The authors show that the m-machine open shop problem in which all operations have unit processing times can be polynomially transformed to a special preemptive scheduling problem on m identical parallel machines. Many results published recently as well as some new results are derived by using this transformation. The new results include solutions of open problems mentioned in a recent paper by Kubiak et al. A similar relationship is derived between no-wait open shop problems with unit time operations and m-machine problems with jobs having unit processing times.
