An example task may be creating symbolic links to files based on queries to SQL DB with filesystem index. Or you can create an encrypted password store with FS interface (so you just echo the needed data to files).
query-fs is based on cl-fuse.
Homepage: https://common-lisp.net/project/cl-fuse/
License: LLGPL
There is a CSR2010 paper about cl-fuse-meta.
Topics: StructuredStorage