CORBA35 — Why one to one association between a TcPduUser and TcPduProvider interface?

There is an assumption in the design that there is a one to one
association between a TcPduUser and a TcPduProvider
during a TC Session. This is enforced in the IDL through the
call

TcPduProvider::get_dialog_id()

and the factory call

TcPduProvider create_tc_pdu_provider(
in TcPduUser user,
out DialogId d_id)
raises(NoMoreDialogs);

Since the TcPduUser reference (or some sort of reference)
is not passed over in get_dialog_id(), the only conclusion
is that the reference has to be the one passed over in the
create, and therefore that each TcPduProvider is tied to
one and only one TcPduUser.