@bonifartius I'm in the early stages of building a program to provide a metadata-rich, nonhierarchical abstraction layer over an existing file system that would allow me to organize them with tags (like a booru) and efficiently search them in a filetype-aware fashion (eg, including OCRed images and movie metadata).

I'm writing this program in Common Lisp with what I hope to be a fairly generic and versatile API that could be used by plugins to provide narrow "views" into the file system, eg to manage and browse ebooks, audiobooks, music, movies, kiwix archives, and so forth.

I haven't gotten to this point yet, but I'd like to end up with highly extensible CLI, 9p, QT, and web interfaces, as well as an Emacs frontend that makes use of the 9p API.

It was partially inspired by the tag-based object store this article describes as an alternative to hierarchical file systems: http://metamodular.com/Common-Lisp/lispos.html