Query-FS is a FUSE-based filesystem that presents database queries as filesystem
trees. It first loads plugins (lisp source files) to prepare query parsers, and then loads the queries themselves and creates a virtual filesystem with results.
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.
There is a CSR2010 paper about cl-fuse-meta.
ASDF-install package (obsolete) http://common-lisp.net/project/cl-fuse/query-fs.tar.gz