The ``Herd of Unix-Replacing Daemons'' (HURD) from the Free Software Foundation (FSF) is a set of servers running on the Mach 3.0 microkernel that collectively provide a Unix-like environment. HURD file systems are implemented at user level, much the same as in Mach [Accetta86] and CHORUS [Abrosimov92].
The novel concept introduced by HURD is that of the translator. A translator is a program that can be attached to a pathname and perform specialized services when that pathname is accessed.
For example, in the HURD there is no need for the ftp program. Instead, a translator for ftp service is attached to a pathname, for example, /ftp. To access, say, the latest sources for the HURD itself, one could cd to the directory: /ftp/prep.ai.mit.edu/pub/gnu and copy the file hurd-0.1.tar.gz. Common Unix commands such as ls, cp, and rm work normally when applied to remote ftp-accessed files. The ftp translator takes care of logging into the remote server, translating FTP protocol commands to file system commands, and returning result codes back to the user.
Originally, a translator-like idea was used by the ``Alex'' work and allowed for example transparent ftp access via a file system interface [Cate92].