Fig. 5
From: Reactive scheduling based on actual logistics data by applying simulation-based optimization
Constraint-based simulation approach. General iterative process flow of the constraint-based approach is the following: A new simulation event arrives at the entry point and triggers off the evaluation of hard constraint feasibility for to-be scheduled activities. Afterwards, a decision is made, whether any activity exists whose hard constraints are fulfilled. If no such activity exists, then the iteration exits and the simulation engine processes the next simulation event. If at least one such activity exists, then the soft constraints for every single activity are evaluated. The activity with the lowest soft constraint violation is chosen to be scheduled next. Afterwards, the evaluation loop repeats again to evaluate hard constraints for to-be scheduled activities. This step is necessary because the previous scheduled activity may have blocked resources that were available during the first evaluation in this loop