There are variants of this problem

There are variants of this problem wherein jobs are
not allowed to form queues. Zero-buffer and no-wait flowshop problems are some
examples. Having buffers of zero capacity, a job i just finishing on machine r cannot
advance to machine rþ1 if this machine is still processing job i’s predecessor in
job sequence, rather job i must remain at machine r, thus temporarily denying
machine r job i’s successor in the job sequence until such time as job i can advance
to machine rþ1.