registers Head as a virtual tuple in TIPC Linda's tuple space. On
success, any client on the cluster may reference the tuple, Head,
using rd/1 or rd_noblock/1. On reference, Goal is executed by a
separate thread of execution in the host client's Prolog process. The
result is unified with Head, which is then returned to the guest
client. As in linda_eval/(1-2) above, Goal is evaluated using forall/2. The
virtual tuple is unregistered on backtracking into a tuple/(1-2),
receipt of uncaught exception, or cut of choice-points. In tuple/1,
Head and Goal are identical, except that the module name is stripped
from Head.
Note: A virtual tuple is an extension of the server. Even though
it is operating in the client's Prolog environment, it is restricted
in the server operations that it may perform. It is generally safe
for tuple predicates to perform out/1 operations, but it is unsafe
for them to perform any variant of in or rd, either directly or
indirectly. This restriction is however, relaxed if the server and
client are operating in separate heavyweight processes (not threads)
on the node or cluster. This is most easily achieved by starting a
stand-alone Linda server somewhere on the cluster. See
tipc_linda_server/0, below.
