Critical constraints in re-entrant flexible manufacturing systems(FMSs) schedules are those constraints that for some change to their weight (and only the weight), could make the sequence of operation in the schedule infeasible. This paper describes how to find critical constraints by representing the benchmark as a graph and finding its strongly connected components and by exploiting the properties of FMSs.
We also find we can force the schedule to have non-participating constraints at some points in the sequence. Finally, we see two possible relationships between critical constraints and describe how these can be found.
We conclude that the points in the sequence where non-critical edges lay, have infinite temporal flexibility.