? Or even better can they explain the steps involved?