
Re: I think it's an age thing...
Reading your last comment reminded me of working in Birkbeck College library some 30 years ago. Unlike the rest of the universe, Birkbeck used a cataloging system called bliss that was...anything but. Instead of Math being at 510, say, it would be at some code like QEL/EF. They had the loveliest librarians to help you but my word, you were sunk without them.
Put it this way: the second edition of the catalog has been in development for a decade longer than the HURD kernel...They started in 1977.