We consider the problem of scheduling a two-stage processing system wh
ere each stage consists of a set of independent parallel processors. A
job requires processing on a processor from each set and no-wait sche
dules are required. We show that this problem is hard for it generaliz
es jobshop and flowshop scheduling. This observation provides a new co
nceptual framework for process scheduling and allows us to identify se
veral solvable special cases.