Iohan is a 2000-vintage generic "I/O handler" with a couple of different drivers by [jcw], download at [http://www.equi4.com/pub/etc/iohan.tar.gz].  Nothing stellar, but it was a good experiment in decoupling access to a collection of items from the actual implementation (e.g. directories of files, arrays of values, ftp dirs, Metakit views, etc).