It does get a bit involved, there is some recursion needed for a
reasonable implementation, eg a magazine in a file placed on a shelf
or an archive that has boxes on shelves.
I implemented it for my books and manuals, example :-
http://www.collection.archivist.info/shelfview.php?src=artitle&locid=197

All items and locations have a barcode, the database has a location
id(one per shelf+ a special for containers),  and a
status(lost,confirmed,etc) on each item plus another field if the
locid is in/on an item/shelf.
A stock check routine, scan shelf, (mark items located), scan
items(mark confirmed on shelf/add to shelf), finish(mark unscanned as
lost)

The shelf locations have a room and xy location and orientation.
There is a linking table to tie together and a live map drawing and
and arrow image tool.

Dave Caroline