Judging methods for interval perturbation robustness of optimal schedules

In the paper the interval perturbation robustness of an optimal schedule is defined. In Li Jiangeng and Tu Fengsheng (2001) some methods are given by which the interval perturbation robustness of an optimal schedule can be determined for some scheduling problems. In this paper some new methods to judge the interval perturbation robustness of an optimal schedule are given. These are: two if and only if conditions for a single machine total weighted completion time problem, some if conditions for a single machine total weighted completion time problem with precedence constraints which take the form of chains, some if conditions for a single machine maximum lateness problem with precedence constraints which take any form, some if conditions for a single machine tardy jobs problem, and some if conditions for a two machine job shop problem with the objective of maximum completion time