Interlisp-D was built in an environment where people didn't keep files on their local disks. Files were kept on a File Server. Interlisp-D was built on Tenex, a PDP-10 operating system built for Lisp.
Maiko implements a case INsensitive, versioned file system on top of normal Unix/Posix file system using the code in DSK.c.
You may see references to file systems at PARC, at XAIS, at Envos and at Venue. There was a NFS implementation, XNS Filing system, and LEAF.