File Write Permission Rules

[Guy Harris]

 >> At a presentation to the Orange County Unix Users Group last month the
 >> AT&T speaker mentioned that Release 4 will support use of the suid bit
 >> on directories.  He didn't elaberate on its use, but I'll bet this is it.
 >> 
 >Release 3.2 already supports this feature (only file owner & directory owner
 >(and root)) may remove a file.  This is implemented using the 't', sticky
 >bit on the directory.

Release 4.0 will, as far as I know, support use of the set-*group*id bit
on directories, in the fashion of SunOS 4.0; if the directory has the
set-gid bit set, files created in the directory get the group owner of
the directory as their group owner, otherwise they get the effective GID
of the creating process as the group owner. 

That accounts for the set-gid and sticky bits.  Is there also going to
be a meaning assigned to the set-*user*id bit as well, or did the AT&T
speaker, or the person who was reporting it, mishear or misspeak?