root at the top, from which you had to allocate downward (and then recurse), it built _upward_ - if two previously un-connected chunks of graph wanted to unite in a single system, they allocated a new naming layer on top, in which each existing system appeared as a constituent. The Newcastle Connection (aka Unix United) implemented this idea. Name spaces could be pasted together simply by making .. at the roots point "up" to a new superdirectory. I do not remember whether UIDS had to agree across the union (as in NFS) or were mapped (as in RFS). Doug