The Free On-line Dictionary of Computing (30 December 2018):

Prospero

   A tool for organising Internet resources.  Prospero allows
   each user to organise the contents of remote file servers into
   his own virtual file system with his own hierarchical name
   space consisting of links to remote objects.  Remote indexing
   services are made available by treating the results as a
   virtual directory.  A "union link" allows the contents of the
   link's target directory to appear as part of the directory
   containing the link.  Arbitrary filters can be associated with
   links to modify the representation of the target directory as
   desired.  Prospero directories can be shared between users.
   The Prospero protocol is used for communication between
   clients and servers in the archie system.

   A prototype of Prospero has been available since December
   1990.  It interfaces with Sun NFS, the Andrew File System
   and FTP (with local caching) and Archie.  Support for
   web and WAIS is planned (1992).

   E-mail: .
   (ftp://prospero.isi.edu/pub/prospero).