Were these features [arbitrary hard links] in other
Multics had arbitary "links", which were distinguished from
actual file. Links and branches coexisted in directories. Unix was consciously
derived from this model, but simplified so that only links have names
and branches live elsewhere (the inode list). The architecture is
described in http://www.multicians.org/fjcc4.html
. This paper is
dates from 1964 or 1965; it was certainly authoritative in 1969.
I don't know whether it evolved further.
Christopher Strachey and Joe Stoy independently conceived a model
isomorphic to Unix for OS 6 at Oxford. The two systems were
I am not aware of other systems that allowed multiple names for
one file, though clearly the scent was in the air at the time.