That looks similar to the first OS I used, RISC OS, which had paths like

  ADFS::Symbiote.$.SchoolWork.English.Essay

That's Filesystem::DiskLabel.$.Directory.Another.Filename. There were no file extensions, but there was a file type stored as metadata (I think on the directory node?).

Given a current filesystem and a current disk, just the path from the root ($) directory was needed.